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

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000 FXUS64 KMRX 301845 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 245 PM EDT THU OCT 30 2014 .SHORT TERM (TONIGHT THROUGH SATURDAY NIGHT)...
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CURRENT SURFACE ANALYSIS SHOWS AN AREA OF HIGH PRESSURE CENTERED OVER THE LOWER OHIO AND TN RIVER VALLEYS...WITH A SEASONABLY MILD AIR MASS OVER THE FORECAST AREA UNDER MOSTLY CLEAR SKIES. CLOUDS WILL INCREASE TONIGHT AS AN UPPER-LEVEL SHORT WAVE SWINGS OVER THE TN RIVER VALLEY...AHEAD OF AN AMPLIFYING LONG WAVE UPPER-LEVEL PATTERN. THESE CLOUDS MAY EVENTUALLY INHIBIT MOST FOG FORMATION OVERNIGHT...BUT WILL CONTINUE TO MENTION PATCHY FOG EVERYWHERE DUE TO THE WARM WATER TEMPS POSSIBLY CREATING ANOTHER MORNING OF FOG ALONG THE WATERWAYS. THE MAIN STORY DURING THIS FORECAST PERIOD WILL BE THE AMPLIFYING UPPER- LEVEL LONG WAVE TROUGH OVER THE EASTERN HALF OF THE NATION...WHICH WILL EVENTUALLY BECOME A CUT-OFF UPPER LOW MOVING SOUTHEASTWARD RIGHT OVER THE FORECAST AREA. THIS DEEP UPPER TROUGH WILL PUSH A STRONG COLD FRONT THROUGH THE FORECAST AREA FRIDAY AFTERNOON...WITH TEMPS FALLING QUICKLY AS THE SUN SETS FRIDAY EVENING AND RAIN QUICKLY CHANGING TO SNOW OVER THE HIGHER ELEVATIONS. WITH THE DEEP UPPER LOW EXPECTED TO MOVE RIGHT OVER THE FORECAST AREA AFTER MIDNIGHT ON FRIDAY NIGHT...LAPSE RATES WILL STEEPEN CONSIDERABLY OVER THE FORECAST AREA WITH CONVECTIVE SNOWFALL (AND THUS HIGHER SNOWFALL INTENSITIES) POSSIBLE LATE FRIDAY NIGHT AND EARLY SATURDAY MORNING. WHILE SNOW WILL LIKELY BE OBSERVED MOST EVERYWHERE (EVEN IN THE VALLEYS) LATE FRIDAY NIGHT AND SATURDAY MORNING...SNOWFALL ACCUMULATIONS SHOULD BE VERY ELEVATION-DEPENDENT DUE TO THE WARM GROUND TEMPS IN THE LOWER ELEVATIONS. IT STILL APPEARS THAT 4 TO 8 INCHES WILL BE POSSIBLE OVER THE HIGHER ELEVATIONS ABOVE 2500 FEET MSL...BUT A FOOT OR MORE OF SNOWFALL APPEARS POSSIBLE OVER THE HIGHEST PEAKS ABOVE 5000 FEET DUE TO THE DIRECT PASSAGE OF THE DEEP UPPER LOW AND ITS VERY COLD TEMPS ALOFT. SINCE THE MODELS HAVE BEEN CONSISTENT WITH THIS PATTERN FOR SEVERAL RUNS...WILL GO AHEAD AND UPGRADE THE WATCH TO A WINTER STORM WARNING. AS FOR TEMPS...GFS AND NAM GUIDANCE NUMBERS ARE IN GENERAL AGREEMENT THROUGH SATURDAY NIGHT...BUT WILL COMPROMISE WHERE SOME DIFFERENCES ARE NOTED. .LONG TERM /SUNDAY THROUGH THURSDAY/...SOME LOW CLOUD COVER MAY LINGER THROUGH THE MORNING HOURS ON SUNDAY ON THE BACKSIDE OF THE DEPARTING LOW...BUT CLEARING WILL OCCUR BY THE AFTERNOON AND EVENING AS HIGH PRESSURE BEGINS TO BUILD IN. ANOTHER FREEZE /POSSIBLY A HARD ONE IN SW VA/ WILL BE POSSIBLE ACROSS THE NORTHERN AND CENTRAL VALLEYS EARLY MONDAY MORNING. HOWEVER...WITH WINDS INCREASING FROM THE SOUTH AND AMPLE SUNSHINE PREVAILING...A WARM-UP BACK INTO THE MID TO UPPER 60S FOR MONDAY AND TUESDAY HIGH TEMPERATURES ARE EXPECTED...WITH LOWS IN THE UPPER 30S AND 40S IN MOST SPOTS. ANOTHER TROUGH/COLD FRONT LOOKS TO APPROACH THE AREA TUESDAY NIGHT INTO WEDNESDAY...GIVING THE REGION ANOTHER SHOT AT SOME PRECIPITATION FOR THE MIDDLE OF THE WEEK. MODELS STILL DIFFER IN THE EXACT TIMING...BUT IT APPEARS THE BEST WINDOW MAY BE WEDNESDAY AND WEDNESDAY EVENING...SO HAVE THE HIGHEST POPS DURING THIS TIME PERIOD...BEFORE CLEARING THINGS OUT BY THURSDAY.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 41 60 35 49 / 0 30 20 20 KNOXVILLE MCGHEE TYSON AIRPORT, TN 40 57 34 46 / 0 60 60 60 OAK RIDGE, TN 40 58 34 47 / 0 60 50 50 TRI CITIES AIRPORT, TN 36 53 32 43 / 0 80 90 90
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&& .MRX WATCHES/WARNINGS/ADVISORIES...
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NC...NONE. TN...WINTER STORM WARNING FROM 8 PM FRIDAY TO 8 PM EDT SATURDAY FOR BLOUNT SMOKY MOUNTAINS-COCKE SMOKY MOUNTAINS-JOHNSON-SEVIER SMOKY MOUNTAINS-SOUTHEAST CARTER-SOUTHEAST GREENE-UNICOI. VA...WINTER STORM WARNING FROM 8 PM FRIDAY TO 8 PM EDT SATURDAY FOR RUSSELL-WASHINGTON-WISE.
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&& $$ DMG/AMP

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