Since it is now the glorious month of June, I thought that it would be appropriate to post this thread.

As always, I will provide forecasts just before or on each fireworks display date, with preliminaries given about two days prior to each show. Forecasts will include information based on temperature, humidity, cloud coverage, wind speed/direction, and the risk for precipitation, if necessary. If or when precipitation development becomes favorable, especially in the case of deep convection (i.e. thunderstorms), more updates will be provided. You are also more than welcome and encouraged to share updates, so please feel free to do so!

I continue to be active on Facebook in posting analyses when severe/extreme weather becomes possible. My profile is located here:

https://www.facebook.com/travis.moore.5074?ref=tn_tnmn

For those interested, my personal Spring-Summer 2014 outlook can be found using the following link, along with a review of this past late-Fall and Winter (this outlook was originally posted on March 16th, 2014):

https://www.facebook.com/notes/travis-moore/winter-2013-2014-and-a-loo k-ahead-to-spring-summer-2014/10152272641796346

To be brief, like 2013, I am anticipating a generally humid and stormy late-Spring to Summer period for 2014 across Ontario and Quebec, with an increase in thunderstorm/severe thunderstorm days (we have already seen numerous thunderstorm days so far this year in Eastern Ontario to Southern Quebec, with the first occurrence on April 13th). I do not believe that this will be a “spectacularly” hot late-Spring and Summer, so we should generally observe fewer days reaching 30 C or more, relative to 2010, 2011, and 2012, and about similar to 2013. Thus, a temperature distribution somewhat similar to 2013's. Rainfall should be above normal, especially where thunderstorms/convective rains are most dominant. Finally, as I suspected since January, El Nino (potentially at moderate strength) has continued to show stronger indications of emerging later this Summer into the early-Fall. This would imply an improved likelihood of seeing a warmer late-Fall and Winter 2014-2015, as well as fewer Atlantic storms this Summer and Fall, should an El Nino successfully occur (more updates on that as the Summer progresses).

I am hoping for the 30th edition of Montreal fireworks to be free of unsettled/unstable weather!

Trav.

Trav, I am looking forward to read your detailed forecast during the season. At this stage, it seems that we may have very good weather conditions next Saturday. That would be a welcome difference with last year rainy opening night!

Fred

Indeed, Fred, weather conditions are expected to be very inviting over the next several days and are quite the contrast from those that set the stage for 2013's opening. Past and recent short- and long-term model projections continue to favor a typical enduring Summer-like pattern emerging in time for this weekend (June 27th-28th, 2014), and stretching as far as July 2nd, with possible severe weather developing on both July 1st (Canada Day) and July 2nd. A strong Bermuda High will eventually migrate over the Atlantic, and with the aid of a series of low pressure systems far to the SW and West, very warm/hot and moist air will likely circulate from the Gulf of Mexico into much of central and E. North America within this warming period. Technical heat wave status is also possible for many areas. Note that the UV index will also be high during most of this period, so be sure to adequately protect exposed skin if heading out for prolonged periods during the day.

With this atmospheric configuration, for our first display of the 30th edition of the Montreal Fireworks Competition on June 28th, we can expect very warm and moist air to be in place. Maximum temperatures are currently estimated to be as high as 29-30 C across much of extreme S./SW Quebec, along with high humidity that will make it feel closer to 35-37C. Late-evening temperatures should be closer to 23-24 C (25-26 C in the metropolitan area, and feeling like 32-33C). Precipitation chances should be minimal near and beyond sunset for this weekend, but a few extremely sparse convective/air mass showers in the region may occur due to some mild instability. Winds are generally expected to be light throughout the day, with speeds of 9-13 km/h. However, something to still monitor is the generally lighter projected wind speeds in time for the evening, which are currently shown to be 6-8 km/h. Because of the high humidity, this could lead to periods of smoke build up when the display becomes more active, especially at low- to mid-levels. Some disagreement as to overall wind direction, but it is generally shown to be SW, and so the smoke should be moving gently to the right of the audience at La Ronde (left for those on De Lorimier/Notre-Dame) but could also sometimes affect spectators on the far right of the grandstands.

Another update will be provided by tomorrow, or early-Saturday for wind speeds and direction.
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Paul, I will also soon provide a finalized forecast for your display on Sunday (the 29th), although there does not appear to be much in terms of changes to the original forecast. Winds are just expected to be light at about 5-8 km/h during the evening (similar to Saturday evening in Montreal) and continuing to transition to SSW status by that time.

Trav.

Conditions specified in the above post remain generally constant, and there is now more of a consensus with wind patterns for tomorrow evening. As such, here are the weather conditions for Saturday, June 28th for the Montreal area.

Temperature/Humidity

Maximum temperatures are still forecasted to be at about 29-30 C by the mid-afternoon hours, with late-evening temperatures of generally 22-23 C (25-26 C in the metropolitan area). Newest projections generally favor the highest humidity levels arriving into June 29th and onwards, but humidity for today should be more moderate, with a slight boost to borderline moderate-high levels into the evening hours, making it feel like 30-31 C in the metropolitan area (33-34 C during the afternoon).

