Monday, December 29, 2014

The Forecast Has Gone Political


It's just like Washington, nothing agrees and you wonder if it ever will?  There are differences and then there are HUGE differences and the long range forecast reflects the latter.

Let's start off with what we do know and most of that is in the short range.  It's going to get very cold.  This is nothing extreme and nothing we haven't seen before, but it's a little shock to the system because of the mild month so far.  This is very cold, dense arctic air which is difficult to dislodge.  It will begin to retreat by Thursday, but it's like trying to move a heavy brick with a garden hose.  It will take some time and it's SLOW!  The huge closed area of low pressure remains over the far southwestern United States, but a piece of energy gets sent eastward and precipitation breaks out from southwest to northeast Thursday PM.  One of the properties of arctic air is it's very dry.  Through a process called "evaporative cooling", I suspect we'll have a little sleet or rain mixed with sleet as the precipitation starts.  This may occur over a large portion of the state.  However, temperatures should be a touch above freezing.  Across the higher elevations of western Arkansas and across northern Arkansas, readings may be around 32 and we'll have to watch for sleet and freezing rain and it could cause a couple slick spots Thursday night.  Whatever wintry weather occurs will be brief and we will ALL change to a cold, miserable rain!

Then it's Democrats vs. Republicans... the GFS vs. Euro, etc.  The differences are big and you wonder if anything will get settled.  The Euro doesn't bring the southwestern U.S. storm in until SUNDAY!  The GFS has it almost on the east coast at that time.  What's a thousand miles, right? LOL.  

The differences do not stop there.  The GFS sends in another strong arctic surge in one week and the Euro says NO WAY!  The Euro brings in milder temperatures and keeps the arctic air up in Canada.  Check out the maps below.

This is the GFS valid late Thursday courtesy of weatherbell.com.  This is an initial surge of moisture moving into the state.  See the blue line?  That's the 35 degree line at the surface.  With some low level dry air in place, I suspect there could be some sleet or rain mixed with sleet, but temperatures should hover above freezing.  The 32 degree line is across northwest Arkansas and freezing rain/sleet will be possible for a brief time.  Also, watch the higher elevations of the Ouachitas.  Once again, we should transition to a cold rain quickly.
The European model valid Sunday at noon shows the strong piece of energy over Arkansas.  You're looking at the 500 mb map which is about 20K up in the atmosphere.  You can clearly see the reds and purples over Arkansas indicating the location of the strong area of low pressure aloft.  This is the same low that will wait over the southwestern U.S. for a few days.  This would bring some possible wintry weather to northern Arkansas IF this verified, but watch out.  The GFS looks completely different. 
The GFS at the same time period has the upper low moving into Pennsylvania.  That's a little different eh?  MUCH FASTER!
A week from today, the GFS shows another very strong surge of arctic air coming down the plans.  That's a 1050+mb high at the surface located over SE Montana.  The black lines are isobars (lines of equal surface barometric pressure).  That air is very heavy and dense and would drain down the plains into Arkansas early next week.
The Euro during the same time period says, "not so fast, my friends".  It places LOW pressure at the surface over Montana and bottles up the cold air over Canada.  Where the GFS has a major arctic chill, the Euro shows mild temperatures.


In summary, we know we'll have a couple rounds of precipitation later this week into the weekend.  Like I said, it could begin as a little ice, but go over to rain quickly.  After that, it's like the battle in Washington D.C all the time.  However, we can't "kick the can down the road".  We WILL know a winner by this time next week and this will get settled.

No comments: