Valentine's Day flirts with record cold, minus-40 not out of the question

Saturday, February 14, 2015, 2:02 PM - Some of the coldest air of the winter thus far will be in place across much the eastern half of the country … and it's here to stay.

Temperatures early Friday morning are expected to be near -20C to -25C across southern and eastern Ontario as well as for southern Québec, and near -30C to -36C across parts of northeastern Ontario and southwestern to central Québec.

Temperatures early Friday morning are expected to be near -20C to -25C across southern and eastern Ontario as well as for southern Québec, and near -30C to -36C across parts of northeastern Ontario and southwestern to central Québec.

A clipper Friday night through Saturday morning will swing through southern Ontario and then into Atlantic Canada where this clipper is to evolve into another major winter storm. This clipper will actually moderate the temperatures some for Friday night into Saturday for central to southern Ontario and parts east. But that doesn’t mean it won’t be cold. With strong northwesterly winds through the day gusting near 50-70 km/h will bring windchill values down to near -20C to -30C for southern and central Ontario and near -35C to -45C for northern Ontario through Saturday. With the light clipper snow and snow on the ground, these winds will certainly bring widespread blowing snow with white out conditions, with the risk of blizzard conditions as well. Thus travel on Saturday across southern Ontario will be quite traitorous with dangerous windchill values.

Figure 1 below sets up the pattern for Friday night into Saturday. As the clipper slides off to the east northeast an arctic high pressure system will settle southward. The air with this arctic high will drive temperatures down into the -25C to -35C rang across northwestern Ontario, southern Manitoba, and eastern Saskatchewan, and into the -35C to -38C range for central and northern Manitoba.

Saturday night into Sunday as this arctic high pushes southeastward and the temperatures will plummet with lows Sunday morning expected to be near -20C to -30C. From Niagara though the GTA and into eastern Ontario there is still some uncertainty if the cold will be as dramatic likely into the mid to high minus teens as cloud cover from the large Atlantic low may keep temperatures little milder through the early Sunday morning hours. But as the breezy northwest winds continue windchill values near -35C to -45C Saturday night into Sunday morning will certainly make conditions downright dangerous.

Looking beyond the weekend the large scale pattern is really consistent among long range models that the cold will stay through the remainder of February. It’s not expected to remain as extreme as the cold we expect for this weekend but consistently below average. In fact if the projected trend pans out, it is quite likely that the entire month February will not have a day above 0C. Below shows the upper air 500 mb (about 5.5 km elevation) as depicted by the GFS forecast model for today and then for February 20th. Although there are some localized deference’s, the large scale pattern is the same. There is a persistent ridge in the flow over western Canada and through the Atlantic (depicted by the blue zigzags) which allows branches of the polar low (area outlined in red) to swing south into the central and eastern part of the continent. The other aspect to take note of is the cross polar flow as well, which allows for a steady stream of frigid Siberian air into North America.

How does this translate to the temperature pattern at the surface? The bottom shows the average from an ensemble of individual forecasts.

Looking at the average will help to eliminate some of the biases that come into play from various individual operational forecast models and gives a better sense of the large scale trend. Note that this chart does not show actual temperature but a departure from the seasonal normal for this time of year based on the 1980-2010 climatology. For the remainder of the moth it’s clear to see the real core of the cold will sit through southern and central Québec, Ontario, and southern Manitoba where temperatures on average are expected to run nearly 8 to 11 degrees below normal. Atlantic Canada and Saskatchewan will be on the fringes of the cold on average running 1 to 5 degrees below seasonal. Although the Atlantic regions numbers are being skewed some. With the succession of coastal lows temperatures will likely be on a roller coaster ride of mild periods followed by burst of arctic air as the lows depart. When these large swings are averaged then tend to cancel each other out leaving relatively low number. The other area that will see its swings, as usual, is Alberta. With the position of the ridge in the west and the disturbances swing through as branches of the polar low push by, the arctic front will meander in and out of the province which will lead to the usual blast of arctic air followed by a Chinook warmup.

WATCH BELOW: THE POLAR VORTEX EXPLAINED