Tuesday, December 16, 2014

Let's Talk About The Christmas Forecast And Beyond

Before I get into the Christmas forecast, let's give credit where it's due...  the GFS!  In the previous blog post I expressed my opinion the Euro would have the wrong idea for the system this upcoming Friday.  Remember, the GFS idea beat the Euro several days out with the system Monday.  Now the Euro looks a lot like the GFS for the late week weather maker.  The cold air is really lacking with the storms coming through Wednesday night/Thursday and the one Friday/Saturday morning. That was my concern stated in my blog post Monday.   I do see plenty of cold air getting drawn southward into the United States, but that won't happen until around Christmas.

At this time, I am holding my ground and saying it will be a cold rain Wednesday night into Thursday with a small chance for a wintry mix near the Missouri border.  The exact thing may happen Friday into Friday night.  It should be a cold rain with a possible change over to a light wintry mix as it ends near the Missouri border.  Not only does it appear most of the moisture will be shunted off to the east as colder air comes in, but it also looks like it never gets close to 32 degrees for most of the state.

I know many are getting frustrated and wanting cold/snow.  Remember, our winter really hasn't even started yet.  We usually do not get our big snows and cold air until January and February so there's still plenty of time.  As I stated above, I really think temperatures should go below average the last 7 days of this month and there are some interesting things going on around Christmas.  I'm NOT saying snow, but the pattern is active and cold air is on the march.

The pattern begins to amplify later next week and that may send colder air in from Canada. I expect the ridge to strengthen up the west coast into western Canada.  This is ideal for dislodging the cold air and sending it into the lower 48.   The timing of each of these boundaries can't be nailed down this far out, but I'm feeling confident there will be colder air on the march.  It's almost useless to look at the operational models this far out if we're dealing with arctic air.  Many times, these air masses are colder and arrive faster than the models project.  Bottom line, it will be an active week weathewise with much to watch.  At least we don't have a large ridge of the central United States and blowtorch warmth!

This is the 500 mb pattern  (about 20,000 feet) Christmas Day according the the Tuesday morning run of the GFS.  Look at the ridge building along the west coast and eastern Pacific.  That will help dislodge cold air and move it south.
The European shows that ridge developing as well and that should open the door to much colder air from the north diving out of Canada.  The question that has to be answered is: how are south does it get by Christmas?
From weatherbell.com , this is the GFS ensemble temperatures just off the surface.  This chart shows the temperatures anomalies in degrees C.  valid Christmas Day.  It indicates readings will be at or just below average across the southeastern United States including Arkansas.  Look at the colder air building over western Canada!!!
Look how it grows colder than average December 26th according to this one model run.  Again, the timing of cold air will be problematic this far out, but it should arrive around Christmas Day.
By the 27th, it gets even colder.  The temperature anomalies are -2 to -4 degrees C.
By the 30th of December, We're cold!  Temperature anomalies -5 to -6 degrees C.  Look at the temperatures relative to average over Alaska and the eastern Pacific!  That's really showing you the ridging going up there.  When cold air dives south out of Canada, it's completely normal for Alaska to be warmer relative to average and we're colder relative to average.  It's still cold up there, but not as cold as it could be.
By the 31st, it grows even colder with arctic air continuing to build into the United States from Canada.

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