I thought that it would be appropriate to now post this, being now within 10 days of commencing the first edition of Montreal Fireworks in practically three years. That said, it was interesting to still be able to post weather analyses over the last two years in an attempt to better understand the extent to which tentatively assigned fireworks days/evenings would have been impacted by weather conditions, whether positively or negatively.

To that end, weather reports will be provided in this thread for each of the nine (9) fireworks days scheduled for 2022. For each display, a discussion of temperature, humidity, rainfall development, as well as wind speed and direction, will be provided. A preliminary report would first be posted approximately 48 hours in advance of a given fireworks day, followed by a finalized report about 24 hours prior to each display time. Additional updates following finalized reports (i.e. on the fireworks days themselves) would be supplied in situations where rainfall and/or thunderstorms are possible, as well as for unfavorable wind speed and direction.

As always, everyone is also more than welcome to share any weather information!

Hopefully, all displays, especially during actual display time, would face ideal conditions.

Trav.

From now, I am going to visit this forum more frequently. I am glad to know that we may rely on your detailed, specific, and accurate weather forecast once again this year!

I suspect the wind speed may be a particular issue this Saturday for the drones. I don't know the specifics, but I imagine these light devices - and the choreography made with them - are particularly sensitive to wind speed.

Fred

The first display of the 36th edition of the Montreal Fireworks Competition will favorably coincide with borderline very warm to hot conditions in what would be part of a near-heat wave event (June 24th-June 26th). Indeed, for the greater Montreal area, a maximum temperature of 29 C to potentially even 30 C will be possible for June 25th. In light of the high humidity, this would further induce a maximum humidex of 35 C by mid-afternoon. Into the late-evening, the temperature value would only decrease slightly, remaining at 26-27 C by display time (humidex of 32 C).

Precipitation development would be restricted as a result of this region being governed by an area of high pressure, though some fair-weather cumulus and high-altitude cirrus patches are favorable. For the evening, the sky should be largely clear with isolated cirrus clusters in the distance.

In the wake of a strengthening area of low pressure ejecting East (which would amplify warm air advection on June 26th), winds should gradually adopt light SE tendencies by late-afternoon and would carry with them speeds of 6-8 km/h. This would allow fairly rapidly building smoke to drift slowly to the right and slightly away of the La Ronde audience. Higher altitude smoke motion should behave in a similar manner. Periods of extensive smoke accumulation, however, would be possible during more energetic pieces of the display and/or if there are moments where smoke-rich products are used.

Another update to follow late this evening (June 24th) or into predawn June 25th.

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Fred – No problem for the weather updates!

Would drones be a part of this opening display? If so, the latest thinking is that the wind speeds should be light enough for good flying conditions.

Trav

The drones are before the display, not part of it - that's why I didn't really cover them in the interview as they're nothing to do with the actual display itself.

Forecast details specified in the previous update continue to be applicable for this first opening display day. As such, presented here are the dominant weather conditions for Saturday, June 25th for the greater Montreal area.

Temperature/Humidity

Very warm to hot conditions continue to be favorable for Eastern Ontario to Southern Quebec for June 25th. For the greater Montreal area, specifically, a maximum temperature of 29 C to 30 C is likely (mid-afternoon). As a result of the borderline high to very high humidity, the highest achievable humidex should be 36 C to 37 C. For the late-evening period, including display time, a temperature of 26-27 C is likely, and with continued high humidity, the humidex value should be 33-34 C.

Precipitation

Rainfall development in this general area is largely limited, as mentioned previously. However, some of the recent surface data does indicate some localized enhanced lift, especially farther North/NE of the island. This would support a narrow window of opportunity for a briefly-sustained and slow-moving isolated non-severe thunderstorm and/or convective rainfall during the mid-afternoon to late-afternoon, when the available instability is maximized. For this reason, a 30% probably of precipitation is included here. Still, mostly clear conditions are favored, especially after sunset. During the evening, a few residual cumulus and distant isolated clusters of cirrus are favorable.

Wind

Wind speeds continue to be rather light to occasionally calm for most of this day, with the except of the mid- to late-afternoon, when speeds are somewhat breezier. Earlier in the day, wind fields are largely in the form of light Westerlies, but by late-afternoon, as a strengthening area of low pressure advances NE, winds should transition to light ESE, at 3-6 km/h, including into the evening. This would allow rapidly building smoke accumulation to travel (very) gently away from the on-site audience, slowly towards the audience on Notre-Dame Street. This would further apply for higher-altitude smoke. Periods of extensive smoke accumulation are favorable, depending on how frequently active this display realistically is. At some points, the smoke can potentially appear near-stationary along low- to mid-level, though the Easterly component in the wind fields would best help the viewing from La Ronde, and for those positioned on adjacent sections of the bridge nearest to La Ronde.

