Severe Weather in the Plains

November 04, 2011

When Will Winter Come?????

I know that a lot of you out there are snow lovers, and you are getting tired of the "warm" weather.  I also am willing to bet that a lot of people who read this blog are snow haters.  We all know that across the northern regions, snow is inevitable.  Eventually, winter will sweep over, and snow will cover the ground.  At this point, the question is when.  Well, we are already seeing signs that the atmosphere is gearing up for a big cold blast, one that may potentially last through the winter.  First of all, the NAO, or North Atlantic Oscillation, has been positive over the last few months.  This has allowed cold air to build in the Arctic and Western Canada:
However, it is starting to look like a turn to a negative NAO is coming.  This will allow for the cold air that has been building up to spill southward through the United States.  Models are also showing the Greenland Block making a return, which generally leads to cold in the United States.  Let me show you what the models think is coming in the 8-10 day time frame:
I want you first to know that you should not take these maps for given, considering this a long ways out.  The arrival time is likely to be delayed a little bit.  I want you to pay particular attention to the GFS model's interpretation (on the right).  It is a perfect example of the Greenland block.  We see a lot of blocking in Greenland, causing cold air to spill southward into the US.  Again, the question isn't if, but when.  The NAO may hold a clue to that.  The GFS ensembles are showing the NAO diving negative over time:
This would result in some cold air across the eastern USA.  In summary, it looks like the NAO will go negative, and the country will turn cold.  The question is when.  While the models are showing this pattern change arriving in the next 1-2 weeks, I think it may wait until about halfway through November before we truly get cold.  Don't despair snow lovers!  Stay tuned!

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