Precipitation

The risk for precipitation will be minimal this weekend due to the ongoing influence of the upper-level ridge in place. That said, there could be some very localized brief afternoon air mass showers associated with some weak instability, but the air will generally maintain stability. Skies will remain with a mix of sun and high-level cirrus clouds, with isolated clusters of cumulus clouds developing during the afternoon hours. Sky conditions should stay mostly clear this evening, with some high-level clouds lingering.

Wind

Winds continue to be light throughout the day at 9-13 km/h, and generally from the SW. Winds are expected to weaken to very light standards (6-8 km/h) by the evening, along with directional tendencies more from the SSW to eventually South by late-evening. As such, winds should be generally blowing the smoke gently clear to the right of the audience at La Ronde (left for those on Notre-Dame/De Lorimier). However, periods of smoke build up are favorable at low- to mid-levels whenever the display becomes more active because of the combination of very light winds and somewhat high humidity.

In summary, a typical Summer evening is forecasted, with temperatures in the mid-20s C (generally in the metropolitan area), and humidex values into the very low 30s C. Skies should be mostly clear (some remaining high-level clouds), and winds should be very light, and generally from the SSW to South by the late-evening hours.

*Other than that, still something to watch, but we are carefully monitoring the situation on July 1st across S. Ontario to S. Quebec (as highlighted briefly in the above posting), as a severe weather outbreak is possible ahead of a passing cold front later in the day.
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Paul, weather conditions continue to look good for your display late Sunday evening (June 29th). Temperatures remain very warm/hot during the afternoon, with highs of 29-30 C, along with high humidity, generating a humidex of 36-38 C. Weak instability will likely lead to scattered cumulus cloud clusters, along with possible sparse convective showers/air mass thunderstorms during the afternoon. Late-evening temperatures should be closer to 22-23 C with continued high humidity (humidex of 29-30 C). Winds continue to be very light from the SSW by late-evening at 6-8 km/h. Skies will remain mostly clear for the evening hours.

Trav.

Weather conditions for Saturday, July 5th are characterized by a gradually advancing broad area of surface high pressure migrating from the West and passing closely to the South relative to S. Quebec. This system, with the aid of the upper-level longwave trough in the jet stream, will assist in steering the later Tropical Storm Arthur farther East/NE towards the Maritimes as it travels North. The combination of these systems will likely produce mostly clear skies, a few isolated fair weather cumulus clouds, and warm temperature distributions into the mid-20s C (24-25 C), along with late-evening temperatures of 21-22 C across extreme S. Quebec. Humidity levels should generally be low to borderline low-moderate, and precipitation development will likely be kept at a minimum.

All that said, wind speed and direction need to be carefully monitored. Because of the potential increasing pressure gradient forming between the area of high pressure and Tropical Storm Arthur, wind speeds may become gusty into Saturday through to Sunday (July 6th). Present and recent simulations suggest sustained wind speeds and top gusts of 24-31 km/h and 44-48 km/h, respectively, during the afternoon hours, which may then continue into the evening time frame throughout extreme S. Quebec. General directional tendencies are Westerly during the day but then transition to more WSW by the late-afternoon and remaining in that manner thereafter. This would imply that smoke should be blowing very quickly towards the audience at La Ronde, though largely towards right-hand/central sections of the grandstands. In any case, some of the models are comparatively less robust in terms of the interaction occurring between both the high pressure system and Tropical Storm Arthur, which would signify somewhat less significant winds, so we will continue to monitor the situation, and so an update will be provided, either later today, or early July 5th.

Trav.

Weather conditions described in the above posting remain constant across extreme S. Quebec, and there is now more agreement as to overall wind velocity (see wind section below). As such, here are the weather conditions for the Montreal area for Saturday, July 5th:

Temperature/Humidity

Temperatures are expected to reach a maximum of 25 C to locally 26 C, with mostly low humidity levels. By the late-evening hours, values should be closer to 21 C (including the metropolitan area), along with continued low humidity, making humidex readings negligible. Gusty winds could also produce a slight chill in the air.

Precipitation

No precipitation development is expected, courtesy of the aforementioned area of high pressure migrating from the West. Skies should remain mostly clear, with a few isolated clusters of fair weather cumulus/high-level cirrus developing during the afternoon hours.

Wind

As per my posting above, wind speeds and direction continue to remain a concern. Models generally agree as to the strengthening interaction between the advancing area of high pressure and Tropical Storm Arthur. Consequently, wind speeds will very likely become quite gusty during the day. Sustained wind speeds and top gusts during the afternoon are expected to be 31-34 km/h and 48-52 km/h, respectively. By the evening, sustained wind speeds are shown to diminish slightly to 23-27 km/h, but with continued occasional top gusts as high as 44-48 km/h. This situation may cause delays (potentially significant should gusts persistently reach or exceed 40 km/h). Furthermore, wind direction is favored to be Westerly (except NW to WNW during the morning to early-afternoon) to occasional periods of WSW. As such, winds (and smoke) are expected to be blowing towards the audience at La Ronde directly. Winds become even gustier into Sunday, July 6th, from the SW.

