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

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000 FXUS64 KMRX 192016 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 316 PM EST FRI DEC 19 2014 .SHORT TERM...
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(TONIGHT AND SATURDAY)... THERE REMAINS MUCH UNCERTAINTY IN THE SHORT TERM PERIOD DUE TO LARGE DIFFERENCES BETWEEN THE NAM AND THE GFS. THE NAM IS THE WETTER AND COLDER OF THE TWO MODELS. THE PREFERENCE IS MORE TOWARD THE GFS DUE TO THE PRECIP/CONVECTION THAT IS EXPECTED TO DEVELOP ALONG THE GULF COAST...PROVIDING A STABILIZING EFFECT UPSTREAM AND PREVENTING NORTHWARD MOISTURE ADVECTION. THE RAP APPEARS TO AGREE WITH THIS SCENARIO...AND THE LATEST SREF APPEARS TO BE TRENDING DOWNWARD IN POPS/QPF. AS A RESULT...WILL CONFINE LIKELY POPS TO EXTREME SOUTHERN PORTIONS OF THE AREA TONIGHT...FADING TO LOW CHANCE POPS NORTH. QPF WILL BE LIGHT...UP TO A TENTH OF AN INCH SOUTH AND IN THE MOUNTAINS. IN HIGHER ELEVATIONS...MAINLY ABOVE 2500 FT...THE PRECIP SHOULD BE MOSTLY SNOW...BUT WITH A SMALL WINDOW OF ADEQUATE MOISTURE DEPTH INTO THE DENDRITE GROWTH ZONE AND WEAK LIFT...NO MORE THAN ONE INCH IS EXPECTED TO ACCUMULATE. TRI-CITIES AND SW VA COULD SEE SOME SNOW IF THE COLDER NAM IS CORRECT...BUT THE WARMER GFS LOOKS LIKE ALL RAIN. WILL MENTION RAIN OR SNOW IN THAT AREA AS A COMPROMISE...WITH WITH NO ACCUMULATIONS. THE FASTER EXIT OF PRECIP SHOWN BY THE GFS WILL BE FOLLOWED...ENDING POPS IN THE EARLY AFTERNOON. .LONG TERM (SATURDAY NIGHT THROUGH FRIDAY)... A WEAK SYSTEM WILL BE EXITING TO THE NE SATURDAY NIGHT WITH SKY CONDITIONS IMPROVING TO PARTLY CLOUDY. UPPER FLOW IS ZONAL WITH DRIER AIR MASS AND WEAK HIGH PRESSURE SETTLING OVER THE REGION. THE SURFACE HIGH WILL BE OVERHEAD SUNDAY WITH SKIES PARTLY TO MOSTLY SUNNY AND HIGH TEMPERATURES SLIGHTLY ABOVE NORMAL IN THE UPPER 40S TO MID 50S. ANOTHER SOUTHERN SYSTEM DEVELOPS ACROSS THE GULF COAST SUNDAY AND BRINGS CLOUDS AND RAIN ACROSS THE FORECAST AREA SUNDAY NIGHT AND MONDAY. AFTER A BRIEF BREAK IN THE STEADY RAIN MONDAY NIGHT A MUCH STRONGER SYSTEM STILL LOOKS ON TRACK TO MOVE INTO THE MS VALLEY MONDAY. A DEEP TROUGH OVER THE CENTRAL STATES WILL MOVE INTO THE EASTERN STATES TUESDAY AND WEDNESDAY. A STRONG COLD FRONT APPROACHES THE FORECAST AREA TUESDAY NIGHT INTO WEDNESDAY. A SURFACE LOW DEEPENS OVER OH WEDNESDAY. THE SYSTEM FINALLY SHIFTS EAST OF THE AREA ON CHRISTMAS DAY. THERE COULD BE SOME THUNDERSTORMS IF ENOUGH INSTABILITY DEVELOPS TUESDAY AFTERNOON AND EVENING AHEAD OF THE FRONT. MUCH COLDER TEMPERATURES WEDNESDAY AND THURSDAY BEHIND THE FRONT. AS COLDER AIR MOVES IN LATE WEDNESDAY AND WEDNESDAY NIGHT SOME MINOR SNOWFALL ACCUMULATIONS ARE POSSIBLE IN THE HIGHER ELEVATIONS.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 36 51 36 54 / 70 20 0 10 KNOXVILLE MCGHEE TYSON AIRPORT, TN 34 45 33 52 / 40 30 0 10 OAK RIDGE, TN 33 45 33 51 / 40 20 0 10 TRI CITIES AIRPORT, TN 31 43 30 49 / 40 40 10 0
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DGS/TD

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