As the 2015 competition is soon upon us, and due to it being now the approximate half-way point of June (much too fast!), I thought that it would be appropriate to initiate this thread.

As always, I will post weather information here on the day prior to each display, and preliminary reports about two days in advance. Subsequent updates, as needed, will also be provided on the display days themselves. Details will pertain to temperature, humidity/moisture, precipitation, wind speed, and wind direction. If or when chances for precipitation become high enough, especially in situations where (severe) thunderstorms are possible, I will provide additional details and updates as necessary. This may also be applicable for wind speed and/or direction, mostly in cases of stronger wind speeds. You are also most welcome to share weather information, so I encourage you do so!

Once again, for those interested, my late-Spring and Summer 2015 projections (originally released on March 17th) can be found here:

https://www.facebook.com/notes/travis-moore/winter-2014-2015-and-a-loo k-ahead-to-spring-and-summer-2015/10153156041081346?pnref=lhc

In summary, a late-Spring and Summer that is near-normal in temperatures for S. Ontario to S. Quebec, but not "spectacularly" hot. That said, the May-August overall average temperature should be appreciably warmer than 2014's, including more days reaching 30 C or more (10-12 such days possible for the Montreal area, and similar values in nearby locations). An increase in the number of humid days is also favored. Finally, I suspect that this could also be a stormy late-Spring and Summer, with an increase in the number of (severe) thunderstorm days occurring across these regions. Precipitation should generally be above normal, especially where thunderstorms are more repeatedly prevalent.

Let us hope for ideal weather conditions for all of the displays!

Trav.

Hi Trav,

It is a pleasure to read that, once again this year, you are going to present your detailed forecast reports. I anxiously wait for your opening forecast as the weather may not be good, at some point, on Wednesday. I hope to not experience the same conditions than in 2002 : there were severe rainfalls, La Ronde was empty when I arrived that night, and the on-stage opening ceremony - one of the only two ceremonies hosted by Michel Lacroix that year - has been cancelled due to the weather!

Paul Marriott introduced his report by the following:
After a day of heavy rain and unseasonably cool temperatures of only 13oC, the weather managed to cooperate and it dried up just in time for the display, which was delayed for several minutes due to the weather. The smallest crowd I can ever remember seeing were rewarded with a dazzling display from the twice-Jupiter winning Japanese masters of fire.

Fred

An area of low pressure is expected to move NE and affect S. Ontario to S. Quebec by tomorrow (June 30th). As it does, humidity levels will increase to high standards into S. Quebec by late tomorrow afternoon and evening, along with a risk for convective showers and thunderstorms ahead of the low’s warm front during this time (possibly into the early-overnight, as well). Into Wednesday (July 1st/Canada Day), humidity levels should rise further to borderline high/very high levels, and the cold front (initially stationary) associated with the system will begin to have more of an influence, potentially generating scattered thunderstorms, some of which could be strong to severe during the afternoon hours. There is, however, some uncertainty in the degree of cloud coverage ahead of the front on the day Wednesday, which is leading to a narrow spread of scenarios in the robustness of instability and, therefore, affecting thunderstorm/convective coverage. That said, there is agreement as to at least a few breaks in the cloud deck that is contributing to moderate instability, at best. There is also some discrepancy in the timing of the complete passage of the cold front in extreme SW Quebec. One possibility is that the front will move East of this region by the mid-afternoon hours, while the other is more during the late-evening, near midnight. At this point, I see it reasonable to maintain a risk for convective showers and (strong) thunderstorms through to the early-evening (to 9:00 p.m.)., though the better chance should be kept in the afternoon.

Another aspect to watch for is wind speed and direction, particularly speeds. Because of the uncertainty with the front’s passage, winds could either be SW or become more Westerly in time for the evening hours. Wind speeds (specifically gusts) may also be close to the 40 km/h threshold (gusts of 38-42 km/h) for the duration of the afternoon and evening. Thus, winds should be blowing quickly accumulating smoke (especially at low- to mid-levels of the display) rapidly towards extreme right-hand sections of the audience at La Ronde. However, if there are more WSW to Westerly tendencies, then a more direct influence is favorable. Depending on how much solar heating unfolds, daytime temperatures could be optimally 24-25 C, along with humidex readings of 31-32 C. However, if thunderstorms/rain showers occur at times, this would cause temperatures to locally decrease to closer to the lower 20s C (but with slightly increased humidity). By evening, temperatures should be closer to 19-20 C (mostly in the metropolitan area), with humidity levels still high (humidex of 22-23 C) but lower from the afternoon (note that this is also subject to change due to the differing projected timings of the cold front). Skies should be partly cloudy by late-evening.
Another update to follow by tomorrow evening (June 30th).
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Hi Fred,

Thanks for your posting, and it’s always a pleasure providing weather reports. Yes, I do remember the weather conditions for the Japanese display in 2002. Quite memorable, indeed! I do also vividly recall the severe thunderstorms that affected the American display that year! There is a chance that things will not come to that for the opening show on Canada Day, but it is important to keep an eye on this system’s evolution through the day tomorrow and Wednesday.

