Saturday, March 15, 2014

Update... Weekend Soaker and Some Wintry Weather Too


2:30PM Saturday Update... everything seems to be on track and if you want to see the timing of all the rain and thunderstorm activity, check out the post below.  I still think the heaviest of the rain comes through tonight with many areas seeing more than 1'' and some up to 2'' or more, especially northwest.

Now onto the snow chances.  I still think there will be flakes flying across northern Arkansas late Sunday morning into the afternoon.  As I have said, this is a very typical late winter system coming through.  There will be a few things which will act against any major accumulation. 

  • At the time the precipitation changes to snow across northern Arkansas, temperatures will be at or just above freezing.  
  • This will likely happen during the daylight hours and during the late winter season higher sun angle (even with thick cloud cover), this also makes it tough to get any major accumulations.  
  • The ground will also be very wet from the overnight rainfall.
  • Ground temperatures are warm from all the nice weather lately.  
Nevertheless, there could be slushy accumulations on grassy surfaces and elevated objects, IF the precip comes down heavy enough.  Like I have said, the majority of us will stay ALL rain, but once again, there could be snow in Arkansas and it has been that kind of year! 

The following maps are from weatherbell.com

The GFS shows the area where some snow could accumulate, especially those higher elevations of northern Arkansas up towards Boone county.  This indicates up to an inch could fall and maybe two up high.  I don't believe that light swath in central AR
The Euro, IMO, has a good handle on this!  It shows an inch or two in those higher elevations of northwest Arkansas.  The gray ares could receive a dusting to and inch. 
 
The NAM is too bullish on amounts, but may have a good idea on where the snow may fall Sunday.  It's that northern 2 rows of counties.
In summary, not much has changed with my thinking.  I still expect this to be mainly heavy rain and storms.  There will be a few big, wet snowflakes up north.  Why not?  That's Arkansas for ya, especially this winter!  Could we see flakes here in central Arkansas?  Maybe Sunday night, but I have some doubts.  Things can always change and I'll stay on top of the situation for you.  Remember, if you want to read more about the timing of everything, scroll down.


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There are never certainties in weather forecasting until after it happens, but this has become what we call a "high confidence" forecast.  Yes, I still think some of you will be shaking your heads later Sunday at what mother nature may throw at us.  Winter just will not let go.  A change to some light snow will be possible Sunday afternoon and evening, but mainly over northern Arkansas.  There could even be some light accumulations on grassy surfaces close to the Missouri border (northern 2 rows of counties).  The ground is warm enough now that it will be tough to get it to stick.  As I mentioned in previous blog posts, this is a different set up compared to what we have seen this winter.  Cold air will pour into the state Sunday as a strong low pulls away.  Strong northern winds will develop and I think gusts could be around 30-40 mph.   The air aloft will cool drastically as an area of low pressure aloft intensifies over the region.  This may be a case where temperatures are a few degrees above freezing and it's snowing... again, mainly across the north.  Some of you could see some of those big, wet snow flakes up there.  Can this forecast still change?  Absolutely and I'll be keeping you updated.

The following maps are from weatherbell.com.  The green is rain, blue snow, and orange is sleet.  It will show you precip over the previous 6 hours.

Rain is breaking out between noon and 6PM Saturday as a surface low forms over west TX.  The most likely time frame is after 2-3 PM.
Between 6pm and midnight, the rain is becoming heavy and there are a few rumbles of thunder.  The low is just west of Ft. Smith.  Look at the black lines over OK, KS, and TX.  Those are isobars and they are close together.  This means there's a strong pressure gradient and strong northerly winds developing as the low passes by.  Remember, the flow of air is counterclockwise into the low.
Between midnight and 6 AM Sunday, the rain continues.  At 6 AM, the low is just north of the metro.  Notice the precip is cutting off just SW of that low.  That's called a "dry slot".  This will choke off precip Sunday morning so there COULD be a lull over central and southern AR.  The rain continues north.  ALL temperatures at this point are well above freezing, but starting to fall behind the low.
Between 6 AM and noon you can really see the evidence of the dry slot, but precip is now rotating in from the north as moisture wraps around the low.  The GFS even indicates some snow could fall close to the MO border near noon.  The winds are howling at this point and temperatures are falling.  The red line is the 32 degree line and that's nosing into NW AR.  The blue line is the 35 degree line.
Between noon and 6PM, the rain starting to exit and the winds continue to howl.  The rain has changed to some snow across the far north and there's even some sleet.  Notice the red line is along the MO border so most temperatures are still above freezing and this will prevent much if any accumulation, expect near the MO border.   REMEMBER, THIS CAN STILL CHANGE AND I'M WATCHING IT CAREFULLY!!!!!
Most of the precip will be rain and amounts will be around 1-2'' with the most across the NW half.

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