With the 2016 competition commencing fairly soon, and with this now being the mid-point of June, I thought that it would be appropriate to post this thread.

The focus here will be (in large part) on temperature, moisture/humidity, precipitation, wind speed, and wind direction. In situations where thunderstorms become more favorable, more emphasis and subsequent updates will be placed, notably if strong to severe thunderstorms are possible on fireworks days/evenings. This is especially necessary due to the constantly evolving nature of convective precipitation coverage and intensity. Similarly, more updates will be provided if wind speeds are expected to be either too weak or too strong, or when wind direction might be unfavorable.

As always, you are also more than free to share weather updates here!

For those interested in reading my projections for the Spring and Summer of 2016 (even though astronomical Spring is soon coming to an end), the outlook, which was originally released on March 17th, 2016 - St-Patrick's Day -, can be found here:

https://www.facebook.com/notes/travis-moore/winter-2015-2016-and-a-loo k-ahead-to-spring-summer-2016/10153971353701346

In general, for S. Ontario to S. Quebec, I am anticipating a more noticeably very warm to hot late-Spring and Summer period this year (so, an "overall" above to potentially well above normal temperature distribution for the mid-May to mid-September period), including more days reaching maximum temperatures of 30.0+ C (14-16 such days for the island of Montreal and closely surrounding locations, specifically), an increase in the number of days with minimum temperatures of 20.0+ C, and possibly more (severe) thunderstorm development days than normal. Note, however, that due to the nature of thunderstorms, certain areas will obviously observe more occurrences than others within the forecast regions.

I hope for ideal weather for all fireworks days, as well as for setup!

Trav.

Trav, it is great to know that you will supply forecasts this year again!

That being said, I am sure that you will be very interested by this very particular trial:
http://www.journaldemontreal.com/2016/06/21/en-cour-pour-avoir-prevu-d e-la-pluie-il-craint-un-precedent

But, as your forecast reports are remarkably accurate, you should not have any problem!



Fred

Always a pleasure, Fred. I will submit initial forecasts typically two days prior to fireworks dates, with more finalized details the day before (and on the day, as necessary).

And, wow, I have never heard of such a predicament, as presented in that article, but it is very interesting as it is frightful! I do agree with the points made by the meteorologist, though!

Thanks for sharing!

Trav.

Should we get prepared for a rainy, cold, and windy opening night as we experienced last year?

Fred

A strengthening area of low pressure will eject East and continue to produce very warm to increasingly humid conditions for S. Ontario to S. Quebec for Canada Day, followed by pronounced cooling for the forecast period (Saturday, July 2nd). Before this cooling, however, strong to severe thunderstorms will be possible for the late-afternoon to mid-evening period for E. Ontario to extreme S./SW Quebec (more on this below).

Following the cold front later tomorrow (July 1st), an upper-level trough will migrate over the region and will likely, unfortunately, lead to well below normal temperatures for the day. Instability associated with this trough will lead to generally scattered showers (40% probability) and isolated non-severe thunderstorms (30% probability), largely in areas where solar heating is most prevalent. Since precipitation is largely governed by instability on Saturday, scattered showers should progressively subside towards sunset and beyond, leaving mostly cloudy conditions with some clear breaks. Strong cold air advection, mostly cloudy conditions (some sunny periods), possible rain showers, and gusty winds will largely act together to suppress maximum temperatures throughout the day (maximums no more than 19-20 C), and late-evening temperatures of 17-18 C in the Montreal metropolitan area are likely. As a result, a light sweater and/or light jacket will likely be necessary for most people, especially considering the breezy nature of the winds and low moisture content (moisture remains low through the day). Note, though, that this cooling is very temporary, as temperatures should begin to rise fairly sharply by Sunday, July 3rd, and near- to actual heat wave status is very possible next week, beginning July 5th.

Winds need to be monitored closely. Wind speeds are expected to be gusty throughout the day and remain largely WSW to sometimes straight westerlies. Sustained speeds and gusts are shown to be 28-31 km/h and 43-47 km/h, respectively. Speeds should weaken slightly into the evening, but “occasional” gusts are remaining just slightly below the 40 km/h threshold. As such, winds should be pushing the smoke quickly towards the La Ronde audience directly. Low moisture profiles, however, will not favor rapidly accumulating smoke, but smoke blowing frequently towards the La Ronde audience could sometimes cause the display to appear murky, depending on the concentration.

