I thought that it would now be appropriate to introduce this thread, as we are just a little over two weeks until the first display of the 2017 season.

I will include here weather reports that outline temperature patterns, moisture/humidity concentration, precipitation (rainfall), and wind velocity, for each of the fireworks displays. Additional information will be provided in situations where thunderstorms become favorable (notably strong to severe thunderstorms), or if wind speeds are expected to be either too strong or too weak. Some preliminary details will be supplied typically two evenings prior to each display, with a finalized report on the day before a scheduled display, or on the morning of the display date. If necessary, additional postings will follow on the day of the display, especially if/when thunderstorms are possible, or if wind speed/direction is expected to be unfavorable.

Feel free to also post any weather information that you would like to share, as you are more than welcome to do so - local observations can be very useful, so please share your reports!

For those interested, my Spring-Summer 2017 outlook can be found here (the document was originally released on March 17th – St-Patrick’s Day):

https://www.facebook.com/notes/travis-moore/winter-2016-2017-and-a-loo k-ahead-to-spring-summer-2017/10154952251701346/

In summary, I am projecting a late-Spring and Summer that is warm to very warm across S. Ontario to S. Quebec, but not quite as warm as what was observed in 2016. This includes slightly fewer days with maximum temperatures of 30.0+ C (for the island of Montreal, specifically, I am projecting 12-15 such days, with two to perhaps three heat waves possible). That said, this should be more of a humid season that may come close to 2015's overall humidity level over the May-September period. I also anticipate a stormy season, so more thunderstorms than normal are possible this year across these regions, though fewer severe thunderstorms than in 2016. This may also drive an above normal rainfall pattern this Summer, especially in areas where thunderstorms repeatedly influence.

Again, I hope for ideal weather conditions for all displays this year, as well as their respective setup periods (at least in large part).

Trav.

A very buoyant air mass is expected to govern Canada Day across S. Ontario to extreme S./SW Quebec as an area of low pressure brings with it very warm and very moist air. At the same time, a cold front and mostly series of shortwave troughs will be moving East/NE and will the focus for thunderstorm/convective rainfall development through the day. While it is currently unclear how these lifting features will affect the evening period, lift does appear greatest during the pre-dawn to late-afternoon time frame, likely causing at least scattered thunderstorm coverage during that time. Stronger thunderstorms will also be possible in this environment during the day, although with restricted solar heating and weak cooling rates aloft, coverage of these storms should be isolated at best. Latest model guidance suggests a zone of steeper cooling rates into the evening to early-overnight period, which could encourage sustained thunderstorm intensity and coverage (provided enough lift, which needs to be monitored), though convective coverage should be reduced from what it is in the afternoon. Latest indications would suggest that thunderstorms and convective rains will be mostly focused in New York state for the evening because lift is maximized there, leaving mostly cloudy skies for extreme S./SW Quebec.

Early-evening temperatures in the Greater Montreal area should be as much as 25-26 C and dropping to 22-23 C by mid-evening (except 20-21 C, if there is persistent light rain showers). With borderline high to very high humidity, a humidex of 29-30 C is favorable for the mid-evening. Sufficient lift will induce mostly cloudy skies (large clusters of cumulus) with clear breaks. Latest analyses suggest winds to begin with a SE component early in the day, and then transition to the SW by early-evening in extreme S. Quebec, including the island of Montreal. Wind speeds are gusty, from the SE for the afternoon, with sustained speeds and gusts of 23-31 km/h and 43-52 km/h, respectively. Near-saturated surface air and high humidity will favorably induce rapidly accumulating smoke (especially along low- to mid-level and with any smoke-rich products), but with fast wind speeds, the smoke should be moving quickly, and towards right-hand sections (partially central sections) of the La Ronde audience. Wind gusts, however, will need to be followed, as they may be near or slightly above the 40 km/h threshold. Other model solutions show considerably lower wind speeds because of a different trajectory in the area of low pressure.

Another update will follow by tomorrow evening (June 30th), or by pre-dawn July 1st, especially to address wind speed/direction and thunderstorm potential for the evening in this region.

Trav.

Trav, thank you for this detailed report, I am sure that many of us will look at the updates. We'll apparently have to deal with active weather conditions for this opening show, I am especially concerned with the wind. Hopefully, it is going to slow down during the evening.

Fred

The information presented in my previous update is mostly applicable for today (July 1st-Canada Day). As such, here are the most likely conditions to be present for the day for the greater Montreal area:

Your Canada Day forecast

Temperature/Humidity

With ubiquitous cloud coverage, maximum temperatures in extreme S./SW Quebec should reach 24-25 C, but this maximum value is mostly confined to later in the afternoon period, near sunset, when some solar heating should break through the cloud deck. Temperatures should drop slightly to 22-23 C by the mid-evening period (except 20-21 C, if some rainfall occurs). Humidity will also remain very high throughout the day and persist through the evening period, generating a humidex of 29-30 C for the evening period.

