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

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000 FXUS64 KMRX 201850 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 250 PM EDT SAT SEP 20 2014 .SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT)...
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CURRENT SURFACE ANALYSIS SHOWS A LARGE DOME OF HIGH PRESSURE EXTENDING OVER THE APPALACHIANS...WITH A COLD FRONT OVER THE UPPER MS RIVER VALLEY. THIS COLD FRONT IS PROGGED TO SLOWLY MOVE THROUGH THE FORECAST AREA DURING THE EVENING HOURS ON SUNDAY...WITH SCATTERED CONVECTION DEVELOPING AHEAD AND BEHIND IT. GFS AND NAM MODELS REVEAL SOME DISCREPANCIES WITH THE AMOUNT OF MOISTURE ASSOCIATED WITH THIS COLD FRONT...AND WILL GENERALLY COMPROMISE BETWEEN THE TWO BY KEEPING POPS IN THE SCATTERED CATEGORY. GFS MODEL INDICATES SOME MARGINAL INSTABILITY DEVELOPING OVER THE FORECAST AREA AHEAD OF THIS FRONT ON SUNDAY AFTERNOON...BUT THE NAM MODEL INDICATES THE POSSIBILITY OF A MODERATELY UNSTABLE AIR MASS. THUS...IT APPEARS THAT A FEW STRONG TO SEVERE TSTORMS MAY BE POSSIBLE ON SUNDAY AFTERNOON. AS FOR TEMPS... GFS AND NAM GUIDANCE NUMBERS ARE IN GENERAL AGREEMENT WITH MINS FOR TONIGHT AND SUNDAY NIGHT...AND LOOK REASONABLE. WILL COMPROMISE BETWEEN THE TWO SETS OF GUIDANCE IN REGARDS TO MAXES ON SUNDAY. .LONG TERM (MONDAY THROUGH SATURDAY)...VERY QUIET EXTENDED PERIOD FOLLOWING THE SHORT TERMS FRONTAL PASSAGE. BY MONDAY MORNING...THE COLD FRONT SHOULD BE WELL SOUTH OF OUR AREA WITH THE UPPER LEVEL TROUGH CONTINUING TO FURTHER MOVE OFF TO OUR NE OVER THE COURSE OF THE DAY. EXPECT MOSTLY SUNNY SKIES BY LATE MORNING/EARLY AFTERNOON WITH BREEZY WINDS OUT OF THE NORTH DUE TO THE TIGHT PRESSURE GRADIENT OF THE TROUGH. THE POST FRONTAL AIR MASS WILL ALLOW FOR MUCH DRIER AIR ALONG WITH COOLER TEMPERATURES. WITH CLEAR SKIES MONDAY NIGHT...OVERNIGHT LOWS WILL BE 8 TO 10 DEGREES BELOW NORMAL. BY TUESDAY...HIGH PRESSURE RETURNS AND CONTINUES THROUGH THE END OF THE EXTENDED. AS THE HIGH PRESSURE CENTER SLOWLY SHIFTS EASTWARD THROUGH THE WEEK...MOISTURE STARTS TO SLOWLY BUILD BACK IN ACROSS THE AREA BY FRIDAY AND INTO SATURDAY. WILL INCLUDE SLIGHT CHANCE POPS FOR SATURDAY ACROSS CENTRAL VALLEY AND CHANCE ACROSS THE SOUTHERN VALLEY AND SW NC. TEMPERATURES WILL REMAIN BELOW NORMAL THROUGH THE EXTENDED...BUT OVERNIGHT LOWS WILL GRADUAL WARM THROUGHOUT THE PERIOD TO NEAR NORMAL BY DAY 7. EXPECT SEVERAL MORNINGS AND EVENINGS TO HAVE A FALL-LIKE FEEL TO THEM AT THE START OF THE LONG TERM.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 62 85 59 75 / 0 40 30 10 KNOXVILLE MCGHEE TYSON AIRPORT, TN 62 83 58 72 / 0 40 30 10 OAK RIDGE, TN 62 84 57 72 / 0 40 30 10 TRI CITIES AIRPORT, TN 56 82 55 70 / 0 50 40 10
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DMG/SR

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