*A near-average Summer is possible for much of eastern Canada in terms of temperature and precipitation this year (more details below under the Summer outlook section).

Summer is, once again, fast approaching, but after a fairly dreary Spring 2011 across much of the country, many Canadians are wondering what could be awaiting for Summer 2011. As stated in my personal Spring-Summer 2011 outlook (in the reference link provided below) at the beginning of April, and previously on several occasions, I outlined that Spring 2011 could follow an average to below average temperature regime, while precipitation could be average to above average. As it turned out, Spring 2011 was, indeed, quite the contrast from what we had seen last year in 2010 (2010 being an exceptional year for warm weather in its entirety). For this Spring, we had undoubtedly seen well above average precipitation, with March, April and May exhibiting total amounts that easily exceeded 100 mm for each individual month - in fact, May 2011 was the third wettest May in recorded history (covers a timespan of about 70 years), with a final cumulative amount of over 140 mm, just trailing behind 1945 (175.3 mm), and fairly recently in 2006 (173.4 mm). Non-severe thunderstorms also contributed to some of the rainfall that we received, especially towards the end of April into May. The copious rainfall was particularly conducive to the ongoing flooding event that had been taking place just southeast of Montreal, in St-Jean-sur-Richelieu. In the context of monthly daytime highs, temperatures have been about average to slightly above average for March and April, respectively. Conversely, May 2011 had largely directed below average temperatures, which is to be expected, given the very little sunlight received for the month. Winter 2011 had also demonstrated a sharp contrast, as compared to Winter 2010. For a comparative examination of Winter 2010 vs. Winter 2011, please see the following link and refer to the tabulated statistics at the bottom of the final post (note that January’s normal snowfall should read as 52.5 cm, and the actual snowfall for January 2010 was 44.8 cm). My Spring-Summer 2011 outlook can also be found in the same post:

http://www.montreal-fireworks.com/forum/index.php?action=vthread& forum=5&topic=996&page=2

South of the border, I had predicted a fairly active tornado season in the U.S midwest and southeast - however, I never anticipated that it would be as severe and as deadly as it was in April and May. The enduring and violent nature of many of the tornado outbreaks in the U.S this past Spring was primarily attributed to persistent cool air descending into the western U.S and Great Plains from northwest Canada - this, in turn, serves to keep the jet stream farther South into the U.S than is usual. The persistence of the cool airmass itself out West was possibly due to the lingering effects of La Nina. It was largely these episodes of cool air that frequently fueled the development of strong areas of low pressure in the U.S, eventually leading to severe outbreaks of thunderstorms and tornadoes, especially at the end of April in the southeast U.S and more recently in the midwest (namely in Joplin, Missouri). To put things into perspective, the preliminary estimates from the National Weather Service for the total number of tornadoes so far this year is 1,314, and the yearly average over the last decade is about 1,274. Incredibly, a record 875 tornadoes have been reported in April 2011 alone, and the average number for the month of April over the last decade is actually closer to 160. Tragically, 512 fatalities have been reported in association with tornadoes so far this year in the U.S, a death toll figure that has not been observed since 1953. This past tornado season has been a monster.

As far as hurricane activity is concerned, the Atlantic could be facing an average to slightly above average number of total named storms, but if an El Nino develops by end-Summer into the Fall, I suspect that this would reduce activity for the latter part of the hurricane season.

La Nina continues to weaken in the equatorial Pacific, and in doing so we can expect average weather pattterns to eventually respond into the Summer as La Nina completely dissipates, though it is possible that La Nina may continue to have some influence (a lagging-effect in weather patterns adjusting accordingly) for the early part of Summer 2011 in spite of the dissipation. Much of the information that I had presented previously for my personal Spring-Summer 2011 outlook remains mostly unchanged, so I will just briefly re-state what was said beforehand in terms of potential temperature and precipitation trends.

