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

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000 FXUS64 KMRX 192014 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 314 PM EST Thu Jan 19 2017 .SHORT TERM (Tonight and Friday)... Surface low center over NW Mississippi extends a warm front eastward along the Tennessee border then SE into central Georgia. As this low continues to move NE across middle Tennessee tonight, the preceding warm front will lift northward across our area. Water vapor imagery and latest SPC meso analysis of moisture transport indicate a nice slug of moisture, south of the front, over central Mississippi this afternoon that is being captured well by the latest NAM12 run. Model suggests that this moisture will move NE across our area overnight tonight as shortwave energy aloft ejects NE ahead of a lifting middle level low located over central Kansas today. Model forecasted PW values approaching 1.4 inches reach climatological maximum for this time of year and further help to support rainfall amounts of 1 to 1.5 inches across portions of SE Tennessee through tonight. Enough instability exists as the front moves northward that a few evening and overnight thunderstorms will be possible. Although overall flash flood guidance across the area remains on the order of 1.5 inches to 1.8 inches per hour, rainfall rates may be significant enough in these showers and possible thunderstorms to potentially cause localized flooding issues and will need to be monitored. Gradually improving conditions through the second half of Friday as the first system lifts to the NE and some relatively drier air and ridging aloft pushes into the region. Under continued unseasonably warm regime and persistent southerly flow, forecast high temps on Friday may flirt with records of 71 deg F set in 1929 at Chattanooga and 71 deg F set in 1906 at Knoxville. .LONG TERM (Friday Night Through Thursday)... An active weekend shaping up in the weather department across the Southern Appalachians with a couple of episodes of widespread showers and even a decent likelihood of thunderstorms across mainly southern parts of the forecast area. The first feature builds in ahead of the western states long wave trough bringing showers from southwest through northeast during the day Saturday. Sufficient instability will be in place across western through southern parts of the forecast area for the development of thunderstorms. There is a chance that a couple storms could strengthen enough to produce severe weather later Saturday into Saturday night as an even stronger upper level short wave feature rotates into the Southeastern United States in the form of an upper level low. This feature also takes full advantage of the Gulf of Mexico`s moisture supply spreading more showers and even a few thunderstorms across the forecast area later Saturday night through Sunday night. This large pressure system shifts slowly east to the Middle Atlantic Coast Monday night into Tuesday finally allowing some drier air to build into the region. Model solutions diverge during the final two days of the extended period leading to typical uncertainty during this remote part of the forecast. It appears another upper trough and frontal system presses into the Eastern U.S. around Wednesday into Thursday and the superblend broadbrushes some slight and low chance pops for rain showers in association with this system. $$ && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 54 70 55 65 / 100 30 20 70 Knoxville McGhee Tyson Airport, TN 53 69 53 64 / 90 40 10 60 Oak Ridge, TN 53 69 53 64 / 90 30 10 70 Tri Cities Airport, TN 49 65 48 63 / 90 50 10 50 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.