If necessary, another update concerning principally wind speed/direction will be provided by the mid-afternoon of today (June 25th).
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Paul – Thanks for that clarification! Indeed, after reading about your interview previously, I was under the impression that the drones would be used at some point prior to the actual display, and that turns out to be the case!

Trav.

Wind speeds continue to be light during this evening (June 25th). Directional tendencies should still undergo a transition to ESE to SE by early this evening, but speeds should also be slightly stronger (6-9 km/h) to allow the smoke to displace a little faster (clear to the right of and away from the La Ronde audience), which would be helpful during times of larger smoke accumulation. For those on Notre-Dame Street, viewing from closer to the bridge would be most suitable to avoid smoke interception.

Trav.

There was an unexpected twist with the wind during the pre-opening display tonight!

For the audience at La Ronde, the speed and direction of the wind were perfect, blowing the smoke gently towards our right, and keeping the view very clear throughout the show. Then, in perfect synchronization with the end of the display, the wind turned to Westerlies, so we were treated with a smell of sulfur that many fireworks aficionados like!

That was a perfect ending!

Fred

Hi Fred,

Yes, that is quite something! Fortunately, the vast majority of the show carried with it a clear view due to the SE to SSE wind fields, but it is interesting how that alteration occurred so neatly with the end! When winds are so light, they become more subject to localized features (such as terrain), which can suddenly cause them to change direction before their regular flow can be restored.

Trav.

Weather conditions for the second opening display (July 2nd) should largely be ideal. Following what would be a very warm and highly humid July 1st/Canada Day, conditions would quickly favor a much less unstable environment as July 2nd progresses. A maximum temperature of 26.5 C to 27 C is likely for the greater Montreal area by mid-afternoon. As humidity drops to moderate standards, the maximum humidex would be 29 C. By late-evening, the temperature would decrease to 21 C, but with a negligible humidex as a result of mostly low humidity at the time.

Rainfall development would be limited beyond early-predawn as increasing stability unfolds, allowing skies to mostly clear by mid-morning and leaving behind some fair weather cumulus. Later in the day, a weakening cold front will advance South/SE and would provide some lift suitable for an increase in some lower-altitude cloud cover (with clear breaks) overspreading the region at the time.

Winds would largely be in the form of breezy to gusty SW to WSW over a large vertical depth, with (near-) surface speeds of 24-28 km/h (gusts of 35-39 km/h, especially during the morning to early-afternoon). By evening, the SW base speeds would decrease to 17-21 km/h (occasional gusts of 29-32 km/h). As such, the smoke would be moving quite rapidly towards far right-hand sections of the La Ronde audience, though higher-altitude smoke would also sometimes be moving towards right-hand and partially central sections (possibly with some occasional pyrotechnic debris). Significant accumulations of smoke are not expected, especially in light of the borderline low-moderate humidity by late-evening. The display, however, could appear frequently hazy when viewing its right-hand sections. The breezy winds would also induce a slight chill at times for some, especially as the humidity is low.

Another update to follow by tomorrow late tomorrow evening to early-predawn (July 1st-July 2nd).

Trav.

Details mentioned in the above posting continue to largely hold for July 2nd. As such, presented here is the overall weather conditions expected for Saturday, July 2nd for the greater Montreal area:

Temperature/Humidity

Temperatures continue to showcase values that are very warm for the day, despite a gradual introduction of cooler, drier air deeper into the day. A maximum temperature of 27 C is favorable by mid-afternoon, and with continued moderate humidity, the highest achievable humidex would be 31 C. By late-evening, the temperature would decrease to 21 C, with a negligible humidex in light of borderline low-moderate moisture levels (low by display time).

Precipitation

While rainfall would be restricted as a result of an increasingly stable environment beyond the predawn of July 2nd, a secondary but weakening cold front would encourage a layer of low-level cloud during the evening (i.e. post-sunset), with some large clear breaks in between.

Wind

Wind speeds would resolutely follow a WSW to occasionally SW pattern throughout the day over a great vertical depth. Wind speeds would be rather gusty later in the morning through to the mid-afternoon, in particular, but these base speeds would weaken slightly by late-afternoon (though still breezy). Speeds during the late-morning to mid-afternoon would be on the order of 23-27 km/h (occasional gusts of 39-43 km/h) but decreasing to 13-17 km/h (occasional gusts of 22-24 km/h) by near sunset. No significant accumulations of smoke are expected, and the smoke itself would be drifting rather quickly towards mostly right-hand sections (occasionally central partially) of the La Ronde audience. High-altitude smoke would more favorably advance even more quickly over right-hand to central sections of the on-site audience. At some points, some pyrotechnic debris could reach these sections. A slight chill in the air could also be felt by some with the breezy SW to WSW wind flow and lower humidity featured by late-evening.

