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

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000 FXUS64 KMRX 020715 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 315 AM EDT TUE SEP 2 2014 .SHORT TERM (TODAY AND TONIGHT)...
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CURRENT SURFACE ANALYSIS SHOWS A WARM AND VERY MOIST AIR MASS OVER THE FORECAST AREA...WITH A WEAK COLD FRONT OVER THE MID MS RIVER VALLEY WHERE A LARGE MCS WAS OCCURRING AHEAD OF IT. THIS COLD FRONT IS PROGGED TO SLOWLY APPROACH THE TN RIVER VALLEY LATE THIS AFTERNOON...WITH A MODERATELY TO POSSIBLY VERY UNSTABLE AIR MASS DEVELOPING AHEAD OF IT OVER THE FORECAST AREA. MODEL SOUNDINGS FOR THIS AFTERNOON REVEAL A FAIRLY STEEP LAPSE RATE UP TO AROUND 700 MB...WITH NOT MUCH CONVECTIVE INHIBITION ABOVE THAT. THUS...THE POTENTIAL FOR SEVERE STORMS APPEARS TO BE BETTER TODAY WITH CAPE VALUES IN THE 2000 TO 2500 J/KG RANGE...A DECENT MID LEVEL WIND FLOW AROUND 25 KT...AND AN INVERTED-V PROFILE BELOW 850 MB WHERE DRY AIR MAY HELP TO ENCOURAGE STRONG DOWNDRAFTS. THE COLD FRONT SHOULD THEN SLOWLY DRIFT ACROSS THE FORECAST AREA TONIGHT...WITH CONVECTION GRADUALLY WEAKENING AFTER MIDNIGHT. AS FOR TEMPS...GFS AND NAM GUIDANCE NUMBERS ARE IN GOOD AGREEMENT FOR TODAY AND TONIGHT...AND ARE ESSENTIALLY A PERSISTENCE FORECAST. .LONG TERM (WEDNESDAY THROUGH MONDAY)...A FAIRLY ZONAL UPPER FLOW ACROSS THE UNITED STATES...EXCEPT FOR A SHORT-WAVE TROUGH MOVING THROUGH SOUTHERN CANADA/NORTHERN GREAT LAKES FRIDAY AND SATURDAY. THIS FAST MOVING TROUGH WILL PULL A FRONT INTO THE AREA FOR SATURDAY. FOR WEDNESDAY...A STATIONARY FRONT WILL BE LOCATED NEAR THE TENNESSEE/GEORGIA STATE-LINE WITH UPSLOPE FLOW INTO THE MOUNTAINS. BEST CHANCES OF CONVECTION WILL BE ACROSS THE SOUTHEAST AND FAR EASTERN TENNESSEE MOUNTAINS. THIS BOUNDARY LIFTS NORTH OVER THE AREA THURSDAY PULLING MOISTURE/INSTABILITY BACK INTO THE REGION. MAIN FORCING FOR STORMS THURSDAY AND FRIDAY WILL MAINLY BE THE LOCAL TERRAIN. FOR SATURDAY...COLD FRONT MOVES INTO THE AREA BEFORE STALLING AS BOUNDARY BECOMES PARALLEL WITH THE UPPER FLOW. THIS BOUNDARY REMAINS OVER THE AREA FOR SUNDAY AND MONDAY. HIGH CHANCE/LIKELY POPS EXPECTED SATURDAY THROUGH MONDAY...ESPECIALLY OVER THE HIGH TERRAIN. MAIN CONCERN THROUGH THE PERIOD WILL BE LOCALLY HEAVY RAINS...BUT ISOLATED TO STRONG TO SEVERE THUNDERSTORMS POSSIBLE...ESPECIALLY FOR SATURDAY.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 92 71 92 70 / 50 40 30 20 KNOXVILLE MCGHEE TYSON AIRPORT, TN 89 69 90 68 / 60 40 30 10 OAK RIDGE, TN 89 69 91 67 / 60 40 30 10 TRI CITIES AIRPORT, TN 88 67 88 61 / 60 50 20 20
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DMG/DH

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