Hello everyone,

As we have reached the month of June, I thought it would now be appropriate to post this thread.

For each of the fireworks displays this Summer, weather reports will be posted here, including a preliminary outlook two days in advance of every display date, followed by finalized forecasts for either later on the day preceeding fireworks days, or early on the fireworks days themselves, if necessary. I will try and keep details short and concise and will commonly focus on temperature, humidity, precipitation (if applicable), and wind (speed and direction). In cases where the potential for thunderstorms, particularly severe thunderstorms, exists, some further detail will be provided. You are also, of course, more than welcome to post weather updates, but be sure to pay particular attention to the aforementioned meteorological factors.

As mentioned previously, I also use Facebook to provide weather information. As of last Summer (2011), I have been more regularly posting weather updates on my Facebook profile, mostly for severe weather events of any kind across S. Quebec. As such, you are also invited to follow me there, especially when the likelihood for severe weather becomes elevated. The page can be accessed here:

http://www.facebook.com/#!/profile.php?id=738801345

Finally, for those interested, I have posted a detailed Summer 2012 outlook, as well as a review of this past Winter, on my Facebook page. This review can be retrieved using the following link:

http://www.facebook.com/#!/notes/travis-moore/winter-2011-2012-and-a-l ook-ahead-to-spring-summer-2012/10150727374171346

In short, I am anticipating a warm (normal) Summer for 2012, just not as warm as what was seen over the last two years (2010 and 2011). This suggests a slight decline in the number of days reaching maximum temperatures of 30 C or more, as compared to the previous two Summer seasons. Additionally, I believe that we could witness an increase in the number of severe weather days across Ontario and Quebec, corresponding to potentially above normal thunderstorm activity - this could imply locally average to above average precipitation for the Summer months.

Note that I released this review around mid-March, but what I had stated then remains unchanged until now. However, I have been monitoring the equatorial Pacific SSTs (sea-surface temperatures) over the last few weeks, and some model projections have exhibited signs that a weak El Nino may emerge by the end of this Summer, and onwards toward Winter 2012-2013. If El Nino conditions do persist in time for the latter part of the Summer and thereafter, this could spell a reduction in the number of Atlantic tropical cyclones that develop. Additionally, this could also have more positive implications for our upcoming Winter, although it has yet to be seen how both the North Atlantic and Arctic Oscillations will behave at that time. That said, I am not entirely convinced that El Nino will, in fact, dominate, as there is much uncertainty in the model projections. At this point, it appears equally probable that either neutral or weak El Nino conditions will prevail for the end of Summer and beyond, so that is something to keep an eye on for the coming months. If neutral conditions are dominant, it could result in near-normal Atlantic tropical cyclone activity, as well as a more typical upcoming Winter. Still, the climate models demonstrate an overall consensus of warming SSTs (toward positive anomalies) over the coming months, but it's now simply a question as to "how much" warming will actually unfold. In either case, our past La Nina episode has dwindled since the latter part of April, and near-neutral conditions will likely be present for the remainder of the Spring, and for much of this Summer, before any potential transitions occur in the equatorial Pacific.

Here's hoping for ideal weather conditions for all of our participants of 2012!

Trav.

Trav: any updates on the weather for Saturday? Also, I'm doing my Canada Day show on Sunday 1st in Knowlton again - would it be possible to get a weather forecast for that?

Thanks!

Paul.

I have not made a close verification of this, but I believe the 2012 debute display is the latest on the calendar since the start of the competition in 1985. So it seems that we are lucky and, instead of cold weather often experienced on early- or mid-June opening displays, we should enjoy summer conditions, with sun, heat and humidity. I can't wait for Trav's detail reports. In such circumstances, I suppose the big question mark is about wind force and direction.

Fred

At this point in time, the weather should be okay for Japan's display on Saturday evening (June 30th), as compared to what previous prognostics were indicating in terms of instability. That said, because of the positioning of the area of low pressure at the time, I am closely monitoring wind patterns for the day, as they may become unfavorable for folks at La Ronde, more so for spectators on the right hand side of the grandstands. Winds could also be quite gusty during the afternoon period (maximum gusts potentially near 45-47 km/h), though I am expecting them to subside by the evening.

I will provide a more preliminary overview of the weather situation later today. As Fred mentioned, wind tendencies are questionable!

Paul, for Canada Day across S. Quebec, convective showers and isolated clusters of thunderstorms may be possible late in the day due to a passing cold front, which will act to, once again, decrease temperature and humidity values in time for Monday. Humidity itself should be high, and winds are expected to switch to Northwesterlies by the evening period. Maximum temperatures should reach 26-28 C. Still, I would like to keep an eye on this weekend altogether - with the newer model output arriving today into tomorrow (the 29th), it will be easier to finalize these conditions.

Fred, I think you may very well be correct in stating that this is the latest that the competition has ever commenced. There is also a good likelihood that last year's opening date could be the second latest! Could this be a new trend?

Trav.

The current area of low pressure, centered over Northern Quebec, will likely remain nearly stationary for today (Friday) into the Canada Day weekend. Consequently, this weather system will govern patterns for this time period for both S. Ontario and S. Quebec, continuing to bring very warm to hot temperature values, borderline moderate-high humidity, and variable SW to WSW winds speeds to these regions.

