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

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000 FXUS64 KMRX 171850 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 250 PM EDT WED SEP 17 2014 .SHORT TERM (TONIGHT THROUGH FRIDAY NIGHT)...
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CURRENT SURFACE ANALYSIS SHOWS A QUASI-STATIONARY FRONTAL BOUNDARY OVER THE DEEP SOUTH...WITH AN INVERTED TROUGH EXTENDING NORTH OF IT OVER THE SOUTHERN APPALACHIANS. RADAR AND SATELLITE IMAGERY REVEAL A MESOSCALE CONVECTIVE SYSTEM OVER THE OZARKS...WHICH WAS MOVING SOUTHWARD BUT ITS ASSOCIATED HIGH CLOUDS WERE MOVING SOUTHEASTWARD ACROSS THE TN RIVER VALLEY. ADDITIONAL MOISTURE OVER THE MID MS RIVER VALLEY WILL MOVE TOWARDS THE FORECAST AREA LATER TONIGHT...SO THINK THAT ANY FOG DEVELOPMENT LATER TONIGHT SHOULD BE PATCHY AND MAINLY NEAR AREA WATERWAYS. AN AREA OF HIGH PRESSURE OVER THE MID WEST THIS AFTERNOON IS PROGGED TO SLOWLY DRIFT EASTWARD INTO THE NORTHEAST BY FRIDAY...WHICH WILL PRODUCE AN EASTERLY FLOW OVER THE CAROLINAS. MODELS INDICATE THAT THIS EASTERLY UPSLOPE FLOW WILL TRIGGER ISOLATED CONVECTION OVER THE SOUTHERN APPALACHIAN MOUNTAINS ON THURSDAY AND FRIDAY AFTERNOONS...SO WILL INCLUDE A SLIGHT CHANCE POP IN THESE ZONES. AS FOR TEMPS...GFS AND NAM GUIDANCE NUMBERS ARE IN GENERAL AGREEMENT THROUGH FRIDAY NIGHT...BUT WILL COMPROMISE BETWEEN THE TWO WHERE SLIGHT DIFFERENCES ARE NOTED. .LONG TERM (SATURDAY THROUGH WEDNESDAY)...THE PERIOD STARTS OUT DRY ON SATURDAY AS THE SOUTHERN APPALACHIAN REGION AWAITS ANOTHER AMPLIFYING UPPER LEVEL TROUGH AND ASSOCIATED COLD FRONT. MODEL FORECASTS HAVE SLOWED THIS FEATURE DOWN WITH THE BRUNT OF THE SYSTEM NOT ARRIVING UNTIL SUNDAY NIGHT INTO MONDAY...SO TWEAKED POPS BACK A BIT ON THE FRONT END. STILL NOT A GREAT DEAL OF LOW LEVEL MOISTURE BECOMES ENTRAINED IN THIS SYSTEM...WITH LOW LEVEL RIDGING REFUSING TO BREAK DOWN TO LARGE DEGREE AHEAD OF THE LOW LEVEL TROUGH/SURFACE FRONT. SO NOT MUCH MOISTURE AND LIMITED CONVERGENCE AT THIS TIME ARGUES FOR THE PROBABILITY OF SHOWERS AND THUNDERSTORMS TO REMAIN IN THE CHANCE CATEGORY. WENT WITH A GO SLOW APPROACH TO THE DEPARTURE OF THIS SYSTEM ON MONDAY...WITH SOME TRAILING MOISTURE AN ENERGY BUILDING INTO THE BACK SIDE OF THE DEPARTING UPPER TROUGH. KEPT TUESDAY AND WEDNESDAY DRY. HOWEVER...MODELS ARE MOVING IN THE DIRECTION OF THE DEVELOPMENT OF AN INVERTED SURFACE TROUGH OVER THE MID SOUTH ABOUT TUESDAY INTO WEDNESDAY...WITH INCREASING ATLANTIC MOISTURE AROUND THE BASE OF THE EASTERN U.S. RIDGE.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 58 83 60 85 / 0 0 0 0 KNOXVILLE MCGHEE TYSON AIRPORT, TN 56 80 58 82 / 0 0 0 0 OAK RIDGE, TN 56 80 58 82 / 0 0 0 0 TRI CITIES AIRPORT, TN 53 78 54 80 / 0 0 0 0
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DMG/

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