Another update to follow by the end of tomorrow, or into early-Saturday, with a focus on wind speed and direction.

*So yes, Fred - there are similarities in weather for both the opening shows of 2015 and 2016, except that this year's is chilly throughout the day, but evening conditions are virtually identical.

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Your Canada Day forecast

Temperature/Humidity

Maximum temperatures in extreme S./SW Quebec should reach 27-28 C (locally 29 C is possible, especially in areas farther East, where solar heating is more prolonged) before extensive cloud coverage arrives by the mid-afternoon period because of the advancing cold front. Humidity remains low for the early part of the day but becomes moderate by mid-afternoon, and then high by early-evening. With increasingly saturated air, a humidex of 28-29 C is favorable into the early-evening (base temperature of 21-22 C).

Precipitation

Due to the sharp cold front, rainfall is likely to occur by late-afternoon into the evening. Thunderstorms could also accompany the rains, a few of which could reach strong to severe standards. Damaging winds and small hail will be the primary threats with the strongest storms, and a few storms will be capable of intense lightning, although this will be dependent on how high moisture availability actually becomes. How widespread stronger thunderstorms become, though, is questionable due to the lack of pronounced warm air advection, but, for other reasons, at least scattered coverage is expected. As mentioned, increased high- and eventually mid- to low-level cloud coverage should begin to unfold by mid-afternoon. The convective threat should begin to diminish towards 11:00 p.m. and onward, although delays will be possible with local fireworks events if thunderstorms are in the area beforehand.

Wind

Winds remain light for the first half of the day, with southerly to SSE directional tendencies (7-11 km/h). By mid-afternoon, SSE winds begin to increase to 18-22 km/h, gradually shifting to a SW flow by the mid-evening. Note, however, that if thunderstorms are directly overhead, wind speeds will be briefly strong ahead of their gust fronts and will temporarily alter the wind direction locally.

Trav.

No significant changes to the forecast details specified above. As such, here are the most likely weather conditions to affect the Montreal area for Saturday, July 2nd.

Temperature/Humidity

With the upper-trough moving over the area, temperatures will generally struggle to reach normal values due to fairly strong cold air advection, extensive cloud coverage and isolated rain showers. Latest sounding data, however, does suggest more periods for solar heating through more clear breaks in the cloud deck, so maximum temperatures could reach 20-21 C by mid-afternoon (cooler if showers do occur). This would also lead to slightly higher evening temperatures, so 19-20 C is favorable during the early-evening, but falling to 18-19 C by display time. Humidity continues to be low, so no humidex is expected. A light sweater may be necessary for some, especially due to the chilling effect of breezy westerly/WNW winds.

Precipitation

Light rain showers should become scattered (40% probability) into the afternoon hours, notably where solar heating is maximized. Very sparsely distributed non-severe thunderstorms are possible, but weak instability should keep them very isolated. Because lift is purely governed by instability, convective rain showers should gradually subside as we move closer to sunset and onward. Skies should be partly cloudy (more and larger clear breaks) during the evening, but mostly cloudy skies should occupy most of the morning to early-afternoon, with the sun making more of an appearance towards mid- to late-afternoon.

Wind

Wind speeds continue to be gusty throughout the day, but with slightly less sustained speeds and maximum gusts of 29-33 km/h and 42-46 km/h, respectively, mostly during the late-morning to late-afternoon period. By about sunset and onward, speeds should diminish further to 17-21 km/h (occasional gusts of 29-32 km/h). Winds continue to be generally westerly (sometimes WNW) throughout the day. As such, smoke from the fireworks should be moving fairly quickly towards the La Ronde audience directly (with some slight tendency towards left-hand sections of the seating area), sometimes causing the display to appear murky. However, excessive smoke buildup is not expected due to breezy winds and low humidity.

In summary, a cool evening, with low humidity, partly cloudy skies and breezy westerly/WNW winds.

Another update to follow, if necessary, by early this afternoon (July 2nd).