Precipitation

As mentioned in the previous posting, a cold front and shortwave trough will eject East through the day and will be the focus for (deep) convective development. Although persistent cloud coverage should significantly limit instability, the degree of lift with these features, coupled with rich surface moisture, will be conducive to thunderstorm development. Lift associated with these features still appears greatest during the mid-afternoon period. However, the lack of instability will likely keep thunderstorm coverage isolated to scattered, at best, through the day and into the evening period. Instability, though, is shown to be increasing slightly into the evening, likely due to the aforementioned cold pool of air aloft moving into the region by about sunset, along with more broken skies.

The convective/thunderstorm threat should begin to diminish more substantially by the late-evening, towards 11:00 p.m. and onward. Coverage becomes more isolated by about 9:30 p.m. (30% probability), with most of the thunderstorms/rainfall farther East/NE/NNE, but the thunderstorm/convective rainfall threat should continue in and around the island through the evening, but especially the early-evening, when colder air aloft could sustain/encourage thunderstorm development. The primary threat with thunderstorms in this environment will be torrential rains and locally damaging winds. Intense lightning will also be possible, particularly up to the early-evening.

Wind

Some uncertainty as to wind velocity for the evening period (especially since thunderstorms are still possible), but wind speeds are shown to still be gusty through the mid-afternoon (mostly from the 4:00-6:00 p.m. time frame), from the ESE to eventually SE. Speeds, though, should decrease to lighter standards (13-17 km/h) by about sunset and onward before increasing again by later overnight. Directional tendencies are still expected to be SW (with a slight SSW component) for the evening, so the rapidly accumulating smoke should be moving reasonably quickly to the right of the La Ronde audience. However, extreme right-hand sections could still encounter smoke. Due to very high humidity and near-saturated surface air, periods of smoke accumulation will be favorable during times of higher activity, especially along low- to mid-levels, and if smoke-rich products are extensively used. Note that if thunderstorms are in the area, or close by, the local wind flow will be temporarily disrupted.

Other updates will follow into this afternoon to further assess the thunderstorm risk for the evening period, as well as wind speed and direction. If not, then the information presented here would still be applicable.

And no problem for the reports, Fred!

Trav.

It seems to be less rainy and less windy than expected. Chances for improvement with tonight forecast?

Fred

It seems to be less rainy and less windy than expected. Chances for improvement with tonight forecast?

Indeed, the sun is even coming out a bit! The radar looks hopeful, for now, too!

Paul

No real changes to the information presented in the previous posting. However, instead of wind speeds increasing during the mid-afternoon period, as suggested above (4:00-6:00 p.m.), they should more favorably increase (from the SSW to SW) closer towards midnight. Speeds of 11-14 km/h are favorable for the mid-evening (including display time). Periods of smoke accumulation are still favorable with the somewhat light wind speeds (directional tendencies are the same).

The emergence of more breaks in the cloud deck for solar heating at this point is also consistent with the details in the "Temperature/Humidity" section, although this, in addition to cooler temperatures aloft overspreading the region shortly, will likely encourage thunderstorm development over the coming hours. Thunderstorm coverage, though, should remain scattered, at best, and still become more isolated by about 9:30 p.m., with partly cloudy skies. Severe thunderstorm watches are currently enforced for sections of E. Ontario and may briefly spread farther East if thunderstorm coverage increases. The number of storms should decrease beyond the early-evening, but they will exist in an isolated distribution (mostly focused North/NNE of the island).

Trav.

The reason for the sudden transition to a Westerly wind direction towards the final few minutes of the display was that rainfall was moving into the area at the time, as you specified. Due to instability present throughout most of the evening, isolated convective rainfall was still very much possible. That particular rainfall itself was associated with a small, weakening thunderstorm cluster previously forming to the North, and occasional lightning was observed in that direction by not long after 9:00 p.m.

Thank you for these specifications, which I paste from the Opening review thread. I believed that some lighting appeared north-east from La Ronde around that time, but I saw it just once, so I was not sure whether it actually happened or not.

Fred

A series of shortwave troughs behind today’s (July 7th) surface cold front will be the focus for convective rain showers and mostly non-severe thunderstorms for Saturday, July 8th, mostly during the morning to mid-afternoon period. During the morning hours, however, there appears to be a narrow window of opportunity for a few stronger thunderstorms to develop due to instability being maximized at the time. By the mid- to especially late-afternoon, convective coverage should decrease and become sparse as the shortwaves eject East, but some instability for brief convective rain showers will persist up to about sunset. More breaks in the cloud deck for sunlight should emerge by the early-afternoon, and skies should be mostly clear by late-evening (a few large patches of cumulus and cirrus).