Summer 2011 outlook

Temperature

I am still expecting a near-average temperature pattern to govern much of eastern Canada this Summer in terms of monthly daytime highs - that is, we could see a reasonable Summer, but this suggests fewer heat waves (in the technical sense), and, therefore, a reduction in days reaching 30 C or more, as compared to Summer 2010 (in short, I don't believe that it will be a blazing hot Summer, as was seen last year). It is possible to see a particularly warm August, but this depends on if an El Nino builds towards the end of the season. If an El Nino does develop, even if weak in nature, this may have positive implications for the end-Fall to Winter period, and so we could see a more forgiving Winter in that respect. We'll continue to monitor the progress of the sea-surface temperature anomalies in the equatorial Pacific in the coming months.

Precipitation

As always, precipitation forecasting is challenging, especially on a seasonal scale, and when transitions are taking place in the equatorial Pacific. That said, I believe that Summer 2011 precipitation could be average to above average, much like the Spring, although there is a better chance of Summer 2011 being closer to average. The principal reason behind this potential trend is because the average configuration of the sub-tropical jet stream during a transition from La Nina to near-neutral conditions tends to lie near the Canadian-American border across much of the country. Consequently, the jet stream allows for a storm track that traces closely along much of the southern periphery of Canada. At the same time, as mentioned previously, this may also invite an accompanied slight increase in severe weather this Summer for southern Ontario, southern Quebec and the U.S northeast, especially towards the end of June spanning towards mid August - the jet stream's influence enhances vertical wind shear (speed shear, in this case) at the upper levels of the atmosphere, permitting a better likelihood for storms to become more organized, most notably those storms that form along cold frontal waves. Enhanced precipitation may also be partly favored, again, by the already saturated soil surface, which would increase the amount of water vapor, or moisture, released to the atmosphere. Depending on the number of thunderstorms received, total precipitation may vary greatly at a local scale, simply because of the stochastic nature of thunderstorms.
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Concerning the fireworks displays of 2011, weather updates will be prepared and posted on this thread just before each of the displays, starting with a (usual) preliminary review about two days in advance. Again, I will try to keep the forecasts condensed and brief for the sake of simplicity, but a little more detail would be required if or when the atmosphere shows indications of instability, particularly in the event of thunderstorms or severe thunderstorms. As always, you are more than welcome and encouraged to post weather updates as well, but always be sure to pay particular attention to wind speed/direction, moisture (humidity), and the potential for unsettled conditions, if it exists. I sincerely hope that all of the 2011 entrants will be blessed with ideal Summer weather, especially in terms of wind (wind-related problems seem to be trending in recent years)!

Here's to a successful season!

Trav.

I just had wanted to share some footage (two parts) of the severe weather that affected the Montreal area on the late afternoon of June 8th:

http://www.youtube.com/watch?v=xMlOqlkpBuk&feature=related

http://www.youtube.com/watch?v=oM44G_GGlqI&feature=related

^^^
There is a nice anvil crawler capture at the end of the second part. Also note that this storm had a history of rotation.

Trav.

Cool, humid and damp weather has settled into much of eastern Canada since about two days, as an area of low pressure had pushed in from the West and brought with it mostly cloudy conditions, periods of heavy rains, and embedded thundershowers/thunderstorms. The computer models have been showing that this system would remain nearly stationary due to a blocking area of high pressure situated just North of Newfoundland, so this surface low is expected to provide a fair deal more rain throughout at least the next 24-36 hours, especially if we see multiple thunderstorms.

As far as the first fireworks display of 2011 is concerned, it is a possibility that the periods of rain/showers could lighten by the evening hours tomorrow (Saturday), but the current projections do not indicate a gradual clearing until roughly noon on Sunday, June 26th. Embedded thundershowers are also possible to develop both today and Saturday, partly because of the available energy present. I will continue to monitor the movement of this system in the newer model outputs. On another note, I would, additionally, like to keep an eye on both wind speed and direction - because of the position of the center of the low through Saturday, winds may be unfavorable in both direction and speed, but more so in terms of speed. Temperatures are expected to be suppressed (daytime highs in the high teens/very low 20s Celsius) through Saturday because of our position relative to the low at the time, and because of the cloud cover and periodic rainfall, so you will likely need to bring a light jacket for the evening.