In summary, a warm evening is forecasted, with temperatures in the very low 20s C, low humidity, largely clear skies, but with gusty conditions.

***Should any (significant) changes in wind speed and/or direction become apparent, I will post an update by early this afternoon (July 5th).

Trav.

Thank you, Trav, for this important update. It seems that velocity and wind direction may be a major issue tonight. I cross my fingers that Pirotecnica Morsani will be allowed to present its show as scheduled. We stay tuned!

No problem, Fred.

There is no change in the forecast information stated above concerning wind speed and direction and so still remains effective. Hopefully, during show time, we will have suitable enough wind speeds to fire the show safely, but conditions generally continue to be gusty into this evening and into tomorrow (July 6th).

Trav.

How likely are the ""occasional top gusts" > 30 km/h? Should it be nothing more than one gust somewhere in the area, during the evening, or may it be more frequent and spread throughout the area?

Hi Fred,

Gusts above 30 km/h this evening across the island (and throughout extreme S. Quebec) are likely and may be frequent. Gusts around 44-48 km/h are also favorable, and winds are generally sustained between 24-27 km/h. As always, it is difficult to say precisely where and when we will observe the highest gusts, but gusty Westerly (sometimes WSW) winds continue to be favored across the region throughout this evening.

Trav.

Thanks. Definitely not a good time to wear white clothes in the grandstands tonight! Whether we are lucky, the show will be fired at 10pm, as scheduled. And we may experience as much smoke and dust than during the Macedo's Pirotecnnia show in 2010!

Fred

Some local weak convection has also recently developed near the Montreal area and is generally driven by solar heating. This could produce some brief passing isolated showers this afternoon. Convection should diminish near dusk and onwards.

Trav.

A vigorous, broad area of low pressure advancing from the West is expected to influence S. Ontario to S. Quebec this weekend (July 11th-13th), and into the early part of the work week next week. This will promote a return to more July-like weather this weekend but will also enhance the risk for severe thunderstorms into Monday (July 14th), and possibly Tuesday (July 15th), just before a sharp cooling into Wednesday (July 16th) in time for Canada’s display. The anticipated cooling is associated with a large and unusually steep upper-longwave trough and accompanying surface high that will likely eventually eject quickly to the SE from the Arctic. For the Canadian display, sweaters may be required. By contrast, the cooler weather may be followed by a possible heat wave emerging by around July 20th, as suggested by some long-range models, but that will have to be monitored over the coming week.

As the system approaches, humidity levels are expected to gradually increase through the day Saturday (July 12th), along with a shift to SW to SSW and Southerly winds as the day progresses. Consequently, maximum temperatures should return to the very high 20s C (locally 30 C). The associated warm front will gradually increase cloud coverage (mid- to high-level clouds) later in the day Saturday, but the day itself should be mostly sunny. Rainfall associated with the warm front should occur until after midnight. Latest sounding data suggests maximum temperatures of 29-30 C for the island of Montreal, and by the evening hours, temperatures could remain as high as 25-26 C, especially in the metropolitan area. Humidity levels should also increase to high standards by the evening hours, making it feel like 29-30 C. Humidity should be moderate earlier in the day. There is still some disagreement as to when the shift to SSW to Southerly winds will occur, but there is a consensus for the evening hours. Speeds should also be fairly light at 9-12 km/h. As such, at this point, winds should be blowing the smoke clear to the right of the audience at La Ronde (left for those viewing on Notre-Dame). The UV is also expected to be high to very high, so be sure to protect exposed skin if heading out for prolonged periods.

Another update will follow by either the end of tomorrow (July 11th) or early-day Saturday (July 12th).

Trav.

Overall weather conditions specified in the above post are still generally constant across extreme S. Quebec, including the Montreal area. There are some minor modifications to the forecast, though, that needed to be made, which are provided below. As such, here are the dominant conditions for the Montreal area for Saturday, July 12th.

Temperature/Humidity

Temperatures are expected to reach as much as 29 C to locally 30 C by the mid-afternoon hours, along with moderate humidity, making it feel slightly warmer at 32-33 C. By the late-evening, temperatures should drop to about 25-26 C in the metropolitan area, but humidity levels are expected to rise to high standards for the evening, which could make it feel closer to 31-32 C. Again, because of the high/very high UV, be sure to adequately protect exposed skin if planning to remain out for prolonged periods during the day.