For Japan's display on Saturday, the newest model projections indicate very warm temperatures and continued borderline moderate-high humidity. Because of a passing cold front moving through this morning, humidity levels will decrease somewhat during the afternoon hours and will be held constant thereafter into Saturday, producing humidex readings into the low 30s Celsius (high 20s C by the evening). The latest surface analysis, however, reveals a secondary cold frontal wave descending from the NW into Saturday. The front itself, though, is shown to be relatively weak in nature (as per convergence strength), so I don't expect widespread convection with this system. Still, partly cloudy skies (towering cumulus clusters) could be generated by the late afternoon period into the evening here in S. Quebec with a few isolated convective showers and non-severe thunderstorms (concentrated mostly to our North). Once this front passes through, it will push humidity levels down to more moderate levels in time for Canada Day, along with temperatures closer to seasonal (24-25 C).

Winds (speed and direction) are still something that need to be monitored for Saturday evening. The latest surface analysis continues to exhibit SW winds for early Saturday into the afternoon hours and becoming gusty (top gusts at about 45-47 km/h with sustained speeds between 33-36 km/h) for the afternoon period. By the evening, directional tendencies may shift to WSW, along with lighter sustained speeds at around 17-21 km/h (further decreasing to 11-15 km/h by late evening). This would suggest that the smoke could be blowing towards mostly the right hand sections of the grandstands at La Ronde. However, some simulations are showing Northwesterly patterns by late evening, which would push smoke to the left, although it would head towards spectators on the bridge adjacent to the park. As such, it is still required to wait for the models to come more into agreement.

That's the way the weather should generally work for today into the weekend. I will provide a finalized report later today (for Canada Day and Saturday), although an additional update may be necessary early Saturday for winds and potential precipitation.

Paul, for the evening of Canada Day in Knowlton, winds should generally be light (8-11 km/h) from the WSW, though breezier Westerlies (15-19 km/h) will likely take place during the afternoon period. The probability for precipitation is now less, as the cold front will have gone through Saturday night, East of Montreal, leaving mostly pleasant conditions for Canada Day. Maximum temperatures should be around 24-25 C, coupled with moderate humidity. Temperatures decline to 18-20 C by late evening, along with near-constant humidity levels. Again, I will post finalized details later today, just in case of any changes, but this should give a good overview as to what to likely expect.

Trav.

Apologies for the delay!

After reviewing the latest model runs, these are the conditions that will likely be prevalent through Saturday (June 30th) across S. Quebec. An analysis for Canada Day is also prepared in the following section, though it is possible for some adjustments to be made into tomorrow.

June 30th

Temperature/Humidity

Temperatures are still expected to remain very warm/hot for daily maximums for Saturday, where values may attain as much as 29 to 31 C. Humidity levels are also within the moderate-high range, making it feel into the 30s C (33-35 C), mostly for the early to mid parts of the afternoon before a secondary cold front advances from the NW later in the afternoon to the early evening. Late evening temperatures should be closer to 24-25 C (as much as 26-27 C in the metropolitan area), along with moderate humidity, generating a humidex of about 29-30 C.

Precipitation

As mentioned previously, a secondary cold front will be advancing from the NW later tomorrow afternoon into the early evening, generating increased cloudiness by mid afternoon, along with a few possible isolated convective showers and non-severe thunderstorms. The greatest area of convergence/moist convergence along and ahead of the cold front is still shown to be North of Montreal, so I am expecting greater likelihoods for more widespread storm initiation over those areas. Precipitation for Southern portions of Quebec (Montreal included) should generally be more isolated in nature, so a 30% probability is in order for the late afternoon-early evening period. Instability should subside by the late evening time frame with building convective inhibition.

Wind

The current area of low pressure has not shifted positioning significantly from previous simulations. As such, winds are expected to still be largely coming out from the SW through tomorrow and will be gusty throughout the afternoon, with maximum gusts between 47-51 km/h and sustained between 33-36 km/h (highest sustained winds and gusts should occur between 1:00-4:00 p.m. Speeds should subside with the onset of the evening as the system slowly migrates East, declining to as much as 17-21 km/h (gusts at 27-30 km/h) and further down to even as low as 7-11 km/h by late evening. In terms of direction, winds are shifting more to NW tendencies for the early to late evening (more from the WSW by mid to late afternoon), so this could gently displace smoke towards the left hand sections of the grandstands, as well as possibly left hand-most parts of the central section. Smoke may also influence those on the bridge just adjacent to the park and behind (going East). Some smoke accumulation may take place during more active sections of the display due to the combination of lighter winds and moderate humidity.

In summary, borderline moderate-high humidity and very warm to hot temperatures will be present for Saturday. Isolated convective showers and non-severe thunderstorms (30% probability) are possible for the late afternoon and early evening period due to a passing secondary cold front. Winds are gusty for the day and are mostly from the SW but could change to WNW to NW tendencies by late evening, pushing the smoke to left hand sections of the La Ronde audience. Speeds also die down significantly by the evening, which could lead to some occasional smoke build up. If necessary, I will provide a brief update concerning the winds early tomorrow.
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Your Canada Day forecast:

Temperature/Humidity

With the passage of the secondary cold front later Saturday through S. Quebec, maximum temperatures for both Montreal and to the East/NE will likely reach 25-26 C with continued moderate humidity, making it feel closer to 28-30 C. By late evening, temperatures decline to 19-20 C, along with near-constant humidity (humidex not significant).