In spite of the wet conditions that were experienced yesterday, the 23rd, and possibly still through the next 48-60 hours, there are signs of a nice warming trend into the start of the final week of June, with the slight possibility of a potential first heat wave by the very end of the month into the start of July. For June itself, temperatures have, so far, generally been above average (in terms of average daytime highs and overnight lows), along with near-average rainfall. So far this year, two days have exceeded 30 C.

I will post an update later today to determine Saturday’s final weather conditions. In the meantime, if you are planning to head to any existing fireworks displays for St-Jean Baptiste tonight, be sure to have an umbrella and light jacket handy, as periods of heavy rain and thunderstorms are a possibility.

Trav.

I apologize for the delay with this, as I just wanted to continue to track the speed of the system, as well as the associated wind tendencies.

After revising the newer model runs, most of what was stated in the above post still applies to the weather for today (June 25th), but there are some additional details that I would like mention. As such, here are the forecast details in terms of temperature, precipitation and wind for today.

Temperature/Humidity

Because this current system continues to move at a very slow pace, temperatures are expected to continue to exhibit below seasonal values. Daytime highs could be reaching a maximum of 21-22 Celsius (if there are at least some pockets of sunshine - if not, then closer to 18-19C), and evening values steady around 17-18 C (perhaps 19 C in the greater Montreal area). Humidity levels, however, should be moderate to high, so this will make the air temperature feel warmer than it actually is.

Precipitation

The air will remain near saturated at low to mid levels of the atmosphere because of the lingering effects of this system, so skies will stay mostly cloudy (some pockets of sun, again, are possible), along with periods of rain/showers. The models are still showing signs that the amount of available convective energy is still fairly abundant (likely because of the moderate to high humidity), particularly for the afternoon-early evening period, so the possibility for thunderstorms (largely non-severe) is still there. I also would not rule out isolated severe thunderstorm cells for the mid-afternoon to early evening period, given the history of this system over the last few days, although the chance is less today due to this system weakening. Note that the nature of the precipitation is widely scattered in association with this system, so I would accompany a 70-80% probability through the day (40% for thunderstorms/embedded thundershowers), and slightly lower chances for the evening at 60% (most thunderstorms and thundershowers should cease by the later evening period) - otherwise, mostly cloudy skies. The scattered nature of the showers also indicate that it should not rain for the entire day - rather, just on and off periods of rain/showers, with the risk for thunderstorms or embedded thundershowers. I would recommend having an umbrella and light jacket handy (or at least a hooded jacket), just in case of anything this evening.

Wind

Winds are a little tricky, but I no longer believe that wind direction will be much of a problem for the majority of spectators. The models are currently indicating that the winds are blowing from the South to South-southeast (SSE), but the speeds are quite light in nature during the evening period at roughly 4-7 km/h (possibly closer to 11 km/h by the later evening) - speeds are higher during the afternoon at 14-17 km/h. Winds may tilt slightly from the South-southwest by the later evening. As such, smoke should be gently blowing mostly to the right of the audience at La Ronde. There may be periods of smoke buildup, however, because of the moderate-high humidity and overall light winds, particularly when the display becomes more active at low to high level.

That’s the way the weather should typically behave for today. In summary, we should see mostly cloudy conditions accompanied by periods of ubiquitous rain/showers. Thunderstorms and embedded thundershowers are also possible. Winds should be very light from the South to, occasionally, the SSE. A shift to SSW tendencies is possible later in the evening as the system pushes slowly eastward. Temperatures are likely cool during the evening, so you may want to either have a light jacket or sweater equipped. The humidity is moderate to high, so it will feel a touch sticky. With some luck, the wet weather will hold off just before and during China’s display, and we will just, instead, be faced with overcast conditions. Again, expect Summer-like weather to gracefully return for most of the work week. Severe weather is possible later Tuesday, however.

Trav.

Summer-like weather is expected to resume in much of eastern Canada to bring in the month of July, as a defined ridge in the jet stream (as well as an associated surface low pressure system) that recently formed over western Canada is now on its way East. Consequently, seasonal to above seasonal temperatures are expected, with high to potentially very high humidity for this coming weekend. This warming trend was the prospective “heat wave” that I had mentioned last week, but although it is no longer a formal heat wave in nature, it is still a nice warming trend, nonetheless.

