After revising the newest model output from yesterday (July 30th), here are the most probable weather conditions for today, July 31st, for the Montreal area.

Temperature/Humidity

Temperatures across S. Ontario and S. Quebec should, due to a fairly strong South to SSW flow, reach maximums of 31-32 C to locally 33 C by mid-afternoon, most applicable for areas of E. Ontario and S. Quebec. Humidity levels, again, are expected to be borderline high to very high, so humidex readings during the afternoon could attain as high as 38-39 C. Temperatures should drop to 26-27 C by the late-evening in the metropolitan area of Montreal. Humidity remains constant through the evening for S. Quebec, so expect humidex readings to range from 31-32 C.

Precipitation

As the area of low pressure described briefly in the above posting travels East to our North, the associated cold front will enhance atmospheric instability (mostly at low-level) ahead of it for later tomorrow. However, as the newest simulations illustrate, for most of S. Ontario, this is expected to be more of an afternoon event, while for E. Ontario and S. Quebec, convective initiation could begin to take place more by the late-evening period towards the early-overnight. This slight change in the timing of the frontal wave (and its parent low to the North) for S. Quebec suggests to me that the severe thunderstorm potential should be suppressed, but instability is still strong enough to support the development of a few isolated convective showers and non-severe thunderstorms (30% probability) by the late-evening and onwards - otherwise, partly cloudy skies. In either case, you will likely notice a gradual increase in cloudiness by mid to late-afternoon, with developing clusters of towering cumulus. The greatest likelihood for severe weather is through central and S. Ontario this afternoon.

Wind

Winds should continue to come out from the South through most of the day but could occasionally shift to more South-Southwesterlies by mid-afternoon into the early-evening period. Wind speeds have changed somewhat from earlier runs, however, but speeds are expected to remain breeziest from the late-morning to early afternoon period, with a sustained range of 15-19 km/h for the late-morning to 19-23 km/h (occasional gusts of 30-33 km/h) for the early-afternoon. By mid-afternoon, winds decrease to 7-11 km/h and possibly even further to 5-8 km/h by late-evening. As such, the smoke should be very slowly moving largely to the right of the audience at La Ronde (left for those on Notre-Dame). Note, though, that periods of smoke accumulation could occur (especially during the more active segments) due to the combination of light/very light winds and borderline high to very humidity.

In summary, very warm temperatures and borderline high to very high humidity for the late-evening hours for S. Quebec. Skies should become generally partly cloudy by the mid to late-afternoon, with clusters of large towering cumulus developing in response to increased low-level atmospheric instability. Isolated convective showers and mostly non-severe thunderstorms (30% probability) are possible by the late-evening period as the cold front advances from the West - otherwise, partly cloudy skies. Winds are breezy during the late-morning to early-afternoon, but quickly diminish by mid-afternoon through to the evening.

If necessary, I will provide additional updates concerning wind patterns (mostly speed) and convective potential through the early part of today.

Trav.

Model simulations from today continue to indicate enhanced convective activity for S. Quebec and E. Ontario this evening. In addition, however, I would also not rule out the possibility of isolated late-afternoon to early-evening convective showers and thunderstorms, as previously outlined in my initial posting (last post of page 1) due to a pre-frontal short wave trough. In this case, the isolated nature of the instability warrants a 30% probability of precipitation for that time frame. As also expected, large towering cumulus clouds (even a few distant cumulonimbii) have already developed in response to increased low-level atmospheric instability.

Latest prognostics also show a slight increase in convective coverage by later this evening, so I would now place a 40% probability of precipitation because of an enhancement to more scattered instability. Again, most thunderstorms, if any, should remain non-severe later this evening, but even in the absence of weaker vertical/speed shear, instability continues to be strong enough to support a few isolated severe cells. The risk for thunderstorms for the overnight hours through the day tomorrow is attributed to the passing cold front.

As for the winds, directional tendencies are mostly constant, but there are signs of a slight tilt to the SSE later this afternoon into the evening (there have been signs of this already). I will also change late-evening speeds to 12-16 km/h (as stated similarly in the initial posting). As a result, smoke should still be blowing to the right of the audience at La Ronde, just at a faster rate. Winds should also begin to diminish somewhat towards the late-afternoon and late-evening temperatures could remain as high as 27-28 C for the metropolitan area.

Note that if thunderstorms do occur, dominant wind patterns (speed and direction) could be temporarily altered, and temperatures will decrease in response to evaporative cooling.

Trav.

As today's cold front gradually pushes through from the NW, high pressure will gradually settle for tomorrow (August 3rd). As a result, we should expect mostly pleasant conditions for the Panzera display, including late-evening temperatures of 25-26 C (mostly in the metropolitan area) and moderate humidity, making it feel like 28-29 C. Daytime highs should attain 28 C. Note, however, that convective showers are still possible early Friday morning as the cold front continues to move through.

The winds are still something to watch, as they may be blowing towards the audience at La Ronde, or possibly left-hand sections. Current model projections are favoring West to WNW winds for the evening period, with speeds of 11-14 km/h. Sustained speeds should be closer to 19-23 km/h early in the afternoon (occasional gusts of 30-33 km/h). Speeds die down by the late-afternoon to 15-19 km/h, and eventually further to 11-14 km/h by the evening period. Winds also should first come out from the NW for the morning and afternoon hours, but there are signs of them becoming more Westerly for the evening. Some models favor a NW flow, which would be a little more ideal.

I will provide an update later today once I have revised the newer output data.

Edit: *Also, just to state that severe thunderstorms are possible on Sunday, August 5th.

Trav.