Another update, if necessary, for wind speed/direction will be provided by the mid-afternoon of today (July 2nd).

Trav.

Reviewing some of the newest data, there have been some indications of somewhat stronger lift (and in light of recent evidence of more vertical definition among some of the current cumulus) ahead of the aforementioned weakening cold front around sunset. This would invite a narrow window of opportunity for sparsely-distributed convective rainfall - typically between 7:30 p.m. and 9:15 p.m. (July 2nd). The probability of precipitation in this situation would be 30%, but if rainfall does occur, it would be brief, as the convective clouds that carry them are fast-moving. The air would cool locally, (to 19-20 C) however, as a result of rain-cooled air, while moistening would send humidity levels to temporarily near-moderate standards. Cloud cover should gradually decrease thereafter with increasing atmospheric stability, though a layer of fair-weather cumulus cloud with large clear breaks between them would be present.

Also, wind speeds would continue behaving in a WSW to SW pattern, though more SW for the late-afternoon to evening. This would allow the smoke to focus more at right-hand sections of the La Ronde audience, though higher altitude smoke would still move more directly towards right-hand and partially central sections, as mentioned above. The pattern would still allow for a fast evacuation of smoke (notably at the highest altitudes), though causing the display to sometimes appear hazy/murky when mostly watching its right-hand portion.

All other details presented above hold constant.

Trav.

For July 9th, an area of high pressure will take hold of much of Ontario and Quebec, leaving dry conditions and largely clear skies. Consequently, the risk for rainfall development would be kept at a minimum. The maximum temperature would be 24 C during the mid-afternoon for the greater Montreal area, and then 21 C during display time. As the humidity would remain low, no real humidex is favored.

Winds would typically be flowing lightly from the North to gradually NNW early in the day, though a transition to WNW to eventually WSW would is likely by mid-afternoon to evening, respectively. Unlike the situation during the last display (on July 2nd), wind speeds would be rather light over the course of the evening, at 4-7 km/h, allowing the smoke, from all altitudes, to drift gently towards right-hand to partially central sections of the La Ronde audience. Although periods of larger smoke accumulation are favored at certain points of the Mexican display, particularly extensive accumulations are not expected in light of low humidity.

Another update to follow late this evening to early-predawn (July 8th-July 9th).

Trav.

Details mentioned in the above posting continue to be valid. As such, here are the dominant weather conditions for the greater Montreal area for Saturday, July 9th.

Temperature/Humidity

A maximum temperature of 24 C is favorable by mid-afternoon, declining to 21 C by display time. As a result of low humidity, a humidex is not relevant.

Precipitation

As the region would be governed by a large area of high pressure, convection would be kept at a minimum. Some modest lift in the area would be suitable for sparsely-distributed fair-weather cumulus, but sky conditions would be largely clear, especially during the evening.

Wind

Winds continue to be in the form of light NNW to NW for the early part of the day. By the afternoon, directional tendencies become more Westerly, but these do transition to more WNW near sunset and beyond. Throughout the day, speeds are largely light, from 7-11 km/h, though breezier during the mid-afternoon before becoming 4-7 km/h over the course of the evening. As such, the smoke would be moving gently (a touch faster at the highest altitudes) towards central to left-hand sections of the La Ronde audience, causing the display to sometimes appear hazy/murky from there, and when the display is viewed to the left, in general. Although periods of larger smoke accumulation are favorable at low- to mid-level, as well as during more active segments of the display, particularly extensive amounts of smoke are not expected due to marginally-sufficient wind speeds and low humidity.

Another update, if necessary, will follow by mid-afternoon today (July 9th) to address evening wind direction.

Trav.

Thank you again, Trav, for this specific forecast.

Is 21 Celsius the forecast for 10pm or an average for the evening? MeteoMedia daily forecast predicts 21 in the evening, but its hourly forecast indicates 18 Celsius at 10pm (and 16 Celsius at midnight, when many people who attend the show at La Ronde are still in transit to go home). I feel that long sleeves or a jacket may be very useful tonight!

Fred

Hi Fred,

Yes, the 21 C would be the estimated temperature for the greater Montreal area at 10:00 p.m. However, since the maximum temperature achieved for today narrowly missed the expected maximum of 24 C, it is necessary to reduce this estimated display time temperature slightly (20 C).

As a consequence of clear sky conditions, low humidity and light winds, the air can more efficiently cool post-sunset. That said, this cooling process is relatively slower over the metropolitan area, and so the temperature should hold at 20 C (17-18 C farther West, over the West Island) during display time. Although cooler, the light winds would generally help to partly mitigate the discomfort induced by the chilled air, though a long-sleeved shirt would, indeed, be useful especially closer to midnight and beyond. This morning’s temperature out here, in the Southwestern portion of West Island, decreased to 11 C this morning, so I would envision a similar minimum here by mid-predawn/overnight tonight (July 10th).

