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Ontario

Spectacular Shelf Cloud Spotted Near Tilbury Ontario

It’s been an active evening across extreme Southwestern Ontario. Severe storms produced torrential downpours, damaging winds, intense frequent lightning, and eerie skies. One storm chaser tracking the storms got more than he anticipated today.

https://twitter.com/IWeatherON/status/1146217122890223622
There has been some damage and minor flooding reported.
A roll cloud ended the evening of severe weather as the storms became outflow dominated, turning into a large area of moderate to locally heavy rainfall.



Manitoba

Powerful Line of Storms Threaten Damaging Winds in Manitoba

Temperatures are set to surge near the 30 degree mark today in Southern Manitoba, once the humidity is factored in it will feel closer to 40 degrees celsius. Relief will come in the form of thunderstorms; atmospheric conditions will be primed for severe weather.

A potent system will track eastwards out of Saskatchewan into Manitoba this afternoon acting as a trigger for severe thunderstorms. Strong southwesterly winds aloft will overspread southeasterly winds at the surface; a summer-time signal the atmosphere is primed to produce severe thunderstorms.

Lets play out how storm evolution will likely occur today.

[Valid 4pm] In this model projection, we see ongoing storms in Southeastern Saskatchewan. Manitoba still largely remains thunderstorm free – until the forcing for ascent arrives and the capping inversion erodes.


[Valid 7pm] Explosive thunderstorm development follows around the dinner hour across Southwestern Manitoba; including Brandon, Neepawa, Morden, and Portage. Quickly growing into a large line of severe thunderstorms that will produce damaging winds up to 110km/h, 3-5cm hail, torrential rainfall, frequent lightning, and the risk of a tornado.

[Valid 10pm] an expansive line of windstorms will progress throughout Southeastern Manitoba. Likely clipping the Ontario/Manitoba border. This severe complex could become a powerful, long-track Mesoscale Convective Complex (MCS); as it transverses North Dakota & Minnesota through the overnight hours.


Note the triple-point – an axis of intersection between a warm, cold and occluded front. South of this intersection point (warm front), storm energy will likely build to a very-unstable value nearing 4000J/Kg. This is the region that will be watching for the potential of a tornado. The risk may continue into southeastern Manitoba through the late evening.

Environment Canada Thunderstorm Outlook valid today. Noting an ‘Extreme Risk’ for Severe Thunderstorms. Navigate to their forecast here.
Alberta

Severe Weather Envelopes the Southwestern Prairies Thursday; Reloads Friday

A potent upper-air pattern will create extreme instability across the Southwestern Prairies Thursday. A surface trough will slice through the summer air offering a trigger for explosive thunderstorm development in the unstable atmosphere.

Winds at the surface out of the southeast and upper-level winds from the southwest suggest a well-sheared warm sector. The strongest surface heating will remain just south of the border. In spite of that, ample moisture delivery, temperatures falling aloft, effective shear, and plenty of energy will provide a breeding grounding for severe thunderstorms Thursday.

Thunderstorms will develop across Southern Alberta and Northern Montana around 2 pm. Trans-versing northeastwards throughout the afternoon and evening, Initial storm develop may feature discrete cells and bowing segments; a threat for large hail, damaging winds, and an isolated tornado is possible. As progression into the evening continues, a powerful nocturnal complex of thunderstorms known as a Mesoscale Convective Complex (MCS), may develop. These convective weather systems are notorious producers of damaging winds, intense frequent lightning, large hail, and localized flooding in torrential downpours. Moreover, these systems are known to persist well into the pre-dawn hours.

click to navigate forecast map.

HAZARDS: 90-110km/h wind gusts, 2-5cm hail, torrential rainfall, frequent lightning, and an isolated tornado.

We will be monitoring the thunderstorms throughout Saskatchewan and Alberta attentively on Thursday. Be sure to closely monitor watches and warnings throughout the afternoon, evening and overnight. We will be issuing another forecast for severe thunderstorm risk in Saskatchewan, Friday. The risk depends greatly on the evolution of thunderstorms Thursday into pre-dawn Friday.

HEAVY RAINFALL CONTINUES WEST OF EDMONTON

Much of the focus is rightfully centered around substantial thunderstorm risk further south, but appreciable rainfall amounts along the Highway 16 & 40 corridor is worth mentioning. This region has already seen very-heavy rainfall over the last several days. Another 50-75mm is on tap between Hinton and Edmonton, through Friday.

Alberta

Much NEEDED RAINFALL & SNOW to Kick off the…

A potent upper-level system will stall all week across Alberta and Saskatchewan. The unsettled pattern will bring much-needed rainfall, thunderstorms, much below seasonal temperatures, and even accumulating S*** for Banff & Jasper.

