Saturday, January 12, 2013

Some Ice and the Arctic Express?


Told ya this weather would get active and present challenges.  With extensive cloud cover Saturday, Little Rock managed to hit the mid 70s and that's close to a record high.  Can you imagine if we had some sun?  Temperatures would have likely soared to 80.  Amazing stuff considering the air heading our way for the next few days.  Temperature highs will likely drop 30-35 degrees.

Now onto the precipitation challenges.  At this time, I still don't think any major ice or snow storm will affect Arkansas.  However, as we all know, it does not take much frozen precipitation to cause problems on the roads.  I'll explain all the chances below using the European model and the North American Model (NAM)

Also, I tweeted an image of the Canadian model Friday.  It was valid 10 days down the road.  I thought it had lost its mind forecasting the dramatic plunge of arctic air.  While such an EXTREME solution may be unlikely, it may be onto something.  Remember the stratospheric warming event I blogged about a week or so ago?  Well the lag time between that and having an effect on our weather would give the Canadian model some credibility.  Also, the American GFS and the European model also show an arctic intrusion into the United States.  I'll explain it all in the maps below.

The European model valid at noon Sunday indicates the front is well past Arkansas and the colder air is here.  However, is it cold enough for anything frozen?  The data suggest the precip. along the northern edge of this shield could be.  While this is mostly rainfall, it will have to be watched.  Remember, the blue dashed line is generally the rain/snow line.  We're south of it so we're talking about rain or ice.  It's ice if the surface temperatures are 32 degrees or colder.  Most of the data shows readings holding just a few degrees above this crucial threshold, but I'll monitor that.  BTW, the greens represent precipitation over the past 6 hours.  You can see the legend at the bottom of the graphic.  The black lines are isobars (lines of equal barometric pressure).  There's a surface high coming out of Canada here and that's the colder air! The black closed line near the Great Lakes is an area of low pressure and the cold front extends south of that through middle TN into Louisiana.
The front is well east Monday at noon.  Most of the state is dry with high pressure building in.  However, a wave of moisture is noted here in southeast Arkansas.  The blue dashed line is generally the rain/snow line.  This precip is south, but we must consider icing along the northern fringe.  Again, nothing major, just minor amounts which could cause some concerns early Monday morning into the PM.
Again, it 's more of the same just 24 hours later at noon Tuesday.  It's southeastern Arkansas which stands a chance for some precipitation.
In my opinion, the NAM has been horrible this winter, but I thought I would show this to you valid Tuesday at 3 PM.  The precipitation shield is further north into central Arkansas.  This COULD be a little icy, but other models keep us dry.
Now onto the forecast in 10 days.  It's important to note we are very much in the long range and you have seen how forecasts change in the short range.  However, as mentioned above, this does time out well with the strat warming event and the arrival of the cold air.  How intense the cold air is and where it's aimed can always change.  The European shows the white line (32 degrees) well south through the western, southern, and eastern U.S.  Everything north is below freezing and in the Great Lakes, it's frigid with temps of -5 to -10.  This is very cold for much of the country if this verifies.
The GFS is even colder in 10 days and directs the coldest air along the front range of the Rockies eastward.  This would slide the cold air down the plains and into the south.  The 32 degree line is already south of Arkansas.  The air in the Dakota's is unbelievably cold!  It's showing readings around -25 up there! BRRRRRRRRRRR

1 comment:

Will said...

Better late than never, Todd. As I have been saying for awhile now the cold is coming. Just as I picked out the Christmas day storm for you I also gave you the upcoming arctic express. Just send me a blog shirt and we will call it even!!

Seriously though, there is some very good model consensus as well as other atmospheric factors that are predicting a major cold outbreak in about a week and a half.

NOAA Winter Guidance