Under these conditions, Saturday’s fireworks display (by the Czech Republic) is forecasted to have typical July weather, with plenty of sunshine, high to very high humidity, and a few defined clusters of cumulus clouds, due to some atmospheric instability. I do not anticipate precipitation for the day, but thunderstorms could be moving in by the overnight hours and through the day Sunday. Winds seem to be more cooperative this week than what was seen last week in terms of speed (I will continue to monitor this in the future model runs, however), and the direction is likely South-southwesterlies (SSW), so the smoke should be moving relatively quickly to the right of the audience at La Ronde (to the left of those stationed on Notre-Dame). The breezy winds should also compensate for possible rapid smoke build up attributed to the high humidity. The warmer weather is also beginning to build in for Canada’s 144th birthday (more details for Canada Day’s forecast below).

I will post a final update later today to confirm these conditions, but I still would like to keep an eye on wind tendency towards the late afternoon-evening hours for Saturday.

Welcome to July, the warmest month of the year (my personal favorite month, as well). Enjoy the upcoming weather for the long weekend.
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Your Canada Day forecast:

As an area of high pressure slowly migrates eastward, this gloomy, unsettled weather pattern will gradually break by early tomorrow morning, and more Summer-like conditions will return, slowly building into a very nice warming trend for the long weekend. Here are the forecast details for the Canada Day festivities, including for the fireworks displays that may be taking place this evening.

Temperature/Humidity

Temperatures are on the rise, and values should reach a maximum of 25 C for Friday by the mid-late afternoon. Humidity levels are similarly on the rise and could reach borderline moderate to high standards by day’s end. With the moisture levels, temperatures should stay steady at 22-23 C for the later evening hours. Humidity levels themselves will rise further into Saturday as that area of low pressure moves in.

Precipitation

As this area of high pressure advances, the clouds should begin to increasingly break as the morning hours progress, and more so into the afternoon, but some lingering showers are a possibility for the very early morning hours, as we still be under the wrap-around influence of this current area of low pressure. The atmosphere becomes increasingly stable through the day (still a few cloud clusters lingering), so the chances for wet weather are negligible for the evening hours. As such, expect mainly clear skies for the evening.

Wind

Winds are expected to be very light, but directional tendencies are shifting through the day, as the area of low pressure moves in from the West. As such, expect winds to firstly be coming out lightly and variably between the North-northwest (NNW) to North-northeast, and then shifting to South-southeasterlies (SSE) by the late evening hours. Winds, again, are light, regardless of the direction, and they will likely be anywhere from 7-11 km/h for the morning hours to the early afternoon, and then becoming, overall, lighter at 3-6 km/h by the mid afternoon and onwards. Periods of calm conditions are also possible later in the day.

That’s the way the weather should behave for Canada Day. In summary, temperatures are likely at 25 to possibly 26 C for daytime highs and evening values that are in the low 20s C at 22-23 C. Humidity is building through the day and could reach high standards towards the evening. Unsettled weather is not expected, except possibly for very early in the day, so expect a fair amount of sunshine. Winds are generally very light to occasionally calm, especially for the afternoon. In short, a pleasant Canada Day on the way, but be sure to protect yourself accordingly from the sun (if you plan to be out for extended periods), as the UV level is very high for this afternoon.

Trav.

Most of what was mentioned in the first section of the above post still adheres to today's dominant weather conditions, but there are a couple of additional things that I would like to point out in terms of wind speed, after revising the latest model runs. Here are the details for Saturday, July 2nd.

Temperature/Humidity

Temperatures are expected to rise into the very high 20s C to as much as 31 C by the mid afternoon period. Late-evening temperatures should remain steady between 23-24 C (possibly as much as 25 C in the metropolitan area). Humidity levels are currently high and will remain so through the day today. Values could reach very high standards through the overnight hours.