Beneficial rainfall will persist all week in Alberta & Saskatchewan as an upper-level system stalls across the region. The heaviest rainfall is anticipated across Central Alberta where 50-75mm+ is expected by Friday. With much of that rain falling between Wednesday and Thursday. Some rainfall is in the forecast for drought-stricken High Level (Northern Alberta) & Moose Jaw (Southwestern Saskatchewan).

The much below seasonal temperatures and a soaking rainfall will make it feel more like the middle of October across the foothills. By Wednesday, temperatures will plummet nearly 10c below seasonal. Continuing through the day Thursday.

DAYS OF THUNDERSTORMS CONTINUE WITH THE THREAT OF SEVERE TUESDAY

Thunderstorms have been an almost daily occurrence over the last several days in the Prairies. The thunderstorm risk is expected to continue this week.

Monday: thunderstorms producing heavy downpours and small hail across Interior British Columbia and Northern Alberta.

Locally strong to severe thunderstorms expected across the yellow shaded area today.

Tuesday: better dynamics for potent thunderstorms across Southern Alberta (Calgary to Medicine Hat). Discrete cells or supercells could be capable of producing damaging winds and large hail.

Wednesday: daytime heating thunderstorm risk moves further East into Saskatchewan.

ACCUMULATING SNOW KICKS OFF SUMMER IN BANFF & JASPER

Between Wednesday night through Friday, accumulating up-sloping snow is expected over the high-elevation topography of Banff and Jasper National Parks. Believe or not, Friday is officially the first day of summer.

Alberta

Convective Outlook: Thunderstorms & Flood Risk

Our forecasting team at TransCanada Weather is cautiously watching long range model guidance. Between Tuesday May 28th – Thursday, June 6th, the evolution of a pattern supportive of heavy rain, severe thunderstorms & unsettled conditions will envelop parts of Canada. Read below to find out where.

PRAIRIES: Unsettled Conditions, Risk of Cold Core Funnels, Threat of Thunderstorms

The Prairies will have to contend with unsettled conditions. Including a pattern that may support the risk of cold core funnel clouds & areas of severe thunderstorms between late May to early June. This is be welcomed news for Alberta; contending with out-of-control forest fires.

GREAT LAKES: Heavy Rain & Severe Thunderstorms

A second area we are watching closely: the Great Lakes/Ontario region. A supportive pattern for flooding and/or severe thunderstorms is possible between Tuesday May 28th to Thursday May 30th.

Abnormally, deep troughing, seasonably deep height-falls, strong waves of low-pressure, concurrent with a southeast ridge. Will bring surges of warm moist air along with supportive wind profiles for severe thunderstorms and/or flood risk. A significant severe day will be possible within this regime across Southern or Northeastern Ontario.

Saturday, May 25th: after Thursday, the next threat for severe across Southern Ontario will come Saturday. Risks across Southwestern Ontario include: isolated damaging wind gusts, large hail & torrential downpours.

Additional considerations: drought conditions in the Southeastern US allowing mid-level dry/warm air to migrate north within stronger circulations. Abnormally-wet southern plains, increasing low-level moisture transport/PWAT values in stronger 850mb flows.

-troy

Ontario

Thunderstorms Threaten Damaging Winds in Southern Ontario

A sudden surge of warm, summer-like air will herald in the risk of thunderstorms across the Lower Great Lakes. These thunderstorms may turn severe; capable of producing damaging winds & hail across portions of Southern Ontario. 

SURGING TEMPERATURES, THUNDERSTORMS & RAIN

An area of low-pressure will transverse through the Midwestern United States towards Ontario, throughout the day Sunday. Ahead of the system, temperatures will surge into the mid-20s and humidity readings into the low-30s. Near the Lake-shore, cooler conditions are expected.

Showers are expected before midnight tonight, lasting into the pre-dawn hours. Persistent rain-showers and embedded thunderstorms are expected for Central Ontario – mainly East of Georgian Bay. Sunny breaks are anticipated through the morning hours, allowing for some instability to build before the arrival of a cold front.

A soaking rainfall and single-digit temperatures North of the warm front. Heavy thunderstorms ahead & along a cold front in the South.

At this point, it appears the setup will feature two potential waves of thunderstorms. The primary wave will consist of a complex of heavy rain showers with embedded thunderstorms impacting Southern Ontario between 4-10 pm. Initiating at approximately 4 pm in Windsor and exiting Eastern Ontario by 11 pm. Risks include: torrential downpours, lighting and isolated damaging winds. A potentially stronger second round of thunderstorms (along an advancing cold front) may happen on Sunday evening/overnight, across Extreme Southwestern Ontario. There is some uncertainty regarding the evolution of thunderstorm development. If thunderstorms do develop, risk factors include: hail and isolated damaging wind gusts.

Across Northern Ontario, a large swath of heavy rainfall is expected. Local rainfall totals nearing 50mm is anticipated.