Hi Paul,

Weather conditions are, so far, looking very good for your display in Knowlton on Sunday, July 5th, a very steep contrast to those conditions observed on June 28th (even though it remained mostly rain-free for the evening hours). An area of high pressure is expected to move into this region by early July 5th, bringing mostly sunny skies (a few isolated fair weather cumulus and high-level cirrus), low humidity (borderline low-moderate later in the day), and daytime highs of 25-26 C (humidex negligible). Mid-evening temperatures should be closer to 20-21 C. Wind speeds, through the day, however, will likely be very light to occasionally calm (3-6 km/h into the evening), with a NNW directional component, though they may transition to more SSE tendencies by late-evening.

More updates to come over the next few days.

Trav.

Your Canada Day forecast:

Weather conditions specified in the above post still remain mostly constant, though there are small modifications. As such, here are the predominant patterns for Saturday, July 1st for the Montreal area:

Temperature/Humidity

Temperatures could rise to as much 23-24 C during the afternoon hours, and rich moisture (borderline high-very high humidity) will make it feel like 31-32 C. Persistent rainfall, however, could cause temperatures to drop and be maintained closer to 20 C (but with increased moisture). By late-evening, temperatures decline quite noticeably behind the aforementioned cold front to a cool 16-17 C (17-18 C in the metropolitan area), along with moderate humidity (lowered from the afternoon and early-evening), generating a slight humidex of 19-20 C. Humidity begins to drop just prior to dusk and onwards. Gusty winds will likely produce an extra chill in the air, so a light jacket and/or sweater may be necessary.

Precipitation

Periods of convective rains associated with the system’s cold front and shortwave trough are favorable across E. Ontario to S. Quebec throughout most of the day, but especially into the afternoon. Cloud coverage continues to be considerable through the day, with the possibility of some sunny breaks into the afternoon. This should limit instability from becoming overly high, but with enriched surface moisture, instability will likely be moderate, at most, into the afternoon. Thunderstorms are also possible, including strong to severe thunderstorms. However, somewhat more limited instability and marginally significant wind shear profiles should lead to more isolated convective coverage, though coverage should become more scattered into the afternoon. The dominant threats with the strongest thunderstorms will be heavy rain and intense lightning. The risk for thunderstorms/convective showers should end and shift East of the island by the late-afternoon to early-evening (by 8:30 to 9:00 p.m.) However, the best chance for thunderstorms/rain showers remains for the afternoon hours. Skies should continue to be cloudy (but with clear breaks) by late-evening.

Wind

Wind speeds (notably gusts) continue to be a concern. Winds are more Southerly late in the morning to South-Southwesterly during the early-afternoon before becoming SW by mid-afternoon, with sustained speeds and gusts of 23-27 km/h and 37-41 km/h, respectively. As the cold front completely passes through into the early-evening, winds are expected to shift to more WSW tendencies by late-evening. Sustained speeds and gusts are also expected to increase during the evening hours behind the front, and gusts could sometimes reach 43-47 km/h (sustained at 28-32 km/h). As such, somewhat quickly accumulating smoke (mostly at low- to mid-levels of the display when becoming more active) should be blowing rapidly towards right-hand and sometimes central sections of the La Ronde audience. Wind-related delays (potentially significant) will be possible.

In summary, a chilly late-evening, with temperatures of 17-18 C, moderate humidity, mostly cloudy skies (with some clear breaks) and gusty WSW winds. Have a light jacket or sweater handy.

Edit:More updates to follow into tomorrow (July 1st), if necessary, especially with respect to wind speed and direction.

Trav.

Thank you for this report. Warm clothes and some accessories should be enough to deal with the cold temperatures and potential rainfall. I am more concerned with the wind issue, now.

Fred

You're welcome, Fred.

Latest analysis remains virtually identical to what was stated in my previous posting. However, recent projections favor wind gusts to be even a little stronger behind the cold front this evening, especially by late-evening, where gusts may sometimes exceed 50 km/h (49-53 km/h). Sustained speeds are approximately the same (29-33 km/h), and from the WSW. This should continue into the early-overnight.

Trav.

These new wind speed projections are not a good news, especially given the direction, that is, toward the close, on-site audience. I suppose that organizers and the fire safety department will carefully monitor the situation through the night. In 2009, very accurate forecast led these people to pre-empt the Hong Kong display by 5 minutes, so the show ended immediately before a rise in wind speed.