I believe the second half of July would be fairly strong for more regularly warmer than normal conditions, offsetting slightly the cooler first half, though this would begin encouraging more days suitable for thunderstorms. This warmer and much more humid pattern should also prove to hold well throughout much of August, potentially leading to a very warm to hot August, overall.

*Winds continue to be in the form of WNW for this evening (at 4-7 km/h). At times, due to the light nature of the winds, this flow could undergo a transition to WSW during the display, which would allow the smoke to suddenly begin moving more towards right-hand and central sections of the on-site audience, but in either case, central sections would still be intercepting smoke at least partially.

Trav.

Weather conditions for July 13th would be influenced by a weak area of low pressure, followed by a broader high pressure system late-day. Under this atmospheric configuration, the maximum temperature for the greater Montreal area would be 27-28 C under moderate humidity, creating a maximum humidex of 31 C. By evening, the temperature would decrease to 22 C, along with a humidex value of 25 C.

Convective development would be limited as the day progresses in response to the area of high pressure ejecting SE. Therefore, sparsely-distributed rainfall would mostly be focused to the morning hours as a result of the ongoing instability from the July 12th situation. That said, lift would be suitable for a discontinuous layer of mid- to high-level cloud overspreading the region throughout the day, which would include large clear breaks in this cloud deck. Unlike July 9th, the combination of a larger cloud cover extent and moderate humidity during the evening would limit the amount of cooling after sunset.

Wind velocity should behave as light Westerlies for the day before transitioning to light WSW post-sunset (5-8 km/h). This would allow accumulations of smoke to move gently towards principally right-hand and partially central sections of the La Ronde audience. This would eventually cause the display to appear hazy/murky along low- to mid-altitude, mostly when viewing the display at its right (La Ronde’s right). Due to moderate humidity and light wind fields, somewhat larger amounts of accumulation will be possible, though as mentioned in Paul’s interview, the use of less smoke-rich products in the Hungarian display could help improve viewing to some degree. Nevertheless, although periods of large smoke accumulation would be favorable, particularly extensive and thick amounts are not expected. *Should the aforementioned area of high pressure migrate into this area a little quicker, then this would become a situation where wind direction assumes a more WNW to even NW tendency - the latter being more beneficial for the La Ronde audience. This trajectory would, thus, need to be closely monitored.

Another update to follow late this evening into early-predawn (July 12th-July 13th), mostly addressing wind speed and direction.

Trav.

My apologies for the delay – my area just recently came out of a power failure that occupied the predawn period of today (July 13th). The details presented in the above posting continue to apply, and so here are the weather conditions that would be present for the greater Montreal area for Wednesday, July 13th.

Temperature/Humidity

A maximum temperature of 26 C is favorable by this mid-afternoon, declining slightly to 23 C by during display time. Humidity levels would be sustained at borderline low to moderate, beginning this afternoon, inducing a maximum humidex of 30 C this mid-afternoon, and then 25 C during the late-evening.

Precipitation

As the aforementioned area of high pressure begins interacting with this region progressively through the day, increased stability would ensue, leaving mostly pleasant conditions. The mingling with the current weaker area of low pressure affecting this region would create zones of lift that would later encourage some cloud cover (with some clear breaks creating discontinuities in this cloud deck) along mid- to high-altitude this afternoon to evening. Note that as lift becomes more aggressive, some light to moderate rainfall development will become more important during the early- to mid-predawn hours, and so I would assign a 70% probability of precipitation for that time.

Wind

Winds would be in the form of principally straight Westerlies for late this morning through to the afternoon today. Wind speeds would initially be light (7-9 km/h) before becoming breezier during the afternoon (17-21 km/h). Beyond sunset, however, winds do resume with their lighter speeds, at 4-7 km/h. Under the influence of high pressure, winds become Northwesterly to occasionally WNW just before display time, allowing the smoke to drift fairly gently towards left-hand sections of the La Ronde audience from all altitudes, and moving in the direction of those located on the bridge behind the park. Smoke at the highest altitudes would drift towards the audience more directly (central and left-hand sections).Some periods of larger smoke accumulation would be favorable deeper into the display, sometimes causing a hazy/murky appearance when viewed to the left along lower to mid-altitudes. This would largely be the result of weaker wind speeds and moderate humidity, though with the presence of less smoke-producing products in this display, this could help to improve visibility to some extent during times of higher activity.

Another update concerning wind direction will be given by this mid-afternoon (July 13th).

Trav.

