Tag: southern ontario

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

Fall Windstorm Targets Great Lakes Tuesday

A classic fall windstorm will track through the Great Lakes Tuesday, bringing strong winds, snow, and rain across Ontario.

A compact area of low-pressure is forecast to deepen overnight Monday, as it tracks through Michigan. Bringing strong wind & rain across Southern Ontario. Concurrently, bringing snow to Northwestern Ontario.

SOUTHERN ONTARIO: STRONG WINDS & RAIN SHOWERS

By Tuesday morning, rain showers will become more numerous as a large area of precipitation moves north from the United States. 5-15mm of rainfall in the morning, preceded by sunny breaks across South Central & Southwestern Ontario by the early/mid afternoon. Temperatures will likely spike into the low teens by the afternoon.

Winds will become stronger throughout the late morning. Becoming the strongest through the afternoon and evening. Widespread wind gusts between 60-80km/h is expected through the afternoon/evening Tuesday. The strongest winds, potentially exceeding 90km/h, are possible in the Niagara Region, Prince Edward, Bruce & Grey Counties.

Projected wind gusts Tuesday 4pm EST. Wind speeds are in knots. 1 knot=1.85km/h.

The strong winds will likely strip many of the remaining leaves from trees. Remember to clean fallen leaves from storm drains.

NORTHWESTERN ONTARIO

While the South contends with wind & rain, Northwestern Ontario will see snowfall. The heaviest snowfall is expected across far-Northwestern Ontario. Another area of snowfall is expected northwest of Thunder Bay. General amounts between 5-10cms is expected Tuesday.

Much colder air with light-snow, is expected for Thunder Bay through Wednesday & Thursday.

Snowfall projections for Northwestern Ontario through Tuesday.

COLDEST AIR OF THE SEASON IS ON THE HORIZON

The warm up will be short-lived. The coldest air of the season, accompanied by lake effect snow arrives this weekend. Daily low temperatures will become consistently negative beyond Friday, November 9th across Southern Ontario. With daytime highs around the freezing mark for several days. Lake effect snow will really begin to ramp up beginning late week. 

Ontario

Reinforcing Cold Shot & Wet Snow Risk for Southern…

A frosty Saturday night ahead across much of Southern Ontario. Pleasant conditions Sunday, give way to a pair of clipper systems to start the work week. 

It will be a cool and frosty Sunday morning across Southern Ontario. Sunny conditions, and light southwesterly winds, will allow temperatures to rebound in the afternoon.  The first of two clipper systems brings rain showers (beginning) Monday morning. Dreary and cool conditions continue through the afternoon. 

Frost advisory issued by Environment Canada Saturday night.

First Shot of Lake Effect Snow?

A clipper system will track through the Great Lakes late Tuesday through Wednesday. The passage of the low will be followed by a reinforcing shot of cold and dry air. Lake effect rainfall may bring graupel or hail to some locales in Central Ontario (Tuesday evening into Wednesday morning). Owing to, instability, and seasonably cold air building aloft.

Lake effect rainfall bands will transition to wet snowfall Wednesday night, Southeast of Lake Huron, and Georgian Bay.

A few wet centimetres may accumulate through Wednesday night. Especially across higher elevations. 

Seasonably cool air 1.5km above the surface, will support lake effect snow. Abundant dry air, warm ground temperatures, and a building area of high pressure, should mitigate any risk of significant accumulation. We will monitor the risk over the coming days. 

Ontario

Winter Reminder: Lake Effect Rain Showers across The Great…

Colder air is beginning it’s decent across Southern & Central Ontario. Gusty winds this evening gives-way to Lake Effect rainfall Thursday night through Friday. First ‘bout of the season serves as a reminder that winter is coming.     

Inland sections surrounding Agawa Bay to Montreal River Harbour will see Lake Effect rainfall beginning this evening. A transition to mixing or large flakes of wet snow is anticipated during the early morning hours Friday.     Location: East of Lake Superior.

Accumulating snow will develop in Lake Effect bands near Wawa Friday night through Saturday.

Lake Effect model simulation for early Friday morning. Animation curtesy of Weather Bell Analytics

Southern Ontario

Lake effect rainbands will setup tonight southwest of Georgian Bay and East of Lake huron. Owen Sound to Barrie to Orillia will be in for a chilly wet reminder that winter is coming. With rainfall bands meandering through the area.