Precipitation

Not too much to report here, but you will notice some scattered cumulus clouds as the day progresses due to increasing atmospheric instability. There could also be an increase in cloud cover towards the late afternoon into the evening hours because of an approaching cold front - this front may set off some convective showers and possible thunderstorms (mostly non-severe, if any) overnight into the early morning of Sunday. The chance for severe thunderstorms increases slightly for the late-morning into the afternoon on Sunday, but this is dependent on how quickly the low pressure system tracks eastward.

Wind

Wind tendencies are largely from the southwest for the day, and I suspect that they will gradually shift from the South-southwest (SSW) by the early evening period in accordance with the eastward migrating speed of this system. Ideally, the smoke should be mostly blowing slowly to the right of the audience of La Ronde (to the left of those spectators on Notre-Dame). Speeds are breezy through the day at 15-19 km/h but diminish to 8-12 km/h for the evening period. Lighter winds during the evening may cause periods of smoke build up (with the high humidity) when the display becomes more active, but, overall, the smoke should mostly be clearing quickly enough.

That's the way the weather should behave for today. To summarize, mainly sunny skies coupled with a few cumulus cloudsas the day progresses. There will likely be an increase in cloud cover towards the end of the day, but unsettled conditions are more possible for the overnight hours into Sunday. Temperatures are very warm, possibly attaining slightly above 30 C. Humidity levels are high, and the winds are expected to be firstly breezy during the day before becoming lighter by evening.

I hope that everyone had a fantastic Canada Day!

Trav.

Thank you for your updates, Trav. While I don't often post on this topic, I read carefully your forecast before each display. It is very useful!

Fred

Weather patterns are expected to continue to exhibit Summer-like conditions for the coming weekend. An area of high pressure is slowly moving in from the West and is expected to provide rather pleasant weather for both Saturday and Sunday. At the same time, a rapidly developing low pressure area is also going to be moving up the eastern seaboard, but this high pressure system will act to keep it well to the East, as it is serving as a blocking mechanism.

With the atmospheric setup in place for England’s display, this favors mainly sunny conditions with some scattered overhead cirrus clouds and a few cumulus cloud clusters. UV levels are expected to be high to very high during the day, though. Humidity levels are likely moderate, and the temperature readings should be hovering around seasonal (about 25-26 C), along with evening values into the lower 20s C (likely 22 C). With this area of high pressure, as well as the area of low pressure tracking northward in the Atlantic, winds are likely to display North-northwest (NNW) to straight northerly tendencies at 15-19 km/h. Speeds will then then diminish slightly by the evening to 11-14 km/h. Winds may, however, shift from the West-northwest (WNW) to even possibly westerly by evening, which could potentially mean that the smoke may be blowing towards the audience of La Ronde this time around. I will continue to monitor this, as the shift in wind direction ultimately depends on the track of the system in the Atlantic.

I will post a final update either later today or early Saturday to confirm these conditions, particularly for wind speed and directional tendencies for the evening hours.

And it is absolutely no problem for posting the weather forecasts, Fred, as it is always a pleasure - I am just delighted to know that they are useful.

Trav.

After revising the latest model projections, conditions are still mostly in agreement with what was stated in the above post. Here are the details for Saturday, July 9th.

Temperature/Humidity

Temperatures are expected to climb to a seasonal 25-26 C (locally 27-28 C) for daytime highs, and late evening temperatures should, again, decline to roughly 22 C (as much as 23 C in the metropolitan area). Moisture levels should be borderline low-moderate, so humidex values are negligible, although expect humidity to rise to high standards for tomorrow (Sunday).

Precipitation

As an area of high pressure is governing much of this weekend, there is, naturally, not much to report in this section. There will, however, be a few scattered cirrus clouds (those whispy high-level clouds) and some isolated cumulus clouds. Expect mainly sunny conditions for the day (with a high to very high UV level), and mainly clear skies for the evening.

