Severe thunderstorm watch in effect for Montreal

By now you know the drill in Montreal. We have a very unstable, warm and humid airmass in place, with a cold front arriving this evening. There is a risk for very strong thunderstorms today, a few capable of flooding downpours, strong winds, dangerous lightning and hail. Be weather aware today and  pay close attention to any weather warnings that may be issued. The best chance for thunderstorms will be very late this afternoon into the early evening in Montreal.

You know the drill by now in Montreal with this July producing countless thunderstorm days. A severe thunderstorm watch has been issued for southern Quebec for Friday afternoon into the evening hours. Thursday's heavy rain has left behind a very warm and humid airmass across the region. The low clouds and fog are in the process of burring off Friday morning, leaving behind a very muggy, warm and unstable airmass across our area. Temperatures will rise close to 30C (86F) this afternoon under partly cloudy, humid and hazy skies.

A rather strong cold front will arrive from Ontario this evening, igniting some strong to severe thunderstorms in the Montreal region. The storms will be scattered in nature, so not everyone will see one today. If they do occur, some will be capable of very heavy rainfall, gusty winds and hail. There is even the risk for rotation with some of the cells, so an isolated tornado can't be ruled out. The strongest storms will be from Montreal south and east of the city to the US border. Most of the activity will be in the late afternoon into the evening hours, before moving south into New York State by midnight and weakening overnight.

Saturday will cloudy and much cooler, with scattered showers and temperatures in the low to middle 20s.

We are closing in on the rainfall record for the wettest July in Montreal. As of Friday morning, Trudeau Airport had measured 176.2mm (6.93 inches) of rain for July. The all time record was 182.6mm (7.18 inches) set way back in 1980. We could break the record today, if storms occur close to the airport in Dorval. Many parts of the city have already received well over 200mm (8 inches) of rain this month.

Another round of heavy rain forecast for southern Quebec

Another round of heavy rain is expected across the Montreal region during the morning commute on Friday. While excessive amounts of rain are possible, we are not expecting any severe weather at this time.

Environment Canada has posted a special weather statement for southern Quebec including metro Montreal, for the overnight period into Friday morning. Another round of heavy rain along with embedded thunderstorms is expected to drop 30 to 50mm (1-2 inches) of rain across the region, with more possible in the most persistent storms. Some flash flooding is likely once again.

Thursday will be the best day of the week, expect mostly sunny skies, with a warm high of 28C (83F). Clouds will be on the increase this evening, as low pressure over Michigan moves northeast to lie near Cornwall, Ontario early Friday morning, and Quebec City by late in the day. Thunderstorms will develop during the pre-dawn hours, moving through Montreal during the morning commute. At this time I am not expecting any severe weather (strong winds, hail), just heavy rain. Some flash flooding is possible, along with ponding of water on area roadways. There will be a break in the rain mid-morning, with more precipitation developing during the afternoon hours.

Isolated thunderstorms during the afternoon will bring the threat for more heavy rain. Showers will persist into Saturday before skies begin to clear out late in the day. Temperatures will be cooler on Friday along with the clouds and precipitation, with a high of 22C (72F) expected. The highs over the weekend will be around 26C (79F), with lows of 18C (65F).

Waterways across all of southern Quebec are running high at this time, and the ground is saturated in many locations. Lac Memphremagog in the Eastern Townships, southward into northeast Vermont was under a flood warning on Wednesday, responding to the copious amounts of rain that has fallen in that region over the last week. 

July has been excessively wet across our all of southern Quebec, northern New York and New England. Montreal, Trudeau Airport has measured 106.8mm of rain through Wednesday. Other locations across the metro region have received even more, well in excess of 150mm. Meanwhile, 225.4mm has already fallen in Sherbrooke since July 1st, with 202.6mm in Quebec City, 141mm in Trois-Rivieres and 108mm in Vaudreuil-Dorion.

There is some good news in the forecast, the blocking pattern that has kept us so wet this month is showing some signs of relaxing it's grip next week. While the week will not be entirely dry, there will be a decent stretch of sunny, warm weather with precipitation finally at or slightly below normal for the week.

