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

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000 FXUS64 KMRX 171941 AFDMRX AREA FORECAST DISCUSSION National Weather Service Morristown TN 341 PM EDT Sat Apr 17 2021 .SHORT TERM...(Tonight and Sunday)... Upper level flow has transitioned to zonal today as the shortwave moving through the Ohio Valley continues to wash out. At the surface, lower pressure was noted east of the southern Appalachians, while high pressure encompasses much of the plains. Recent visible satellite imagery continues to depict some clearing taking place this afternoon as much drier air moves into the area. The short term period will be quiet, as the region remains underneath zonal flow tonight and on Sunday. A disturbance begins to move into the Ohio Valley late Sunday and Sunday night. As a result, may see an increase in upper lvl clouds Sunday afternoon. Otherwise, temperatures will remain near to slightly below average with overnight lows in the upper 30s to mid 40s and highs on Sunday in the upper 50s to upper 60s. Diegan .LONG TERM...(Sunday night through Saturday)... Warming temperatures to start the week with a cold front at mid week bringing colder temperatures Wednesday and Thursday. Warming temperatures again Friday and Saturday with a new system moving in Saturday. Weak upper troughing across the forecast area to start the extended period Sunday night with a few showers northern Cumberland Plateau. Skies will be partly cloudy and lows in the 40s. Monday improving weather with skies mostly sunny as weak high pressure at the surface builds in. Mid and upper trough shifts east. Monday night the weak surface high pressure at the surface and aloft will shift east. Winds stay light but shift to a more south southeast direction. Highs Monday closer to average in the mid 60s o lower 70s and lows Tuesday lower to mid 40s. Tuesday forecast area is still mostly dry with continued warming with highs in the upper 60s to mid 70s. Showers develop Tuesday afternoon and evening ahead of frontal system moving into the Ohio and mid Mississippi Valley ahead of troughing moving into the mid section of the country. A surface low is forecast to track from north Texas early Tuesday toward the lower Ohio Valley later in the day and then deepening as it moves into Ohio Tuesday night. A few storms are possible late afternoon and evening. Showers linger overnight ahead of front but not much rain expected initially. Late Tuesday night and Wednesday a large area of showers will accompany the front. Much colder airmass moves in behind the front with precipitation behind the front through the day Wednesday. Temperatures will be much colder with highs in the 50s and temperatures possibly falling through the day. Cold air advection behind the front will drop temperatures down into the 30s with frost possible western sections if winds lower enough overnight. Thursday will be another cool day but sunny. Friday lows again in the 30s and lower 40s but some increase in clouds ahead of next system. The next system will approach late Friday and Saturday. More significant rainfall possible late Friday night and Saturday and continued warmer temperatures. TD && .AVIATION... 18Z TAF DISCUSSION. Overall expecting a VFR forecast with some MVFR later in the period at TYS and TRI. Cannot rule out an occasional isolated shower this afternoon mainly near TRI but confidence is to low to include mention. Otherwise, expect a BKN layer around 040-060 through the afternoon and evening with possibilty of gradual lowering to 025-030 from 09-12Z at TYS and TRI. For CHA, expect clouds to scatter out overnight. While guidance develops fog Sunday morning at TYS and TRI, believe clouds may stick around and inhibit fog formation so will leave this out of the forecast for now. Winds will remain light and variable. Diegan && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 46 70 47 72 48 / 0 0 0 0 10 Knoxville McGhee Tyson Airport, TN 45 67 45 69 45 / 0 10 10 0 10 Oak Ridge, TN 42 67 46 69 46 / 0 10 10 0 0 Tri Cities Airport, TN 42 63 40 67 42 / 10 10 10 10 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.