Fred

A more Summer-like weather pattern is expected to establish itself into S. Ontario to S. Quebec this weekend and will likely restore temperatures to normal to above normal standards, beginning on July 3rd. As the advancing area of high pressure shifts East later Sunday (July 5th), a strong surge of very warm, moist air will circulate into these regions, potentially yielding near-technical heat wave status for many locations, beginning on July 6th.

Maximum temperatures should reach 27-28 C for the island of Montreal and surrounding locations Saturday (July 4th), along with low humidity for the beginning of the day. Values should remain as warm as 22-23 C in the metropolitan area by late-evening, with humidity becoming high towards midnight (humidex of 27-28 C). At the same time, there is a shortwave trough ejecting East/SE with an attendant weak cold front through the day, which should increase low- to high-level cloud coverage by the end of the afternoon into the evening hours. Skies should, therefore, become partly cloudy during this time and remain mostly sunny earlier in the day (with some high-level cirrus). Isolated convective showers associated with these atmospheric features should generally stay farther North and mostly NW, where frontal convergence and lift are somewhat more defined. That said, these showers may also spread farther South into the late-afternoon to early-evening, so a slight risk for convective showers could exist during that time. I will keep an eye on this in future model runs.

Winds should be much less breezy than on Wednesday, July 1st, and more from the SSW (by about 2:00 p.m.). At this point, speeds are slightly breezy at 10-14 km/h (except 3-7 km/h during the morning) but become a little lighter at 9-12 km/h by the evening hours. Therefore, smoke from the fireworks should be moving adequately to the right of the audience at La Ronde (left for those on Notre-Dame).

Another update to follow by tomorrow evening (July 3rd).
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Paul, I will have an updated forecast prepared for you by later tomorrow (July 3rd) for July 5th. One notable difference to my second posting above, though, is that the humidity should be high through the day, beginning by late-morning on July 5th. Cloudy periods are also more favorable due to that shortwave trough. Winds continue to be light into the evening, but more from the SW.

Trav.

What was stated in the above posting still remains largely applicable. As such, here are the dominant patterns for Saturday, July 4th for the Montreal area:

Temperature/Humidity

Temperatures are expected to rise to 27-28 C by the mid-afternoon, with generally borderline low-moderate humidity, making it feel like C. By late-evening, temperatures should decrease to 22-23 C in the metropolitan area, and humidity will have increased to borderline moderate-high levels, producing a humidex of 27-28 C.

Precipitation

As per my previous post, a shortwave trough and weak surface cold front are ejecting East/SE through the day tomorrow. However, overall lift and instability ahead of these features are expected to be a little stronger into the late-afternoon to mid-evening hours (7:00-9:30 p.m.) to the North and NW of the island during this time, producing isolated convective showers and possibly non-severe thunderstorms. Weak lift should allow for some isolated clusters of low- to mid-level cumulus clouds to develop by late-afternoon through to the evening hours in this area. High-level cirrus clouds should be present earlier in the day, with mostly sunny skies.

Wind

Winds should be light throughout the day at 8-11 km/h (3-6 km/h during the morning). Wind direction should also be SSW before becoming more southerly for the evening. As such, winds should be pushing smoke gently clear to the right of the audience at La Ronde (left for those on Notre-Dame). Some periods of smoke accumulation are possible at low- to mid-levels of the display (mostly at more active sections) due to higher humidity levels and overall lighter winds.

In summary, a comparatively warm evening, with temperatures in the low 20s C, near-high humidity, a few isolated low- to mid-level clouds, and light SSW to southerly winds.

If necessary, I will post another update by into tomorrow morning or early-afternoon.

Trav.

As the current area of high pressure moves into S. Ontario to S. Quebec into tomorrow (July 10th) and then push East through the day Saturday (July 11th), a very July-/tropical-like air mass will favorably circulate into these regions. This will yield high to very high humidity and maximum temperatures of 29 C or more from mid-Saturday to Monday (July 13th). This pattern has the potential to produce a heat wave in some locations, beginning July 11th.

With this pattern, July 11th will likely see very warm to hot temperatures, with maximum values reaching as high as 30-31 C, along with maximum humidex temperatures of 36-37 C (possibly crossing 40 C into mid-afternoon Sunday, July 12th). Late-evening temperatures in the metropolitan area may remain as high as 26-27 C for the Italian display, and with borderline high to very humidity, a humidex of 33-34 C is likely.

No precipitation is expected, but some lift should give way to cloudy periods (low- mid- and high-altitude clouds) through the day, including the evening. Winds are expected to be breezy through the day from the SW, with sustained speeds of 21-25 km/h. One aspect to watch, however, is the wind gusts, as they are projected to be not too far from the 40 km/h threshold. At this point, maximum gusts of 34-38 km/h are likely during the mid-afternoon and evening hours. Smoke from the fireworks, especially those at low- to mid-levels of the display should be accumulating quickly, but the breezy conditions should also help to clear these accumulations fast, though smoke is expected to be pushing quickly towards right-hand sections of the La Ronde audience.