First two Quebec tornadoes of 2023

One final note, the Northern Tornadoes Project from Western University in Ontario has concluded its investigation into last Thursday's severe weather.  They determined that 6 tornadoes occurred along with 5 significant wind downbursts during the severe weather outbreak July 13 across Ontario and Quebec. In Quebec, two tornadoes occurred, both rated as EF-0, with estimated winds of 130km/h. One was reported near Saint-Thomas with second observed close to Mirabel Airport. Other storms produced hail and flash flooding in Montreal and Laval along with widespread tree damage and power outages.

Flash flooding - power outages sweep Montreal region

One of at least a dozen underpasses that flooded in Montreal after severe thunderstorms on Thursday afternoon. The flooding created traffic gridlock in the central part of the city, with the afternoon commute lasting late into the evening for many. (Photo Courtesy Ragini Patel)

I have been a weather enthusiast since just shortly after I could walk, and days like yesterday still amaze me as to how powerful mother nature can be. It was an extremely active day across eastern Ontario and southern Quebec, with several waves of severe thunderstorms. 

A supercell thunderstorm, one of several observed on Thursday across Quebec and Ontario, advancing on downtown Montreal during the late afternoon hours. (Photo Courtesy George Michel Boutros)

Environment Canada posted rare tornado watches for most of the region, and the storms delivered just after the noon hour, first in the Ottawa Valley, and then unfortunately, during the afternoon commute in Montreal.

Several supercell storms showed rotation, with a confirmed tornado touching down in Barrhaven, southwest of downtown Ottawa. The tornado, yet to be rated, produced significant damage to homes and cars, with at least one injury.

As the storms pressed east, more rotation was observed along the Ottawa River, with a funnel cloud reported in Vaudreuil-Dorion. There was also a confirmed tornado in Mirabel, north of Montreal. This prompted tornado warnings for the entire Island of Montreal. Wind damage was reported across Ile Perrot and the West Island, with several trees and branches down. Wind gusts to 111km/h (68.9 mph) was observed at Trudeau Airport, along with 2cm hail. Dozens of tress were toppled, many on the West Island along the Saint Lawrence River. Power outages mounted, with Hydro-Quebec already having trouble with transmission lines form the north due to forest fires. In all, nearly 500,000 were left without power in the province. This morning that number is down to 216,000 across Qubec, with 86,000 on the Island of Montreal. 

The Barrhaven, Ontario tornado. (Photo via Twitter@TheTaoOvMan)

Flash Flooding

The big problem for most of Montreal turned out to be water not wind. Torrential rain fell with the storms, this time over the central portion of the city. I measured officially 20.4mm in only a few minutes at my home on Ile Perrot, but the storms moved over my location quickly. Such was not the case in Montreal, where 38.2mm fell at the airport, with reports of up to 100mm in several neigbourhoods just to the east of the airport and towards the downtown core. 

At least a dozen underpasses flooded in the usually locations. Oddly enough on just about the 36th anniversary of the Decarie Flood of 1987, the Expressway once again flooded Thursday afternoon. It created traffic gridlock in the central part of the city. Other areas flooded included Cote-des-Neiges, Cote-St-Luc and Lachine, where several cars were inundated up to their roofs.

The severe weather pushed east of the city, with more rotation and funnel clouds observed around Trois-Rivieres.

Friday will be the calm after the storm, with lower humidity and a pleasant high of 26C (79F) under bright sunshine. A rare gem indeed, in what is turning out to be a very odd weather year across our region.

The calm after the storm, as the setting sun reflects off the debris clouds behind the cold front late Thursday on Ile Perrot. (Valley Weather Photo)

Elevated risk for strong thunderstorms in Montreal

Strong to severe thunderstorms are likely Thursday afternoon across the region, with another round of flooding possible in parts of southern Quebec, New York and Vermont. The main risk in metro Montreal will be gusty winds, small hail and heavy downpours. The greatest risk will be between 4-7pm for the city. Isolated tornadoes are possible across the region today.

Severe Thunderstorm Watch posted for southern Quebec

Flood Watch for New York and Vermont

There is an elevated risk of severe thunderstorms across southern Quebec and eastern Ontario during the afternoon and early evening hours today. Storms will develop in eastern Ontario and the Ottawa Valley around 2pm, arriving in Montreal during the afternoon commute. Heavy rain, frequent lightning, strong winds and isolated tornadoes are possible. This system has a history of strong thunderstorms across southern Ontario, Michigan and in the Chicago area last evening.

