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

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596 FXUS64 KMRX 221858 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 258 PM EDT Tue May 22 2018 .SHORT TERM (Tonight and Wednesday)...Still a decent chance of some showers and possibly a thunderstorm or two across the forecast area tonight as the advertised Midwest upper trough and surface frontal wave build east across the Appalachians. Would expect loss of heating to allow for development to diminish in coverage later in the evening. Maintained a smaller chance for a shower or thunderstorm across mainly southern and eastern parts of the forecast area during the first part of the day Wednesday as the weak boundary makes progress south. The drier and more stable air behind the boundary should keep Wednesday night and Thursday largely precipitation free. Stayed close to guidance mins in the 60s tonight with highs a few degrees warmer on Wednesday; ranging from the lower 80s north to the middle 80s south. .LONG TERM (Wednesday night through Tuesday)...A front will be pushing south across the area to start the period, which will necessitate a low PoP mention Wednesday evening across southern sections. High pressure over the Great Lakes will provide a northeasterly low level flow Thursday morning, but as the high shifts to the Mid Atlantic region in the afternoon, an easterly flow develops across the Carolinas with an inverted trough over our area. This may allow for some scattered convection to develop in the afternoon hours, mainly in the southern sections. With the ridge offshore and a northward-moving low over the Gulf of Mexico, we will have a deep southerly flow developing across the area on Friday that will persist trough the remainder of the forecast. The sub-tropical low will move into the Southeast states on Sunday, then stall over AL (GFS) or MS (ECMWF). Model differences in its position will affect the finer details of QPF and timing of the best rain chances, both of which are too uncertain at the time to specify. However, with general agreement on the pattern, the forecast will keep high chance to likely PoPs going for each period, with mostly cloudy skies and temperatures above normal. && .POINT TEMPS/POPS... Chattanooga Airport, TN 68 86 67 86 / 40 30 20 40 Knoxville McGhee Tyson Airport, TN 66 85 65 86 / 30 30 10 20 Oak Ridge, TN 66 85 64 86 / 30 20 10 10 Tri Cities Airport, TN 63 81 59 83 / 50 30 0 10 && .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.