Serious flood threat, drenching rains in southern Ontario
Tuesday, February 20, 2018, 11:46 AM - There's a serious threat for localized flooding in southern Ontario as some areas could see 70+ mm of rain through Wednesday. Expect temperature records to be shattered as well with daytime highs soaring into the mid-teens. This spring-like weather does NOT signal an end to winter however, with March likely bringing more "significant winter weather." More on that below.
"Gulf of Mexico moisture tracking into the region along a semi-stationary boundary will bring excessive rainfall for parts of southern Ontario through Wednesday," says Weather Network meteorologist Nadine Hinds-Powell.
For a more comprehensive look at weather conditions in the GTA, here's a detailed analysis.
- Rain to continue into Wednesday morning
- 50-70+ mm likely for southwestern Ontario, 30-50 mm elsewhere
- Melting snow, still frozen ground to make for elevated risk of localized flooding
- Toronto and Region Conservation Authority's Flood Outlook in effect through Thursday, Feb. 22.
- Flood warning issued for entire Grand River watershed
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Heavy, persistent rain
Rainfall warnings and special weather statements also cover the region with "several rounds of rain" persisting through Wednesday.
The heavy rain combined with soaring temperatures well into the double digits has heightened the risk for localized flooding and ice jams.
"Flooding is a serious concern as heavy rain continues to fall on the frozen ground," warns Weather Network meteorologist Dr. Doug Gillham. "Rainfall totals will reach 40-70+ mm for most of the region by Wednesday morning."
In addition, the remainder of the snow will be melting and ice jams are a concern on creeks and rivers that are still frozen. Localized rainfall totals could reach 70-100 mm in some places.
Flood WARNING and road closures
A flood warning has been issued for the entire Grand River watershed, while the Toronto and Region Conservation Authority has a watershed statement in effect.
Flooding was reported on some Toronto roads through the overnight hours on Monday prompting road closures on northbound Bayview Avenue. Two westbound lanes at Eglington Avenue and Rosemount Avenue were also blocked due to flooding Tuesday morning.
"These conditions are expected to result in a total melt of the remaining snowpack and very high flows in rivers and streams across the watershed," warns the Grand River Conservation Authority in their flood message posted over the weekend. "This will result in flows similar to those experienced during normal spring flooding."
Ice jams currently in place in the Grand River through the City of Kitchener (Freeport), the City of Cambridge, City of Brantford and community of Cayuga have a high potential of causing additional flooding.
"It is anticipated that ice jams will release during this event," says the GRCA. "Ice jams can form and release without warning and extreme caution should be used in areas where they are occurring."
GRCA warns that this volume of rainfall in February has not been seen since record keeping began in the 1940's.
As a proactive measure, City of Cambridge fire officials went door-to-door this weekend in the areas of concern to advise residents of the situation and to hand out information about flood preparedness and safety.
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Soaring, record breaking temperatures
The warm air accompanying this system will continue to spread from west to east across the region on Tuesday, breaking temperature records for this date.
"The record high of 12.5°C at Toronto's Pearson Airport will likely be broken (shattered) as temperatures reach the mid teens in many areas, but a few degrees cooler from Downtown Toronto to Oshawa," Gillham says. "Wednesday's record of 12.9°C is also in jeopardy during the predawn hours ahead of the cold front."
Colder weather will return by Wednesday afternoon as temperatures quickly fall below the freezing mark.
"Thursday will be the coldest day of the week, but temperatures will still be just above seasonal," says Gillham. "Above seasonal temperatures will dominate until the beginning of March."
Return to wintry pattern on the horizon
While rain will be the dominant precipitation type with two more systems impacting the region late week, a return to a more wintry pattern is likely during the first week of March.
"We are seeing a spring-like ending to February in southern Ontario, but there is an abundance of Arctic air and wintry weather across western Canada and eventually we expect a return to a more wintry pattern," Gillham warns. "Winter is not over just yet and March will likely still bring some significant winter weather (as it often does)."
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