Details presented in the above post remain valid. Thus, winds continue to be in the form of WNW to occasionally NW for later this evening, causing the smoke to move slowly towards left-hand and partially central sections of the La Ronde audience (smoke at the highest altitudes moving a touch faster but also a little more directly towards central sections of the audience).

Trav.

At the gateway to a possible near-significant heat wave, July 16th will favorably carry with it the warmest conditions of all fireworks days so far this year. This would further likely be surpassed in warmth by the July 20th situation. For July 16th across the greater Montreal area, a maximum temperature of 28 C is envisioned as a stronger push of warm air advection begins infiltrating Southern Quebec. Although humidity would be somewhat limited, its moderate tendency would send the humidex to a maximum of 31 C during the mid-afternoon, and then 29 C during display time (base temperature of 26 C).

While no rainfall is expected within this environment, more widespread convection would be ideal for large clusters of cumulus by the late- morning period and onward, leaving a progressively larger cloud cover extent by mid-afternoon to evening.

Winds would largely be in the form of breezy Southwesterlies for the day (17-21 km/h, with occasional gusts of 29-33 km/h). However, by the evening (i.e. post-sunset), these speeds do weaken to lighter standards, at 8-11 km/h and becoming more SSW. As such, accumulations of smoke from the Canadian display should drift reasonably quickly to the right of the La Ronde audience, although smoke at the highest altitudes would drift towards far right-hand sections of this audience. At times, the display would appear hazy when solely at its right-hand portion, at low- to mid-level, though this should not be anything too significant.

Another update to follow this late-evening to early-predawn (July 15th-July 16th).

Trav.

Conditions specified in the above posting remain applicable. As such, here is the dominant pattern envisioned for Saturday, July 16th for the greater Montreal area.

Temperature/Humidity

The temperature could reach a maximum of 29 C to even 30.0+ C this mid-afternoon, which could very well be the first time that 30.0+ C has made an appearance (without humidex) on the island since June 26th. By late-evening, 25 C is likely, making this the warmest fireworks evening so far this year (though likely to be surpassed on July 20th of there is no rainfall). As the humidity would steadily be borderline moderate to high, a maximum humidex of 33 C is favorable, while during the evening, the value should be 29 C.

Precipitation

No rainfall development is envisioned. That said, modest lift would support some cloudy periods composed primarily of high-level cloud (cirrus) and large clusters of cumulus extending from low- to mid-level. Such a combination would subside somewhat by evening, leaving larger clear breaks at the time. The risk for thunderstorms/convective rainfall would become more frequently important this week and beyond, however.

Wind

Winds would be an interplay of breezy SW and WSW flow during the late-morning to afternoon period (17-21 km/h, with occasional gusts of 28-31 km/h). However, the directional tendency would likely undergo a transition to SSW by mid-evening, and speeds weaken to lighter status mostly post-sunset (8-11 km/h). As such, accumulations of smoke would drift gently to the right of the La Ronde audience, though smoke at the highest altitudes would be reaching far right-hand sections. Due to mostly moderate humidity and light winds, periods of larger smoke accumulation would be favorable deeper in the display during more active segments along low- to mid-level when viewing to principally the right.

If necessary, another update concerning wind direction will be provided by tomorrow mid-afternoon (July 16th).

Trav.

Winds should be more in the form of SW for this evening before becoming the aforementioned SSW late this evening. As such, accumulations of smoke would be moving towards right-hand sections of the La Ronde audience, from all altitudes (though moving somewhat faster at the highest altitudes). All other conditions specified above continue to apply.

Trav.

Initiating on July 16th, a hot and (significantly) humid air mass continues to affect Southern Ontario to Southern Quebec this week. At the same time, an area of strengthening low pressure will advance East and amplify the degree of warmth and moistening during especially July 20th and July 21st. As mentioned in the above postings, this would very likely crown this fireworks evening (July 20th) with the title for most hot/humid this year and, thus, surpassing the warmth observed during the Canadian display. As such, a maximum temperature of 31-32 C is favorable for this day in the greater Montreal area, but with very high humidity, the corresponding maximum humidex would be 42 C. In light of the very high humidity, the temperature will not decrease much by late-evening, and so it is possible for a value of 30 C to remain in place during display time (humidex of 39 C).

Instability is expected to be very strong in such an environment, lingering well into the evening through to July 21st. That said, the degree of lift should remain limited throughout the day, though large and defined cumulus clusters would quickly appear by late-morning and onward. As such, partly cloudy conditions are favorable through most of the day, including the evening period. By late-evening, lift remains restricted to significantly make use of the large instability that would be present. There would, however, be a narrow window of opportunity for sparsely-distributed non-severe thunderstorms to appear in the distance to the NW during the late-evening period. Beyond midnight, lift does improve slightly, enough to begin encouraging a somewhat larger number of thunderstorms in the area. Therefore, for the evening period, a 30% probability of precipitation is relevant, though the thunderstorm situation will be monitored closely.

