A strong Colorado low is set to deliver a fall storm to much of Ontario, ranging from significant snow in the north, to prolonged showers and damaging winds in the 80-110 km/h range across the south, along with the risk of shoreline flooding. Beyond, the lake-effect snow machine gets going once again for the early part of next week.
Potentially damaging fall storm Sunday to bring rain, powerful winds to southern Ontario, risk of shoreline flooding, power outages, downed trees
Heavy snow expected north and east of Lake Superior with 10-15+ cm forecast through Monday
Sporadic lake-effect snow for the early part of next week
SUNDAY INTO MONDAY: COLORADO LOW THREATENS STRONG WINDS AND RAIN
People in southern Ontario will wake up to temperatures somewhat recovered from Saturday, but accompanied by the first of two rounds of rain from the Colorado low that began impacting the province late the previous evening.
These will be relatively steady downpours, with 20-30 mm possible for the southwest and parts of the GTA, and higher in the Nickel Belt, where as much as 50 mm could fall.
More remarkable, and potentially damaging, will be the winds, increasing through the morning and peaking through the afternoon and evening.
The strongest gusts, potentially damaging, will be along the lakeshores, where gusts are likely to hit 80-110 km/h. The northern shores of lakes Erie and Ontario are likely to see the strongest gusts.
Aside from the normal risks of damage to homes and power infrastructure from downed trees, these strong winds may whip up the waters of the lakes to cause shoreline flooding, known as a seiche. Widespread flood watches and/or watershed condition statements have been issued along the shores of lakes Huron, Erie and Ontario, as well as Georgian Bay.
“Our greatest concern is for the north shore of Lake Erie, from Long Point to Fort Erie, as a seiche is expected with significant lakeshore flooding," says Weather Network meteorologist Dr. Doug Gillham. "Wind gusts could reach 120 km/h along the north shore of Lake Erie."
Aside from some light amounts in cottage country and the Dundalk Highlands, most of the south will be spared the snow from this system. However, amounts will be considerable across parts of northern Ontario, with 10-15+ cm forecast for areas north and east of Lake Superior. The snow will change to rain across much of northeastern Ontario through the morning.
INTO NEXT WEEK: LAKE-EFFECT SQUALL SETUP
As the low tracks into Quebec Monday, rain changes back to snow for central Ontario and areas northwest of the GTA. In fact, the icy winds of the still unfrozen Lake Huron and Georgian Bay will set up lake-effect snow squalls.
West-southwesterly winds will be the launching point of the lake-effect snow, occurring through Monday afternoon across southern Georgian Bay and along Lake Huron shores.
Through Tuesday, the winds switch to a northwesterly direction, generating lake-effect snow from southern Georgian Bay into the GTA, and from the shores of Lake Huron -- from Kincardine to Grand Bend and across to London.
As the wind shifts directions, lake-effect snow will extend across the GTA Tuesday.
"Heavy snow and difficult travel are likely across the snow belts. Flurries and quick bursts of heavier snow will extend into parts of the GTA. Wednesday will be the coldest day with temperatures remaining well below freezing north of the GTA and across southern Quebec," adds Gillham.
TEMPERATURES RECOVER LATE NEXT WEEK
Milder weather will return for late week and on the weekend with temperatures recovering to near or above seasonal. However, forecasters are keeping an eye on the warm front and possibly a system with the transition to milder weather around Thursday.
"The cold air could resist and bring a period of messy/wintry weather, especially for areas well north of the GTA, eastern Ontario and southern Quebec," Gillham says.
Check back as this system's impacts unfold.