Friday, February 10, 2012

Monday's Arkansas Slushie

I like to call it a "slushie" because I think almost every form of precipitation will be possible in the state.  From rain to freezing rain, sleet and snow, this forecast will give us headaches pinpointing exactly where all this sets up.  The computer models are becoming more aggressive with the chance for frozen precipitation.  Remember in the videos below, I said the cold air was leaving as the moisture arrives.  However, due to the nature of cold, dry arctic air which should be in place.  Evaporative cooling will take temperatures down a few degrees Monday morning.  With clouds and precipitation in place, the cold air at the surface will be very slow to warm, but it will.  This may be a case where the high temperature Monday will not be reached until late Monday night.  The period of frozen precipitation in central Arkansas should be limited to the morning hours, but will last much longer across the north.

Remember my disclaimer, this can and WILL change with each run of the models.  Regardless, I'm not expecting any sort of paralyzing winter storm whatsoever!  This will be a reminder that ole man winter is still in control.  Check out the maps below from the overnight run of the models.  I'll keep you updated here and.


6:40 PM Friday Update...  I have no real changes to what I have below, but I do have something to add.  The WeatherNinja and WeatherClipper brought up a very, very good point.  We do not get significant snow or ice storms unless there is an east or northeast wind at the surface.  Forecast surface winds during this event will be out of the southeast and south.  This could limit snow and ice across portions of Arkansas.  Nevertheless, this is a significant event due to the fact we haven't had much winter this year.  I'll continue to keep up updated on the "Arkansas Slushie".

8:45AM Friday Update...

I wanted to add a couple model soundings from the GFS on Monday.  This takes a look at the atmosphere from the ground up giving us an idea of the temperature and moisture profile.  I have selected Little Rock as the point of reference.

6AM Monday...At the bottom of the graphic, you will see a black line going upward from left to right.  This is the freezing line from the ground upward.  The red line is the forecast temperature and this stays to the left of the black line meaning the readings will be at or below freezing all the way up.  This is a profile for snow.  Notice the warm nose of air several thousand feet up.  While temperatures at the surface will struggle to recover, there is a push of warmer air aloft which would eventually change the snow over to freezing rain/ sleet, then rain.  Remember, this is just one models interpretation.
6 PM Monday... notice the warm nose of air has surpassed the freezing line.  This melting layer would cause the snow to fall and melt within this layer.  Notice surface temperatures (at the very bottom) are still near freezing!!!!  The question is, how long will it take for the snow to turn to ice, then to rain.  These will be answered in the days to come.  I'll keep you updated.

This is the GFS valid Monday morning at 6 AM.  It may be a little too aggressive painting the whole state in pink (snow).  I do think there will be at least a chance for that across the northern half of Arkansas.
By noon, the snow is confined to the northern portions of the state with sleet and freezing rain beginning to come to an end across central sections as temperature SLOWLY climb above freezing.  It's all rain (green) south.
By late Monday (6 PM) the thermal profile is more conducive to sleet across the north and rain elsewhere as warmer air continues to move north.  As you can see, it's the northern portions of the state who will stay in the frozen precip. longest.
This is the GFS snowfall accumulations indicating northern Arkansas could see 2-4''.  This is NOT a forecast, just a piece of model information.  Here in central AR, if we start out as snow, there could be very light accumulations before the changeover occurs.

This is the GFS indicating total amount of freezing rain accumulations.  This is targeting west central into portions of central Arkansas.  A light glaze of ice would not be out of the question.  Keep an eye on this.  If freezing rain amounts exceed .25'' then problems could start on trees and powerlines.
This is the GFS indicating where sleet would accumulate just north of the freezing rain area.  Sleet is the preferred form of precip vs. freezing rain.  This does not cause powerlines to get weighted down with ice.  Again, these are just maps from one model run. MUCH CAN AND WILL CHANGE.  I'll keep you updated.


Anonymous said...

I think little rock gets just rain with maybe a sleet pellet or two when precipitation first starts. Then just a cold damp day in store. Same for south arkansas. Now for the northern 2 or 3 rows of counties i say 1 to 3 inches sleet/snow. Those wanting the big one will be disappointed. This system will be moisture starved and the upper levels to warm. Maybe next year.

Anonymous said...

I wish we could have a collosal ice storm like we used to in past winters.

JB said...

Why is the first commentator saying "moisture starved"? That is not the proper way to put it. The thing to look into is temperature, not moisture. All of the parameters aren't perfect though. I just want some winter WX before the winter is up

snowfreak15 said...

18z gfs is my friend right now........ NAM is soooo disappointing

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