Wind

This is where it becomes a little tricky. With this area of high pressure, as well as the positioning of that area of low pressure in the Atlantic, a small pressure gradient will slowly build, creating breezy conditions for today (Saturday). Winds are still expected to be firstly coming out primarily from the North-northwest (NNW) to, occasionally, straight northerlies for the morning-early afternoon hours before transitioning to more northwesterlies by mid-afternoon. Winds are quite breezy at 19-23 km/h for the morning hours before weakening slightly to 16-19 km/h for the afternoon. By the very late afternoon through to the evening hours, I am still detecting a directional shift to West-northwesterlies (WNW) to potentially, on occasion, straight westerlies, simply because of this area of high pressure moving South, along with the relative positioning of the area of low pressure to the East. Winds, then, could be frequently pushing the smoke towards the audience of La Ronde - otherwise, the smoke would be moving steadily to the left of the audience (if NW tendencies are maintained), though possibly affecting left sections of the seating area. Speeds themselves should diminish slightly to 11-15 km/h by evening. There shouldn’t be too much in the way of smoke build up because of the humidity levels. Winds will eventually change to southwesterlies by the overnight hours.

That’s the way the weather should mostly behave for the day. In summary, we should see a pleasant Saturday (morning to evening), with mainly sunny conditions, coupled with borderline low-moderate humidity. Winds are breezy for most of the day but diminish slightly by the evening. If you are planning on staying outdoors for extended periods during the day, be sure to protect yourself accordingly from the high to very high UV. Humidity levels gradually rise into Sunday, but severe weather is possible for Monday as a cold front moves through from the West.

If I notice any changes with the wind behavior in the newer model runs, I will post an additional update covering this - otherwise, what is mentioned here still holds true.

Trav.

Weather conditions are expected to gradually cool to near-seasonal values following the end of today (Tuesday), as a large area of high pressure will slowly advance from the West, bringing with it fair weather by Wednesday up to early Saturday, potentially assisting to give rise to the start of our first official heat wave by this weekend in both southern Ontario and southern Quebec as it pushes east - we’ll continue to monitor the progress of that setup over the next few days.

It is actually quite something that the atmospheric pattern in place for tomorrow is somewhat identical to what we had seen this past Saturday. However, we may be receiving the wrap-around effect of the recent low that brought us some rainfall, which may bring some early isolated showers - the chance for wet weather early in the day may diminish depending on how fast the area of high pressure advances, so I will monitor this. As such, I am expecting largely fair weather conditions to govern much of Wednesday, July 13th, and, as a result, relatively small probabilities for precipitation, mostly as the day progresses. There will likely be a some lingering clusters of cumulus clouds, however, creating, at times, partly cloudy skies, but things should increasingly clear through the day. Temperatures are going to be a touch cooler for the late-evening period into the high teens Celsius (as much as 20-21 C in the metropolitan area), and humidity levels are, again, borderline low-moderate.

Wind tendencies are still a little uncertain at this point (common with high pressure systems), especially for the late-afternoon to evening period, but with the current positioning of the area of high pressure to the West, I believe the winds should be firstly coming out from the West-northwest (WNW) for the morning hours, and then gradually shifting to northwesterlies for the afternoon to eventually North-northwesterlies (NNW) to even straight northerlies by evening. The alternative is that winds maintain NW to WNW status through the evening, because, like this past Saturday, high level winds are similarly pushing this area of high pressure a little to the South, and the area of low pressure that recently brought us wet weather, as well as some severe thunderstorms across parts of southern Quebec, is eventually settling just South of Nova Scotia. With the potential wind behavior by evening, this would suggest that the smoke from the display should be moving steadily to the left of the audience at La Ronde, but it still remains a question of how much to the left. Speeds themselves are breezy through the day between 18-21 km/h but diminish to roughly 10-13 km/h by evening.

I will continue to keep an eye on future model runs and post a final update later today, or early Wednesday, to confirm the specified conditions and note any changes, if necessary, particularly with respect to wind behavior and how quickly this upcoming area of high pressure settles in.

Trav.

I understand from the above post that we shouldn't experience precipitations tomorrow night, am I right? That is a good news since I just saw a risk of some sort of precipitations estimated at 60% on the Weather Channel. It doesn't specify what time of the day these showers/thunderstorms are expected.