For the Greater Montreal area, maximum temperatures are expected to be about 22-23 C, with high (not very high) humidity. Humidity should become moderate in time for the late-evening (including display time), and temperatures should fall to 18-19 C (humidex of 21-22 C.
Winds will also be somewhat light (12-16 km/h, except breezier during the mid-afternoon, at 17-21 km/h) through the day, first from the NNE during the morning, and then switching to WSW tendencies by the early-afternoon, persisting through to the evening. By late-evening, a slight shift towards the SW is possible, but the predominant directional tendencies are mostly WSW into the evening period. As such, the smoke should be moving at a reasonable pace, though some smoke accumulation will be possible during more active sections of the display due to moderate humidity. At this point, the wind should be directing the smoke towards the La Ronde audience, with a focus towards right-hand and central sections. This will often times cause the display to appear murky, especially during times of larger activity. If a SW component becomes more predominant in later data, then more smoke concentration to right-hand sections of the audience will be favored.

Another update to follow later today or pre-dawn July 8th to finalize conditions, especially to address wind direction.

*Fred – thank you for sharing your observations concerning July 1st’s lightning occurrences – indeed, lightning detection data is consistent with what you had seen at the time.

Trav.

Details specified in the above posting still largely remain constant. As such, here are the predominant weather conditions for the greater Montreal area for Saturday, July 8th.

Temperature/Humidity

Temperatures are expected to rise to 22-23 C by mid-afternoon. If periods of rain are persistent, then the maximum temperature should be about 19 C. By the late-evening period, including display time, a value of 18-19 C is largely applicable. Humidity will remain high (not very high) through the day and fall to borderline moderate-high standards by the mid-evening, creating a slightly humidex of 21-22 C.

Precipitation

As mentioned in the above posting, a series of shortwave troughs will move East/NE through mostly the first half of the day will be the focus for ubiquitous cloud coverage, convective rain showers and isolated non-severe thunderstorm clusters. A few more organized thunderstorms, however, appear possible during the morning to early-afternoon period, but convective coverage should become sparser by the mid-afternoon. Some instability will persist in the area, however, until about sunset, so isolated convective rain showers will exist up to roughly that point (30% probability), leaving partly cloudy skies (with large clear breaks) by the mid- to late-evening (patches of large cumulus and cirrus). More periods of sunlight should emerge by the mid-afternoon.

Wind

Winds continue to be mostly in the form of West-Southwesterlies (WSW) by the late-afternoon period (more NNW to NW during the early- to mid-afternoon). Speeds of 12-16 km/h are favored throughout the day, including the evening. As such, the smoke (and some pyrotechnic debris) should still be moving towards the La Ronde audience, mostly focused on central and right-hand sections. With borderline moderate-high humidity, some periods of smoke accumulation will be possible during times of higher activity, but the smoke should be usually moving at a reasonable pace. The display could often appear murky for those at La Ronde.

If necessary, another update will follow by the mid-afternoon today (July 8th) for wind direction.

Trav.

According to the projection shown by the radar of MeteoMedia, a line of rain/heavy rain would move through La Ronde area around 8:00-8:30pm. I hope that it is going to change for the best.

Fred

Hi Fred,

It is quite possible, as isolated convective rainfall should continue up to about sunset - potentially a little after.

Simulated radar, while useful, can often have difficulty in projecting the character and distribution of convection-related precipitation, mostly because of the scale at which convection occurs, as well as its complexity. As a result, these simulations are often subject to change for any specific time frame. The assumption of continued convective rainfall development over the next few hours, though, is consistent with the dynamics in place, just that the actual location of the rainfall is uncertain.

Also, I would reduce wind speeds slightly this evening to 8-11 km/h (same directional tendency), so periods of smoke accumulation are still quite possible (mostly during times of larger activity and if smoke-rich products are extensively used), especially with continued borderline moderate-high humidity. The smoke should be moving somewhat gently.

Trav.

An area of high pressure is expected to drift East/SE through the day Saturday (July 15th) and lead to mostly fair weather conditions. By contrast, a weak low pressure system will more favorably occupy the early-morning hours of the day and lead to more extensive cloud coverage and a sparsely distributed convective rain showers, but more breaks in the cloud deck will emerge by late-morning and onward.

Maximum temperatures for the greater Montreal area should be 25-26 C, with high (not very high) humidity. This moisture level should generate a humidex of 31-32 C. By the late-evening period, including display time, temperatures should fall to 21-22 C, but with continued high humidity, a humidex of 26-27 C is likely. Thus, this should be a warmer and a little more humid evening than what was observed for the Italian display. Skies should be mostly clear, though some weak lift in the area should generate a few isolated clusters of cumulus.