Model simulations from yesterday continue to largely support the overall weather conditions specified in the above posting, and there is now more of an agreement as to the general wind tendencies. As such, here are the details for tomorrow's (August 3rd) weather for the Montreal area:

Temperature/Humidity

In spite of a cold front pushing through tonight into tomorrow morning, daytime highs for tomorrow afternoon will likely attain values as high as 29 C (a touch higher than previously stated), and into the late-evening, temperatures should remain warm at 25-26 C (mostly for the metropolitan area). Humidity levels, however, will decline to more borderline moderate to high standards for tomorrow afternoon towards the evening, generating humidex values of 35-36 C by mid-afternoon, and then 29-30 C by late-evening.

Precipitation

The latest progs continue to indicate that the cold front (not a great deal of energy associated with this front) should have more of an influence tonight through to this morning, generating convective showers and a few isolated non-severe thunderstorms. Weak instability will ensue into the early-afternoon behind the cold front, producing partly cloudy skies (also supported by 50-60% mid-level relative humidities), and a few possible lingering showers. Partly cloudy skies should continue to dominate through to the mid-afternoon into the evening, with a progressive clearing. Chance of precipitation tonight through this morning is 40%, while decreasing to 30% for the early-afternoon.

Wind

Winds continue to exhibit tendencies similar to what had been described previously. The breeziest of winds, again, should occur by the late-morning to early afternoon period, but newer runs indicate an extension towards the mid-afternoon. As such, winds should be coming out from the WSW to West at 19-23 km/h (occasional gusts of 30-33 km/h) from the late-morning to mid-afternoon. By the late-afternoon to early-evening, speeds die down to 12-15 km/h and tilt more from the WNW. Into the late-evening, speeds may diminish further to as low as 8-12 km/h and coming out from the NW. As such, smoke could be blowing gently towards the audience at La Ronde, though more so for left-hand sections, as well as the adjacent parts of the bridge. Smoke accumulation is also possible when the display becomes more active (and from low-level effects).

In summary, warm temperatures for the late-evening period with borderline moderate to high humidity, and skies should remain partly cloudy, but convective activity will be enhanced for the early part of the day due to the passing cold front. Winds are light from the NW.

If necessary, I will provide a final update concerning wind patterns by the early afternoon.

Trav.

Just to provide an update, wind patterns seem mostly constant for late this evening, but speeds are a touch lighter at 7-10 km/h. I am still thinking that mostly the left-hand sections of the La Ronde audience could be affected by smoke, as winds begin to change to more Northwesterlies. If not, then expect the smoke to gently be displaced to the left of the audience and heading to adjacent sections of the bridge due to potential NNW tendencies. Periods of smoke accumulation are possible.

Again, severe weather is possible on August 5th, mostly for later in the day. I've provided a synopsis yesterday on Facebook covering the overall atmospheric setup and will continue to follow up through tomorrow and Sunday.

I suppose this closes the weather forecasts for 2012! Yet another challenging year, especially in terms of wind patterns!

Trav.

Correct me if I'm wrong, but I think for the first time, the wind didn't blow the smoke towards Notre Dame street for all shows. You guys must have had a great view this year!

Hi Enkil,

Only once did the smoke head in our direction this year, and that was during the Italian display.

The principal reason as to why the La Ronde audience runs the greater likelihood of seeing smoke is simply because surface/near-surface winds commonly blow out from between the NW to SW, especially the SW during the late-Spring and Summer. Because the grandstands are facing mostly West, there is a better chance to receive smoke there (or at least portions of the grandstands). Straight Easterly (or ESE to ENE) winds, on the other hand, are rare, so those on Notre-Dame and de Lorimier are frequently unaffected by smoke (unless the windspeeds are very light to calm). Smoke accumulations were particularly problematic, however, during the Chinese display in 2008 for those on Notre-Dame, as well as again for the Canadian show in 2009. Later in the display for Sweden 2010, we encountered some trouble (though the display could be seen adequately), and we did not have much problems in 2011.

Other than that, it's nice to see the skies clearing at this time, and right on schedule.

Trav.

Unfortunately, I am unable to attend the final display of the 2012-2013 Fire on Ice event held tomorrow (January 5th, 2013), but I understand that some of you will be able to do so. As such, I have prepared a forecast for tomorrow evening.

Temperature/Humidity

Temperatures will be dropping fast into the overnight hours due to decreased cloudiness and progressively light winds. Values during the mid-evening hours will likely be at -11 to -12 C, with slight windchills of -14 to -16 C. Humidity is very low.

Precipitation

No precipitation expected, though a surface low and associated upper-level disturbance (trough) will bring some accumulations of snow (5-8 cm) into Sunday to early-Monday, before temperatures rapidly drop Sunday night into Monday morning into the low -20s C (-22 to -23 C). A few isolated cloud clusters should be present for Saturday evening.

Wind

Winds are expected to be light by the evening hours, with shifting directional tendencies from between the SW to SSW. Speeds will vary between 5-9 km/h. I am not certain which direction viewers will be facing relative to the fireworks, but if memory serves me well, the general vantage point is looking more and less to the SW. If such is the case, smoke from the fireworks could be gently blowing towards some spectators downwind of the firing site to the ENE to NNE.

Dress warmly, and enjoy the display by Royal Pyrotechnie.

Trav.

For those interested, I have posted my personal weather predictions for this Spring and Summer, as well as a review of this past Winter (2012-2013). The report was initially written/posted on March 17th, 2013 and can be found here:

http://www.facebook.com/notes/travis-moore/winter-2012-2013-and-a-look -ahead-to-spring-summer-2013/10151528552166346

Trav.