Me too. Current MeteoMedia radar projections make me afraid that we may have thunderstorms conditions from 9:00 to 11:30pm or so
,with the bulk of rain in northern areas. Let’s hope for positive changes.

The lift continues to be quite robust for this late-afternoon towards midnight, and the last few hours spent with more prominent solar heating, together with the high humidity, has sent instability to moderate status as of now. Wind speeds should be sufficient to clear the smoke, regardless, but the smoke accumulation itself could be quite thick once the air saturates, and in light of high humidity. The smoke itself would also turn towards the audience if thunderstorms are in close proximity to the firing site, which is quite possible (otherwise, clear to the right of the audience. The lightning would also be quite intense in most cases with these multi-cell thunderstorm families, but the primary hazards remain with locally damaging straight-line winds and torrential rainfall that would cause locally significant water accumulation.

Trav.

Weather conditions for the final display day (August 10th) will be governed by an area of low pressure advancing NE. This system’s cold front, along with a series of shortwave troughs, will be the principal modes of lift for ubiquitously-distributed convective rainfall, as well as isolated non-severe thunderstorms for the late-morning to late-evening (collectively 75% probability during this range of time, with 30% probability for thunderstorms). There is, however, some suggestion that the periods of light to moderate rainfall could narrowly end by just at the beginning of display time if this system speeds up in its NE progression. Thus, this will need to be monitored. Before rain-cooled air occurs, a maximum temperature of 22-23 C is favorable, under very high humidity at saturation (humidex of 29-30 C). The air remains almost saturated throughout the afternoon to evening, with a display temperature of 19-20 C, though with a slight decline in humidity late-evening (humidex of 24-25 C).

Winds would be light from the SSW (8-11 km/h) until the mid-afternoon, but there is some suggestion that they could undergo a transition to light NNE (also 8-11 km/h) by early-evening and going forward. This would allow the (thick) smoke accumulations to drift clear to the left of the La Ronde audience, moving towards adjacent sections of the bridge for the first time this year. Wind direction needs to be carefully monitored, as well.

Another update to follow this late-evening (August 9th) to early-predawn (August 10th).

Trav.

Forecast details presented in the above posting remain mostly valid. As such, presented here are the overall weather conditions expected for August 10th for the greater Montreal area.

Temperature/Humidity

Prior to saturation under rain-cooled air, a maximum temperature of 25-26 C is more likely due to more sunlight getting through early in the day (see section below). Under very high humidity at and near saturation, a humidex of 33-34 C is favored. The air remains almost saturated throughout the afternoon to evening, with a display temperature of 18-19 C with a slight decline in humidity late-evening, governing a humidex of 23-24 C.

Precipitation

An area of low pressure will advance NE today. As previously mentioned in the above post, the cold front associated with this system, together with a series of attendant shortwave troughs, will be the principal modes of lift for ubiquitously-distributed convective rainfall during mostly the afternoon period. However, the latest thinking is that periods of sunshine will get through the cumulus cloud deck this morning into the early-afternoon in response to broken skies. As a result of this, together with very high to very high humidity, atmospheric instability would reach higher magnitudes by late-morning and, thus, support a more significant thunderstorm risk, including strong to severe thunderstorms for the afternoon to early-evening period. As such, a Severe Thunderstorm Watch could very well appear by late this morning, followed by possible Severe Thunderstorm Warnings for the afternoon. Collectively, the probability for rainfall would be 80% for the afternoon to early-evening, along with a 60% probability for thunderstorms in light of aggressive lift in the area during this time frame. The primary hazards with the more organized thunderstorm families would be locally damaging straight-line winds, intense lightning and torrential rainfall leading to significant local water accumulation. As such, there exists again some potential for technical issues during this closing display, though hopefully the outcome would be the same as it was with the Finnish display.

Nevertheless, there remain indications that the greatest lift would eject East/SE just narrowly before display time to more likely allow for drier conditions at that point. This will continue to be monitored in the newest data analyses. Under saturated air, skies would be cloudy under a low-cloud layer.

Wind

Winds would be light from the SW (8-11 km/h) until the mid-afternoon. However, differing from the above post for the late-afternoon to evening, there is further concern that the winds could become quite light (3-6 km/h) behind the convective rainfall and/or thunderstorms, and from the WSW during the evening under saturated air. As such, thick accumulations of smoke could be drifting rather gently towards right-hand and partially central portions of the La Ronde audience, from all altitudes. This could potentially obscure large portions of the display deeper into it, especially along low- to mid-altitude, and if/when smoke-rich products are used. As such, much like convective rainfall/thunderstorms, wind speed and direction need to continue to be carefully monitored.

Another update to follow throughout this afternoon (August 10th).

Trav.

As a final update, following up on the previous two posts, the convective rainfall should, indeed, still come to a close before display time (August 10th), though some isolated convective rainfall is still possible in the area late-evening (30%) in response to lingering instability driven partly by the brief late-afternoon sunshine and high humidity. Winds should also be in the form of approximately WNW to West (3-6 km/h), allowing the (thick) smoke to drift quite slowly towards left-hand to central sections of the La Ronde audience - just enough to move the smoke but modestly. However, when speeds are quite light, wind direction can change spontaneously. Thus, periods of extensive smoke accumulation are favorable depending on how frequently energetic the display realistically is.

Fortunately, the greater Montreal area did not receive the thunderstorms as forcefully as the West Island did (and westward/NW/SW of there). Skies should be partly cloudy (clusters of cumulus) with clear breaks for this late-evening.

Trav.