Precipitation

Generally comfortable conditions should prevail for early to mid sections of the day. However, newer (and a few previous) prognostics indicate a developing upper level trough following the departing surface low. This trough will enhance instability for the mid-afternoon period for Western/SW sections of Quebec, producing isolated convective showers and a few possible non-severe thunderstorms. The risk gradually pushes East by the late afternoon to early evening period, but instability should gradually cease thereafter with nocturnal cooling, leaving predominantly partly cloudy skies. Precipitation may become more scattered in association with this trough, so a 40% probability for W/SW sections of the province (considering also the timing during the afternoon) is appropriate, as well as for areas East and NE of Montreal towards Sherbrooke and Quebec City, though decreasing to 30% by the early evening. In either case, expect increased cloudiness by the afternoon - this increase is also supported by mid level analyses showing elevated relative humidities at those levels of the atmosphere.

Wind

Winds should be breezy throughout the late morning to afternoon period for Southern and Eastern/NE Quebec. Wind direction should be primarily from the West, but should begin to change to Northwesterlies by the evening for the Montreal area to WNW to the East of the island. Speeds also uniformly decrease by the evening to 5-11 km/h for the aforementioned regions.

Trav.

As expected, a few isolated convective showers have developed ahead of the cold front and will continue to do so to the NW while pushing SE over the next few hours. Again, most of the thunderstorms, and even severe thunderstorms, lies to our NE.

In terms of winds, they should remain as Northwesterlies for the duration of the evening, although models now indicate slightly higher wind speeds at 12-15 km/h, which would facilitate smoke clearance a little more.

Enjoy the show by Japan!

Trav.

As this upcoming area of low pressure slowly advances Eastward, both S. Ontario and S. Quebec will slowly resume a very warm/hot and humid air mass for tomorrow (Friday, July 6th), with temperatures locally attaining as much as 34-36 C, along with humidity values ranging in the high 30s to low 40s C. However, as a cold front pushes in from the WNW by late tomorrow afternoon, clusters of convective showers and thunderstorms (a few of which may reach severe criteria) could develop along and ahead of it. It's still questionable, however, how widespread convective activity will become. Consequently, the best chance for any convection to take place across S. Quebec should span from late Friday afternoon to the pre-dawn hours of Saturday. This also suggests that humidity levels will be declining to moderate values for Saturday, along with maximum temperatures closer to 26-28 C (late evening temperatures should decline to 22 C). I am additionally keeping an eye on a secondary cold frontal wave descending quickly from the NW, which may have some influence later in the afternoon, although this is not suggested in current model simulations.

One aspect that I am closely watching is the wind, mostly in terms of direction. By Saturday evening, winds may be blowing toward central and right hand sections of the audience at La Ronde. Once the cold front moves toward the SE, winds will gradually shift to West-Southwesterlies Saturday morning and oscillating between WSW to straight Westerlies for the mid afternoon to evening time frame. Wind speeds themselves should be breezy through the morning to afternoon and early evening periods, with sustained speeds between 23-27 km/h (ocassional gusts of 34-37 km/h). Wind speeds should decrease to 15-19 km/h by late evening.

I will provide an update for later tomorrow, and, if necessary, early Saturday afternoon, to confirm prevailing conditions.

Trav.

Weather conditions described in the previous posting remain similar for the day tomorrow, although there are a number of additional details that I'd like to incorporate. As such, here are the updated forecast details for Saturday, July 7th:

Temperature

Temperatures continue to remain very warm through tomorrow, with maximum values reaching as high as 27-28 C. Humidity levels, however, are reduced to borderline moderate/high levels, and so humidex readings should be around 31-32 C during the afternoon period. By late evening, temperatures decline to 22 C (as much as 23-24 C in the metropolitan area), along with mild humidex readings around 25-26 C (moderate humidity by late evening). Both temperature and humidity further decline into the overnight period, as cooler and drier air progressively settle in.

Precipitation

Model simulations continue to show that the greatest potential for convective activity remains for tonight into the morning hours, although the frontal wave will likely generate increased cloud cover and a few rain showers tonight toward the early afternoon. Following 2:00-2:30 p.m., the sun should slowly make more more appearances as the front slides SE. The simulations also continue to display a secondary cold front (as mentioned in the previous posting) descending quickly from the NW by late tomorrow afternoon. This front is relatively weak, however, and so the threat for defined convection should be minimal. The increased cloud cover early in the day associated with the previous front will also limit stronger instability. Still, this frontal wave could produce some brief increased cloudiness during the late afternoon, along with a few isolated showers (30% probability) distributed across S. Quebec and E. Ontario. The speed and timing of the front suggests that any instability associated with it should cease by the late afternoon-early evening period - this is also further supported by decreased relative humidities at mid levels of the atmosphere, as well as changes in surface/near-surface wind direction by the late afternoon (see next section).

Wind

Latest surface analysis projections remain fairly close to what had been illustrated in previous runs in terms of both speed and direction. However, newer analyses show that winds are shifting direction by the late afternoon period, where West-Northwesterlies and Westerlies become straight Northwesterlies. With this directional shift, winds should be pushing the smoke towards the "left" of the audience at La Ronde, although the extreme left hand section of the grandstands could occasionally be affected. Those positioned on the bridge behind the park (near the ramp and heading East) would be most influenced by smoke. In terms of the progression of directional tendencies through the day, winds become Westerly by the morning hours and transition to the WNW by the early afternoon. By the late afternoon period, winds should be more from the WNW and, into the early evening, from the NW. Speeds will be greatest from the late morning to early-mid afternoon, with sustained speeds at 23-27 km/h (occasional gusts between 31-34 km/h). The breezy nature of the winds is expected to continue into the late afternoon to early evening period at 19-23 km/h (occasional gusts at 27-30 km/h), and then to 18-21 km/h by the late evening.

