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

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000 FXUS64 KMRX 251931 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 231 PM EST SUN JAN 25 2015 .SHORT TERM (TONIGHT AND TOMORROW)...
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THE LOW PRESSURE WILL CONTINUE TO MOVE TOWARDS THE AREA THROUGH THE EVENING...PASSING JUST TO THE NORTHERN CWA BORDER OVERNIGHT. WITH THE MOSTLY CLEAR SKIES TODAY...TEMPS WERE BUMPED UP SEVERAL DEGREES...WHICH WILL CAUSE A WARM START TO THIS SYSTEM MOVING IN. MID AND LOW LEVEL MOISTURE WILL INCREASE THROUGH THE LATE AFTERNOON AND EVENING ACROSS THE AREA...LOWERING CLOUDS AHEAD OF THE PRECIP. SCATTERED RAIN SHOWERS ARE EXPECTED TO BEGIN ON THE PLATEAU AND MAKE THEIR WAY EAST. AS THE TEMPERATURES DROP BELOW FREEZING OVERNIGHT...THESE RAIN SHOWERS ARE EXPECTED TO CHANGE TO SNOW SHOWERS. MODELS ARE IN DECENTLY GOOD AGREEMENT THAT THE ATMOSPHERE WILL STAY FAIRLY MOIST THROUGH THE MIDLEVELS UNTIL THE EARLY MORNING. HOWEVER...WITH THE WARM TEMPERATURES TODAY...AND THE TIMING OF THE COLD AIR ADVECTION...THE TEMPERATURES ARE NOT EXPECTED TO DROP BELOW FREEZING UNTIL AFTER THE DRIER AIR MOVES IN. MODELS DIFFER ON TIMING OF THE BELOW FREEZING TEMPERATURES...SO THERE IS STILL UNCERTAINTY WITH EXACT SNOW AMOUNTS THROUGH MONDAY MID MORNING. WITH THE TREND THE MODELS HAVE BEEN SHOWING...AND THE TEMPERATURE PROFILE THROUGH THE NIGHT...HAVE SETTLED ON 1-3 INCHES IN THE MOUNTAINS...WITH UP TO 1 INCH IN SOUTHWEST VIRGINIA AND PLATEAU COUNTIES. OTHERWISE IN THE VALLEY AND SOUTHWEST NORTH CAROLINA...TEMPERATURES LOOK TO BE TOO WARM FOR MORE THAN FLURRIES OR A DUSTING TO DEVELOP. DUE TO THESE AMOUNTS...WILL GO WITH AN SPS FOR THE NORTHERN PLATEAU AND SOUTHWEST VIRGINIA COUNTIES...WITH AN ADVISORY FOR THE HIGHER ELEVATIONS IN EAST TENNESSEE. TOMORROW...TEMPERATURES WILL WARM TO ABOVE FREEZING IN ALL AREAS EXCEPT THE HIGHEST ELEVATIONS. NORTHWEST FLOW WILL SET UP...WITH JUST ENOUGH MOISTURE TO WARRANT MORE SNOWFALL ACCUMULATION IN THE HIGHER ELEVATIONS. OTHERWISE...SKIES WILL REMAIN OVERCAST THROUGH THE EXTENDED AND TEMPERATURES WILL BE A COUPLE OF DEGREES ABOVE NORMAL OVERNIGHT...AND AFTER THE COLD AIR FILTERS IN...TEMPERATURES WILL BE SEVERAL DEGREES BELOW NORMAL TOMORROW. .LONG TERM (MONDAY NIGHT THROUGH SUNDAY)...PROBABLY A BRIEF BREAK IN PRECIPITATION INTO MONDAY EVENING...BEFORE AN UPSTREAM SHORTWAVE AND A SURGE OF MOISTURE SWEEP ACROSS MONDAY NIGHT AND TUESDAY. I OPTED TO BACK OFF ON THE QPF AND LIGHT SNOW AMOUNTS...GIVEN THE LIMITED MOISTURE AND LACK OF SIGNIFICANT INSTABILITY DURING THE DAYTIME HOURS TUESDAY. NOT REALLY LOOKING LIKE EVEN ADDITIONAL AMOUNTS SUFFICIENT FOR A WINTER WEATHER ADVISORY FOR FAVORED HIGH TERRAIN LOCATIONS. DRY FOR TUESDAY NIGHT THROUGH WEDNESDAY NIGHT BEFORE A LOW PRESSURE SYSTEM TRACKS EAST ACROSS THE MID MISSISSIPPI AND OHIO VALLEY REGIONS THURSDAY. KEPT CONTINUITY WITH PREVIOUS GRIDS FOR JUST CHANCE POPS FOR OUR REGION IN LINE WITH THE LIGHTER QPF NOTED FROM 12Z GFS MODEL. THE LOW POPS INTO EARLY FRIDAY ARE FOR THE BACKSIDE OF THIS EXITING LOW PRESSURE SYSTEM. FOR SATURDAY THROUGH SUNDAY NIGHT...GFS AND ECMWF MODELS DIFFER A GREAT DEAL WITH ONLY THE ECMWF SHOWING ANY PRECIPITATION CHANCES. DAY 4 THROUGH DAY 7 MODEL BLEND AND NEIGHBORING NWS OFFICES CARRY 20 TO 30 PERCENT POPS FOR BOTH SATURDAY NIGHT AND SUNDAY...WHICH I BLENDED WITH. OF COURSE...GIVEN THE TIME OF YEAR (WINTER) OUR PRECIPITATION TYPES WILL BE BOTH RAIN AND SNOW.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 37 42 31 46 / 70 20 10 10 KNOXVILLE MCGHEE TYSON AIRPORT, TN 35 42 26 40 / 80 60 10 20 OAK RIDGE, TN 34 41 29 41 / 80 50 20 20 TRI CITIES AIRPORT, TN 34 40 24 35 / 80 60 30 30
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&& .MRX WATCHES/WARNINGS/ADVISORIES...
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NC...NONE. TN...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST MONDAY FOR BLOUNT SMOKY MOUNTAINS-COCKE SMOKY MOUNTAINS-JOHNSON- NORTHWEST CARTER-SEVIER SMOKY MOUNTAINS-SOUTHEAST CARTER- SOUTHEAST GREENE-SOUTHEAST MONROE-UNICOI. VA...NONE.
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&& $$ JW/TG

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