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FXUS64 KMRX 210730

Area Forecast Discussion
National Weather Service Morristown TN
330 AM EDT Mon Oct 21 2019

.SHORT TERM (Today through Tuesday)...
We will begin the day with a low overcast ceiling as boundary layer 
cooling and a strong inversion has led to extensive stratus and fog 
this morning. This should lift and scatter through the morning, but 
high to midlevel clouds will start to increase in the afternoon. We 
will also have a strengthening southerly LLJ late in the day, which 
may create some downslope warming/drying in the lee of the 

Showers are expected to enter the Plateau counties late in the 
afternoon. Convection to our west is expected to be weakening as it 
approaches due to weakening frontogenetic forcing and a lack of 
instability. The models depict a pre-frontal convective line moving 
across AL/GA that will cut off the northward advection of higher 
theta-e air into our area. As a result, the forecast will delay the 
onset of categorical PoPs in the Valley until midnight when forcing 
along the cold front starts to enter the area. The model trend has 
been toward less instabilty, which was already low with previous 
runs, so a severe threat is unlikely. Will maintain a mention of 
slight chance of thunderstorms, and a mention of gusty winds 
possible in the HWO. The cold front will exit Tuesday morning with 
advection of drier and cooler air following in the afternoon.

.LONG TERM (Tuesday Night through Sunday)... 
Quiet pattern Tuesday night through Thursday night as high pressure 
builds over the forecast area. Zonal flow and cooler temperatures 
will cause lows to drop again into the upper 30s to lower 40s both 
Wednesday and Thursday mornings. More frost possible both days but 
no widespread freeze yet. Temperatures only in the 60s Wednesday but 
warming to the lower 70s Thursday.

Next change in the pattern begins Thursday night into the weekend 
with The Canadian and ECMWF showing a closed low develop over the 
southwest states and northern Mexico with a surface low and front 
moving out of the plains by Saturday with rain spreading over the 
area through the weekend. GFS model shows next system as an open 
wave that forms with a central plains trough Thursday night and then 
spreading precipitation into the area early Friday and moving out by 
early Saturday with high pressure overhead for the weekend. Will use 
a blend and have rain move in Friday with front but linger through 
the weekend as secondary low pressure system moves up from the 
southwest Saturday and moves through Sunday. Colder temperatures 
Friday and Saturday but warming Sunday as system shifts east and 
slight ridging aloft develops.


Chattanooga Airport, TN             76  54  70  43 /  60 100  20   0 
Knoxville McGhee Tyson Airport, TN  77  55  68  43 /  30 100  30   0 
Oak Ridge, TN                       75  53  68  42 /  40 100  20   0 
Tri Cities Airport, TN              76  56  67  38 /  10 100  70  10 



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