Precipitation

Precipitation is not generally expected. However, due to some mild instability projected in extreme S. Quebec, some very isolated convective showers may develop during the mid-afternoon in response to solar heating. Other than that, an increase in mid-level cloud coverage (and some isolated low-level cumulus clusters) should take place by the afternoon and onwards into the evening, largely due to the approaching warm front. Skies should remain mostly sunny. In terms of the aforementioned severe weather potential, I will keep the greatest risk for Sunday afternoon (July 13th), although thunderstorms should remain relatively sparse in coverage because of projected extensive cloud coverage restricting more widespread large instability.

Wind

There is now better agreement that winds should be largely out from the SSW during the evening hours (more SW for the afternoon). Wind speeds will likely become lighter in time for the evening, with speeds of 9-12 km/h and occasional slight gusts of 17-20 km/h. Wind speeds are generally breezier during the afternoon at 13-17 km/h, with occasional gusts of 23-26 km/h. As such, smoke from the fireworks should be blowing at a reasonable pace mostly clear to the right of the audience at La Ronde (left for those on Notre-Dame).

In summary, a very warm evening for the Spanish display, with temperatures in the mid-20s C, high humidity, partly cloudy skies, and light winds from the SSW.

Trav.

A secondary area of low pressure and upper-level longwave trough are expected to continue influencing much of the province of Quebec into the day on Wednesday (July 16th). The low’s associated cold front will likely bring periods of rain and embedded thunderstorms to S. Quebec today (July 15th) and into the pre-dawn hours of the 16th. As the upper trough advances, afternoon isolated showers will still be possible into the 16th, although instability should weaken across the region near dusk and onwards. Temperatures, as mentioned previously, are forecasted to be cooler for the day Wednesday, with maximum values of 23-24 C, but by late-evening, values are projected to drop to 19-20 C in the metropolitan area of Montreal (17-18 C outside the city, especially after midnight). Humidity should be borderline low-moderate, so the humidex is negligible.

Winds need to be closely monitored in the coming model runs, more so with respect to wind speed on the 16th. Because of a developing sharp temperature gradient, winds are expected to become gusty throughout the day, although there is agreement as to some weakening by the evening hours. Afternoon sustained wind speeds are shown to be 23-26 km/h across much of extreme S./SW Quebec, with gusts of 37-41 km/h. By the evening, speeds are predicted to subside somewhat to 16-19 km/h, but with continued gusts as high as 33-36 km/h. Winds should maintain SW tendencies throughout the day, and so the smoke from the fireworks should be blowing quickly towards right-hand sections of the La Ronde audience during the Canadian display. Also note that continued breezy winds following dusk will likely provide that extra chill in the air, so, depending on your tolerance level, a light sweater may be needed.

Another update to follow, either later today (July 15th), or early-Wednesday (July 16th).

Trav.

Synoptic and local weather specified in the above post continue to apply, although some revisions to wind speed and direction were made. As such, here are the dominant conditions for conditions for the Montreal area for July 16th.

Temperature/Humidity

Temperatures are expected to be somewhat unseasonably cool for the day, along with low humidity. Daytime highs should reach 23-24 C, and by late-evening, temperatures should drop to 19-20 C in the metropolitan area. As such, considering the breezy winds, light sweaters may be necessary. Humidex values will be negligible. The UV is also expected to be high to very high.

Precipitation

Because of the previously mentioned upper-level trough, mid- to late-afternoon brief isolated showers will be possible across the region, but conditions should typically be dry. Precipitation development should largely end towards dusk and onwards. Otherwise, expect a mix of sun and low- and high-level cloudy periods during the afternoon and giving way to mostly clear skies during the evening (a few isolated clusters of low-level cumulus clouds).

Wind

As per the above posting, winds are projected to be gusty throughout the day, and from the SW. Top wind speeds and gusts are forecasted to be at 23-27 km/h and 37-41 km/h, respectively, during the afternoon hours. By evening, speeds are still expected to diminish to 14-18 km/h, along with “occasional” gusts of 25-28 km/h. However, there is now agreement that winds could transition from the afternoon Southwesterlies to more WSW tendencies in time for the evening. This would suggest that smoke from the fireworks should be blowing quickly and more directly towards the audience at La Ronde, though with more concentration towards central and right-hand sections of the grandstands. This may cause the display to sometimes appear murky (notably towards its right-hand sections), but large amounts of smoke accumulation are not generally expected due to the combination of somewhat breezy winds and low humidity.

To summarize, a cooler evening, with temperatures in the very high teens to low 20s C, low humidity, and mostly clear skies. Winds should remain breezy into the evening and will likely create a chill in the air.

*If it becomes necessary, I will post an update concerning wind speed and direction by early this afternoon (July 16th).

Trav.

