Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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620 FXUS64 KMRX 060828 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 328 AM EST Tue Dec 6 2016 .SHORT TERM (Today through Thursday night)...
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The low pressure system over the lower MS Valley region will track NE across middle TN this morning to OH by this afternoon. The strongest forcing in the coupled jet zone will move across our area this morning, along with some elevated instability ahead of the midlevel shortwave trough. The trough axis will be to our east by 21z, and POPs will drop sharply through the afternoon. A 30 kt NW flow may keep some precip going in the mountains this evening, but soundings appear too dry to support and precip after midnight. The Wind Advisory will be maintained, but so far observations have been well below criteria. The LLJ is expected to pick up later this morning, and higher elevations may approach the advisory thresholds of 40 mph gusts. The Flash Flood Watch for Sevier County due to the burn scar will also be maintained, although expected rainfall rates look marginal at best. Models agree on a dry day on Wednesday, but diverge significantly beginning Wednesday night. NAM and SREF spread rain into the area from the west after midnight, continuing into Thursday morning ahead of a cold front passage around midday. The GFS is much drier and quicker to bring in the cold front early Thursday morning. The GFS has not performed well of late, and has tended to move toward the NAM solution with the last few systems. Will lean toward the NAM timing but cut back on its QPF and POPs. Strong cold advection behind the fropa will result in temps falling through the afternoon on Thursday, producing a change to snow for northern sections and higher elevations Thursday afternoon and evening before precip ends by midnight. Much of the area will have lows in the teens Thursday night. .LONG TERM (Friday through Sunday)... An arctic airmass will be in place on Friday with the coldest air of the season; and yes, it will be cold. The day starts out mostly in the teens and ends up in the 20s across Southwest Virginia and 30s across much of the remainder of the lower elevations of East Tennessee and Southwest North Carolina despite a return to some sunshine. The good news is that the cold upper level trough will be on its way out of the area for the weekend with a southerly component to the flow developing in advance of another system due in the region on Sunday. There will still be some sub-freezing air in place early in the day Sunday, and depending on the timing of precipitation building back northeast across the Southern Appalachian region; some of the morning precip could be in a mixed state with a wee bit of freezing rain, sleet and snow before temperatures quickly rise above freezing around mid to late morning. This late extended period event is broadbrushed across two days because the superblend concept merges the faster GFS solution with a slower ECMWF. Future forecasts of course, should be able to depict greater temporal resolution during this early week time period. Some most pleasant warming should be realized toward the end of the extended on Monday with high temperatures warming in the lower to middle 50s across almost the entire forecast area.
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&& .PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN 57 39 55 40 / 100 10 0 40 Knoxville McGhee Tyson Airport, TN 57 37 53 38 / 100 10 0 40 Oak Ridge, TN 57 38 53 38 / 100 10 0 40 Tri Cities Airport, TN 55 36 52 38 / 100 30 0 30
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&& .MRX WATCHES/WARNINGS/ADVISORIES...
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NC...None. TN...Wind Advisory until 4 PM EST this afternoon for Blount Smoky Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi. Flash Flood Watch through this afternoon for North Sevier-Sevier Smoky Mountains. VA...None.
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