That's the way the weather should generally work. To recap, warm temperatures should be present for the evening period, coupled with moderate humidity and breezy conditions from the NW. Isolated showers (30% probability) are possible during the late afternoon with the approaching secondary cold front but should gradually subside by the onset of the evening.

Trav.

As this potential heat wave continues to build across S. Ontario and S. Quebec, expect temperatures to attain borderline hot to very hot standards, as well as high to very high humidity, for both today (Friday) into the weekend. As mentioned previously, for a "heat wave" to emerge in Quebec, maximum temperatures must reach 30 C or more for at least three consecutive days, and seeing that we struck an hourly maximum of 31 C yesterday (the 12th), and given the potential temperature distribution for today and tomorrow, I have reason to believe that this weather pattern will, indeed, become a formal heat wave for many parts of S. Quebec.

Saturday's (July 14th) weather conditions will be a part of this pattern. Consequently, temperatures across E. Ontario and S. Quebec could locally reach as high as 34-36 C for daytime highs, along with high to very high humidity, making it feel as warm as 42-43 C. Evening to late evening temperatures will also remain quite high, largely because of the elevated atmospheric moisture content. As a result, values may remain around 28-29 C, especially in the metropolitan area, while the humidity will make it feel around 34-35 C. Conditions should also remain mostly dry for the evening, although I am monitoring an upper-level disturbance South of the border for early in the day - this should remain South into New York, but I'd still like to keep an eye on it in the newer model runs from today. The greatest chance for enhanced convection and severe weather is late Sunday night through the day Monday.

There seems to be a general agreement about wind tendencies in the model runs, where all are exhibiting SW to SSW patterns for the day (except WSW for the late-morning to mid-afternoon) into the evening period. Winds are breezy during the late-morning through most of the afternoon at 15-19 km/h but subside to 8-11 km/h by the evening. Some projections, however, are showing continued Southwesterlies into the evening, while others show a shift to the SSW direction. In either case, smoke from the fireworks should be blowing to the "right" of the audience at La Ronde, but it remains a question of how much to the right.

I'll provide an update later today Saturday's weather conditions.

Trav.

After reviewing the latest model analyses from today (Friday), overall conditions remain largely unchanged from what had been described in the previous posting. As such, here are the prevailing weather conditions for Saturday, July 14th for the Montreal area.

Temperature/Humidity

Because of an advancing area of low pressure moving in from the West, and a strong, dominant area of high pressure that has been centered over the North Atlantic for the last while, the resulting circulation of warm, moist air will push maximum temperatures to locally as hot as 33-35 C (a touch less from previous forecasts) during the mid-afternoon, along with continued very warm to hot temperatures during the late-evening period at 28-29 C, especially in the metropolitan area. Humidity levels are also remaining borderline high to very high, making it feel around 38-39 C during the mid-afternoon and 35-36 C throughout the evening, consistent with slightly rising humidity levels later in the day.

Precipitation

The models continue to show mostly dry conditions across S. Quebec, with roughly 30-40% relative humidity values at mid-levels of the atmosphere and suppressed/weak instability. As I had also expected, the upper-level disturbance (an upper-level trough) that I had mentioned previously is still shown to stay farther South of the border into extreme S. New York and southward. Weak instability may produce a few isolated cumulus clouds with limited vertical development during the afternoon, but skies should remain mostly clear.

Note that these conditions will quickly change into Sunday (the 15th) afternoon-evening, as enhanced convection becomes more prominent with an approaching cold frontal wave and preceding shortwave trough (this system is shown to move in a little faster, as compared to previous runs). As a result, convective showers and thunderstorms (some possibly becoming severe thunderstorms) may develop through the afternoon-evening period. Also note that this front will not sharply cut temperatures and humidity into the work week - this will likely occur by the end of the week (Thursday and Friday) as another cold front pushes through.

Wind

Wind tendencies (speed and direction) remain mostly constant in the newer projections. However, it appears that winds, after coming out from the WSW (early to mid-afternoon) to SW (morning and late-afternoon), should transition to South-Southwesterlies (SSW) by the late-evening period. Wind speeds still remain light but are slightly higher at 9-12 km/h. As such, smoke should be gently blowing to the right of the audience at La Ronde (left of the audience positioned on Notre-Dame street), although some smoke accumulation could occur during more active segments of the display due to the high humidity present.

That’s the way the weather should work. To summarize, very warm and humid conditions for Saturday evening, along with light SSW winds and a few scattered cumulus clouds. If necessary, I will post a brief update concerning the winds early tomorrow afternoon, at the very latest.

Should be another enjoyable July-like evening.

Trav.

Consistent with the information posted above, it is no surprise that Environment Canada has issued a high heat and humidity warning over much of S. Quebec. I would not rule out the possibility of humidex readings reaching as high as 42 C this afternoon. I personally adore this weather, but for those who have little tolerance for this kind of heat and humidity, it is important to remain indoors in an air-conditioned environment and to stay well hydrated (preferably with water). It is also important to stay out of the sun between 11:00 a.m. to 4:30 p.m., not only with respect to the heat, but also due to the high UV index forecasted for today.

As for the winds this evening, they are still expected to behave in patterns specified in the above posting. For everything else, please refer to the above post.