The last thing the region needs is more rain at this time, unfortunately that is exactly what is in the forecast. A warm front is in the process of lifting north of the St. Lawrence Valley Thursday morning, which will result in some brief showers and isolated thunderstorms for the next hour or so. After that Montreal will be in the warm sector for a few hours before strong low pressure and a trailing cold front arrive from the west.

Look for strong thunderstorms during the afternoon hours, producing 15-25mm of rain in some spots. This is not what the flood ravaged regions of the Townships Quebec City and Vermont need right now.

The threat for severe weather will diminish after sunset this evening. Look for muggy weather today and throughout the upcoming weekend. The high today in Montreal will be 27C (81F), with humidex reading well into the 30s.

Major flooding stabilizes in Quebec/Vermont - but more rainy humid weather expected

Water surges along the Montmorency River near the town of Saint-Brigette-de-Laval northeast of Quebec City. Flooding has forced numerous families from their homes in parts of southern Quebec after torrential rain fell Monday and Tuesday. (Photo via Facebook)

The historic flooding across Vermont and parts of southeastern Quebec is stabilizing on Wednesday as rivers fall near or below flood stage. The severe flooding was the result of a months worth of rain in leas than 48 hours across the region. Montreal remained on the western edge of the heaviest precipitation, and still managed 25mm to locally 50mm of rainfall. Across the Townships, Quebec City, the Charlevoix region and into Vermont and New York, between 100 and 200mm of rain was reported.

In Quebec, dozens of families have been evacuated along the Saint-Francois River in Sherbrooke, with several homes flooded. A local state of emergency is in effect in Sainte-Brigitte-de-Laval after the Montmorency River surged through parts of the community, washing out roads and flooding homes.

The Lamoille and Gihon Rivers combined to produce catastrophic flooding in Johnson, Vermont. Between 100-200mm of rain fell in 48 hours across the state producing severe flooding. All 14 counties in the state have received a federal disaster declaration. The water is receding slowly on Wednesday but sadly more rain is in the forecast. (Reddit Photo via Twitter)

South of the border, the entire state of Vermont has been declared a federal disaster area. Several agencies including FEMA are on the ground Wednesday assessing the damage caused by major flooding. Communities along the spine of the Green Mountains were the hardest hit, with the Town of Ludlow basically cut off from the rest of the state. Damage is severe, with dozens of roads in the state damaged or impassable. Every dwelling in downtown Montpelier, the state capital, sustained water damage after the Winooski River left its banks. Images are heartbreaking, showing the worst flooding since tropical storm Irene in 2011.

The good news is that outside of a few isolated showers on Wednesday, we actually have a relatively dry day ongoing. Temperatures and humidity levels will be more comfortable for the clean-up effort to begin. Unfortunately it will not last.

The same stubborn upper level low over Hudson Bay will continue to control the weather into next week, with fronts pinwheeling into the region. A warm front Thursday will generate more showers and thunderstorms, followed by the arrival of a cold front late in the day. Showers and thunderstorms will persist into Friday across the entire region. The temperature and humidity will also be on the rise making the outdoors rather uncomfortable into the weekend. More showers and storms are likely both Saturday and Sunday.

As far as new rainfall amounts are concerned, between 15-25mm is very possible in the most persistent thunderstorms by late Friday. Some areas in hard-hit central and southern Vermont may have as much as 50mm (2 inches) by Friday night. Keep in mind the ground is beyond saturated across most of the region (excluding Montreal) and any rain will cause sharp rises in waterways as well as potential flash flooding. Also with all the flood water flowing eventually into Lake Champlain, the lake is expected to rise by as much as 30-45cm (1 to 1.5 feet). This will also help to increase levels and flows in the Richelieu Valley.

Rainfall warning for metro Montreal

The storm system moving northward into our region Monday, has a history of severe flash flooding. Rainfall warnings are in effect for southern Quebec. Above, rushing flood waters inundate a parking lot in Orange County, New York on Sunday afternoon. (New York State Police Photo)

A slow moving saturated weather system is moving northward along the eastern seaboard on Monday, spreading more heavy rain and tropical moisture northward into New England and Quebec.