Fred

Hi Fred,

Yes, that is correct. I am still holding the belief that instability should subside by dusk tomorrow. The chance for precipitation itself is for the reason I stated previously - that is, we are eventually being influenced by the "wrap-around" effect of the recent low pressure system that had delivered some rainfall and isolated severe thunderstorms in parts of southern Quebec yesterday evening (one storm being just East of Montreal, near Saint-Hyacinthe). More specifically, the reason as to why you are seeing the chance for precipitation for tomorrow is because of a developing upper level short wave trough associated with the departing low. A "short wave trough" occurs when there is a relatively small pocket of cool air settling, or advecting, from the North/northeast/northwest (in this case, the northeast) at high levels of the atmosphere over a given region, as indicated by a valley-like formation on an upper level synoptic weather chart. Coupled with daytime heating at the surface, cool air aloft commonly enhances instability, merely because the air is unstable at mid to high levels of the atmosphere.

Precipitation associated with troughs is usually isolated to scattered in nature, so I would accompany a 30-40% probability of precipitation for mostly the late-morning to afternoon hours, which shifts my initial forecast for precipitation (in the above post) a little forward, but instability should still dwindle towards dusk. I also agree with the risk for isolated thunderstorms (30% probability), given the available convective energy readings for the afternoon.

I will post a final update to confirm these conditions by this evening, or early tomorrow morning, especially for wind tendencies, and the movement of the area of low pressure to the East.

Trav.

After a Summer-like week, a brief cooling will take place in Ontario and Quebec through today (July 13th). Southern Quebec and eastern Ontario are under the influence of an upper level disturbance (a short wave trough), providing some unsettled weather prior to a large area of high pressure that will eventually move in later today. This trough is associated with the departed low that affected southern Quebec Monday evening, bringing with it periods of rain and isolated severe thunderstorms. With the atmospheric setup, here are the weather details for Wednesday, July 13th.

Temperature/Humidity

Temperatures are still expected to be about seasonal to just a little below seasonal for daytime highs tomorrow, with maximum values of 24-25 C, while late-evening readings are roughly at 19 C in the suburbs (potentially as much as 21-22 C in the metropolitan area). Humidity levels are similar to this past Saturday, with borderline low-moderate values through the day and into the evening.

Precipitation

The trough in place will increase atmospheric instability, particularly from the late-morning throughout the afternoon period. Consequently, isolated to scattered showers will develop across the region (30-40% probability) during this time frame. Isolated non-severe thunderstorms (30% probability) are also possible during the afternoon period, as the available convective energy is sufficient. Instability should begin to subside towards sunset, and there should be a few lingering clusters of cumulus clouds thereafter until skies clear completely overnight with the approaching area of high pressure to the West.

Wind

The models seem to be more in agreement with respect to wind direction and speed in relation to the positioning of the advancing area of high pressure to the West, and the low to the East. The latest runs indicate that winds should firstly be coming out from the northwest (NW) by the very early morning hours, maintaining these tendencies through to the early afternoon. As the area of high pressure pushes a little more eastward, northwesterlies should transition to North-northwesterlies (NNW) to, on occasion, straight northerlies by the mid-afternoon through to the evening and overnight. As such, winds should be pushing the smoke gently to the left of the audience at La Ronde, avoiding all seating areas there. Wind speeds are light for the early morning at 7-11 km/h, but they become breezy for most of the afternoon at 18-21 km/h, with occasional gusts of up to 32 km/h. Speeds are still expected to diminish by evening to 10-13 km/h. Smoke build up should not be too extensive, as the humidity levels are borderline low-moderate, and the winds should be at decent speeds. *It should be noted that for those viewing the fireworks on the bridge just adjacent to the firing site likely will experience smoke slowly advancing towards them, so, if possible, avoid those sections. The smoke may also, at times, hamper viewing conditions for those stationed at the Old Port (especially with the display possibly being active at many points).

That’s the way the weather should generally behave for today. In summary, isolated to scattered showers (30-40% probability) are possible for mostly the afternoon due to an upper level trough. Isolated non-severe thunderstorms are also possible (30% probability). Instability should subside by evening. Winds are breezy during the day but diminishing slightly by the evening. Temperatures are pleasant for the day (and evening), and humidity levels are borderline low-moderate. Following this brief cooling, July-like weather will likely resume by the end of the work week into the weekend.

Trav.