Winds would largely take on light to occasionally breezy SSW (morning to early-afternoon) to eventually light SSE (mid-afternoon and onward) tendencies. For the evening, a generally light SSE flow (8-11 km/h) is envisioned, allowing the smoke to displace clear to the right of the La Ronde audience, at all altitudes. The enhanced circulation would allow for smoke at the highest altitudes to move a little quicker, and so such winds fields would be beneficial as a result of particularly significant humidification. Assuming no influence from thunderstorms/convective rainfall, this would further present a situation where the La Ronde audience does not intercept smoke accumulations for the first time since the first opening show. Still, periods of significant smoke accumulate will be favorable along low- to mid-levels deeper into the show, and focused to far right-hand sides of the show (La Ronde’s right).

Another update will follow late this evening into early-predawn (July 19th-July 20th).

Trav.

Conditions specified in the above-posting remain largely applicable. As such, presented here is the overall pattern for the greater Montreal area for Wednesday, July 20th.

Temperature/Humidity

With an amplified circulation of very warm to hot and increasingly humid air in this region, a maximum temperature of 31 C is favorable, creating what may very well become at least a near-official heat wave over the July 19th-July 23rd period. Very high humidity would likely send the maximum humidex to 40 C to potentially 41 C by mid-afternoon. By late-evening, including display time temperatures drop only slightly, to 29 C to possibly even 30 C, with a humidex of 38-39 C. If convective rainfall occurs, the temperature would cool slightly more, to 25 C (humidex of 34 C).

Precipitation

Lift remains fairly modest throughout the day to take significant advantage of the large amount of instability that would be available. However, it would be suitable for a partly cloudy sky that would be governed by gradually large clusters of defined/towering cumulus and some high-level cirrus by late-morning through to the evening. That said, for the mid-afternoon through to more so evening, the magnitude of lift has recently shown more indications of appreciable improvement. This would begin encouraging sparsely-distributed to gradually scattered convective rainfall and thunderstorms (some strong) during this time. For this reason, a 30% probability of precipitation is favored for the mid-afternoon to early-evening period, followed by a 40% for late-evening, and then a slightly greater risk thereafter, near midnight and during predawn. Rainfall from the families of convective systems would be locally quite torrential, even if not accompanied by thunder/lightning, though note that the lightning can be intense with the strongest thunderstorms.

The latest thinking is that display time would be unaffected by the convective rainfall/thunderstorms, with lightning from initial thunderstorms potentially being seen illuminating the sky in the distance to the NW/West prior to and during the display, as mentioned in the above posting. This would then be followed by rainfall and/or thunderstorms shortly after the display and beyond.

Wind

Winds continue to be in the form of SW to eventually SSW during the day (8-11 km/h), with a transition to SSE tendencies by late-afternoon to evening. Speeds would be a touch breezier during the afternoon, at 14-18 km/h. This would allow the smoke, from all altitudes, to gently move clear to the right of and slightly away from the on-site audience, with slightly faster displacement at the highest altitudes. Large smoke accumulation would still be favorable deeper into the Italian display, but focused to La Ronde’s far right. This would sometimes cause the display to appear somewhat hazy/murky at its extreme right-hand portions. However, should convective rainfall or thunderstorms occur during display time, the rapidly accumulating smoke would suddenly turn towards the La Ronde audience.

Another follow-up concerning the thunderstorm situation would come this mid-afternoon (July 20th).

Trav.

Conditions specified in the above posting continue to be valid. Without the direct influence of thunderstorms/convective rainfall, wind direction would just be slightly more to the SE than SSE this late-evening (July 20th), which would still allow the (rapidly) accumulating smoke to drift clear to the right of the La Ronde audience, but also a little more directly away at the same time. Smoke at the highest altitudes would also still be displacing a little faster in the same direction.

The risk for isolated thunderstorms/convective rainfall would remain for this coming late-afternoon to evening and become more scattered in tendency closer to midnight and onward, as mentioned previously. In light of the extent of somewhat limited localized lift at the time, I continue to suspect that actual display time would be unaffected by rainfall/thunderstorms directly, but it would still be very possible to see lightning flickering in the NW/Western distance before, during and after display time, with rainfall/thunderstorms potentially appearing directly shortly after (and before) the display.

All other information presented in the above post continues to apply.

Trav.

July 27th would be affected by an area of low pressure quickly advancing NE through the day. As this occurs, a returning flow of very warm and moderately humid air would infiltrate these regions. The air mass would, thus, allow the greater Montreal area to achieve a maximum temperature of 27 C that would be accompanied by a humidex value of 31 C. By late-evening, this base temperature decreases to 25 C (humidex of 29 C as a result of continued moderate humidity).