Another update to follow into tomorrow evening (July 10th).

Trav.

What was stated in the previous post still remains largely applicable for tomorrow’s weather. As a result, here are the predominant conditions for the Montreal area for Saturday, July 11th.

Temperature/Humidity

A maximum temperature of 30 C is favorable, especially in the metropolitan area, and by late-evening, temperatures should still be as high as 26-27 C. Humidity remains moderate during the morning but increases to high standards by late-afternoon and evening. Mid-afternoon humidex values should be 35 C (locally 36 C), and by late-evening, 32-33 C.

Precipitation

A cold front to the NW will likely produce convective showers and non-severe thunderstorms North of the island late tomorrow afternoon into the early-evening. Some lift in this area (and closely surrounding locations) will generate some brief cloudy periods through the day, mostly with variable clouds (low-, mid- and high-level clouds). Increased instability occurring later in the day should lead to more vertically developed cumulus cloud clusters, and there will exist a slight risk for isolated non-severe thunderstorms or convective showers during the overnight hours.

Wind

Wind speeds may, again, become an issue. Due to a strengthening pressure gradient, wind speeds become progressively breezy after lunch time, with sustained values of 23-27 km/h, especially towards mid-afternoon. Associated gusts, however, are still shown to be reaching near the 40 km/h level by mid-afternoon through to the duration of the evening hours. Maximum gusts are typically 34-38 km/h, but gusts of 39-44 km/h are possible into the mid- to late-evening hours, though sustained speeds decrease to 19-22 km/h. This may induce delays. Directional tendencies are SW (sometimes WSW), so rapidly accumulating smoke (due to high humidity), especially at low- to mid-levels of the display when more active, should be moving quickly towards right-hand sections of the La Ronde audience.

In summary, a very warm and humid evening, with temperatures just slightly above 25 C, breezy/gusty SW winds, and high humidity. Skies should be partly cloudy into the evening hours.

*If necessary, I will post another update into tomorrow morning to mid-afternoon (July 11th) concerning wind gusts.

Trav.

Thank you, Trav. Whether you do an update, in addition to the wind issue, could you provide more information about probability of thunderstorm? MeteoMedia currently projects a probability of 40%, and I wonder whether the risk is increasing since last night.

Fred

Hi Fred,

I continue to have the mindset that the risk for convective showers and non-severe thunderstorms for this area (and closely surrounding locations) will be more applicable until after midnight (during the pre-dawn hours). After midnight, too, convective coverage should become sparser ahead of the front, so I would hold the risk at 30% at that time frame. Skies should remain partly cloudy this evening here.

As for the winds, projected sustained wind speeds and accompanying gusts are still identical in the newest analyses (gusts close to or slightly above the 40 km/h mark (39-44 km/h), with sustained speeds closer to 19-23 km/h). Recent gusts at the airport were registered at 34-37 km/h, with similar speeds at nearby stations. I am also going to drop late-evening temperatures slightly to 25-26 C to account for the breezy winds.

Trav.

Thanks!

You're very welcome, Fred.
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A defined area of high pressure is expected to follow behind a cold front that will move through S. Quebec tomorrow evening (July 14th), which may generate thunderstorms (a few of which could be strong, but thunderstorms should generally be non-severe). As the cold front passes, humidity levels will drop to low standards, and maximum temperatures will more favorably remain close to the mid-20s C into Wednesday (July 15th), and Thursday (the 16th). Late-evening temperatures should be 20-21 C in the metropolitan area. From July 17th to July 22nd, a return to very warm/hot and increasingly humid (more so by the 18th) conditions should take place again for S. Ontario to S. Quebec.

No precipitation is anticipated for the day Wednesday, and skies should remain mainly clear (with some sparse fair-weather cumulus). Wind direction is more NNW to near-straight northerly (later in the day). Wind speeds remain more uncertain but should generally be light (at this point, 9-12 km/h) by the late-afternoon to evening hours. As a result, smoke from the fireworks should be moving gently clear to the left of the La Ronde audience (right for those on Notre-Dame) and towards those spectators on the bridge immediately adjacent/perpendicular to the park/fireworks site. This may cause the display to sometimes appear murky for those viewing from the Old Port (and nearby sections of the bridge), especially if winds are very light.

Another update to follow into tomorrow evening (July 14th).

Trav.

Weather conditions specified in the above posting continue to hold mostly constant. As a result, here is the dominant pattern for the Montreal area for Wednesday, July 15th.