Environment Canada has expanded the heavy rainfall warnings westward to now include the City of Montreal. Look for rain, heavy at times to develop later this morning, accompanied by occasional thunderstorms. Amounts may exceed 50mm (2 inches) over the next 24 hours, with the heaviest rainfall expected over eastern and southeastern regions. The rain should taper off Tuesday morning, but the rest of the week will remain warm and humid with more thunderstorms.

Major flooding is occurring across New York and Vermont. The photo above was taken in Canandaigua, New York on Sunday. (Canandaigua Fire Department Photo)

So far around 5-10mm has fallen in southern Quebec, but radar is showing heavy rain just south of the international border, moving northward. I believe if any flooding were to occur in southern Quebec, it would be southeast of Montreal, in the Townships and Beauce. However, we will have to see where the axis of heaviest precipitation lines up later this afternoon and evening.

On Sunday, the storm system produced devastating flash flooding in the Hudson Valley of New York, spreading northward into southern Vermont. Radar estimates of up to 300mm have been reported in New York, described as a 1-in-1000 year flood for places such as West Point and Rockland. More heavy rain is falling today in Vermont, with strong wording from the National Weather Service about the potential impacts from flooding. Numerous water rescues have already been carried out. So far one fatality has been reported in New York State. In Vermont, between 25 and 100mm of rain has already fallen, with more on the way. Vermont Gov. Phil Scott has declared a state of emergency.

There is widespread damage and roads washed out in many places. Keep this in mind if your travels take you south into New York or New England.

Major flood event unfolding over the next 24-48 hours across portions of our region

Torrential rain and thunderstorms are likely to produce major flooding over the next 48 hours across southeastern Quebec, New York and New England.

Serious language is being used by several forecasters regarding heavy rain and the potential for dangerous flooding across a large portion of southeastern Quebec and northern New York and New England over the next 48 hours. If you live in a flood prone area pay close attention to weather conditions and additional warnings.

Heavy rainfall warnings are now in effect for a large portion of southern Quebec, just east and southeast of the metro Montreal region, including parts of the South Shore, the Townships and Quebec City. At this time, 25 to 50mm (1-2 inches) of rain is forecast for Montreal, with up to 100mm (4 inches) or more southeast of the city and across Vermont and northern New York. Flash flood watches and warnings are numerous across the northeastern US and New England. Isolated amounts may approach 200mm (8 inches).

Strong wording from the National Weather Service in Burlington, Vermont, comparing this event to that of Hurricane Irene back in 2011. Major flooding is anticipated, extending into southeastern Quebec. (NOAA/NWS)

Deep tropical moisture is moving northward into very unstable, humid air. The circulation along a warm front will draw in copious amounts of moisture from the Atlantic Ocean into our region. Rounds of heavy rain and thunderstorms are forecast to develop tonight and persist into Tuesday morning across the entire region. The rain will be torrential at times, with some locations along the US border and in the Champlain Valley receiving up to 50mm in less than an hour. The ground is already saturated in those locations, so any additional rainfall will simply runoff into local waterways producing major flooding.

Flash flooding has already been reported in southern New York and across northeast Pennsylvania on Sunday.

The National Weather Service in Burlington, Vermont is comparing the rain potential to that of Hurricane Irene back in 2011 that devastated parts of Vermont. They are calling this potentially a 100 year flood event for Vermont and portions of New York. The same wording is now be extended northward into parts of southern Quebec, especially the Eastern Townships.

Unsettled, humid weather to persist into next week for Montreal

A towering thunderstorm developing in the tropical airmass across the West Island of Montreal during Thursday afternoon. (ValleyWeather Photo)

A heat warning remains in effect for metro Montreal through Saturday. The combination of warm temperatures and high humidity will make it rather uncomfortable for outdoor activities.

A weak cold front is in the process of moving across southern Quebec early Friday afternoon. The front is expected to produce some widely scattered showers and thunderstorms, with the bulk of the activity occurring south and east of the city. The front will wash out over the next 24 hours, leaving us in the same warm and humid airmass well into next week.

Several rounds of showers and possible thunderstorms are forecast right through Tuesday. Most of the time the weather will be dry, but when the storms do occur, they have the potential to produce torrential rain locally, with the risk for flooding.

A flood watch is in effect for northeast New York and Vermont Friday, where flooding has already occurred this week. Conditions have been fairly dry in the Montreal region, with only a few millimetres falling at my home on Ile Perrot this week. Other parts of southern Quebec, New York and New England have reported much higher amounts, mainly in areas that have received persistent thunderstorm activity.