New Brunswick

Texas Low: Severe Outbreak Precedes Potent Storm for Eastern…

A significant trough crossing the Guadelupe Mountains will drive the development of a potent area of low-pressure across Texas Saturday. Favorable conditions for the development of severe thunderstorms, will exist along the warm front axis; ahead of a vigorous cold front. This will be significant “severe weather event” for Northern Louisiana, Southern Arkansas, Western Mississippi, and Eastern Texas. Reloading for a second day of severe weather, across the Eastern United States.

Moisture laden low developing in Texas bringing severe thunderstorms. With impacts across Eastern Canada to end the week. Persisting into early next week.

During the day Sunday, the low is forecast to take a northeast hook towards the lower Great Lakes bringing a plume of rain and snow for Southern/Central Ontario & Southern Quebec.

Atlantic Canada is poised to see the most tempestuous conditions, with rapid deepening of the low-pressure center late Monday. This system will be a heavy-rain story for the Maritimes. On the contrary, Newfoundland could see heavy snow, significant freezing rain and strong winds.

COOL, WET & LOUSY COUPLE DAYS FOR SOUTHERN ONTARIO

Get out and enjoy the abundant sunshine and warm temperatures Saturday. A messy, moisture-laden system out of Texas will deliver below seasonal temperatures, a soaking rainfall, mixed precipitation and accumulating wet snow. The heaviest rainfall will be situated along the Lake Ontario shoreline into the Niagara Region. The heaviest of the snowfall will be seen across parts of Central Ontario – through cottage country.

A lousy system for the Great Lakes. Below seasonal temperatures, a soaking rainfall and more snow expected.

SIGNIFICANT RAINFALL & GUSTY WINDS FOR THE MARITIMES

Significant rainfall will encompass much of Nova Scotia, the Bay of Fundy region in New Brunswick & Prince Edward Island. There is still considerable uncertainty how this low will develop in the Maritimes. Current projections have most of the precipitation falling as rainfall. As much as, 40-75mm of rain is possible, between Sunday night through Tuesday morning.

Click to navigate a larger image of the map.

POTENTIAL ‘WEATHERBOMB’ FOR NEWFOUNDLAND

The system is expected to undergo rapid deepening Monday night. Slowing as it transverses through Gulf of St. Lawrence. A strengthening wind field along the Northwestern coast, persists all-day Tuesday. Refinements to the forecast will come throughout the coming days. Nevertheless, this is looking like a potent system for Newfoundland.

We are becoming increasingly concerned regarding a freezing rain threat for the north coast of Newfoundland. Including Fogo Island, Bonavista North & Green Bay. 10-15mm+ of freezing rain, ending as snow and strong winds could bring localized power outages.

Heavy snowfall will be the story across Northwestern Newfoundland with as much as 20-40cm falling over the hardest hit areas. Concurrent, with strong winds leading to blowing and drifting snow.

Ontario

How a Major Blizzard Stateside Will Impact Ontario

An area of low-pressure sliding out of Colorado will undergo explosive intensification through the day Wednesday. This will be an blockbuster blizzard for portions of the Upper Midwest including South Dakota & Minnesota. 40-60cm+ of snow concurrent with 70-90km/h winds will cripple the region.

BLIZZARD WEAKENS AS IT MOVES INTO NORTHWESTERN ONTARIO

The explosive Colorado Low that will cripple South Dakota, will thankfully be weakening as it approaches Ontario. Snow will move into the Thunder Bay, Nipigon, Atikokan, Upsala area before midnight Thursday. Accumulating snow will combine with gusty winds between 40-55km/h, through Thursday night and Friday. It will be a good day to stay home and off the roads if you can.

Moderate to heavy snow transitioning to rain across Northeastern Ontario. Northwestern Ontario sees all snow from this system. Click to navigate the map and find your region.

Wawa to Timmins will see more ice pellets and wet snow, than rain. A transition to rain showers is expected throughout Friday Afternoon.

Kapuskasing to Hearst will remain as snow, where 15-20cm is expected to fall.

SOUTHERN ONTARIO IMPACTS

Strong wind, a surge of warmer air and rainfall will be the story across Southern Ontario Friday. A cool and partly-cloudy day Thursday, with patchy mixed precipitation. Largely confined to Southwestern Ontario.

Strong wind anticipated across Southwestern Ontario Friday morning. Strong Southeasterly gusts between 70-80km/h is expected north of Lake Erie and East of Lake Huron.

Temperatures in the afternoon will spike into the double digits across Southern Ontario. The Nations Capital Region will see the temperature climb near 9c. The trade-off will be a lousy day with occasional rain or showers Thursday. There is even a risk for localized thunderstorms early in the day Friday.