The current area of high pressure (and accompanying deep upper-level longwave trough) that has been producing unseasonably cool weather over the last 48 hours is expected to advance farther East into today (July 18th). As it does, its circulation, in collaboration with a series of low pressures systems migrating from the West and SW, will favorably work to produce a returning flow of warm, moist air into S. Ontario to S. Quebec by this weekend, potentially generating a technical heat wave (defined as at least three consecutive days with maximum temperatures of strictly 32 C or more (30 C for Quebec)), typically from July 20th to 23rd. Humidity is also expected to gradually become high into Sunday (July 20th), and then possibly very high by July 21st. There may also be a window of opportunity for severe thunderstorms late-day July 23rd (perhaps the 24th, depending on cold front timing), just prior to a sharp cooling taking place thereafter.

Saturday (July 19th) will likely be under the influence of this atmospheric pattern. As such, we can expect a mix of sun with variable cloudiness across extreme S. Quebec. Humidity levels should increase to moderate standards for the day, along with maximum temperatures reaching 28-29 C (including for the island of Montreal), but feeling like 32-33 C. For the late-evening hours, temperatures should remain around 24-25 C in the greater Montreal area, with continued moderate humidity generating a fairly mild humidex of 28-29 C. Skies should remain with periods of variable cloudiness mixed with clear breaks. No precipitation is expected for the day. With the configuration of surface pressure systems, winds will likely be light through the day at 8-11 km/h and from the SSE (except SSW during the morning) and into the evening, although there are some signatures of possible SE winds by the evening in some of latest model guidance. In either case, however, smoke from the fireworks should be slowly moving to the right of the audience of La Ronde (left for those on Notre-Dame), although should SE winds dominate, smoke may affect far left sections of Notre-Dame street. Some periods of smoke accumulation at low- to mid-levels (mostly towards right-hand sections of the display for those at La Ronde) may also occur due to the light winds and moderate humidity.

Another update will be provided, either by later today (July 18th) or by early-July 19th.

Trav.

Weather conditions specified in the above post continue to hold mostly constant. As such, here are the dominant conditions for the Montreal area for Saturday, July 19th.

Temperature/Humidity

Maximum temperatures are projected to reach as high as 27-28 C, along with moderate humidity, making it feel like 31-32 C. By late-evening, values should decrease to about 24-25 C in the metropolitan area, but feeling like 28-29 C with the moderate humidity in place. Once again, the UV is expected to be high to very high during the day, so be sure to protect exposed skin if planning to be out for prolonged periods of time.

Precipitation

No precipitation is expected. There will generally be a mix of sun and periods of variable cloudiness (low-, mid- and high-level cloudiness) during the afternoon, with similar cloudy periods into the evening hours. Skies should be mostly cloudy (some clear breaks) by the late-afternoon into the evening.

Wind

Winds continue to be light from the SSE for the afternoon hours (SSW during the morning hours) at 9-12 km/h. SSE winds gradually transition to SE tendencies by mid-afternoon with identical speeds. By the evening, winds become slightly lighter, at 7-10 km/h, and continuing from the SE. The implication of these evening wind patterns is that the smoke from the fireworks should gently blow towards those spectators stationed on the far left of Notre-Dame street (the closer to the bridge on that street, the better). For those at La Ronde, the smoke should be "slowly" moving to the right and away. Moderate humidity coupled with lighter wind speeds also suggest periods of smoke build up, especially along low-level, and when the display becomes more active.

In summary, a more Summer-like evening (as compared to what was experienced during the Canadian display), with temperatures in the mid-20s C, moderate humidity, and light SE winds.

*If necessary, I will post an update concerning wind speed and direction by early this afternoon (July 19th).

Trav.

Latest model guidance suggests a continuation of SSE winds into this evening (July 19th), along with speeds of 8-11 km/h. As such, the smoke from the fireworks should be moving mostly adequately to the right of audience at La Ronde (left for those on Notre-Dame), but those on the very far left of Notre-Dame street may be sometimes affected by smoke. Given the moderate humidity and light winds, though, some periods of smoke accumulation at low-levels of the display (mostly towards right-hand sections, relative to those at La Ronde) will continue to be possible. All other weather information specified above still applies.

Trav.

A vigorous area of low pressure is expected to continue advancing towards S. Ontario to S. Quebec. As mentioned three posts above, this system, with the aid of a Bermuda High currently circulating in the North Atlantic, may result in a near-technical heat wave for many areas within these regions. As it advances, the low pressure system will further boost temperatures and humidity over the next 42 hours, where maximum temperatures could attain 31-32 C during these days, especially on July 22nd, along with humidex values reaching or surpassing 40 C locally due to the high to very high humidity.

At the same time, however, the (strong) cold front associated with the same low pressure system and upper-trough could result in scattered thunderstorms during the late-morning to afternoon of July 23rd, especially across S. Quebec. As mentioned briefly three posts above, some of these thunderstorms may reach severe standards, with damaging winds being the main threat with the strongest storms. The greatest risk for severe weather, though, will lie East/SE of Montreal, since the cold front is coinciding more with the late-afternoon/early-evening hours in those locations, where solar heating is expected to be more at a maximum. Latest model guidance suggests thunderstorms gradually evolving into a large squall line by the mid-afternoon hours, with some embedded thunderstorm segments capable of damaging winds and small hail. Recent and latest thinking are that the cold front should influence most of extreme S./SW Quebec during the late-morning to mid-afternoon hours, with improving conditions beyond 4:00 p.m. EDT for the Montreal area (and surrounding locations), leaving mostly cloudy skies (some clear breaks) in time for the evening.

