Monday, January 06, 2014

Here We Go Again


I think this cold air is every bit as harsh as we have been talking about.  The low Monday morning in Little Rock was 13 degrees.  The GFS has 12 and the NAM has 9 degrees Tuesday morning in Little Rock, but the winds will not be as high.  Will we get down into the single digits for the first time since February of 1996?  I have my doubts.  Remember, we need three things:  clear skies, NO wind, and snow cover.  We obviously don't have the snow on the ground in Little Rock.  I think the official will be 10 or 11 degrees, BUT outlying areas will go into the single digits.  I'm not saying it's impossible for Little Rock to drop into the single digits, it's just very difficult if you don't have all three of those key ingredients.  It will be interesting to watch.

We'll come out of this deep freeze as we go into Wednesday and Thursday, but a round of ice and snow will be likely late Wednesday into Thursday morning.  I expect the models are warming us up too much Thursday, but we should easily manage to get above freezing so I only expect problems for a few hours.  The target area will be western and northern Arkansas, but I think central areas have a chance as well.  At this time, I think snow will fall across at least the northern 1/3 of the state with a mix of freezing rain and sleet further south and west.  There are differences in the modeling that must be sorted out.  For instance, the GFS appears colder than the NAM.  I might be issuing another SCHOOL:CON index map Tuesday.

Here are a few maps below...

This is the Euro surface temperature maps.  The solid white line is the 32 degree line.  Everything north of it is at freezing or below.  At 6PM Wednesday, you can clearly see there's a dip in this line over western AR.  That's likely due to the fact precipitation is just starting there and the model sees some evaporative cooling over there.  With dry low level air in place, the temperature will actually drop a few degrees during the onset of the precipitation.
By midnight, most of the state is at or below freezing, except the south and southeast.
At 6AM Thursday, the freezing line is still over southern Arkansas.
According to the Euro state snowfall map from weatherbell.com, there's a good bit of snow that falls over a large majority of the state.  HOWEVER, I caution you, DON'T take this literally right now.  I think it makes more sense for snow further north given the vertical temperature profile.  While I'm not 100% sure, I think the model may be seeing sleet further south.  This is NOT our forecast at this time, just a computer model
This makes more sense to me.  The GFS from weatherbell.com.   This shows you the amount and type of precip over the previous 6 hours.  Purple is freezing rain, orange is sleet, blue is snow, and green is rain.  The red solid line is the 32 degree line at the surface.  This is valid at 6PM Wednesday.  Just like the Euro, evaporative cooling during the onset of the precip lowers temperatures over the western portion of the state.  Freezing rain and sleet is falling.  I think it's underdoing the snow across northern Arkansas.
By midnight Thursday, you can see icing problems across the north and west.  Little Rock is borderline with this model
By 6AM Thursday, we see a wintry mix across the northern half of the state.  Shortly after sunrise, temperatures should climb above freezing from south to north changing the mix to plain, cold rain.



This is from a program called "BUFKIT".  It's the GFS and it's read from right to left.  The orange lines indicate sleet from around 6PM to about 10 PM Wednesday in Little Rock.  The red lines show freezing rain from about 10PM until late Thursday, then green is rain.  I think it's holding onto freezing rain wayyyy too long.  Much still can change.



In summary, there are a few things that still need to be resolved with this Wednesday PM/Thursday AM forecast.  Precip type will be quite tricky.  Many times, arctic air is more stubborn leaving than the models indicate which would lead to a more icy scenario and a colder Thursday, however, I still think temperatures will go above freezing Thursday morning.  At this time, I think it's best to say western and northern Arkansas stand the best chance for seeing snow and ice and it could be enough to cause plenty of travel headaches.  Central Arkansas is more questionable.  STAY TUNED!

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