Wednesday, December 19, 2012

Christmas Day Storm System


11:15 AM Wednesday Update... Another round of data and another solution.    First thing I want to talk about is the huge snowstorm which will start today and last through Thursday across the plains into the Great Lakes.  This fresh snowpack could influence our temperatures here in Arkansas.  With a strong west to northwest wind Thursday, the air will flow across this fresh layer of snow into Arkansas.  This will help keep it chilled so our forecast highs may need to be taken down a couple degrees Thursday and Friday.

Winter storm warnings and blizzard warnings up north.

Now onto a quick update about next week.  I think it's very obvious right now there will be a system Tuesday into Wednesday.  I know you don't like to hear me say this, but how this impacts our weather is not fully known yet.  It still looks like rain to me.  Depending on the track of the low, thunderstorms could also be a factor, especially across southern and eastern Arkansas according to the latest GFS on Tuesday.  IF there's a change over to snow, the GFS says it will be northern Arkansas only.  The GFS also suggests that we would get "dry slotted" Tuesday night into Wednesday, then wrap around moisture would bring flurries and snow showers to far northern Arkansas.  Too early to get too specific, but that's what it says.

Here are the maps from the GFS.  Below you will find the Euro which is a little more aggressive with moisture on the back side.

Christmas Eve morning shows a warm front extending from an area of low pressure located in the TX panhandle.  That front is just south of the state and we have a chilly easterly flow here at the surface for much of Arkansas.  Rain is developing across the south.

By Christmas morning, the GFS says RAIN!  the low is tracking across southern AR with heavy rain and storms there.  Look on the back side.  There's snow north of the blue dashed line in OK and KS as cold air gets pulled around the low.
The GFS shows dry air punching into the system from the southwest cutting off precip here, but look at that wrap around moisture in NW AR.  That's light snow!  Once again, this is just one of four model runs today.  Bottom line, nothing is set in stone with the system next week.
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Sorry, but I just don't have much time for a big update this morning.  Hopefully later today I will.  As I have said, we will not have a good handle on a dynamic system like the one next week until we get to within the 3-5 day window.  The models continue to have problems dealing with the storm and the track and I expect future model runs to struggle.  For all you snow lovers, there's still hope late Christmas or the 26th.  Nothing is guaranteed, but at least there's a storm on the table to watch.

Below is the overnight run of the European model

This is valid noon on Christmas Day.  There's a surface low southeast of AR which would greatly diminish the severe weather threat.  Remember, it's still within the realm of possibility depending on the track of the surface low.  This 1 run of the European has colder air moving into Arkansas with rain showers across most of the state.  The upper level system is bringing snow (light) to Oklahoma and Missouri.  The blue dashed line is a good indicator of the rain/snow line.  It also depends greatly on surface temperatures.
By late Christmas Day around 6 PM, the rain snow line is further south and thru central Arkansas.  The low pressure at the surface is in NE MS.  That's the closed back line.  Those solid back lines show a circulation around that low out of the north/northeast.  This is bringing very cold air into the state.  Also, the upper level system is producing some light snow across northern AR and Missouri.  There could be a few flurries further south IF this model is correct, BUT TAKE IT WITH A GRAIN OF SALT FOR NOW.
By midnight on the 26th, strong northerly winds continue across the state with snow showers for northern AR and flurries further south.  Remember, we do not get significant snows with a northerly or northwesterly wind at the surface.  HOWEVER, flakes can still fly and that possibility is certainly on the table. More later.

2 comments:

Will said...

This storm today / tonight is the pattern changer we've been waiting for and I've been hyping, (hoping for). I mentioned a couple of weeks ago about a Christmas day present and I still think it's going to happen. The models are coming into better agreement with a significant cool down heading into January and it all starts with this big storm today, IMO. January looks cold and stormy. Might be time for a snow sled contest between Ninja, SNBob and Todd, although I think Todd likes to ski..........

Chris McCrillis said...

Averaging the storm track locations from last nights model runs and the most recent GFS 12z today would be favorable. Like Will mentioned above, historically it seems we need need the midwest storm track and the snow cover it provides first before we can get in on the winter weather fun. With today's midwest storm, we can check that off the list.

NOAA Winter Guidance