Due to a strong pressure gradient associated with the low, winds are expected to be very gusty throughout much of the day, with the strongest gusts (from the SSW in the morning to eventually SW in the afternoon) during the afternoon hours. Gusts during this time could be reaching 52-56 km/h (sustained at 29-32 km/h). By the evening hours, winds should diminish significantly but will become more NW, with speeds of 13-17 km/h (occasional gusts of 21-24 km/h). As such, the winds should be blowing the smoke fairly quickly to extreme left-hand sections of the La Ronde audience, as well as towards those spectators on adjacent sections of the bridge just behind the park, near the castle structure. The humidity should also sharply drop to more moderate standards by the evening, and temperatures should cool to values of 21-22 C (feeling like 24-25 C) in the Montreal metropolitan area. The cold front will put an end to the very warm/hot and very humid weather, unfortunately (or fortunately, depending on your point of view) – the difference will mostly be felt during the pre-dawn hours of July 24th.

Another update will be provided by either late-day July 22nd, or early-day July 23rd.

Trav.

Conditions specified in the above post (from July 21st) continue to remain effective, although there have been some modifications to wind speed and direction for the evening. As such, here are the dominant weather conditions for the Montreal area for Wednesday, July 23rd.

Temperature/Humidity

Temperatures and humidity levels are expected to reach their maximum late in the morning, just before the aforementioned sharp cold front passes through during the early- to mid-afternoon hours. Maximum temperatures are projected to reach 25-26 C during the late-morning, but with the very high humidity, it should feel more like 32-33 C. Temperatures remain steady into the afternoon, but humidity drops to low levels and continues in that manner into the evening. Temperatures fall to 22-23 C by the late-evening in the metropolitan area. The humidex is negligible. Values drop to as low as 14-15 C locally overnight, mostly outside the city (even as cool as 12-13 C on both Thursday and Friday early-morning). Overall, temperatures and humidity drop sharply behind this front, and no “significant” warming is forecasted until possibly the first week of August.

Precipitation

Thunderstorms (some strong to severe) and/or convective rainfall ahead of the passing cold front are still expected by late this morning (towards 9:30 a.m.) through to the mid-afternoon. Conditions should largely improve beyond 3:00-3:30 p.m. Note that damaging winds and small hail will be the primary threats with the strongest storms, but the greatest widespread risk for severe weather should remain well East and SE of Montreal due to frontal timing in those locations. Skies remain partly cloudy (low-level cloudiness) with some clear breaks.

Wind

Winds continue to be gusty from the SW during the late-morning hours (becoming WSW to West near noon into the early-afternoon), with sustained speeds and maximum gusts of 22-26 km/h and 47-51 km/h, respectively. By the mid-afternoon, directional tendencies shift to more Northwesterlies, and by the early-evening, they are shown to be more from the NNW, and speeds should be somewhat breezy at 14-18 km/h (occasional gusts of 23-26 km/h). As such, smoke from the fireworks should be blowing quickly clear to the left of the La Ronde audience, but, consequently, to those viewers on the bridge immediately adjacent/perpendicular to the fireworks site. The display may sometimes also appear murky to those viewing from the Old Port, but due to the somewhat breezy winds and low humidity, large amounts of smoke buildup are generally not expected.

To summarize, a warm night, with temperatures in the low 20s C, partly cloudy skies, low humidity, and somewhat breezy NNW winds.

*If necessary, I will provide an update by early this afternoon (July 23rd) concerning wind speed and direction for this evening.

Trav.

An area of low pressure, and its associated warm front, will likely advance from the U.S. Great Plains/Midwest and affect weather conditions across S. Ontario to extreme S./SW Quebec by Saturday (July 26th). This system will progressively restore humidity levels to high standards in time for the overnight period of Saturday through to Sunday (July 27th).

As the warm front migrates farther NE towards extreme S./SW Quebec, cloud coverage should increase (some breaks of sun during the morning to early-afternoon) as the day progresses Saturday. However, it is not yet entirely clear as to when rainfall associated with the front (some uncertainty with frontal timing) will begin across the region. That said, latest model guidance favors the greatest likelihood for precipitation just after midnight, along with a larger increase in surface moisture/humidity at that time. Maximum temperatures should reach about 26-27 C for the island during the mid-afternoon, along with mild humidex values of 30-31 C, due to the moderate humidity. Temperatures should fall to 22-23 in the metropolitan area by the late-evening but feeling like 25-26 C with the continued moderate humidity.

For generally the same reasons, like precipitation, wind speed and direction also remain uncertain for the evening hours, although there are currently indications of breezy WSW tendencies (18-21 km/h, with occasional gusts of 23-27 km/h). This would suggest that the smoke should be largely moving towards the audience at La Ronde directly (and fairly quickly), but some models also display a more SW direction, which would indicate that the smoke should be blowing more so towards right-hand sections of the grandstands. Wind speeds, however, are expected to be fairly gusty during the late-morning to afternoon hours, with speeds of 24-28 km/h, and frequent gusts of 34-38 km/h.

Another update will be provided, either later tomorrow (July 25th), or by early-July 26th.

Trav.

Weather information provided in the above post continues to mostly remain effective, but I have made some modifications to both wind velocity and precipitation, since models are now in more agreement for these parameters. As such, here are the weather conditions for the Montreal area for Saturday, July 26th.

Temperature/Humidity

Maximum temperatures should be 25-26 C, owing to excessive cloud coverage and gusty winds developing during the afternoon hours. By late-evening, temperatures drop to 22-23 C in the metropolitan area. Humidity levels should remain moderate throughout the day but will rise to high standards near and beyond midnight. The humidex during the day is projected to be 30-31 C and 25-26 C by late-evening. Note that should light showers occur, temperatures during the late evening should gradually fall to 20 C (with similar humidex values).

Precipitation

The aforementioned warm/occluded front continues to be the focus for convective initiation and cloud coverage for S. Ontario to extreme S./SW Quebec through the day. Skies should remain cloudy into the afternoon hours across extreme S. Quebec, with some breaks of sun during the morning to early-afternoon. Models indicate a greater amount of lift occurring ahead of the front for extreme SW Quebec by the late-evening hours, with greater chances for scattered showers (40% P.O.P) beyond 8:30 p.m. (higher probabilities by 11:00 p.m. and thereafter). Sufficient lift associated with the front and weak instability could also generate isolated non-severe thunderstorms during the evening. Otherwise, expect overcast skies. I would advise having an umbrella, or some form of head covering, handy, just in case. There will be a slight risk for severe thunderstorms tomorrow (July 27th).

Wind

Winds are expected to remain breezy throughout the day, and from the SW (occasionally WSW during the late-afternoon). Speeds are shown to be sustained at 24-28 km/h (frequent gusts of 33-38 km/h) for the late-morning to afternoon hours. By evening, wind directions withhold SW tendencies, and speeds diminish to 16-19 km/h (with occasional gusts of 28-32 km/h). As a result, smoke from the fireworks should be quickly moving towards right-hand sections of the La Ronde audience. If a thunderstorm does occur, however, note that dominant wind direction will likely become disrupted locally.

In summary, a warm evening, with temperatures in the low 20s C, moderate humidity, breezy SW winds, overcast skies, and the increased risk for scattered showers. Isolated non-severe thunderstorms are also possible.

*Should it become necessary, an additional update will be provided for precipitation and/or wind velocity by early this afternoon (July 26th).

Trav.

I am going to keep the greatest risk for convective showers/rains and (non-severe) thunderstorms until just after midnight, towards 1:30 a.m. and onwards (due to a shortwave trough, not the previously mentioned front - the front, itself, should have more of an influence through the day tomorrow). However, brief scattered showers and isolated non-severe thunderstorms still remain possible late this evening in E. Ontario to extreme S. Quebec.

As for the winds, I will reduce the speeds for this evening to 11-14 km/h (occasional gusts of 20-23 km/h), and directional tendencies should actually become somewhat more SSW (with intervals of Southwesterlies) late this evening. As such, the smoke should be moving generally (and fairly quickly) to the right of the audience at La Ronde (left for those on Notre-Dame) though sometimes still heading to extreme right-hand sections of the viewing area. The display could also sometimes appear murky on its right-hand section at and near low-levels (relative to those at La Ronde).

All other information still applies.

Trav.

A low pressure system advancing from the U.S. SE, along with the continued influence of the upper-level trough to the West, is expected to have an influence on the weather patterns across S. Quebec this weekend. However, temperatures and humidity levels should return to more Summer-like standards.

Short- and long-term models are not quite in agreement as to how far North the area of low pressure will advance, but it should be close enough to yield mostly cloudy skies (especially by late-afternoon), including low-, mid-, and high-level cloudiness (more sunny breaks earlier in the day). Moderate instability ahead of the low’s warm front may also support the risk for convective showers and non-severe thunderstorms later in the afternoon to the evening hours, so this needs to be monitored in future model runs. Humidity levels are expected to be borderline high to very high by late-afternoon and evening, and maximum temperatures should be 26-27 C by mid-afternoon across the island. By late-evening, temperatures should drop only slightly and remain as warm as 25-26 C (feeling like 32-33 C) in the metropolitan area. Winds are projected to be light throughout the day at 11-14 km/h but dropping to 8-11 km/h by the evening. Winds should be generally from the SSW (SW possible) through the day (evening included), and so the smoke should push gently clear to the right of audience at La Ronde (left for those on Notre-Dame). However, note that periods of large amounts of smoke accumulations may occur, especially at low-levels and right-hand sections of the display (relative to those at La Ronde) due to the combination of high humidity and light winds.