Trav.

It's been great, this year, not to have to look at the radar for storm threats before heading over to La Ronde!

Enjoy this great summer weather everyone!

Paul.

Indeed, the weather has been treating fireworks days well so far this year. Conditions for Tuesday evening (the 17th) are a little tricky, however, as convective showers and thunderstorms may develop across S. Quebec ahead of the aforementioned cold front (which will lead to a sharper cooling by Wednesday). It's still a little early to say how strong thunderstorms (if any) will become, though.

More details later tomorrow.

Trav.

Mentioned previously, this current heat wave will gradually subside as a cold front associated with the next area of low pressure passes through S. Quebec and S./E. Ontario Tuesday night. As a result, temperatures and humidity levels decline by Wednesday morning, with the cooler and drier conditions persisting towards early Saturday (the 21st) - overnight lows for both Wednesday and Thursday night may be as cool as 12-13 C for parts of S. Quebec (Montreal included, mostly outside the city). Until then, expect continued hot and humid weather until overnight Tuesday, including temperatures as high as 27-28 C (feeling closer to 34-35 C with the borderline high to very high humidity) in the metropolitan area for Tuesday evening/late-evening.

Note that periods of convective rains and thunderstorms (some potentially severe) are possible through the morning to afternoon period due to the low’s warm front, while the risk during the late-afternoon to evening period is attributed to the passing cold front. The atmosphere, at this point, is shown to be moderately unstable (for various reasons) through the early evening period and persisting (though weaker) into the early-overnight hours.

With this upcoming secondary area of low pressure intensifying as it travels ENE, relatively strong gusts of wind will likely develop during the late-morning to early-afternoon hours, where speeds are sustained between 27-31 km/h, while occasional gusts may reach as high as 42-45 km/h. Wind speeds (and gusts), however, are shown to decline by the late-afternoon to early evening hours to 19-23 km/h (occasional gusts between 29-32 km/h) and further to 14-18 km/h by late evening. Winds shift to various directions through the course of the day, consistent with the ENE progression of the low. Winds first begin from the SSW during the morning hours and then transition to the SW for the early to mid-afternoon period, becoming WSW by late-afternoon and Westerly for the early-evening period. By late-evening, models indicate a shift to NW tendencies, but the challenge is forecasting how quickly the previous Westerlies will undergo this transition. As a result, some projections show Westerlies throughout the evening (which would push smoke towards the audience at La Ronde), or a change to the NW (pushing the smoke to the left of the audience, although occasionally affecting extreme left sections of the grandstands).

In any case, a more careful examination of newer prognostics is essential to have a better overview of Tuesday evening’s weather conditions, especially in terms of wind patterns and atmospheric instability. Additional updates may be needed into early Tuesday, as well.

Trav.

I anticipate your updates tomorrow about the risk of late thunderstorms. Hopefully, we will not have to deal with precipitations in addition to the very high humidity.

Thank you very much for your forecast reports. They are very appreciated.

Fred

Recent prognostics continue to reveal near-identical patterns to what had been described in the above posting. There are some adjustments, however, that will be outlined in the following analysis. Here are the most probable weather conditions for today (July 17th) for the Montreal area:

Temperature/Humidity

Temperatures continue to remain very warm to hot through the afternoon hours, with highs reaching around 30-31 C across much of S. Quebec, and as hot as the mid 30s C through to E./S./SW Ontario. Humidity levels also continue to remain borderline high to very high, pushing maximum humidex readings as high as 39-40 C. By the late-evening period, as newer model simulations indicate, temperatures should fall toward the 25-26 C range (as much as 27 C in the metropolitan area), consistent with the near-complete passage of the cold front at that time. This is also further suggested by humidity declines closer within the “high” range, making it feel like 32 C. Note, however, that if thunderstorms (or convective rains) do occur, temperatures will rapidly decrease and limit the maximum forecasted temperature from taking place.

Precipitation

With the atmospheric setup, this is a great day to be storm chasing across E. Ontario and S. Quebec.

As mentioned in the above posts, a cold frontal wave associated with a secondary area of low pressure is quickly descending from the NW this afternoon into the early-evening. Ahead of the front, surface and near-surface moisture/dewpoint levels are high to very high, and sufficient surface heating through the early part of the day will likely enhance low-level instability, together yielding a moderately unstable atmosphere during the afternoon hours. In addition, deep-layer speed and directional wind shear are enhanced, largely owing to the upper-level Westerlies associated with the jet stream flowing over the area. Consequently, the risk for widespread convective rains and thunderstorms exists across mostly E. Ontario, S. Quebec and Northern New England throughout the afternoon. Also note that some thunderstorms may be reaching severe criteria over these regions, and the environmental conditions are favorable for producing a few rotating thunderstorms, so this needs to be carefully monitored through the day. It is interesting that the potential for severe weather occurred for three years consecutively on July 17th (2010, 2011, and now possibly for 2012).

Some good news, however, is that yesterday’s model runs showed indications that the area of low pressure is speeding up in its eastward propagation. This suggests that the cold front should pass through S. Quebec by the late-afternoon to early-evening period (rather than early-overnight), leaving partly cloudy skies into the late-evening time frame. The passage of the front is further supported by decreasing mid-level relative humidities, slightly decreasing dewpoints, shifting winds to the NNW to NW (see next section), and the highest convective available potential energy pushing into New York.

