Flash freeze expected in Montreal after record warmth

Only patches of snow remain in Montreal on Tuesday afternoon, after a record setting high of 14.9C at Trudeau Airport. The normal high for February 26 is -1C (30F)

UPDATE: Wednesday, February 28  7:45AM: We have a very active weather day ahead for the Montreal region. First off we have established a record high for today's date already, it occurred overnight at 10C (50F). We may add several degrees to that value, but for now it breaks the previous record of 8.3C (47F) set way back in 1902. Also on Tuesday, Ormstown reached 20.5C (69F) establishing an all-time record high for the province of Quebec for the month of February. The previous record was 19.5C set on February 22, 1981 in Franklin, Quebec.

We have a warm, wet day ahead of us for southern Quebec, but that will come abruptly to end this evening. Heavy rain along a potent arctic front developing this afternoon, will change to snow this evening and end by midnight. There is even a chance of a rumble or two of thunder. 

Winds along and behind the front will gust 70- 90km/h between 6pm and midnight. In addition, the temperature will fall 15 to 20 degrees between 6pm and 10pm, from double-digit highs above freezing to well below freezing across southern Quebec. Prepare for icy conditions, and frigid windchill values tonight and Thursday morning.

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High Wind Warnings posted for southern Quebec  for Wednesday evening.

Flash Freeze Warnings issued for all of southern Quebec and Ontario for Wednesday afternoon and evening.

What a weather day across the region as dozens of record high temperatures have been established. Montreal's Trudeau Airport reached 14.9C (58.8F) shattering the previous record of 10.9C (51.6F) set back in 2000. We were just one tenth of a degree shy of the all-time February record high of 15C (59F) set in 1981. I recorded 15.6C on Ile Perrot, while St. Anicet reached an incredible 19.1C (66F). Even Mont Tremblant reached a record-breaking 15.3C (59.5F). In Ontario, Windsor reached 20C (68F). 

The warm air has surged northward from the Gulf of Mexico in advance of a strong storm system and frontal boundary lifting northeast into the Great Lakes on Tuesday afternoon. This storm will bring abrupt changes to our weather on Wednesday. In advance of the front, warm summer-like temperatures have spread across the central US into Ontario and Quebec. Thunderstorms even developed across southern Ontario on Tuesday, and a few may occur in southern Quebec on Wednesday. Behind the front, winter rushes back in very quickly.

Lows tonight in Montreal will be very mild, 7C (45F), with gusty south winds persisting. On Wednesday, we can expect another record high, as temperatures reach 13C (55F). Thickening clouds will lead to steady rain in the afternoon along with increasing winds in the St. Lawrence Valley. 

By the supper hour, the cold front arrives, with winds gusting 70-90km/h in the Montreal region for a few hours. Temperatures are expected to plummet after 6pm from well-above freezing to well below. Any leftover rain will change to snow and end by midnight.  The combination of precipitation and rapidly dropping temperatures will result in slippery sidewalks and roads. Extreme caution is advised if venturing out Wednesday night. The low by Thursday morning will be close to -15C (5F), with windchill values in the -20s.

Skies will clear out on Thursday, with a cold high of -7C (19F) forecast. Our cold snap will be short-lived, with warm air returning by the weekend.