While convective rainfall would not become more important until early-July 28th, sufficient lift within the warm sector of the aforementioned area of low pressure would be sufficient for partly cloudy skies that are comprised of a blend of high-level cirrus and clusters of fair-weather cumulus. This would endure into the evening, with a slight increase in cloud cover.

Winds are largely from the SW throughout much of the day at light speeds (8-11 km/h), though a touch breezier during the early- to mid-afternoon (14-18 km/h). However, by late-afternoon and onward, as the circulation of warm, moist air increases, directional tendencies should undergo a transition to SSW to eventually SSE in time for the Croatian display time. This would allow the smoke the displace lightly clear to the right of and slightly away from the La Ronde audience (clear to the left for those on Notre-Dame Street). No significant periods of smoke accumulation are favored.

Another update to follow late this evening into early-predawn (July 26th-July 27th).

Trav.

The weather conditions described in the above post remain valid. As such, here is the dominant pattern for the greater Montreal area for Wednesday, July 27th.

Temperature/Humidity

As an area of low pressure advances East/NE, it will gradually re-introduce a circulation of warmer and somewhat moister air. In light of this configuration, a maximum temperature of 27 C is favorable, and with moderate humidity, the highest humidex should be 31 C. By evening, the temperature value should decrease to 24 C, carrying a humidex of 28 C under the guidance of continued moderate humidity.

Precipitation

No rainfall development is favorable, though this becomes more significant the following afternoon (July 28th). That said, there would be sufficient lift for a mixture of high-level cirrus and clusters of sparsely-distributed fair-weather cumulus. Large high-altitude cloud cover with clear breaks between them would largely remain for the evening.

Wind

Winds continue to be in the form of light Southwesterlies for the morning to late-afternoon (8-11 km/h), though breezier during the early- to mid-afternoon (17-21 km/h). Just after sunset, directional tendencies do begin to adopt a light SSW to Southerly pattern (4-7 km/h). This would allow the smoke to drift gently clear to the right of the La Ronde audience, with slightly faster movement at the highest altitudes. Some periods of larger smoke accumulation would occur towards La Ronde’s far right during more vigorous moments along low- to mid-altitudes (due to light winds and moderate humidity), but no particularly significant accumulation is favored.

If necessary, another update concerning wind direction would come this mid-afternoon (July 27th).

Trav.

Following a brief cooling for August 2nd, a re-introduction of warmer, moister air will advance into this region for the day August 3rd. As this unfolds, very warm temperatures and moderate humidity will become more likely. For the greater Montreal area, specifically, a maximum of 27 C is favorable, accompanied by a maximum humidex value of 31 C. By late-evening, including during the British display, a temperature of 24 C is favored (humidex of 28 C).

In tandem with this atmospheric configuration would be a shortwave trough advancing East later in the day. This feature would enhance the degree to which lift would sufficiently promote a gradual increase in high-level cirrus and low-to mid-level cumulus clusters by mid-afternoon and beyond. As such, the sky would be occupied by this combination of cloud cover for the evening, but by late-evening (notably near midnight and onward), some periods of light convective rainfall would be possible before evolving into a more persistent light to moderate rainfall during predawn August 4th.

Wind fields would largely be in the form of light SSE (9-12 km/h) for the day (ESE during the morning). These speeds would become breezier by the early-afternoon (18-22 km/h) before weakening slightly to 13-17 km/h during the evening period. As such, the smoke from the British display would be advancing reasonably quickly clear to the right of and slightly away from the La Ronde audience, with faster displacement at the highest altitudes of the display. Although the smoke would be moving adequately fast most of the time, some periods of larger smoke accumulation, as a result of high humidity, would occur at low- to mid-level to La Ronde’s far right (i.e. near the Ferris wheel).

Another update will follow this late-evening to early-predawn (August 2nd-August 3rd).

Trav.

Weather details presented in the above posting remain applicable for the situation tomorrow. As such, here are the conditions expected for the greater Montreal area for Wednesday, August 3rd.

Temperature/Humidity

Much like the situation last Wednesday (July 27th), a strengthening area of low pressure will migrate East/NE, re-introducing a very warm and moderately moist air mass across Southern Ontario to Southern Quebec. Such a flow would permit the temperature to reach a maximum of 27 C by mid-afternoon, followed by a decrease to 24 C by display time. Due to moderate humidity, the highest achievable humidex would be 31 C, while for the evening, the value would be 28 C.