Winds are projected to be largely light for the day, beginning as NNE for the morning period and transitioning to WSW for the early-afternoon. SW tendencies then develop by the late-afternoon to early-evening period, and then potentially SSW by late-evening (this will have to be monitored). Speeds of 12-16 km/h are likely during the afternoon period but 9-12 km/h for the evening, especially late-evening. As such, smoke should be moving fairly gently to the right of the La Ronde audience, although right-hand sections may receive some smoke, typically smoke from high-level shells. Due to continued high humidity, a few periods of smoke accumulation are possible, but mostly along low- to mid-levels, and mostly towards right-hand sections of the display, notably during more active sections.

Another update to follow later tomorrow evening, or during the pre-dawn of July 15th.

Trav.

Information presented in the above posting are still largely applicable. Therefore, here are the weather conditions projected for the greater Montreal area for Saturday, July 15th:

Temperature/Humidity

A SW flow will be strengthening through the day, and coupled with more periods for solar heating by the late-morning to early-afternoon, maximum temperatures should reach 26-27 C, with high humidity (at times borderline high-very high). Thus, a humidex of 33-34 C is still favored. By the late-evening, including display time, temperatures drop to 22-23 C, with continued high humidity. This will make it feel like 29 C.

Precipitation

Due to the aforementioned area of weak low pressure, some early-day convection will be possible during the morning period, with extensive cloud coverage and sparsely distributed light rain showers. By late-morning (near noon), more breaks in the cloud deck should emerge and allow for the sun to break through. By the evening, large clear breaks should continue, accompanied by clusters of low-level cumulus, alto-cumulus, as well as cirrus. The thunderstorm/convective rain shower risk will resume by Sunday, July 16th.

Wind

Winds are still expected to be light through most of the day, notably the morning period. By the early-afternoon, a SW flow should develop and continue into the evening period. Speeds of 8-11 km/h are expected during the morning hours (from the North to NNW) but increase to 12-16 km/h (so, slightly breezy) for the late-afternoon to evening (from the SW). As such, the smoke should be moving mostly to the right of the La Ronde audience, although extreme right-hand sections could receive accumulations (mostly overhead smoke from high-level shells due to a more WSW component at those altitudes). Due to high humidity, some periods of smoke accumulation will be possible, mostly during times of higher activity, and typically focused towards right-hand sections of the display along low- to mid-level. That said, the smoke should be moving at a reasonable pace, which is important at these moisture levels.

If it becomes necessary, another update will follow by the mid-afternoon of today (July 15th), mostly to address wind direction, wind speed and cloud coverage extent. If not, then what is stated in this posting will still apply.

Trav.

A developing circulation of very warm and humid air will affect S. Ontario to S. Quebec by July 18th and persist through to most of July 21st. As such, Wednesday, July 19th will be a part of this tropical-like pattern, with very warm to locally hot temperatures and borderline high to very high humidity. At the same time, however, a weak cold front and accompanying shortwave trough will be advancing towards E. Ontario to extreme S./SW Quebec later in the day and could generate scattered thunderstorms/convective rainfall during the late-afternoon to early-overnight period.

For the greater Montreal area, maximum temperatures of 28-29 C are expected, with mostly borderline high to very high humidity, creating a humidex of 35-36 C. Temperatures decline to 23-24 C by late-evening, but with continued high humidity, a humidex of 29-30 C is likely. If rainfall occurs, then temperatures will more favorably drop to 19-20 C. Skies should be partly cloudy during the evening, mostly consisting of large clusters of vertically developed cumulus.

Winds are typically from the SW during the day (except SSW for the morning), which is likely to persist into the evening. The overall flow resembles that of the Polish display, so the smoke should be moving reasonably quickly towards mostly right-hand sections of the La Ronde audience. However, note that the overhead smoke from higher-level shells could be moving more directly towards right-hand sections of the audience and partially central sections. Also note that if thunderstorms/convective rainfall are in the area, the wind would more likely shift towards the audience (mostly left-hand sections). Speeds of 11-14 km/h are likely for the evening period (including display time). Smoke accumulations should be mostly focused to the right-hand sections of the display, along low- to mid-level. Breezier SW winds (19-24 km/h – occasional gusts of 31-34 km/h) should be present for the mid-afternoon.

The thunderstorm risk will have to be monitored. Although solar heating should be ample, along with rich surface moisture, the degree of lift is not entirely clear, casting uncertainty in the overall convective coverage – this is especially the case for the evening period. However, latest data analysis suggests dynamics supportive of scattered thunderstorm development by the mid- to late-afternoon, with some thunderstorm sustenance beyond sunset. Given this, I would, at this point, assign a 40% probability of precipitation for the mid-afternoon to early-overnight time frame for this general area (greatest likelihoods to the NW of the island). Thunderstorms should typically be non-severe, but a few isolated stronger thunderstorms will exist.

Another update to follow late tomorrow evening (July 18th) to pre-dawn July 19th, mostly to address the thunderstorm risk.

Trav.