Thursday was suffocating, with a high of 32.5C (90F) in Montreal, with humidex readings close to 40C. Montreal was actually one of the "cooler" locations, with many spots reaching into the middle 30s. The temperature remained warm overnight in the low to middle 20s. The heat prompted a record consumption of power across Quebec. During the afternoon hours, at the peak of daytime heating, a high tension line from Laval to the West Island of Montreal failed, plunging over 200,000 Hydro-Quebec customers into the dark and without air conditioning on one of the warmest days of the year. Traffic lights were out and some intersections became chaotic during the afternoon commute. Most of the power was restored by 5pm. 

Temperatures this weekend will be slightly cooler, in the upper 20s as a result of abundant cloud cover, but the muggy weather will persist.

Warm and humid weather week ahead for southern Quebec

Stationary thunderstorms over northwestern Clinton County, New York, along the Quebec border, produced flash flooding on Saturday night into Sunday. Up to 200mm of rain is estimated to have fallen in just a few hours. Above, the Great Chazy River flooded the Blue Haven Campground in Ellenburg Depot, NY, forcing evacuations. (Photo courtesy Tammy Arbour)

The coming week will be very warm and humid in Montreal.

Another round of scattered showers and thunderstorms is possible on Monday and Tuesday, with southern Quebec remaining entrenched in a warm, humid and unstable airmass. Temperatures will be warm to even hot all week, with highs ranging from the upper 20s into the low 30s across the region. Factoring in the humidity, and conditions will feel oppressive at times in the middle to upper 30s. Little relief is expected during the overnight hours, with lows around 20C (68F). 

A flooded home along US Route 11 near Ellenburg, New York on Sunday, July 2.  Ellenburg is 100 kilometres southwest of Montreal. (WCAX)

Over the weekend, strong thunderstorms developed along a warm front Saturday morning, with thousands of lightning strike observed as the storms moved across the Island of Montreal and Laval. A lightning strike in Laval-sur-le-Lac ignited a fire damaging a two storey residence. Heavy rainfall and hail up to 3cm was also reported. The rain was much needed here on Île Perrot, where 34mm fell Saturday (I recorded only 49mm for the entire month of June). At Trudeau Airport, 30.8mm was reported, with 55mm in both Riguad and St. Anicet.

Further south, nearly stationary "back building" thunderstorms dumped between 100-200mm (4-8 inches) of rain across northeastern New York State, specifically Clinton and Franklin Counties. There are radar estimates of even more locally. The torrential rain, falling in just a few hours Saturday night, produced severe flash flooding along the Great Chazy River. A friend was staying at the Blue Haven Campground in Ellenburg, New York, where evacuations were ordered in the wee of hours of Sunday morning. Numerous swift water rescues were carried out. Several homes and businesses are flooded as well, with numerous roads closed and washouts reported. More storms are forecast for the same area Monday.

Extensive flooding from thunderstorms at Blue Haven Campground in Ellenburg Depot, New York. (Tammy Arbour)

Back in Quebec, flash flooding was reported in the Saguenay region after 130mm of rain fell Saturday. In Rivière-Éternité, a state of emergency has been declared after flash flooding in that community forced more than 200 residents to be evacuated. The SQ and firefighters are searching for at  least two individuals missing after their cars were swept away in the flood waters.

Strong thunderstorms for southern Quebec through midnight

Severe thunderstorms are possible in Montreal through midnight. (ValleyWeather Photo)

 

Severe Thunderstorm Watch for metro Montreal - Tornado Watch for Eastern Ontario

A line of very strong thunderstorms is moving across eastern Ontario and western Quebec Saturday afternoon. The storms are bubbling up in the very warm and humid airmass along a cold front. Widespread severe thunderstorm watches are in effect, as well as a tornado watch across eastern Ontario.

Very dangerous frequent lightning, gusty winds, hail and even an isolated tornado is possible within the strongest cells.

More recently a tornado warning was issued for the Papineau region, for a storm showing rotation near Lac-Simon in western Quebec.

The storms will vary in intensity and persist for most of the evening hours before weakening after midnight.

A line of storms early Saturday morning produced thousands of lightning strikes across southwestern Quebec, with an almost constant rumble of thunder for over an hour.