Trav.

A broad area of low pressure is expected to move NE in time for Wednesday, July 6th, and amplify the circulation of warm, moist air into the day Thursday (July 7th). Along the system’s warm front, however, a risk for convective rain showers and thunderstorms into the late-evening hours and overnight period could exist. The situation will need to be monitored, but if thunderstorms do occur, latest thinking is that most will remain sub-severe due to widespread cloud coverage ahead of the front during most of the day, but isolated stronger storms will still be possible for various reasons. Strong to severe thunderstorms will be possible into Thursday.

As mentioned in my third posting in this thread, temperatures are expected to be considerably warmer than they were for the opening display. Maximum temperatures during the day should reach 29-30 C, along with building humidity as the day progresses. By the mid-afternoon period, humidity should be high, continuing through the evening, so a humidex of 32-33 C is likely (base temperature of 25-26 C in the metropolitan area) during the late-evening. During the day, a maximum humidex of 35-36 C is favorable, along with mostly cloudy skies (due to the advancing warm front), but sunny breaks will be present, mostly during the morning to early-afternoon.

Winds are also important to monitor. Latest data indicates that winds could be quite light to very light (possibly near calm, at times), and from the East to ESE. Overall speeds are expected to be 7-10 km/h throughout the day. This situation would suggest that the smoke could be (very) gently blowing towards those spectators on Notre-Dame street and closely surrounding areas. That said, the smoke also could be accumulating fairly rapidly due to the light winds and high humidity, especially during more active sections of the display, and along low- to mid-levels over time, though the easterlies should “slightly” help to move the smoke directly away from the La Ronde audience.

Another update to come later tomorrow evening (July 5th) or early July 6th, with a focus on the possible risk for thunderstorms and light easterly to ESE winds.

Trav.

Forecast details specified in the above post remain mostly consistent for tomorrow, although changes to wind speed and direction are in order. As such, here are the expected weather conditions for Saturday, July 6th, for the Montreal area.

Temperature/Humidity

Maximum temperatures are expected to reach 30-31 C by the mid-afternoon period along with an increase in humidity. With high humidity, a maximum humidex of 36-37 C is likely. By late-evening, temperatures are not expected to drop excessively (especially in the metropolitan area), owing to higher humidity levels and stronger warm air advection. Temperatures should remain as high as 27-28 C by display time, with a humidex of 34-35 C is still favorable due to borderline high to very high humidity. If rain does occur persistently, then temperatures should be closer to 23-24 C. Increased cloud coverage by mid-afternoon should prevent temperatures from becoming overly high, but gradually stronger warm air advection and continued periods for solar heating should help the maximum temperature reach at least 30 C before rain showers (if any) can interfere later on.

Precipitation

The aforementioned warm front is still expected to eject NE through the day tomorrow, becoming stationary as it reaches closer to S. Quebec by late-tomorrow afternoon into the early-evening. This boundary will continue to be the focus for convective rain shower and isolated non-severe thunderstorm development through the evening hours and potentially overnight. Some thunderstorms may attain stronger levels due to the jet stream in the area and progressively higher degrees of warm and moist air circulation late-day, which is increasing instability at the time. Convective development becomes more likely by 7:00 p.m. Convective coverage, at this point, is scattered, so I would hold precipitation probabilities at 40% (30% for “strong” thunderstorms). Have an umbrella or another form of head covering at your disposal for the evening. Otherwise, skies should be mostly cloudy for the evening.

Wind

Recent and latest model guidance are in better agreement as to more SW to WSW wind tendencies throughout most of the day, and with stronger wind speeds during the afternoon period. Into the afternoon, wind speeds of 18-22 km/h are more favorable. By the evening, however, a slight directional shift and significant reduction in wind speed are expected, notably by just prior to sunset. By early-evening, speeds of 13-16 km/h are expected, but this should further be reduced to 4-7 km/h by mid- to late-evening. In addition, winds should become more westerly to eventually WNW during by mid- to late-evening. This suggests that smoke from the fireworks should be moving very slowly towards the La Ronde audience, but with more of a tendency toward left-hand sections of the seating area. Periods of extensive smoke accumulation are possible due to lighter wind speeds and higher humidity levels by late-evening, but accumulations are mostly pronounced when the display becomes more active, and along low- to mid-levels of the display. This could, again, cause the display to appear sometimes murky for those at La Ronde. *Also note that if thunderstorms do occur, the general wind flow will become altered and be more influenced by the winds produced by the thunderstorms.

