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

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000 FXUS64 KMRX 261952 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 252 PM EST Sun Feb 26 2017 .SHORT TERM (Tonight and Tomorrow)... Surface high pressure centered over the area this afternoon will begin to shift NE off the Middle Atlantic coast by Monday morning. Meanwhile, latest water vapor and RAP upper air analysis indicates a shortwave trough embedded within the larger scale zonal flow over central Kansas this afternoon, will move rapidly east across the area by Monday evening. Although current visible imagery indicated perfectly clear skies across much of the area this afternoon, a broad area of middle and upper level cloudiness will move in ahead of the disturbance overnight tonight. This will cut off radiational cooling after midnight and will keep temperatures above freezing for a large portion of the area tonight. This is in slight contrast to the latest GFS and NAM MOS guidance that continue to suggest subfreezing temperatures throughout the area, exception being CHA and points south and west. With passage of this disturbance late tomorrow, areas in the SW corner of the CWA will have likely chance of pcpn by the end of the day while the remainder of the area will see only a slight chance of pcpn into the afternoon hours. With the current low level air mass being so dry (dewpoints below 40 degree for much of the day on Monday) any appreciable pcpn will have to wait until beyond the fcst period. .LONG TERM (Tomorrow Night through Sunday)... An upper level trough will make it`s way slowly east from the Western U.S. through the Mississippi Valley through mid week. As it does so, warm and moist air will override a cooler air mass in place across the Southern Appalachians. Scattered showers and even a few thunderstorms will occur in this warm frontal push into the Southern Appalachian region. But the big event will be on Wednesday into Wednesday evening as another strong cold front sweeps through the Eastern U.S. Sufficient instability and shear will be available for storm strengthening with this feature, and the thunderstorms that accompany this frontal passage could become severe. The front should move across the Appalachian spine later Wednesday night with drier and cooler air streaming back into the region on northwesterly winds. The remainder of the forecast will be dry with a gradual warming trend into the weekend as the low level ridge shifts east to the Southeast Atlantic Coast. $$ && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 36 55 50 69 / 0 60 60 70 Knoxville McGhee Tyson Airport, TN 33 59 48 69 / 0 30 40 70 Oak Ridge, TN 33 58 47 67 / 10 30 50 70 Tri Cities Airport, TN 29 59 42 68 / 0 20 40 50 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.