Tag: localized flooding

Ontario

Colorado Low Threatens Snow, Heavy Rain & Strong Winds…

Don’t let the calendar fool you – a bitter sweet transition to spring is expected. The final two weeks of winter will feature drastic temperature swings and at least one notable storm system this weekend.

An area of low-pressure will form lee of the Rockies in Colorado Friday. Deepening as it tracks northeastwards through the United States towards the Great Lakes Region Saturday evening.

Key Details:
15-25mm of rain across deep Southwestern Ontario & North of Lake Erie. Rain combined with snow-melt may lead to localized flooding.
10-20cm of snow for Northern Ontario. Heaviest snow falling East of Lake Superior & across the Nickel Belt.
Strong to damaging wind gusts for Southwestern & Central Ontario.
A surge of warm air in Southern Ontario precedes wrap around strong winds & snow

*Click image to toggle zoom.

SNOW FOR NORTHERN ONTARIO

Like many of the storms this season, this system will feature appreciable snow across Northern Ontario. A large swath of 10-15cm is forecast for Wawa, Timmins and Sudbury areas. Local amounts may approach 20cm.

MESSY WINDSTORM FOR SOUTHERN ONTARIO

First and foremost, this is a messy system for Southern Ontario. Precipitation will move into Windsor in deep Southwestern Ontario around 6pm Saturday. Progressing Northeastwards across Southern Ontario during the evening and overnight. Main concern for along the Lake Erie shoreline will be heavy downpours combined with warmer temperatures, snow melt, and runoff. Minor flooding is possible; stretching into the GTA. Be sure to monitor any statements from your local conservation authority, as we progress through the weekend.

Strong to damaging easterly winds will develop ahead of the storm Saturday evening & overnight. The strongest wind gusts are expected East of Lake Huron. Including Goderich, where peak winds could exceed 100km/h late Saturday evening & overnight. The rest of Southern Ontario will have to contend with strong easterly winds gusting 60-90km/h through the overnight into Sunday morning. Once again, winds will strengthen out of the West Sunday, with the passage of a cold front. Frequent gusts between 50-70km/h is expected.

Considering temperatures will be teetering around the freezing mark, precipitation may begin as snow, freezing rain or ice pellets. Especially, South of Georgian Bay where elevation and heavy precipitation rates will aide in keeping temperatures below freezing for a longer duration. For Eastern Ontario, this system will bring more wet snow than rain. Refer to our forecast map for further details.

Manitoba

A Weekend of Severe Thunderstorms in the Prairies Persists

Isolated severe thunderstorms expected today (Sunday, June 10th) in Saskatchewan & Manitoba.

Isolated severe thunderstorms are expected to develop in Central and Eastern Saskatchewan beginning by the mid-afternoon and persisting well into the evening hours in Western Manitoba.

We have highlighted an area in orange where the greatest risk develops. Regions is yellow can expect primarily non-severe showers and thunderstorms. Note: this risk continues into Western Manitoba.

Risk factors associated with these thunderstorms include: large hail, torrential rainfall, frequent lightning, and damaging wind gusts in excess of 100km/h.

Much cooler and less humid conditions are expected for Monday.

Severe thunderstorm risk for today expected in the orange section of our map. 

ANALYSIS

A surface low will decent across Southwestern Saskatchewan early in the morning Sunday. The first low has led to rain and heavy thunderstorms in Southwestern areas of the province early this morning. At the same time, a secondary low pressure center/vort max will be deepening as it approaches Western Saskatchewan during the afternoon. A trough in the Jet-stream will be progressing Eastwards across Saskatchewan during the period.

A eastward progressing front associated with the deepening low-pressure system, will act as a trigger from the mid-afternoon through the late evening – across Central and Eastern Saskatchewan.

Deep moisture transport aided by a 30-40kt low-level Jet out of the Southeast will result in dew-points in the high teens. Concurrently, temperatures will likely rise into the high 20s. Convective Available Potential Energy (CAPE) will likely build above 2000 J/KG across the warm sector, providing plentiful energy for strong thunderstorms. Warmer air aloft (a “cap”) will have to erode before storms can erupt – perhaps after peak energy.

Marginal wind shear and helicity readings, little veering with height, and a high LCL is expected to limited any tornado activity despite a south-easterly surface wind. The south-easterly flow and storm mode/track may allow for “training” – which heightens the threat for localized flooding.

Environment Canada (PASPC) has issued a map highlighting Southeastern Saskatchewan and Western Manitoba in a “moderate” risk for severe thunderstorms. Primary hazards include: 110km/h wind-gusts and 3-5cm hail. NOTE: these maps are still in the experimental stage. 

Near the low center (which is expected to exist in the North Battleford corridor), a soaking rainfall and heavy thunderstorms is expected. This activity should remain non-severe. Rainfall amounts of 15-35mm are expected.

The risk for severe thunderstorms continues Eastwards into Manitoba. Reloading again, for Manitoba and Northwestern Ontario on Monday.

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– TCW

Ontario

Thunderstorms, Locally Heavy Rainfall & Frequent Lightning for Southern…

Rain and thunderstorms expected early Tuesday (May 15, 2018) in Southern Ontario.

A complex of rain and thunderstorms is developing this hour in the Midwestern United States. This weather system is expected to push East late this evening, bringing widespread rain and thunderstorms after midnight.

Ahead of this system, humidity levels will increase – with temperatures into the high teens lingering late this evening and overnight.

TIMING:

Windsor to Goderich approximately 1am Tuesday.

Port Rowan to K/W to Shelburne approximately 3am Tuesday.

GTA to Barrieapproximately 4am Tuesday.

Peterborough to Eastern Ontarioafter 5am Tuesday.

Kingston to Ottawa approximately 9am Tuesday.

IMPACTS:

Heavy rainfall and frequent lightning for communities impacted by the complex of rainfall and thunderstorms tonight. A lessor threat for small hail and gusty winds also exists.

Due to already saturated soil, and rainfall intensity, a Special Weather Statement has been issued north of Lake Erie.

Rainfall totals between 20-40mm is expected north of Lake Erie. Locally, up to 50mm is possible. Elsewhere, expect 15+mm.

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– TCW