Wind

Winds continue to show similar transitions explained in the previous posting. However, the timing of the directional changes has shifted a little in recent projections. Winds are shown to be first from the South to SSE by morning, becoming breezy at 15-19 km/h by the late-morning to early-afternoon. By the early to mid-afternoon period, winds shift to Southwesterlies at 24-27 km/h (occasional gusts of 33-37 km/h), and into the late-afternoon period, winds change to Northwesterlies and become lighter at 15-19 km/h, and eventually to 11-15 km/h towards the early-evening. By late-evening, winds are shown to further decrease to light/very light standards at 4-8 km/h, mostly from the NNW to NW. As such, the winds should be blowing very slowly to the left of the audience at La Ronde (right for those on Notre-Dame), although the extreme left-hand section of the grandstands could occasionally be affected, but those on the adjacent bridge just overlooking the park will likely be most influence by smoke. Also note that extensive smoke build-up towards the left of the audience at La Ronde may be possible, especially during more active sections of the display, due to the combination of light/very light winds and high humidity.

That’s the way the weather should generally behave. In summary, expect light to very light winds during the late-evening period, mostly coming out from the NNW to gradually NW. Temperatures remain warm to very warm (especially in the metropolitan area) through the evening, and humidity levels are high but decline somewhat by late-evening. Strong, scattered convective activity is greatest during the mid to late-afternoon period, potentially stretching into the early-evening.

It may be required to provide an additional update by early this afternoon in terms of wind tendencies, as well as any changes in atmospheric instability.

Apologies for the lengthy analysis!

Edit: No problem, Fred - always a pleasure.

Trav.

Severe thunderstorms and heavy rain are expected by MétéoMédia. I'm really afraid the pyro material may be flooded for tonight... That would be dramatic.

Fred

Winds continue to exhibit directional tendencies similar to what had been specified previously. As such, smoke from the fireworks should be moving mostly to the left of the audience at La Ronde, although extreme left-hand sections may occasionally be influenced. Those on adjacent parts of the bridge, however, will likely be most affected by smoke, and for viewers at the Old Port, smoke may, at times, obscure the view. I'm only going to increase the wind speed slightly to 8-12 km/h (from the NNW to NW) for the late-evening. Also, humidity levels will still remain quite high into the evening, even when the cold front has gone through - the gradual decline should occur during the overnight.

As for the thunderstorms, indeed, as expected, many severe thunderstorm cells have developed along a squall line over East Ontario, one storm of which recently affected areas near Cornwall. Additional storms have been forming near the island of Montreal and North of Ottawa, and these storms could have some influence very shortly, or passing closely near the island. One storm is currently affecting extreme SW sections of the West Island at this time.

Again, instability should gradually subside by the early-evening, but I would recommend having an umbrella handy for the hours "waiting" for the fireworks.

Trav.

The good news is that, once the current line of storms has passed, it looks like we'll be in the clear. Hopefully setup is complete and everything well protected.

Paul.

I'd still give a few more hours (until the early-evening) for that front to completely pass through S. Quebec and E. Ontario, before partly cloudy conditions prevail.

Trav.

As the cold front that went through and brought widespread severe weather to both E. Ontario and S. Quebec on July 17th, high pressure has now settled in, bringing with it pleasant weather conditions as of July 18th, though overnight lows are cool. This area of high pressure will gradually migrate East towards the Atlantic in time for this weekend (July 21st and 22nd), allowing for a nice Southwest (SW) to South-Southwest (SSW) circulation to influence both S. Ontario and S. Quebec. As a result of this pattern, temperatures will likely return to the higher 20s C, along with a boost in humidity to moderate levels, making it feel into the low 30s C. Maximum temperatures, here in Montreal, could reach 29 C for tomorrow, while late-evening temperatures should stay steady into the mid 20s C.

In terms of wind, as mentioned, they should be in the form of SW to SSW, but they seem to be showing signs of coming out from the SSW throughout the duration of the evening. Winds are also expected to be light at 7-11 km/h during the late-evening period. As such, the smoke from the fireworks should be gently blowing mostly to the right of the audience at La Ronde, although extreme right-hand sections of the grandstands could occasionally be affected.

The only thing that I am watching for now is an approaching cold front from the NW in today’s model projections, but this front should only have an impact by mid-Sunday into Monday, setting off a few isolated convective showers and thunderstorms.

Providing that the cold front maintains its current speed, this should be a very nice Summer-like evening for France.

Trav.

The newest model output remains about identical to what had been described in the previous posting. As such, here are the weather conditions for Saturday, July 21st - the last Saturday of this year’s competition.

Temperature/Humidity

As this current area of high pressure pushes farther East, along with an area of low pressure moving in from the West as the day progresses, a nice circulation of SW to SSW winds will circulate a warmer and progressively more humid air mass into S. Ontario and S. Quebec for this weekend. As a result, temperatures on Saturday could reach as high as 29-30 C (mostly for the metropolitan area), along with late-evening values around 24-25 C (25-26 C in the metropolitan area). Humidity is building to borderline moderate-high levels for tomorrow afternoon into the evening, and so this will be enough to generate humidex readings at about 32 C during the mid to late-afternoon (28-29 C by late-evening).

Precipitation

Precipitation is not expected through the day Saturday. Newer projections are keeping the aforementioned cold front just East of central Ontario into the evening hours of Saturday. As a result, expect mostly clear conditions for the day, along with a few clouds. An increase in cloudiness to partly cloudy skies is possible by the early-evening hours, however, as the cold front advances, which will enhance convection into Sunday. By later Monday, severe weather may be possible with a secondary cold front advancing from the NW, cooling temperatures through Tuesday.

