Our forecasting team is tracking an overachieving Clipper system tracking through the Lower Great Lakes Overnight. Dissipating West to East through Sunday AM.
A quick burst of snow begins near midnight tonight, persisting through the pre-dawn hours (5-6am) Sunday morning. Generally, 3-8cm is expected. Due to the nature of clipper systems amounts will vary throughout the forecast area.
Wind gusts to 60-70km/h are expected along the north shore of Lake Erie (along the Niagara Peninsula), early Sunday morning. Watch for local blowing snow and poor travel in the area.
Exercise caution if you are travelling early Sunday morning. Since it is a weekend, little impact to transportation is anticipated.
Alberta Clippers are synonymous for bringing snowfall lee of the Canadian Rockies, during December and January. These typically moisture-starved systems are fast movers, ejecting quickly out of Alberta, through the Southern Prairies – towards the Great Lakes. Read more about Alberta Clippers here.
A clipper is expected to form
in Northern Alberta Saturday evening. Normally, these systems are more of a
nuisance, accompanied by low snowfall totals and quick forward motion. On the
contrary, this weekends system will flourish. Thanks to clashing temperatures
and abundant Pacific moisture.
Accumulations will vary greatly throughout the Prairies, bearing in mind the heaviest snow will fall along a narrow swath. Current guidance suggests close to 15cm across the northern extent of the darker shaded region (in our forecast map). Including, Northern & Central Alberta. The heaviest snow (~20cm) will fall across Extreme Southwest Manitoba and Southeast Saskatchewan. *Model guidance has increased snowfall totals further into Southwestern Manitoba, where Environment Canada has issued snowfall warnings. Several warnings now stretch across parts of Prairies.
There will be another swath of snow tracking down the Rockies, bringing 10-20cm. It looks like Calgary will be limited to less than 5cm through Friday. By Saturday, a steep contrast in temperature envelopes the Prairies. Calgary will see a high of 9c and sunshine. Whereas, Eastern Saskatchewan will still be below freezing.
STRONG WINDS & BLOWING SNOW
Winds pickup between the
Grande Prairie – Whitecourt corridor early Saturday evening. Winds sustained at
or over 30km/h, gusting 60-80km/h. Gusty winds will overspread much of Alberta and
Southern Saskatchewan overnight Saturday into Sunday morning. The strongest
wind gusts aren’t expected to coincide with the heaviest swath of snow. Still,
freshly fallen snowfall, which is dry and light – will combine with gusty winds.
Bringing local blowing and drifting snow. Stay tuned to weather advisories, or
statements pertaining to any potential road closures.
A system developing in the Southeastern United States will track up the Eastern Seaboard this weekend, becoming a weather story across Eastern Canada.
A developing coastal system will bring a wintery mix across Southern Ontario, Quebec, and Northern New Brunswick.
A boundary will form in Southern Ontario between a cold & dry high-pressure system, and moist air arriving from the Southeast. Colder air will overspread Southern Ontario and Southern Quebec Saturday, owing to a cold Northeasterly wind. Concurrently, a large area of precipitation will push north into Southern Quebec and Southern Ontario.
Snow, mixing, rain and freezing rain is expected from Saturday morning to Sunday evening. Flurries will continue through Monday.
Across, Nova Scotia, PEI and much of New Brunswick will see primarily rain. Although, Northern New Brunswick could remain as a mix or snow depending on the track of the developing system.
Many residents East of Highway 6 and across the GTA have started the day with moderate wet snow.
A cold northeasterly wind will reinforce colder air by Saturday evening. Mixing or rain-showers will transition into a wintery mix of wet snow & ice pellets east of Highway 6, along/north of highway 407/7. Continuing through much of Central and Eastern Ontario (away from the lake shore). A few wet centimetres is possible. Especially for municipalities at higher elevation South and East of Georgian Bay. Please plan accordingly, as conditions will deteriorate through the day Saturday.
MARITIMES: Strong Winds & Heavy Rainfall
This system will be a rain and wind story across much of the Maritimes. The strongest winds, with gusts between 80-90km/h, will be located across the Bay of Fundy. Elsewhere winds across much of Nova Scotia, PEI and New Brunswick are expected to be gusting between 50-70km/h Sunday morning. Total rainfall amounts between 20-50mm is expected by Sunday afternoon. The heaviest rain falling in Southern New Brunswick and coastal Nova Scotia. Across Northern New Brunswick, a period of snow and mixing may persist into the overnight.
Flurries will begin north of the St. Lawrence Saturday evening. Montreal, and the Eastern Townships will likely changeover to rain late Saturday evening/overnight, with the arrival of warmer air.
For regions north of the St. Lawrence, this will be a snow and ice story. Stay tuned to further forecasts Saturday night through Sunday morning, this region could see a 5-8 hour window for freezing rain.
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.
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.
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.