Temperature/Humidity

As compared to the last four days, maximum temperatures will be lowered to 22-23 C due to the passage of a cold front this evening (July 14th) and high pressure settling in. By late-evening, temperatures should drop to 18-19 C (a touch on the cooler side) in the metropolitan area. Humidity levels will be low, so the humidex is negligible. UV will still be high during peak hours, however, so protect yourselves accordingly if expected to be outdoors for prolonged periods.

Precipitation

No precipitation is expected across the region. With weak lift, skies should be mostly clear throughout the day, with a few isolated fair-weather cumulus. Clear skies should be present for the evening.

Wind

Winds should be light at 9-13 km/h (slightly breezier through the morning and afternoon at 16-19 km/h), and from the NNW. As such, the smoke from the fireworks should be pushing gently clear to the left of the audience at La Ronde (right for those on Notre-Dame) and towards spectators positioned on the bridge immediately adjacent to the park. Again, the display may sometimes appear murky for viewers stationed at the Old Port.

In summary, a pleasant evening (a touch cool), with light NNW winds, low humidity, and clear skies.

Trav.

An area of low pressure is slowly moving NE through the day tomorrow (July 17th) and will gradually circulate a more tropical air mass by early-July 18th. As the low’s warm front (and accompanying shortwave trough) ejects East/NE, a few showers and organized thunderstorms will be possible tomorrow evening into the early-overnight hours. Moisture levels are expected to increase to borderline high to very high levels for Saturday (July 18th), along with maximum temperatures as high as 29-30 C, and a humidex of 37-38 C. By evening, temperatures could still be as warm as 26-27 C in the metropolitan area (humidex of 33-34 C). Because instability is projected to be rather strong for the afternoon hours ahead of a weak cold front, a few thunderstorms and/or convective showers will be possible and may persist through to the early-evening (near sunset) before diminishing thereafter. Wind shear profiles are somewhat limited, however, so the risk for more scattered to ubiquitous severe weather should remain isolated. There should be a mix of sun and cloud (vertically defined cumulus) during the day, and skies should be partly cloudy for the evening.

Wind tendencies are still a little uncertain, but recent analyses indicates WSW for the afternoon (more SSE to SSW/South during the morning) but become more SW in time for the evening. However, wind speeds could be very light into the evening hours. This would favor rapidly accumulating smoke to be pushing slowly towards right-hand sections of the La Ronde audience. Periods of extensive smoke build-up are possible, especially during the more active sections, and generally along low- to mid-levels of the display. This may cause the display to sometimes appear murky, especially towards right-hand sections of the display.

Another update to follow by tomorrow evening (July 17th), mostly for precipitation threat and wind speed/direction.

Trav.

Hi Trav. The hourly forecast of MeteoMedia now predicts a change of wind direction, which would become from S to NE before the display. It would be better than SE from my viewpoint. Do you have the same forecast?

Fred

Conditions specified above continue to remain largely applicable. As such, presented below are the dominant conditions for the Montreal area for Saturday, July 18th.

Temperature/Humidity

Due to extensive cloud coverage early in the forecast period (morning), this may limit maximum temperatures to some extent, but increasing breaks in the cloud deck near noon and beyond should promote periods for adequate solar heating. As such, maximum temperatures are likely 28-29 C (30 C is still possible, depending on the onset of solar heating). Humidity increases to borderline high to very high just before noon, inducing a humidex of 36-37 C by mid-afternoon). By late-evening, temperatures are likely to remain at 26-27 C in the metropolitan area, with a humidex of 33-34 C due to very high humidity.

Precipitation

As mentioned above, a weak cold front associated with the area of low pressure and shortwave trough will be the focus for convective showers/rains and thunderstorms (some isolated strong to severe), especially into the early-afternoon hours. Towards the late-afternoon, the risk should diminish behind the front (5:30 p.m. and onwards). Skies are mostly cloudy during the morning but become more of a mix of sun and cloud (large and defined cumulus clouds) into the afternoon. By evening, skies should be partly cloudy.

Wind

Winds continue to be mostly WSW throughout the afternoon (SSW to SSE during the morning), but they appear to be remaining with the tendency into the evening hours. Speeds are breezy through the day (14-18 km/h) but diminish to 6-9 km/h by mid-evening. Due to the very high humidity and very light winds by evening, this suggests that smoke could be accumulating rather quickly (especially along low- to mid-levels of the display and when the more active sections take place). The smoke should also be blowing (very) gently and more directly towards the La Ronde audience (though still somewhat more concentrated at right-hand and central sections). This will likely cause the display to appear frequently murky.

In summary, a real July evening, with likely the warmest temperatures so far for the season. Winds will be light from the WSW and humidity should be very high. Skies should be partly cloudy.

*If necessary, I will post another update by the mid-afternoon of tomorrow (July 18th) for wind speed and direction since there remains some uncertainty with these variables.

