When looking at the modelling and projected indexes (trending -NAO/AO/neut PNA), the arctic air looks to hold strong over the snowfields of Canada with lobes dropping into the Lower 48 next 2 weeks.

Here’s the North America snow cover difference between this time last year and now.

Note most of Canada is white and this will help support minimal weakening of arctic air as to comes south from the arctic.

This weekend looks interesting with a deepening storm system crossing the Rockies, Plains and then really bombs out to the north of the Great Lakes. The warm, moist air which pours north along and ahead of the cold front looks to bring a Sunday afternoon severe threat through the Ohio Valley, perhaps parts of the East (Carolinas, possibly Virginia). Some decent rains too.

Here’s the ECMWF surface chart for later Sunday.

Here’s the SPC severe risk for Sunday/night.

By Monday the low bombs out south of James Bay and this will produce gales through the Lakes and some heavy snow on the backside across Ontario with lake-effect too.

Check out these projected wind speeds in knots Monday.

1am

1pm

As for waves, well the GFS is projecting 20 foot waves over eastern Lake Superior, 15+ feet waves for Erie.

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More arctic air drops south on the backside of the low but it appears to stay much further north this time and is less severe than what we’ve just seen.

By late week another system undercuts, crossing the central or southern Rockies. With a lot of ‘built up’ cold air sitting over a well snow covered Canada, each system which cuts underneath, will tap this arctic pool and drag it south.

Here’s the 144 hour ECMWF surface.

By next Friday the system is seen crossing much further south than the late weekend system and arctic air is noticeably covering the northern tier.

In the 850 temp chart you can see the system draws arctic air all the way into the system which is crossing TX/OK but notice that it’s pulling some of the really potent stuff close to the US-Canada border. Don’t be surprised, given those indexes, the cold air available and the snow cover covering much of Canada, that we see some very cold day and nights from Montana, the Dakotas, Lakes and interior Northeast late next week with a snowstorm over the Southern Plains.

Here’s the 168 hour ECMWF snow chart.

It’s going to be very interesting around Thanksgiving as I suspect there will be plenty of cold air around and with a continued active, undercutting storm track, we could have plenty of fun and games right around the holiday’s and into the early half of December.

Check out the CFSv2 blocking over the arctic next couple of weeks.

CFSv2 has been really bouncing around lately with much warmer looks than back a couple of months ago but I notice it’s trending back towards cold. Check this out.

DECEMBER

JANUARY

FEBRURARY

SEASONAL (DEC THROUGH FEB)

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Tags: great lakes storm, us weather, US winter forecast