Fairweather waterspouts are possible late Friday over Lakes Erie and Ontario, given the cold air aloft.

Manitoba

Tale of Two Seasons: Heavy Snow, Rain, & Summer…

An area of low pressure will strengthen as it tracks through the Upper Midwestern United States. Bringing accumulating snow and gusty winds across Northwestern Ontario. Summer-like heat & humdity returns to Southern Ontario.

TIMING & ACCUMULATIONS 

Snow flurries will begin mixing in along Highway 17 late Wednesday evening. With wet snow falling by Thursday morning. By Thursday afternoon, anywhere along and south of Highway 11 will likely be seeing rain. 

North of Lake Superior, precipitation will fall as a cold rain with gusty winds. Including the Thunder Bay area, where cold rain and gusty winds will lead to a miserable day. 

Projected snowfall divisible by Postal Code. 
PostalCast©: NW. ON SNOWSTORM – Wednesday through Thursday
— MOST Impacted Locales (Based on First 3 Digits of a Postal Code) —
P0L (10-15cm for Southern Regions; 15-25cm for Northern)
P0T (<5cm near Superior; 25-30cm+ for Northern Regions)
P0V (<5cm for Northern Regions; 15-25cm for Southern)
P0W (10-15cm)
P0X (15-20cm)
P0Y (15-20cm)
P8N (20-25cm+)
P8T (20-25cm+)
P9A (8-15cm)
P9N (10-20cm)

By Wednesday afternoon or late evening, cold air will wrap around the deepening system. Heavy snowfall will begin accumulating in a line from Kenora to Dryden to Sioux Lookout to Pickle Lake. Continuing into extreme Southeastern Manitoba. Moderate to heavy snowfall and gusty winds will persist, increasing in coverage across Northwestern Ontario through the day Thursday. 

Projected amounts are subject to change based on the track & timing of the low + Hurricane Michael. Current guidance suggests a large swath of 20-30cm. 30-40cm could fall locally.

Preliminary snowfall projections will be updated throughout the week.

Actual accumulations will be largely dependant upon key factors: track of the low, temperature, and snowfall ratios. Moisture won’t be an issue with tropical moisture from Hurricane Michael. 

HEAVY RAINFALL 

While Northwestern Ontario deals with heavy snow, Northeastern Ontario will be dealing with heavy rainfall. A large swath of 50-75mm is expected East of Lake Superior. 

THE TALE OF TWO SEASONS 

As Northern Ontario deals with heavy rain and snow, Southern Ontario will get one last blast of summer. Temperatures Wednesday will likely be soaring into the mid or high-20s. With abundant humidity making it feel into the 30s. Forecast temperature & humidity readings will challenge all-time October records Tuesday and Wednesday.

Ontario

Potent System: Severe Thunderstorms & Pattern Change for Ontario…

[UPDATED] A strong fall-like system will track across Ontario and Quebec Friday, bringing a risk of severe thunderstorms. Heavy rainfall, strong winds and a pattern change is expected. Find out where.

Through the day Thursday, an area of low-pressure will deepen as it tracks from the Midwest into Northeastern Ontario, Friday morning. The low will mature as it tracks into Quebec by Friday afternoon.

A warm front, associated with the seasonably-deep low will push north across Ontario and Quebec Thursday morning into Friday. Concurrently, temperatures will soar into the high-20s Friday afternoon across Southern Ontario and Southern Quebec (near the border). Increasing dew-points will lead to muggy conditions feeling into the mid-30s.

Instability, very-strong upper-level winds, wind-shear, and marginal energy will lead to severe thunderstorms Friday. Ahead of a vigorous cold front, and strong upper-level trough where heights will be falling.

RISK & COVERAGE

The greatest risk for severe thunderstorms in Ontario will stretch from Central Ontario to Eastern Ontario. Coverage will be more isolated in Ontario than Quebec. These thunderstorms will be capable of producing strong wind gusts. Upscale growth into a squall-line bringing straight-line winds, heavy downpours and frequent lightning is possible.

In Quebec, atmospheric energy & cooler temperatures will be less favorable than Southern Ontario, but better forcing, shear, and instability will lead to isolated-severe thunderstorms. Risks include damaging winds, frequent lightning and heavy downpours. This will include the risk of supercells. The strongest risk will largely affect rural, unpopulated municipalities.

