Arctic Invasion begins this Weekend

A significant pattern change will be underway across North America by this weekend.

A massive storm to the southwest of Alaska (part of which was Typhoon Nuri) will help strengthen an upper level ridge of high pressure over eastern Alaska and northwestern Canada through next week. This in turn will force Arctic air to spill far to the south and eventually east as a piece of the Polar Vortex shifts into northern Ontario for a short period.

Latest indications are that this cold pattern will persist from the Prairies to at least Quebec for a good part of the next two weeks.

In the meantime, As the Arctic air moves into Alberta late Saturday and Sunday there will be an area of expanding snow from northwestern Alberta to southwestern Saskatchewan through Sunday night. With this type of event we can certainly see at least 8-15 cm of snow over southwestern Alberta with locally higher amounts.

Speaking of snow, no significant changes to our snow forecast map for Quebec and northern New Brunswick with this storm coming late tonight through Friday.

There is also the potential for a significant snowfall centered around Tuesday next week over the northern and western half of Ontario. Computer models have trended farther north and west with the storm, which would favor rain over southern Ontario before the core of the cold air works in for the second half of next week.

The combination of the Arctic air and warm lakes could be a recipe for widespread lake-effect snow later next week. Too early for specifics though.

This pattern shift will also lead to a less stormy period over BC with above-normal temperatures for the most part next week.

October 2014 snow cover

According to the Rutgers University snow lab, October 2014 had the 3rd highest snow cover extent on record for the Northern Hemisphere. Records go back 47 years. Other October snow extent rankings below....

Eurasia...2nd highest North America...8th highest Canada....9th highest

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I will post the ECMWF interpretation maps on the next blog. As most of you who follow this blog already know, the weekly models did not catch on to this upcoming pattern shift until early this week. Previous runs were way too warm. I have noticed that the ECMWF weeklies seem to have a warm bias, especially during warmer ENSO events (El Nino) and I expect this to be the case much of this winter, so expect to see plenty of red, even though in reality there may need to be more white (neutral) or blue (cold) anomalies. So far, we are still not officially under an El Nino, but based on current conditions in the Pacific I would un-officially call it a weak El Nino. The CPC guidlines for an El Nino/La Nina to be named are pretty strict.

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