Tuesday, December 1, 2020

Another chance for winter weather this week?

With our first "winter weather event" (cold rain Sunday and flurries Monday) behind us, but cold air still in place, it's time to look ahead to the next weather maker that will move into the region. We'll dissect the chances that additional winter weather might occur in today's blog.

Upper level features

An upper-air trough of low pressure will push into the Central and Southern Plains over the next couple of days, and will become cutoff from the main area of the jet stream that is over central Canada.  The jet stream will begin to push east over the northern Great Lakes, eventually merging with in an area of low pressure currently over the Northeast US that will be located over northeast Canada on Friday.  The cutoff low over the Central and Southern Plains will slowly move east and over the Mid-South this weekend.

Jet stream forecast valid for Thursday night (GFS model)

Surface weather

At the surface, a low pressure system will develop over the Southern Plains on Wednesday, and moisture from the western Gulf of Mexico will begin to be pulled into the low, with rain occurring from eastern Texas into Oklahoma and snow likely in western Oklahoma. 

Surface features valid for Wednesday afternoon (NWS/WPC)

Starting to our north...

On Thursday, the low will move east into Arkansas, and the associated precipitation will move into Missouri, Arkansas and Louisiana, with some mixed precipitation expected early Thursday morning over southern Missouri and possibly northern Arkansas and far northwest Tennessee where temperatures will be in the low to mid 30's.  We will likely see some sleet or graupel ("dippin dots") reports over northern Arkansas and northern Tennessee early Thursday, much like we did on Sunday at the onset of the precipitation, as there will be a layer of dry air in the lower levels of the atmosphere.

Upper air sounding forecast for northeast AR for late Thursday night.

Forecast precipitation type for early Thursday morning (European model)

Closer to home...

For the Memphis area, scattered light rain showers will begin to move into the area early Thursday morning, followed by steadier rain showers around daybreak, with temperatures near 40, which will result in all liquid precipitation for the Memphis area.  This rain should end by early Friday morning as the upper low begins to move over the area and forces the precipitation to our east.

As this low moves east of us on Saturday, the potential for wraparound moisture increases, as temperatures drop into the mid 30's.  This could bring about another chance for a few snow flurries Saturday morning for the Mid-South, which wouldn't be anything to worry about. This would be very similar to what we saw on Monday. Any flurries should come to an end Saturday afternoon as dry air moves in and clouds clear out.

Dry weather looks to continue all next week, with rain chances returning for the weekend (12th & 13th).  So no snow day just yet, kids (and adults)!

Possible alternate scenarios

The only discrepancies I see right now is the timing of the low moving thru the region.  The European model is much faster, and has the low east of us by Friday night, while most of the other models have the low still over Arkansas.  The main issue with that is the timing of the precipitation ends Thursday night according to the European model, and the consensus of the other models have the precipitation ending early Friday morning.  However, the European model has had a tough time trying to figure out where the low will be over the past few days, so I've sided with the consensus of the other models on the timing of the precipitation moving out.  As far as the onset of precipitation and type, the European and other models have pretty good agreement.

Richard Hoseney
MWN Meteorologist

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