Edit: Fred, I am still thinking roughly WSW for wind direction at this point, but I would like to verify upcoming model data to be more certain.

Trav.

Indeed, MeteoMedia has revised its forecast and now announces the same wind direction than you: west. With wind speed lower than 10 km/h, I am now very concerned by the smoke accumulation issue! It would be a shame to have the view blocked by a wall of smoke. It's rare but it already happened!

Fred

Newest analyses, like the previous runs, indicate WSW winds for this evening, with roughly identical speeds (6-9 km/h). Large amount of smoke accumulation are still likely, but I am thinking that the smoke will still be (very) gently pushing more towards right-hand sections (sometimes central) of the La Ronde audience because of the slight SW component.

Also, extensive cloud coverage ahead of the front has significantly limited thunderstorm/rain shower development, in spite of high humidity. It is also likely that convergence ahead of the frontal boundary is relatively weak to really drive more scattered precipitation. As a result, precipitation has remained quite sparse this afternoon. Had the display been tomorrow (July 19th), though, I would have been much, much more concerned about the (severe) thunderstorm risk.

To similarly account for extended cloud coverage, I am also going to decrease evening temperatures slightly to 25-26 C in the metropolitan area this evening. Humidity continues to be high but should still increase to very high standards by late this evening, so a humidex of 33-34 C is appropriate.

Trav.

An area of low pressure migrating East from Ontario will be pushing temperatures and moisture back to seasonal to above seasonal standards, as well as setting the stage for a potential heat wave into the work week next week (at this point, July 27th-31st). The system’s warm front will be ejecting East through the day Saturday (July 25th) across S. Ontario to S. Quebec and is expected to generate widespread convective showers ahead of it.

The timing of this frontal boundary still has some uncertainty, but latest and recent model data have suggested more of an impact for S. Quebec by the early-evening of Saturday. As a result, periods of rain will be possible at that time across this region, with chances increasing by 5:30 p.m. Cloud coverage (mostly high-level cirrus) should be increasing into the early-afternoon hours with more considerable cloudiness towards 4:00 p.m. (with mid- to lower-level clouds) in the wake of this boundary. Isolated non-severe thunderstorms will also be a possibility during the evening hours, but this should be mostly straight rain/light showers.

At this point, winds are ESE through the morning to early-afternoon but should transition to SSE tendencies near dinner time and onwards as the front draws closer. Speeds should also be light at 9-12 km/h during the evening (11-14 km/h during the morning-afternoon). This suggests that smoke from the fireworks should be moving gently clear to the right of the La Ronde audience (clear to the left for those on Notre-Dame). Moisture should be high (a touch lower from borderline high to very high, as was the case on July 18th to July 21st) for the evening (moderate during the afternoon), as well. This could lead to periods of occasionally brief smoke build up (typically whenever the display becomes more active), mostly due to the light winds and with possible rainfall further moistening the air at the time. Mid-afternoon temperatures should be 25-26 C, and late-evening values in the metropolitan area will likely remain at 21-22 C (gradually closer to 19-20 C if periods of rain occur). A humidex of 26-27 C is applicable.

*Another update to follow by tomorrow evening (July 24th).

Trav.

What was described in the above posting continues to remain applicable for the day tomorrow. As such, here are the dominant weather conditions for Saturday, July 25th, for the Montreal area:

Temperature/Humidity

With a returning SSE to Southerly flow regime, temperatures will begin to rise to seasonal standards by tomorrow. Maximum temperatures by mid-afternoon should be 26-27 C (humidex of 31-32 C), and by late-evening, values should still be as warm as 22-23 C in the metropolitan area. However, note that if fairly persistent light showers occur during the evening in the area, temperatures could cool to 20-21 C. Moisture levels become borderline moderate to high near noon and increase to borderline high to very high standards (similar to those humidity levels during Hong Kong/China’s display on July 18th). A humidex of 30-31 C is likely during the late-evening.

Precipitation

As mentioned above, the associated low pressure system’s warm front will be ejecting East through the day. This will cause an increase in high-level cirrus clouds just before lunch time, and more considerable cloudiness by the early-afternoon (accompanying low- to mid-level clouds). At this point, scattered light rain showers (40% probability) are favorable in the area by the early-evening hours, with chances increasing toward 11:00 p.m. (60% probability), and especially after midnight (90% probability). Isolated non-severe thunderstorms (30% probability) are also possible during the evening, though the chance of thunderstorms increases near and after midnight due to more vigorous lift associated with the frontal boundary at the time. An umbrella, or some form of head covering, may be necessary.

