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

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537 FXUS64 KMRX 131934 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 234 PM EST Wed Dec 13 2017 .SHORT TERM...
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(Tonight and Thursday)... Northwesterly flow aloft currently across the area with a shortwave trough to the northwest across the Western Great Lakes. At the surface, high pressure has shifted to the east with southerly to southwesterly flow across the region. In addition, a cold front in association with the shortwave trough stretches from near Chicago to the southwest to near Kansas City. The atmosphere remains dry across the Southern Appalachians with dewpoints currently in the single digits to low teens. Winds are also increasing with the high to the east and low to the northwest. Due to the dry air and winds, have a Fire Danger Statement throughout the remainder of the afternoon. Winds will continue to increase into the evening and overnight hours and have a winds advisory for the mountains along the Tennessee and North Carolina line and Washington County in SW Virginia. In these locations, winds will gust to over 40 mph at times. In the valley, winds will be below advisory criteria but could still see gusts into the 25-30 mph range. The cold front will rapidly move through the forecast area later tonight into Thursday morning. PW values are in the 0.2-0.4 inch range ahead of the boundary but models are showing some flurries across portions of SW VA and NE TN and have continued this in the forecast for late tonight into Thursday morning. Confidence is low and do not expect any impacts or accumulations. Winds should subside on Thursday as the front races quickly to the south and east and have the wind advisory ending at 15z. Skies will be mostly to partly sunny on Thursday but a fresh supply of cold air advection behind the departing boundary will keep highs generally in the upper 30s to mid 40s. .LONG TERM...(Thursday night through Tuesday)... Models seem to have a good handle on the forecast through Sunday, but consistency greatly deteriorates as we head into next week. Models continue to trend drier on Friday with a weak shortwave moving through, and have therefore continued the no-precip forecast. Weak high pressure builds in from the Gulf Coast for Saturday with another system approaching the area by Sunday. Front will push through the area during the second half of the day on Sunday, and with highs in the 40s on Sunday, precip will fall as mainly rain with maybe just a few flakes mixed in over the higher terrain early Sunday morning or later Sunday evening. From here, model solutions digress. Wetter GFS keeps our area in moist SW flow behind the front, with continued precip chances through Tuesday evening when another shortwave rotates through. In contrast, ECMWF is drier with NW flow immediately moving in behind the front and a faster, drier shortwave moving through Monday. For now, have chance PoPs Monday becoming slight chance and decreasing from west to east on Tuesday, but this forecast will likely change as models come into better forecast agreement. Regardless, both models appear to dry out by Wednesday. The model differences also impact temperatures for Monday/Tuesday and current confidence in forecast highs/lows is below average.
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&& .PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN 32 49 29 44 / 0 0 0 10 Knoxville McGhee Tyson Airport, TN 31 44 27 41 / 0 0 0 10 Oak Ridge, TN 31 43 26 42 / 0 0 0 10 Tri Cities Airport, TN 31 39 23 39 / 0 10 0 10
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&& .MRX WATCHES/WARNINGS/ADVISORIES...
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NC...None. TN...Wind Advisory until 10 AM EST Thursday for Blount Smoky Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi. VA...Wind Advisory until 10 AM EST Thursday for Washington.
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&& $$ MA/EMH

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