WIND & HEAVY RAINFALL

Regardless of thunderstorms, synoptic winds will be strong across Southern Ontario and Southern Quebec with this fall-like system. Widespread gusts between 50-80km is expected across a large swath of Ontario and Quebec, preceding the cold front and after its passage.

UPDATE: latest model guidance is suggesting that localized wind gusts of 90-100km will impact Ontario and much of Quebec.

30-50mm of rainfall is expected along a swath East of Lake Superior through Northeastern Ontario.

PATTERN CHANGE INTO FALL

The passage of the cold front will usher is much cooler and drier conditions by Friday night. Temperatures will struggle to get into the mid-teens by the weekend. A hard freeze is looking probable across Northern Quebec and Northern Ontario.

Ontario

Wet & Stormy Tuesday Across the Lower Great Lakes

Heavy thunderstorms expected Tuesday (August 21st, 2018) across Southern Ontario.

Rain-showers or thunderstorms are expected to begin moving into deep Southwestern Ontario overnight Monday into Tuesday. Convection will spread throughout Southern Ontario throughout the morning and afternoon as a maturing-low approaches from the US. Another round is possible by the mid-evening along the shores of Lake Huron.

BRIEF CLEARING? & HEAVY RAINFALL

There may be some brief clearing stretching from the Golden Horseshoe into Southwestern Ontario. This would add more energy and instability, allowing for some isolated severe thunderstorms capable of very-strong winds and short-lived rotation.

Much of the day however, is expected to be dominated by cloud, showers and passing heavy thunderstorms – perhaps several rounds. This could lead to locally significant rainfall-totals. With the threat of localized flooding. Widespread amounts between 30-50mm is expected.

BENEFICIAL RAIN:

East of Georgian Bay stretching into East of Superior will see a beneficial, soaking rainfall from this system. Which will help alleviate forest fire concerns, plaguing the region this summer.

WIND:

This will be an early fall-like system for the Great Lakes. As we move deeper into August we are beginning to enter a transitional period, where low-pressure systems produce synoptic rain and wind over a larger area. Widespread winds gusting between 50-70km/h are expected between Tuesday late-afternoon, and through the evening.

No need for “the end of sunmer blues” quite yet, temperatures by this weekend will be near 30c feeling closer to 40c with the humdity factored in.

Ontario

The Remnants of Tropical Storm Alberto Approach the Great…

Alberto has been blamed for flash flooding, mudslides and power outages in parts of the Southern United States. The remnants of Alberto will churn into Michigan this evening – increasing humidity readings and creating unsettled conditions for Southern Ontario, beginning late this evening.

High dew-point values will envelop much of Southern Ontario Wednesday through Thursday. Overnight lows near or above 20C Wednesday night, coupled with dew-points in the high teens, will lead to stifling conditions in doors for residences without air-conditioning or central-air.

High humidity with temperatures in the middle to high teens will act as fuel for Thunderstorms Wednesday night in Southwestern Ontario – with a widespread risk for Thursday morning through evening for the rest of Southern Ontario.

The remnant low of Tropical Storm Alberto will act as a trigger Wednesday night and Thursday. As the remnant low approaches Michigan, bands of showers and thunderstorms will wrap around the low.

What is left of Tropical Storm Alberto as it churns north – towards Michigan. Still displaying well defined circulation and heavy rainfall. 

On Thursday, the low will coalesce will a cold front and get absorbed by the Jet-stream. Upper-level energy and a cold front is expected to act as a trigger for widespread thunderstorms, some of which could turn severe. The primary risk with any thunderstorms that develop Thursday will be torrential rainfall and gusty winds. We will be watching Southwestern Ontario where rainfall could be an issue with minor flooding concerns.

A secondary cold front passage is expected Friday – which may act as a trigger for another round of thunderstorms. Again, rainfall will be the primary concern. Small hail is also a possibility.

It’s important to note, the next couple days aren’t expected to be a wash-out for everyone. Some locales may only see a few millimetres of rain. Whereas other locales, who receive several rounds of thunderstorms or training thunderstorms, could see locally 50mm or more.

Some solace from the humidity is expected by Saturday. Temperatures return to normal with brilliant sunshine and no humidity.

NORTHERN ONTARIO

A deep-layer of tropical moisture will move well north into Canada. Reaching as far North as James Bay and Northern Quebec. Heavy rainfall is expected along a boundary between Lake Superior and James Bay continuing into Northern Quebec. Totals rainfall amounts between 40-75mm are expected in the next 48 hours in the region.