Wind

Winds continue to be SSE to even straight southerlies (SE during the late-morning to early-afternoon) by the late-afternoon and evening. Speeds also continue to be light but should be adequate enough to move accumulating smoke gently. Speeds of 9-12 km/h are expected, so the smoke should be, again, pushing gently clear to the right of the La Ronde audience (clear to the left for those on Notre-Dame). Some brief periods of smoke accumulation may be possible (mostly to La Ronde’s right during more active sections of the display, and mostly along low to mid-levels of the display) due to the borderline high to very high humidity (enhanced by possible further moistening from light rain showers) and light winds. Note also that if thunderstorms do occur, local wind direction could become disrupted from the overall wind pattern.

In summary, a warm and quite humid evening, with light SSE to Southerly winds and cloudy skies. Scattered light rain showers will be possible throughout the evening before becoming more widespread near and especially after midnight. Have an umbrella and/or head covering handy.

*If necessary, I will post another update by tomorrow mid-afternoon (July 25th) addressing mostly the precipitation/thunderstorm risk.

Trav.

Conditions specified above still hold largely constant. However, I am going to increase wind speeds slightly to 11-15 km/h (occasional gusts of 19-22 km/h) to account for a somewhat more robust circulation into this evening. Directional tendencies remain unchanged, so smoke accumulations should be moving reasonably quick clear to the right of the La Ronde audience. Temperatures should also be 23-24 C (21-22 C if persistent showers occur). Humidity is identical to what was specified previously.

The risk for scattered light rain showers and isolated non-severe thunderstorms (40% probability collectively) still continues for this evening, more so towards 8:30 p.m. (near sunset) and onwards, but especially by 10:30 p.m. and beyond, when more widespread (deep) convection is more favorable. The thunderstorm risk should similarly become higher until late this evening and after midnight. Distant lightning is also possible. Again, have an umbrella (or some form of head covering) handy, especially for the later evening hours.

Trav.

The risk for scattered light rain showers and isolated non-severe thunderstorms (40% probability collectively) still continues for this evening, more so towards 8:30 p.m. (near sunset) and onwards, but especially by 10:30 p.m. and beyond, when more widespread (deep) convection is more favorable. The thunderstorm risk should similarly become higher until late this evening and after midnight. Distant lightning is also possible. Again, have an umbrella (or some form of head covering) handy, especially for the later evening hours.

Well, you called it. As usual.



Bring a hat, folks.

Thanks for sharing that radar image, Duncan_S. As that band of light rain showers advanced towards the island near sunset, it began to exhibit some discontinuities, leading to patches of dry slots, but re-intensification behind it led to some very heavy rains just after midnight. Convective precipitation, in particular, is always changing in spatial coverage and intensity (often spontaneously), so it's always good to have the latest imageries when monitoring it.
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As mentioned four posts above, a potential heat wave has begun to establish itself yesterday (July 27th) across S. Ontario to S. Quebec, along with severe weather occurring late yesterday afternoon through to the mid-evening. As another area of low pressure advances, its circulation will further amplify temperatures and humidity into the day Wednesday (July 29th), easily leading to the warmest conditions of the year (so far), and this could be one of the warmest/hottest fireworks days in recent years.

Indeed, temperatures are expected to reach to as much as 33-34 C across the island of Montreal (especially the metropolitan area), and humidity is projected to be very high (mostly by the evening hours). By late-evening, temperatures may still be as warm as 28-29 C in the metropolitan area, and considering the very high humidity, a humidex of 35-36 C (38-39 C during the afternoon) is sufficient. Convective rain showers and thunderstorms (some possibly severe) are not expected until Thursday, July 30th due to a passing cold front.

Winds will likely be light at 9-12 km/h, and wind direction should be WSW throughout the day but becomes more SW by evening to SSW by late-evening. This would favor rapidly building smoke accumulations to be blowing gently to the right of the La Ronde audience (left for those on Notre-Dame), though there is a possibility that the smoke could be moving towards extreme right-hand sections of the audience (notably smoke associated with high-level shells). This will be monitored in future runs. Periods of large smoke accumulations will be possible when the display becomes more active (and at low- to mid-altitudes of the display) due to the light winds and very high atmospheric moisture, but build-up should be especially towards La Ronde’s right.

*Another update to follow later this evening (July 28th).

Trav.

What was specified in the above posting still holds mostly constant. As such, here are the dominant conditions for Wednesday, July 29th for the Montreal area:

Temperature/Humidity

Temperatures continue to be hot for the day, with a daily maximum of 33-34 C, while late-evening temperatures in the metropolitan area should still be as high as 28-29 C. Atmospheric moisture continues to be very high, so a humidex of 41-42 C is likely during the mid-afternoon and 38-39 C during the late-evening.

Precipitation

Due to strong instability, very sparse air mass showers and non-severe thunderstorms may occur during the afternoon hours but will quickly subside toward sunset. Skies should be mostly clear during the evening, with a few isolated clusters of cumulus clouds due to some lift.