Wind

Winds are likely coming out from the SSW through most of the day (South for the early-morning to early-afternoon, and perhaps again by the late-evening), with speeds steady between 8-12 km/h, including for the late-evening period. I am thinking now that the smoke should stay clear of La Ronde spectators as it slowly passes to their right (left of those on Notre-Dame).

In summary, a beautiful (and arguably perfect) Summer evening for the French display (conditions were also very pleasant for the setup period), with partly cloudy skies, borderline moderate-high humidity, and temperatures into the mid 20s C. Winds should be light from the SSW.

Trav.

Just to provide an update, but newer projections indicate that there is a slight possibility for a few scattered showers late this evening ahead of the cold frontal wave. Conditions should remain generally partly cloudy (as mentioned above), but newer runs show an increase in relative humidity at mid-levels of the atmosphere, so I just wanted to outline this risk.

I apologize for the late notification to this.

Trav.

Just to provide an update, but newer projections indicate that there is a slight possibility for a few scattered showers late this evening ahead of the cold frontal wave.

Trav, some of us praised the incredible accuracy of your forecast, once again, tonight, as a light rain started around 9:00pm, as I moved in the grandstands with Simon. Fortunately, it stopped about 30 minutes later...

Many thanks for this update and always appreciated contribution to this forum!

Fred

As the upcoming area of low pressure advances from the West, a continued surge of hot and humid air will circulate into S./E. Ontario and S. Quebec for today, allowing temperatures to locally reach the mid 30s C, along with humidex values attaining near or above 40 C. However, the passing secondary cold front later in the day (mentioned three posts above) could set off widespread convective showers and thunderstorms, several of which could be reaching severe standards. Here, in S. Quebec, the better chance for severe weather is during the late-afternoon to evening/early-overnight hours. Note also that some of these thunderstorms could also become supercell thunderstorms (thunderstorms with a persistently rotating updraft) due to enhanced deep layer shear/directional shear, so, much like on July 17th, this needs to be monitored through today due to the elevated possibility of isolated tornadoes.

As the cold front passes through later tonight, a gradual cooling will take place into tomorrow (Tuesday), along with a sharp cut in the humidity level. Behind the front, gusty NW winds will also likely occur by the later-morning hours towards the afternoon and evening period. Consequently, Portugual’s display likely could be dealing with breezy conditions, coupled with cooler temperatures (late-evening temperatures around 18-19 C) and low humidity. No precipitation is expected.

At this point, winds for the late-morning throughout the afternoon period should be sustained between 27-31 km/h (occasional gusts of 41-44 km/h). Winds continue to be breezy during the evening hours, but I believe that they will diminish to more suitable speeds at 23-26 km/h (occasional gusts between 32-35 km/h), and further down to 15-19 km/h by late-evening. As such, the smoke should be blowing quickly to the left of spectators at La Ronde, although occasionally influencing those stationed at left-hand sections of the grandstands, and more so for those on the adjacent bridge.

This is somewhat of a tricky forecast, but I will provide an update later today. I will also be occasionally following up with the severe weather potential for today on Facebook.
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Fred, indeed, once the newer model projections were released Saturday afternoon, I noticed the slightly increased instability and higher mid-level relative humidities, prompting me to issue the risk for scattered light showers during the later-evening hours, even though those showers were not expected to be significant. My only worry was that I released the information too late, but I’m glad that wasn’t totally the case! The change also eliminated the “perfect” weather conditions that I had previously envisioned, and I was awaiting slightly stronger wind speeds to clear away the smoke a little faster - this was somewhat frustrating, as the wind patterns were ideal up to 9:32 p.m. I suppose that such is the complex reality of weather!

As always, it is no problem for the weather updates.

Trav.

Once again, my apologies for the delay - I've been rather busy with yesterday's severe weather! I kept thinking to myself last night that Portugual was fortunate in not being scheduled to present yesterday, although I sincerely hope that the weather did not inferfere with the setup process.

Today's weather conditions remain largely similar to what had been described in the above posting. As such, here are the conditions that are most probable for this evening (July 24th).

Temperature/Humidity

After the severe thunderstorms passed through yesterday afternoon into the evening (July 23rd) ahead of the sharp cold front mentioned previously, both mean temperature and humidity values have progressively been declining into today. As the late-evening approaches, temperatures should drop to 19-20 C (as much as 20-21 C in the metropolitan area), and the humidity should also be reduced to borderline light-moderate standards (no humidex). You may, however, feel the occasional slight chill with the somewhat breezy winds this evening.

Precipitation

Instability associated with the current upper-level trough should weaken by later this afternoon. Cloudy periods (less defined cumulus cloud clusters) will contine into the early-evening time frame in association with this trough but will be gradually clearing later in the evening to the early overnight.

Wind

As the cold front has now passed pushed East to ESE and SE for today, a fairly strong NW flow has quickly followed behind it. As a result, winds, as mentioned previously, will often be gusty though this afternoon from the NW to NNW, with sustained speeds between 23-27 km/h (gusts from 32-36 km/h - slightly reduced from the previous post). Again, by this evening, winds should diminish to average sustained speeds of 15-19 km/h, which will likely persist into the late-evening hours (closer to 14-17 km/h) but diminishing further to 12-15 km/h during the overnight. Winds should remain Northwesterly this evening, so smoke should be blowing relatively quickly to the "left" of the audience at La Ronde ("right" for those on Notre-Dame), though left-hand sections could occasionally be affected, and more so those on the adjacent sections of the bridge overlooking the park.