In summary, a comparatively very warm to hot day, with continued very warm temperatures into the evening hours, along with high to gradually very high humidity, mostly cloudy skies (mid- to late-day), and light WNW winds. Scattered convective rain showers and thunderstorms (a few strong) are also possible along that stationary front.

*Another update will follow by late tomorrow morning to early afternoon (July 6th) to address and changes to winds, and the existing thunderstorm risk.

Trav.

No significant changes to the forecast with respect to wind speed and the convective shower/thunderstorm risk this evening (a few thunderstorms have already developed, mostly North and West of the Island). There is, however, a slight directional change during the mid- to late-evening. Instead of WNW to westerly tendencies (which should be case during the late-afternoon to early-evening), the eastward progression of the parent low pressure system should induce more NNW winds to northerly winds around display time before becoming more NNE to eventually NE near midnight and onward. This would imply that smoke should be blowing very gently to the left of the La Ronde audience (right for those on Notre-Dame) and towards adjacent sections of the bridge (and still potentially far left sections of the La Ronde audience). However, being near the center of the low pressure system will still likely lead to light wind speeds in the area for the duration of the evening to early-overnight. Periods of extensive smoke accumulation will still be favorable due to (very) light wind speeds and borderline high to very high humidity. Wind speeds should be 5-8 km/h throughout the evening. Again, if thunderstorms do occur (overhead or nearby), the general wind flow will be affected temporarily locally. Thunderstorms should remain non-severe.

Also, I am going to boost late-evening temperatures to 28-29 C (including during display time) in the metropolitan area, assuming no persistent rainfall.

All other factors hold constant.

Trav.

A broad and weakening area of low pressure is expected to affect this weekend’s weather (July 9th and 10th) across S. Ontario to S. Quebec, bringing with it a return to unseasonably cool conditions and possibly copious rainfall. This cooler and unsettled pattern, however, should be temporary and allow for a return to a very warm to hot pattern for some time (notably the July 12th-July 22nd period), within which a significant heat wave could be born (July 13th-July 16th).

As the area of low pressure advances towards S. Quebec on Saturday (July 9th), it will gradually become occluded, and ahead of the occluded front, persistent and copious rains could take place by the time the system departs. Current and recent analyses suggest that the air will likely remain very saturated over a great vertical depth through the day Saturday. As a result, not much lift will be needed in order for precipitation to develop. Because the air is saturated, however, this will keep instability minimal, and so while thunderstorms are possible, they are not expected to be severe. Thunderstorms, themselves, have the best chance of occurring during the morning hours of Saturday, with straight rain during the afternoon to evening hours (sparse embedded non-severe thunderstorms still possible) Rainfall will be enhanced where thunderstorms have the greatest influence. Rainfall, at this point, appears widespread, so precipitation probabilities of 80-90% are in order, especially for the afternoon period. Periods of steady rain will be possible, as well. There is, however, a possibility for a dry slot to emerge during the mid-evening period, but models do not fully agree on this feature. The air continues to be saturated well into the evening, though, so rainfall is still favorable to develop. This will be monitored in future data analyses.

As far as temperatures are concerned, because the air will quickly become saturated by the early-afternoon hours, the warmest temperature of the day will actually occur during the morning hours. Once saturation occurs, the temperature should fall to 17-18 C into the early-afternoon and remain steady through to the evening. Maximum moisture/humidity levels are a little restrictive because of the lower temperature distributions, but temperatures should still be high enough to allow humidity to attain high levels. Thus, though cool, the air will likely feel moist/damp.