British Columbia

How Two Storms Dancing in the Pacific Will Impact…

What is a dancing storm? Good question. The Fujiwara effect “dancing storms” refers to the interaction between two cyclonic vortices. When two low-pressure systems near each other, they begin to orbit one another around a mid-point separating the two systems. The effect gets its nickname from the interaction of two systems appearing to “dance” around one another. Read more here.

A pair of systems interacting in the Gulf of Alaska through the weekend. By Saturday afternoon, the systems merge into one stronger storm and stall in the Gulf. Heralding waves of precipitation & unsettled conditions along the coast.

WINDY DAY SATURDAY ALONG THE HAIDA GWAII ARCHIPELAGO

Southeasterly winds will pick-up along the channel separating the islands and the Mainland, Saturday. The most powerful wind & waves will remain off-shore. Still, gusty winds & rainfall along Vancouver Island and the Archipelago will lead to a lousy day. Wind gusts between 60-90km/h are likely.

WET ALONG THE COAST WITH SNOW IN THE MOUNTAINS

An unsettled couple of days across the Lower Mainland & Vancouver Island. 25-35mm of rainfall is expected across Vancouver & Victoria through Friday & Saturday. This will be a beneficial rainfall across the region, where its been an unusually-dry start to spring. Unfortunately, the rainfall isn’t expected to penetrate far enough into the interior to bring any relief to the dry conditions.

Projected Rainfall through the weekend.

A more prolonged and significant rainfall is expected along Western sections of Vancouver Island. 40-70mm of rainfall is expected by the end of the day Saturday. The mountain peaks along the coast will see heavy snow – mixing or light accumulation is possible along sections of Highway 19.

Heavy snow expected above 1500m.
New Brunswick

Bomb Cyclone Threatens Damaging Windstorm, Snow & Heavy Rain…

A weatherbomb is rapidly strengthening Tuesday off Cape Hatteras, North Carolina. Bringing hurricane-force winds, significant rain & lighting just off-shore. This system will undergo bombogenesis as it tracks up the Eastern Seaboard, through the Gulf of St. Lawrence into Labrador. 

Significant rainfall & snowfall accompanied by damaging winds gusting over 100km/h is anticipated. The most tempestuous conditions being felt across the Maritimes Wednesday afternoon & evening. For Newfoundland & Labrador conditions deteriorate rapidly overnight Wednesday. Persisting through most of the day Thursday.

DAMAGING WIND THREAT

Damaging winds will be the main story with this powerful storm. Atmospheric pressure is expected to drop 28mb within 24 hours. An expansive – strengthening wind field will result. Hurricane-force winds (gusts over 120km/h) expected along the Western coast of Newfoundland & Cape Breton Island.

Les Suetes winds gusting up 160 km/h are forecast to develop Wednesday afternoon, shifting southwesterly before dissipating. Wreckhouse winds could peak between 160-180km/h.

Click to navigate the wind impact map.

SIGNIFICANT WIND DRIVEN RAINFALL FOR COASTAL NOVA SCOTIA

Environment Canada has issued a Rainfall warning across Nova Scotia. The agency is warning up to 70mm of rain could fall, in the hardest hit regions along coastal Nova Scotia.

Rain at times heavy will develop early Wednesday morning over southwestern Nova Scotia and quickly spread to the remainder of the province by Wednesday afternoon. The rain will be mixed with snow to start over parts of mainland Nova Scotia Wednesday morning. Over Cape Breton, the rain will likely be preceded by a period of snow over some areas.

Rainfall amounts will be highest over Atlantic coastal regions of mainland Nova Scotia where 50 to 70 millimetres are forecast. Elsewhere, 25 to 40 millimetres of rain is expected.

Heavy downpours can cause flash floods and water pooling on roads. Localized flooding in low-lying areas is possible.

SNOWFALL ACROSS NEW BRUNSWICK & BLIZZARD CONDITIONS ACROSS LABRADOR

Environment Canada has issued several warning across New Brunswick. This is what they wrote in their statement. Snow will begin Wednesday morning over southwestern New Brunswick and then spread quickly across the province by noon. The snow will likely mix with rain in the afternoon. Snowfall amounts of up to 10 cm are possible. Over eastern regions of the province, snowfall amounts in excess of 15 cm are likely and snowfall warnings are in effect there. Along the Fundy coast, rainfall amounts near 25 mm are possible and rainfall warnings are in effect there. Northwestern New Brunswick will only receive light amounts of precipitation from this system.

Western Newfoundland will have to contend with sea-effect snow and blizzard-like conditions through the day Thursday. 5-15cm of accumulation is expected by Thursday evening. Heavy flurries and snowsqualls may continue Thursday overnight and Friday.

This will be a major winter storm for Labrador. Who has been no stranger to significant storms this season. Winter refuses to relinquish its icy grip. 25-40cm of fresh snow concurrent with 90km/h+ winds & blizzard conditions.