Friday, February 17, 2012

Wacky Weekend Weather Update

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11:30 AM Friday Update...  I have a couple of things I want to mention with this update.  After reviewing the latest data, I still think most of this will be rain Saturday afternoon and evening.  There will be an area north of the upper low which will have the opportunity to mix with or change to wet snow.  The most likely place for this to happen, as I have maintained for the past couple of days, is north central into northeast Arkansas Saturday night.  While this is an absolutely perfect track for snow, the surface temperatures are way too warm for anything but rain across most of Arkansas.  The only way to get snow will be with cooling from the upper low itself.  This will be a situation where north central and northeast Arkansas will have temperatures around 33-36 degrees with snow or a mix.  The ONLY way to get accumulations is if the snowfall rate is high enough not to allow melting, then you end up with slush all over the place.  Even if there are accumulations across the far north, it would be mainly confined to elevated objects and grassy surfaces.  I will maintain my disclaimer here... we're dealing with a tricky situation.  These upper lows have a tendency to throw one or two surprises.  They also have the tendency to under perform what the models say.  So as I always say, stay tuned and never say never about Arkansas weather.  Keep in mind, our forecast is for only north central and northeast Arkansas to have any chance for flakes.

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This will be a quick update.  I will hopefully have more later today.  Just as I have stressed on facebook and twitter, this will mostly be a rain event Saturday for much of the state. There will also be a lot of wind late Saturday into Sunday morning.  The only chance for snow will be Saturday night into Sunday morning.  An upper level low will track through the area.  Despite surface temperatures too warm for snow, there is still a chance this upper low will be able to cool the atmosphere and produce a swath of wet snow.  The most likely place for this is north central into northeast Arkansas.  Just like with the upper low which gave us 1-2'' in December, you do not need arctic air in place for frozen precipitation.  It helps, but it's not necessary.

All the model data I have looked at continues to point to mostly rain due to the warm temperatures at the surface Saturday (40s).  We will have to wait for the upper low to take temperatures down after sunset Saturday.  Remember, with very cold air aloft, your surface temperature can be above freezing and it still snows.  I think this will happen north of a Russellville to Jonesboro line with readings in the mid 30s.  Remember, this can always change so stay tuned!!!

Our model "Futurecast" shows small snow amounts for northern AR only.  (ignore the time stamp).  The remainder of central and southern Arkansas will have rain
The 00Z NAM is lining up with Futurecast showing basically the same thing.  So there is model agreement that this area of the state will stand the best chance for some snow Saturday night while the rest of us will have rain.
The 00Z Euro even shows accumulations as  far south as Little Rock.  I'm not buying that right now.  The last storm (Monday) it did a very poor job forecasting snow amounts. 
Then there's the 00Z GFS which shows basically nothing, but a few flurries for the far north.

4 comments:

jimmylee42 said...

Todd-

This situation with the upper level low possibly causing snowfall in Arkansas with the very marginal mild temps in place has jogged my memory on two events from the past.

The first was in late winter of 1968. It produced one of the heaviest snows ever to hit parts of eastern Arkansas and Memphis. I believe snows ranged up to as high as 16 to 20 inches. LR was missed except for a dusting if I'm remembering correctly. The snow melted very fast and only drifts were left on the ground after a few days.

The second one happened the winter of 83-84 in early March. The snow came in after some warm weather and piled up to about 5 inches in LR. I know we have had many events in Arkansas that caused snow without the cold air in place. I would imagine most of these happen with the upper level low cooling that column of air enough to form snowfall.

Todd Yakoubian said...

Jimmylee42, I remember the one in March of 83 or 84. I think it was a Saturday. My aunt got married that day!!

Raj said...

Todd, can you do something so that when on a mobile device, typing in katv.com/weather doesn't redirect anyone to the mobile site? Being one who checks the site multiple times a day, it can get rather annoying having to click the web version link, than retyping the URL.

Thanks.

And as for this warm winter, it truly does try the soul after a record heat summer. It's especially disappointing to see yet another 7 day forecast with more 60's.

jimmylee42 said...

Todd-I looked up in the NWS climate book and there was a record snowfall on March 10 1984 of 4.5 inches at LR. Don't know what time of day that fell or if there could have been a higher storm total if some of the total fell either on the 9th or 11th.