Wind

Winds continue to be light during the evening, at 8-11 km/h. Directional tendencies should be SW throughout the day (with similar speeds as the evening) but should transition to more SSW by late-evening. As a result, smoke accumulations should be moving gently and mostly clear to the right of the La Ronde audience (left for those on Notre-Dame). However, smoke associated with high-level effects may sometimes be pushing towards extreme right-hand sections of the La Ronde audience. Periods of large smoke accumulation are possible due to the light winds and very high humidity (mostly during active sections of the display, and sometimes along low- to mid-levels), though mostly to La Ronde’s right.

In summary, a very warm to hot evening (one of the warmest fireworks nights in recent history), with very high humidity, light SW to eventually SSW winds, and a few isolated clusters of cumulus clouds. A real July evening on the way.

*If necessary, I will provide another update by mid-afternoon tomorrow (July 29th) concerning wind direction for the late-evening.

Trav.

A broad area of low pressure will continue to circulate warm and fairly moist air to S. Ontario to S. Quebec into this weekend (August 1st-2nd). A secondary cold front associated with this system is expected to also produce some afternoon to early-evening convective rain showers and isolated, mostly non-severe thunderstorms. Precipitation coverage should be scattered along the front, and extensive cloud coverage is likely throughout the day into the evening hours.

Temperatures will remain seasonably warm across S. Quebec on Saturday (August 1st), including here, on the island of Montreal, along with borderline moderate to high humidity throughout the day. Late-evening temperatures in the greater Montreal area should be as warm as 20-21 C (humidex of 24-25 C), and daytime highs should be 24-25 C (humidex of 28-29 C). In the case of persistent rain showers during the evening hours, temperatures should be closer to 18-19 C.

Winds are projected to be WSW throughout the day and breezy at 19-22 km/h (occasional gusts of 27-31 km/h) during the afternoon hours. By evening, directional tendencies should remain identical, but speeds become light, at 9-12 km/h. As such, smoke should be moving gently towards the La Ronde audience directly, with more concentration at right-hand and central sections of the La Ronde audience. Smoke accumulations are not expected to be overly large due to lesser humidity levels, but the display will likely appear somewhat murky. Note, however, that there is a chance that winds could become SW by the late-evening, which would allow the smoke to move towards right-hand sections of the La Ronde audience. This will have to be monitored in upcoming runs.

Another update to follow by tomorrow evening (July 31st).

Trav.

Weather conditions specified above continue to remain mostly identical to what was described above, though there are some minor modifications. As such, here are the dominant conditions for the Montreal area for Saturday, August 1st.

Temperature/Humidity

Temperatures continue to be warm during the afternoon hours, with maximum highs of 25-26 C. By late-evening, in the metropolitan area, temperatures should decline to 21-22 C. Humidity is moderate through the day, generating a mild humidex of 27-28 C, and by late-evening, humidity should increase to borderline moderate to high levels, inducing a humidex of 24-25 C.

Precipitation

An upper-level trough has settled over S. Ontario to S. Quebec and will be the focus for (deep) convection into the afternoon to early-evening hours. Scattered thunderstorms/convective rain showers (40% probability) will likely develop into the afternoon due to enhanced instability supplied by the trough. Given periods for solar heating and strengthening wind shear profiles, a few organized multi-cell thunderstorms may attain severe limits. Because thunderstorms and rain showers are largely driven by instability, convection should gradually diminish towards sunset and beyond (8:30 p.m. and onwards). Skies should be partly cloudy by late-evening (low-, mid-, and high-level clouds).

Wind

Winds continue to be breezy through most of the day, and from the WSW. Speeds during the afternoon are sustained at 19-23 km/h, with gusts of 28-33 km/h. By evening, however, winds become light (9-12 km/h) and should shift to more SW tendencies. As a result, smoke accumulations should be pushing at a reasonable speed towards right-hand sections of the La Ronde audience, notably smoke associated with high-level activity.

In summary, a warm evening, with temperatures in the lower 20s C, borderline moderate to high humidity, light SW winds, and partly cloudy skies.

*If necessary, another update will be provided by mid-afternoon today (August 1st) that will address largely wind velocity and thunderstorms/rain showers.

Trav.

Wind tendencies remain virtually identical to what was specified previously. However, I am going to increase wind speeds to 13-17 km/h, given a continued fairly strong circulation. Directional tendencies should remain mostly as WSW through to early this evening and gradually shift to the SW near display time and onwards. This means smoke should be moving relatively quickly towards right-hand sections (sometimes central) of the La Ronde audience, especially smoke associated with high-level activity.

Thunderstorms/rain showers should gradually subside near sunset and beyond (risk should run up to 8:30-9:00 p.m.).

And so concludes the weather reports for 2015!

Trav.