As stated previously, typical Summer conditions are expected to engage eastern Canada by the end of the work week, and that heat wave that I introduced about three days ago is still a possibility for both southern Ontario and southern Quebec for this weekend into Monday.

The atmospheric setup for Saturday, July 16th, and the weekend, in general, is such that this current area of high pressure will eventually move southeast towards the Atlantic, while a rather vigorous low is slowly traveling West to East across northern Canada. The positioning of these two systems will draw moisture from the Gulf of Mexico, and a developing area of low pressure churning in the western U.S will additionally facilitate this circulation process. Consequently, much of central and eastern portions of Canada and the U.S will experience very warm to hot and humid conditions for the weekend. In the case of southern Quebec, the humidity slowly builds in for Saturday and approaches near oppressive levels for Sunday before potentially severe thunderstorms move through late Sunday through Monday.

I am not expecting precipitation for Saturday (again, this is more for later Sunday and onwards), but there will be some scattered cumulus clouds later in the day, as well as some cirrus, which are, again, those wispy-looking clouds at high level. Temperatures could be as warm as 25-26 C in the metropolitan area for later Saturday evening, and high humidity levels could make it feel into the low 30s C. Winds should generally be light in nature (7-11 km/h at this point) and are likely out from the South-southwest (SSW) to possibly southwest (SW) - as a result, winds should be blowing smoke mostly to the right of the audience at La Ronde this time, although the extreme right end of the seating area has a chance to encounter smoke, if SW tendencies dominate. I’ll keep an eye on this over the next little while.

I will post a final update later today, or early Saturday, to confirm these conditions, especially in terms of wind behavior (speed and direction). Shaping up to be a nice July day, regardless.

Trav.

Virtually everything that was described in the above post still applies to today’s overall weather conditions, so, in summary, here are the details for Saturday, July 16th:

Temperature/Humidity

As compared to the last two fireworks days, temperatures are expected to climb to more July-like standards to as much as 31 C during the day and possibly 24-25 C by the late evening hours (potentially 26 C in the metropolitan area by late evening). Humidity levels are likely to be high today, so maximum humidex values by afternoon could be approaching 36 C, while during the evening, readings should be closer to 32 C, especially in the metropolitan area.

Precipitation

No precipitation is expected for the day. There will, again, be some scattered clusters of cumulus clouds, which may provide a few localized cloudy periods. Some scattered cirrus clouds will also occasionally be present. Convective rains, thunderstorms and possibly severe thunderstorms gradually become a threat into Sunday night through to most of Monday, partly due to an approaching cold front and high available convective energy.

Wind

The models seem to be largely in agreement about the overall wind speed and directional tendencies for the day. The atmospheric setup described in my previous post certainly favors southwesterly (SW) winds for the Ontario and Quebec this weekend. For Montreal, the same wind direction pattern is true, but I am expecting a West-southwesterly (WSW) shift for the afternoon hours before gradually returning to southwesterlies to potentially South-southwesterlies (SSW) by evening, and then South-southwesterlies to straight southerlies by the overnight hours. Wind speeds should predominantly be light for most of the day at 7-11 km/h, including for the evening. As such, the winds should be gently blowing the smoke to the right of the audience of La Ronde. There may be periods of smoke accumulation due to the light winds and high humidity.

That’s the way the weather should generally unfold for today. To summarize, very warm to hot conditions are likely across many areas of eastern and central Canada, along with high humidity levels, making it feel into the mid 30s C for the afternoon and lower 30s C by evening, including here in Montreal. Precipitation is not expected until later Sunday, with the risk for severe thunderstorms that night into Monday. Winds are light and coming out mostly from the SW for the day. The UV is expected to be high to very high today, so be sure to protect yourself accordingly against the sun if you plan to be outdoors for extended periods. I still would, however, like to verify the later model runs to see if SW winds would be maintained by evening, as this would, at times, affect the extreme right end of the seating area at La Ronde. If I detect this, I will post a final brief update, but if not, then whatever is stated here still holds true.

A typical July weekend on the way, with the potential of attaining heat wave standards, providing that both today and Monday surpass 30 C.

Trav.