Due to the trajectory of the parent low pressure system, it will prevent S. Quebec from entering its warm air sector directly (it will remain well South), so predominantly breezy ESE to occasionally SE winds (13-16 km/h) should take precedence through the day. As such, fairly rapidly accumulating smoke from from the fireworks (due to saturated air) should be moving at a reasonable pace, and virtually directly away from the La Ronde audience. As a consequence, the smoke should be drifting towards those on Notre-Dame Street, mostly left-hand sections (when facing the river) of the street. Directional tendencies, however, will still need to be studied, as there is some uncertainty (varies between SE to ENE – in either case, there is a strong chance for an easterly component).

Another update to follow by either late-day tomorrow (July 8th) or early-day July 9th, with subsequent updates, as needed, by the mid-afternoon of July 9th. Low attendance is possible for Saturday evening, even if rain does not occur during the evening.

Trav.

Weather conditions described in the above posting are still largely applicable for today. Therefore, here are the most favorable conditions for Saturday, July 9th, for the Montreal area (and closely surrounding locations).

Temperature/Humidity

Temperatures are still forecasted to be unseasonably cool for the day due to persistent rainfall, extensive cloud coverage and breezy easterly to ENE winds. The air will not become fully saturated until the afternoon hours, so the maximum temperature should arrive by late-morning (18-19 C), just before dropping to and remaining steady at 16-17 C during the afternoon to evening period. With near complete saturation at these afternoon-evening temperatures, humidity will be high. As a result, the air will be moist and damp. Have a light jacket/sweater with you.

Precipitation

Rainfall will be persistent through mostly the afternoon to early-overnight timeframe (generally overcast for the late-morning) ahead of the aforementioned occluded front. Latest sounding data continues to support saturated air over an extensive vertical depth, and lift along the front will likely generate ongoing rainfall. The moist air mass should persist into the evening, with continued periods of rain (at times heavy) during the time, much like the afternoon. That said, a dry slot is still possible during the late-evening and so will still need to be monitored through today. Higher degrees of instability during the early-morning hours/pre-dawn hours of today could lead to some organized thunderstorms, as well. By the afternoon into the evening, non-severe thunderstorms will still be possible, but they would be sparse and more embedded within the widespread rainfall. Precipitation probabilities are 80-90%, at this point, over the course of the afternoon and evening (except perhaps during the late-evening, if that dry slot appears to be a more dominant feature) due to widespread coverage, and the thunderstorm risk should be 30% (40% during the morning hours due to more scattered coverage). Have an umbrella at your disposal (or another form of head covering of your choice). Copious rains are likely for this weekend.

Wind

Winds are expected to be largely breezy, and from the ENE including during the evening period (sometimes straight easterlies, but consistently ENE is more likely during the evening). Speeds are likely to be 13-17 km/h throughout the day, including the evening. As such, smoke from the fireworks should be building fairly rapidly, at times, due to saturated air, but it should also be moving reasonably quickly, and directly away from the La Ronde audience. This continues to suggest that the smoke would largely be moving towards those positioned on Notre-Dame/de Lorimier street, as well as adjacent sections of the bridge bordering those streets. With the slight NE component to the winds, it would slightly help affected viewers to avoid smoke by positioning themselves farther away from the bridge, in the direction of the Olympic Stadium.

In summary, a wet and cool evening, with high humidity and breezy easterly to ENE winds. Low-attendance is likely in major vantage points. The situation is a little reminiscent of Canadian displays in the mid-90s.

*Another update to follow by early- to mid-afternoon today (July 9th) to address evening rainfall, as well as any revisions to wind speed and/or direction.

Trav.

Thank you for these forecasts and updates, Trav, they are appreciated, as always.

Do you attend the shows this year? I am surprised to not read your reports!

Fred

Forecast details specified in my previous posting are still applicable. Periods of light rain are still favorable this evening but not quite as widespread, and there, thus, remains a fair possibility for a break in the rainfall by late-evening (including display time), or a transition to lighter showers at the time, due to being positioned more in the center of the parent low pressure system. A brief and isolated non-severe thunderstorm is also possible, but the thunderstorms should largely subside by mid-evening, leaving straight rain showers. I would just boost evening temperatures slightly to 17-18 C, with continued high humidity (due to saturated air). Weather conditions are not overly terrible (despite predominantly wet conditions today) since winds should be mostly favorable for those at La Ronde (but not so much for those on Notre-Dame street and surrounding streets).