Precipitation

A shortwave trough will eject East late-day and would, therefore, be the principal mode of ascent at the time. In its wake, an introductory layer of continuous cirrus cloud cover, accompanied by a gradual increase in clusters of cumulus, would begin overspreading the region by mid-afternoon (patches of cirrus and isolated cumulus making themselves known by late in the morning). As such, the evening would largely be spent overcast under the influence of this combination of cloud coverage. As mentioned in the above posting, sparsely-distributed light rainfall would become possible by midnight and beyond (30% probability, and increasing to 60% by mid-predawn as convective coverage increases at the time).

Wind

Winds would predominantly assume light WNW tendencies (6-9 km/h) for the early-morning before undergoing a transition to SSE for the afternoon into the evening (12-16 km/h). This would create a situation where the smoke would be moving clear to the right of and slightly away from the La Ronde audience, much like the previous two displays, except moving at a slightly faster speed – this would especially be true at the highest altitudes of the display, and in general as speeds slightly increase deeper into the display. As such, no periods of extensive smoke accumulation are expected, though during the more active segments, the smoke would briefly increase in concentration around the Ferris wheel at low- to mid-altitudes.

If necessary, another update concerning wind direction would come this mid-afternoon (August 3rd).

Trav.

A flow of hot and very moist air is expected to circulate across Southern Ontario to Southern Quebec this weekend, a pattern that would capture the final display day of the 36th edition of Montreal Fireworks. As such, for the greater Montreal area, a maximum temperature of 32 C is possible by mid-afternoon Saturday (August 6th), with a humidex of 41 C under the influence of very high humidity. By evening, the cooling would be little as this air mass remains strong. Therefore, the late-evening temperature is likely to be as warm as 29 C, with a humidex of 37 C. This would rival the evening of July 20th (i.e. the Italian display day), which currently leads all fireworks days for warmth/heat and humidity this year.

Despite the large amount of atmospheric instability that would be present, convective rainfall development would be limited as a result of very restricted lift. Still, a narrow window of opportunity would exist for a brief convective rainfall and/or briefly-sustained, slow-moving and isolated non-severe thunderstorm during the mid- to late-afternoon. In either case, the probability of precipitation would be 20% during the mid- to late-afternoon. Clusters of defined cumulus would predominate the afternoon, though these would decrease in number post-sunset.

Winds would be in the form of modestly breezy SSW to occasionally SW (12-16 km/h) for the day, including for the evening. That said, a slight tilting towards the SW would become favorable for the evening. As such, the rapidly developing smoke accumulations would be moving towards far right hand-sections of the La Ronde audience, at all altitudes. The smoke at the highest altitudes would be displacing fairly quickly, but the display would appear fairly hazy at its right-hand sections as it unfolds.

Another update to follow this late-evening to early-predawn (August 5th-August 6th).

Trav.

The above posting continues to remain valid concerning the weather pattern expected for today. Therefore, presented here are the dominant conditions for the greater Montreal area for Saturday, August 6th.

Temperature/Humidity

As mentioned above, a strong circulation of hot and very humid air will overspread Southern Ontario to Southern Quebec. As this air mass progresses, a maximum temperature of 32 C is likely, and with very high humidity, the highest achievable humidex would be 41 C. Should this be successful, this would then be the highest humidex observed so far this year, and the second time that a humidex of 40+ C has appeared. For the late-evening, including display time, the temperature would remain at 30 to even 31 C, making this tie July 20th for the warmest display time, if not narrowly surpass it. During this time, the continued very high humidity would induce a humidex of 39-40 C.

Precipitation

Although a suitable environment for convective rainfall and thunderstorms, limited lift in the area would generally discourage development. Still, given the large degree of atmospheric instability, some very sparsely-distributed convective rainfall and isolated/briefly-sustained thunderstorms would be possible over the course of the afternoon (20% probability of precipitation), along with a sky composed of scattered clusters of moderately-defined cumulus and patches of cirrus. The extent of this cloud combination would decrease considerably near and not too long after sunset, allowing for largely clear sky conditions.

Wind

Wind tendencies are in the form of breezy Southerlies to occasionally SSW (12-16 km/h), taking form by late-morning. This would remain as principally SSW for the evening (12-16 km/h). In light of such wind fields, this would allow the rapidly-building smoke to drift closely to the right of the La Ronde audience. That said, the smoke at the highest altitudes would be displacing at slightly faster speeds but also advancing over far-right hand sections of the on-site audience. Due to very high humidity, the display would gradually appear hazy at its right-hand side, though suitable wind speeds would permit the smoke to clear quickly enough most of the time. During more active segments, however, brief periods of significant smoke accumulation would be possible along low- to mid-level due to the very high humidity. The somewhat breezy winds would additionally serve to provide at least some relief for those who struggle with high heat/humidity.

If necessary, another update concerning wind direction would appear here this mid-afternoon (August 6th).

Trav.