A tale of two seasons: Spring surges north, but winter fights back

Friday, April 11, 2014, 6:18 PM -

The past week has brought a long-awaited taste of spring to parts of western and central Canada as British Columbia, Alberta, Saskatchewan and Ontario all seeing their first 20°C days of the year. Another round of warmer weather will reach southern Ontario and southern Quebec during the weekend and track into Atlantic Canada during next week.

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However, winter will also fight back as arctic air plunges back into the Prairies and then slowly spreads east next week. From the Rockies to the Atlantic, many will see a quick transition from May-like weather back to March with the passage of the front.

The image below highlights the tale of two seasons that we will see across the country this weekend. The regions with varying shades of orange (much of B.C. and southern Ontario) will be above seasonal, with temperatures that are more typical of May, while much of Central Canada will see well below seasonal temperatures (indicated by the shades of green & purple) that will be more typical of late February.

Of particular interest is the Great Lakes region where there will be a tight gradient between the areas that will be well above seasonal vs those that will be well below seasonal. A very slow moving front with such a large contrast in temperatures on either side of the front results in a forecasting nightmare for parts of southern Ontario. While confidence is high in the overall pattern any subtle changes in the timing and placement of the front could result in a 10 to 15 degree change in your forecast for Sunday and Monday.

RELATED: Winter tries to push back in April

In addition to the contrasting temperatures, there will also be a large range in rainfall amounts across the region. A few rounds of rain and even thunderstorms will run along the front, while locations south of the front will see scattered showers along with periods of dry weather.

On Monday the well above seasonal temperatures will surge into Quebec and the Maritimes while the arctic air slowly advances towards southern Ontario. During Monday afternoon, it looks like temperatures will be in the low to mid 20s from the Toronto region to across southern while the temperature plummets to near 0°C across southwestern Ontario.

On Tuesday, well above seasonal temperatures are expected across much of Atlantic Canada. However, the warm & humid air crossing the frigid ocean waters will likely result in dense fog and much colder temperatures near the southern shores of each province. Meanwhile, from the Prairies to southern Quebec, temperature will range from 5 to 20°C below seasonal.

By Wednesday afternoon, the cold front will be cross Newfoundland with above seasonal temperatures limited to the eastern half of the province. The rest of Canada east of the Rockies will be well below seasonal.

In addition to the temperature roller coaster, there is also the threat for heavy snow for parts of central and eastern Canada. A swath of snow will fall across central Saskatchewan and southern Manitoba Friday night and Saturday and then spread into northern Ontario during the weekend.

RELATED: Visit the Alerts section of the website to keep on top of active weather across the country

As the Arctic front crosses eastern Canada early next week, a couple of systems will develop along the front and bring the threat for snow behind the front. The Canadian and American models (shown below) have been consistent in showing the heaviest snow east of Lake Superior, across parts of the Nickel Belt and northeast into Quebec.

However, there is more disagreement between the models regarding the threat a significant snowfall for Montreal, Quebec City and the Eastern Townships. The Canadian model brings more snow to the region than the American based GFS model. However, the European model is even more aggressive with bringing much heavier snow totals to this region.

While there is a high level of confidence in the overall weather pattern through the middle of next week, there are several high impacts details that will change during the days ahead, so be sure to check back for updates.