No changes necessary for wind speed and direction.

----------------------
No problem for the forecasts, Fred! I've been somewhat limited with time recently to write my reports, but I will have them ready soon! That said, my thoughts are outlined in my mind - it's just a matter of putting them together. On a side note, it has been increasingly difficult traveling from the SW West Island this Summer due to significant construction activities on the 720 and Decarie expressway (lots of traffic diversions)!

Trav.

My apologies for the delay. Due to severe thunderstorms over the St-Lazare-West Island area later yesterday evening (July 14th), we lost our power temporarily and so was unable to post.

An area of weak high pressure is expected to move SE through the day Saturday, July 16th. As it does, conditions should generally become increasingly stable and dry, mostly by late-day. However, a shortwave trough and jet stream divergence will provide some weak lift durin the afternoon hours in the general area, generating mostly cloudy skies (sunny breaks) and isolated light rain showers (30% probability), especially where solar heating is maximzed. Maximum temperatures should be 24-25 C by mid-afternoon, coupled with moderate humidity. Mid-evening temperatures of 22-23 C (humidex of 25-26 C) are largely favorable in the metropolitan area, including during display time. The probability of light rain showers, though, should remain minimal, especially just prior to sunset and beyond. Most places will more likely be under mostly to partly sunny skies, with isolated patches of cirrus and cumulus clouds remaining into the evening.

With high pressure moving in, winds should be light through the day, and from the WSW. Speeds should be 6-9 km/h during the late-morning to early-afternoon period but diminish to as low as 4-7 km/h by late-evening, although slightly higher speeds are possible for the evening, so this will continue to be monitored closely. The winds should remain westerly during the evening. This would cause the smoke to move gently and and directly towards the La Ronde audience, or potentially extreme right-hand sections of the audience directly if the tendency becomes more WSW (which is also possible). Periods of fairly large smoke accumulations could develop due to the moderate moisture and light to very light evening winds, though the smoke would be most pronounced at low- to mid-levels during active sections of the display. However, the display could appear frequently murky for those at La Ronde, but the very light nature of the winds could often times cause the smoke to appear stagnant deeper into the display.

*Another update to follow by either later today (July 15th) or early-day July 16th, with subsequent updates, as necessary, by mid-afternoon July 16th, mostly to address wind velocity.

Trav.

Forecast details specified in the above posting continue to hold constant. Therefore, here are most likely conditions to affect the Montreal area for Saturday (today), July 16th.

Temperature/Humidity

As high pressure continues to drift SE through the day, gradually more stable conditions will ensue, but mostly into very late-day. Before this system advances, however, the area will still be under the influence of borderline moderate to high humidity. Maximum mid-afternoon temperatures of 24-25 C are still expected (a little restricted due to more cloud coverage). By late-evening, including display time, temperatures of 22-23 C are still projected to occur, and with moderate humidity, and so a humidex of 27-28 C is favorable.

Precipitation

Sparsely distributed light rain showers (30% probability) and overall partly cloudy skies (sunny breaks) will still be possible during the afternoon hours due to a shortwave trough ejecting East, as well as because of the continued influence of the jet stream in the area. This will provide lift for some isolated showers, but these should largely subside near and after sunset. Skies should be partly cloudy into the evening hours (high-level cirrus and low cumulus clouds).

Wind

Wind speeds continue to be very light into the evening hours due to the influence of high pressure. By the evening hours, this general area will be near the center of this system, where winds tend to be weakest. Directional tendencies remain largely WSW to variable (due to the light nature of the winds). When winds are very light to calm, they are more subject to variable directions due to local influences becoming more dominant. That said, projections continue to support very light WSW winds (4-7 km/h) into the evening hours. This suggests that, due to continued borderline moderate-high humidity, smoke could accumulate fairly quickly and become often near-stagnant (mostly deeper into the display), especially along low- to mid-levels, and typically when the display becomes more active. The smoke should also be moving very, very gently towards the La Ronde audience directly.

In summary, a warm and fairly humid evening, with partly cloudy skies and very light WSW to westerly winds.

*Another update to follow to address wind velocity by early- to mid-afternoon today (July 16th).

Trav.