*Another update will be provided, either later today (August 1st), or early tomorrow (August 2nd). Additional updates may also be necessary if precipitation becomes more favorable.

Trav.

Weather conditions presented in the above post remain mostly effective. I have made some minor adjustments to temperatures and humidity, as well as wind speed. Models are also in more agreement as to precipitation development and timing. As such, here are the general patterns expected for the Montreal area for Saturday, August 2nd.

Temperature/Humidity

Maximum temperatures are projected to be 26-27 C (locally 28 C) by the mid-afternoon hours, along with generally high humidity making it feel like 32-33 C. By late-evening, temperatures are shown to drop to 25-26 C in the metropolitan area, but humidity levels are expected stay at high standards, which should generate a humidex of 30-31 C. Note that if rain does occur, then temperatures during the evening should fall closer to 22-23 C (humidex of 27-28 C).

Precipitation

Convective showers and isolated non-severe thunderstorms continue to remain favorable for the mid-afternoon to evening hours for E. Ontario to extreme S. Quebec, as mentioned in the above post. Convection is dynamically driven more so by the persistent effect of the broad upper-level trough to the West, and ubiquitous moderate instability induced by increased surface moisture/humidity and solar heating during the day is expected to coincide with lift associated with the trough. As such, convective rains and thunderstorms will pose the greatest threat during the late-morning through to the early-evening hours. A few more organized, but relatively brief bands of thunderstorms may also develop during the afternoon. Beyond dusk, convective coverage should progressively diminish and become sparser (30% P.O.P), with the risk of isolated convective showers and non-severe thunderstorms for the late-evening (precipitation should, however, generally come to an end beyond midnight and then resume Sunday late-morning to afternoon for the same reasons). Skies should be a mix of sun and cloud (low-, mid- and high-level cloudy periods) during the day with some clear breaks into the evening. Like the Australian display, I would advise having an umbrella (or some form of head covering) handy, mostly for the early-evening while waiting for the fireworks.

Wind

Winds are still shown to be light throughout the day at 8-11 km/h from the SSW (periods of SW during the mid-afternoon). By evening, speeds reduce to slightly lighter speeds at 7-10 km/h and remain from the SSW to South. As such, smoke from the fireworks should be blowing very slowly clear to the right of the La Ronde audience (left for those on Notre-Dame). However, again, periods of large amounts of smoke accumulation are favorable (notably at low-level, and to the right sections of the display, relative to spectators at La Ronde) due to the presence of both light winds and high humidity.

In summary, a typical Summer’s evening, with temperatures in the mid-20s C, high humidity, (very) light winds, partly cloudy skies and the risk for isolated showers and thunderstorms (mostly applicable to the early-evening).

*Once again, if it becomes necessary, I will post an update by early this afternoon (August 2nd) concerning wind tendencies and instability.

Trav.

So, it is likely that we won't experience precipitation during the display tonight, making the 2014 edition a fully "dry year". I also hope to have a "dry" award ceremony, in opposition to last year when we had lightning and rainfall.

Fred

Hi Fred,

Yes, precipitation will most likely not occur in time for the display and beyond, but I would like to emphasize that there remains the risk for very isolated showers and non-severe thunderstorms late this evening in the region before more completely subsiding after midnight. Again, though, precipitation continues to be most favorable between now and early this evening (latest thinking is up to 8:30 to 9:00 p.m. EDT). It is quite the coincidence that this year's closing faces near-similar weather conditions to last year's!

I am also going to change wind direction slightly to SSE (as opposed to SSW) for this afternoon into the evening, with constant speeds. This will continue to blow the smoke slowly towards the right of the audience at La Ronde (left for those on Notre-Dame). All other information holds constant.

And so concludes the weather reports for 2014! I do continue to be active with weather analyses on Facebook whenever severe to extreme weather threatens this region, so please feel free to check my profile from time to time!

Trav.

Consistent with my last two postings, I am going to continue keeping the risk for convective showers and non-severe thunderstorms active beyond the early-evening this evening (August 2nd), as newest model guidance suggests fairly sufficient synoptic lift for extreme S. Quebec during this time frame. Thus, it is possible to see convective development throughout this evening.

Please also be aware that a few isolated thunderstorms have become severe and are currently threatening parts of extreme S. Quebec, notably South of Montreal and East of the island. Due to the lack of strong speed wind shear, however, thunderstorms are not very fast-moving and are maturing and weakening rather quickly. The main threats with the strongest thunderstorms will be torrential rains, small hail and locally intense lightning.

Trav.