In summary, pleasant conditions for today and this evening, though a touch cool late this evening, along with borderline light-moderate humidity, a few clusters of cumulus clouds, and somewhat breezy NW winds.

Trav.

I am currently monitoring an area of low pressure passing closely to our South through the day tomorrow (July 27th). However, models aren't quite in agreement just yet as to how far to the South this system will remain. Still, mostly cloudy (a few sunny breaks) skies should take place for the day, and temperatures should reach as high as 26-27 C, along with moderate humidity levels, generating humidex values of about 30-31 C for the mid to late-afternoon. Humidity levels decrease slightly through the late-evening to overnight period (due to approaching high pressure to the NW), so humidex readings should be into the mid 20s C, at the very highest. Temperatures by the late-evening period should be around 22-23 C for the metropolitan area.

As for the winds, given the area low pressure to the South, and the approaching high pressure system from the NW, they should generally be out from the NNE for the day, including the evening. Speeds should be greatest during the morning hours at 23-27 km/h (gusts of up to 32-35 km/h) but will gradually subside by mid-afternoon. By the evening, speeds become light at 7-11 km/h. As such, winds should be slowly blowing the smoke to the left of the audience at La Ronde, although the NNE to NE winds could occasionally push it toward Southern sections of Notre-Dame street (going past the bridge to the South).

We'll continue to monitor the track of this system in the model runs from today, and I will provide an update once simulations display more of a consensus.

Trav.

Newer model runs seem to be more in agreement with respect to the area of low pressure that I had been monitoring to our South. As such, here are the expected weather conditions for today (July 27th) in the Montreal area.

Temperature/Humidity

Temperatures should continue to remain in the range specified above, where daily maximums should attain 26-27 C and late-evening temperatures around 21-22 C (as much as 22-23 C in the metropolitan area). Humidity should remain largely borderline moderate to high for this afternoon, generating humidex values as high as 30-31 C. Again, humidity will gradually decrease later in the day to more borderline low to moderate levels, as an area of high pressure to the NW slowly settles in.

Precipitation

As the area of low pressure (now a series of lows) is now shown to stay to our South, we should see mostly sunny conditions, along with a few clusters of cumulus clouds developing through the atmosphere. As such, the most active weather should remain over SW Ontario, S. New York and southward this afternoon into the evening. Skies clear further into this evening for S. Quebec, as high pressure slides to the SE.

Wind

Winds continue to exhibit tendencies similar to what had been described previously. Winds were breezy earlier this morning but will subside to a range of 12-15 km/h through this afternoon, and even further down to 7-11 km/h by the late-evening period. In terms of the overall direction, they are maintaining largely North-Northeasterlies (NNE) for this afternoon, but I am detecting a slight shift toward more Northeasterlies late this evening. As such, the smoke should, once again, be blowing gently to the left of the audience at La Ronde (right for those on Notre-Dame), although those on Notre-Dame street near the bridge and heading South could be receiving smoke, at times. Those on the bridge near Notre-Dame could also be similarly affected, as well as those over the river.

That's the way the weather should work for the Italian display. In summary, pleasant conditions for this evening, with borderline low to moderate humidity and warm temperatures. This will be accompanied by light winds this afternoon into the evening from the NNE, but winds could become closer to Northeasterlies late this evening, along with slightly lighter wind speeds from what they will likely be this afternoon. Skies should remain generally clear this evening, with a few isolated cumulus clouds.

Trav.

Over the last number of days, I have been watching an area of low pressure out West that has been responsible for severe weather (severe thunderstorms and tornadoes) across much of the Southern tier of the Prairie provinces. This area of low pressure is now migrating East towards central Ontario, and eventually reaching S. Ontario and S. Quebec. As current prognostics indicate, this low could have some impact as early as late Tuesday afternoon (July 31st) for S. Quebec. Consequently, convective showers and thunderstorms are possible at this time.

It's still obviously somewhat of a challenge to assess the timing of this system, as well as how strong thunderstorms might become over the region if the low maintains its current speed in future simulations. However, given the potential for a moderately unstable atmosphere over S. Quebec (again, if the low maintains its speed), coupled with enhanced vertical shear, I am convinced that a few isolated severe cells are possible, not just for late Tuesday, but into Wednesday, as well (for different reasons). The potential for thunderstorms is ongoing from July 31st to August 5th, though not necessarily occurring on each of these days.

Temperatures are expected to return to hot standards into tomorrow (July 30th), which should persist into Tuesday. Humidity levels will likely maintain borderline high to very high values, so humidex readings could surge into the high 30s C (locally very low 40s C). Tuesday's maximum, here in Montreal, could reach as high as 32 C (locally 33 C), depending on how much sunshine is received at the surface. By late-evening, temperatures should remain at 26-27 C, mostly for the metropolitan area.

As for the winds, they should be largely coming out from the South to SSW (in accordance with the positioning of that low), with somewhat breezy speeds at 14-18 km/h for the late-evening. Note that speeds are higher during the day at 24-27 km/h (occasional gusts of 33-36 km/h). As a result, smoke from the fireworks should be moving clear to the right of the audience at La Ronde.

We'll continue to monitor the weather situation for Tuesday, and I'll try to provide an update later tomorrow.

Trav.