Warm US December Opens With Record Snow Cover

Written by on December 2, 2015 in Autumn 2015, United States of America, Winter 2015/16 with 0 Comments

It’s worth pointing out that while there’s a great deal of hype even excitement regarding the evolving warm December pattern, what’s being overlooked is the fact that Canada is nearly completely snow covered and as well as that there’s a good deal more snow not just over North America but hemisphere wide compared to this time last year.

ims2015335_usa

On Dec 1st there was 38% of the Lower 48 snow covered which is the most for the date since at least 2003 when records began.

Lack of ridging in the West has greatly helped fill in Western Canada compared to the last 2 years.

November 28, 2014 vs November 28, 2015

RecentSnowCoverNHhemisphere

No question, the models continue to drop the red paint bomb over much of the continent and I’ve no beef with that.

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Always remember though that while it may be warm over much of the US or indeed mid-latitudes, the cold is building with the core of the polar vortex projected to drop to between -80 and -85C at 50hpa within the next 10 days.

gfs_t50_nh_f240

If this super cold pool remains intact, that’s fine but with the Canada-wide snow cover and a fullscale SSWE, we could see one heck of a cold outbreak. It happened in 1985, 1994, 1996 and will happen again at some point. This year or 5 years from now, who knows.

Once again, here was Dec 1984. Yes there was abnormally warm December prior to super arctic outbreaks!

dec-1984

This followed the month after!

compday_71_58_109_165_18_9_19_52

Here’s the blowtorch seen by both ECMWF and GFS ensembles in the 11-15 day period.

Credit: Michael Ventrice

Credit: Michael Ventrice

Credit: Michael Ventrice

Credit: Michael Ventrice

Just as the models are consistent with the warmth Dec 5-15th, it’s also become consistent with the northward shift in positive heights in the day 10-15. The exact time of a possible large scale pattern flip is very uncertain but this is worth keeping a close watch. If it happens and we see a major cool down, it may come in the 10-15 day, 15-20 or 25-30 day. If may not happen at all.

Both EPS Control and GFS ensemble keep showing a more negative AO/NAO beyond Dec 15th.

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

GFS ensemble

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

See this morning’s video for the discussion.

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