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

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000 FXUS64 KMRX 200853 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 350 AM EST SAT DEC 20 2014 .SHORT TERM (TODAY AND TONIGHT)...
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SHORT WAVE ENERGY MOVING ACROSS THE AREA WILL EXIT EARLY TODAY. ONLY SOME LIGHT RETURNS ON RADAR SO FAR...AND MUCH OF THAT NOT REACHING THE GROUND. WILL CARRY SOME SLIGHT CHANCE TO CHANCE POPS ALL BUT SOUTHWEST/WEST ZONES EARLY TODAY FOR SOME LIGHT RAIN/SNOW...BUT LOOKS LIKE PRECIP AMOUNTS WILL BE QUITE LIGHT. SURFACE HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST AND NORTH LATER TODAY AND TONIGHT...ALONG WITH SOME DRYING. EXPECT CLOUDS TO DECREASE...ALTHOUGH CONFLICTING SIGNALS IN THE SHORT RANGE MODELS AND WEAK FLOW LEAD TO LOWER THAN NORMAL CONFIDENCE IN SKY FORECAST FOR THE SHORT TERM. JUST SOME MOSTLY MINOR ADJUSTMENTS TO MAV TEMPS...MOSTLY TO TWEAK DOWN SOME HIGHS AND TWEAK UP SOME LOWS. .LONG TERM (SUNDAY THROUGH FRIDAY)...SUNDAY STARTS OUT DRY WITH SOME RIDGING ALTHOUGH ANOTHER WEAK SHORT WAVE WILL BE SWINGING NORTHEAST OUT OF THE LOWER MISSISSIPPI VALLEY SUNDAY NIGHT INTO MONDAY PRODUCING SOME LIGHT RAIN. THERE COULD BE A SNOW FLURRY IN THE HIGHEST TERRAIN ACROSS EXTREME NORTHEAST TENNESSEE AND SOUTHWEST VIRGINIA. THIS WAVE SHOULD BE MOVING AWAY TO THE NORTHEAST DURING THE DAY MONDAY ALLOWING FOR A RETURN TO SOME SUNSHINE MAINLY WESTERN AREAS. FOLLOWING THE DEPARTURE OF THIS SYSTEM THE UPPER LEVEL PATTERN WILL BE UNDERGOING SOME MAJOR LEAGUE AMPLIFICATION WITH A FULL LATITUDE TROUGH FORMING ACROSS THE PLAINS. THIS WILL KEEP THE WEATHER A LITTLE UNSETTLED MONDAY NIGHT WITH A STRENGTHENING MOIST SOUTHERLY FLOW COMPLETE WITH A COUPLE WEAK IMPULSES. THEREFORE KEPT A SMALL CHANCE FOR A SHOWER GOING THROUGH THIS PERIOD. TUESDAY INTO TUESDAY NIGHT THE PROBABILITY FOR SHOWERS...MAYBE EVEN A CLAP OF THUNDER WILL BE ON THE INCREASE AS A DEEPENING SURFACE LOW PRESSURE SYSTEM DRAGS A STRONG COLD FRONT TOWARD THE SOUTHERN APPALACHIANS. THE FRONT WILL MOVE RATHER SLOWLY EAST IN THE HIGHLY AMPLIFIED PATTERN AND SHOULD BE JUST EAST OF THE FORECAST AREA BY 12Z WEDNESDAY. DUE TO THE TIGHT CIRCULATION ASSOCIATED WITH THE UPPER LEVEL TROUGH...A LARGE AREA OF DEEP MOISTURE WILL WRAP AROUND THE BACK SIDE OF THE FEATURE AND THE MOIST AIR WILL BE ACCOMPANIED BY A TRAILING SHORT WAVE. MUCH COLDER AIR WILL BE SPREADING EAST BEHIND THE FRONT DURING THE DAY WEDNESDAY AND BY THE AFTERNOON THE RAIN WILL BE CHANGING TO SNOW IN THE HIGHER TERRAIN AREAS BUT MAINLY OUT WEST ON THE CUMBERLAND PLATEAU. BY WEDNESDAY EVENING TEMPERATURES WILL BE COLD ENOUGH FOR SOME LIGHT SNOW ACROSS MUCH OF THE FORECAST AREA. AGAIN THE DEEPEST MOISTURE AND STRONGEST LIFT WILL BE OVER NORTHERN SECTIONS...MAINLY THE NORTHERN CUMBERLAND PLATEAU...SOUTHWEST VIRGINIA AND NORTHEAST TENNESSEE AS WELL AS THE SMOKY MOUNTAINS. A LITTLE TOO EARLY TO SAY BUT SOME OF THESE HIGHER TERRAIN AREAS COULD PICK UP AN INCH OR TWO OF SNOW WILL OROGRAPHIC SUPPORT. THE MODELS CONTINUE WITH A PROGRESSIVE MODE FOR THIS SYSTEM ON CHRISTMAS DAY ALLOWING DRIER AIR AND A RETURN TO SUNSHINE FOR MOST AREAS. THE UPPER FLOW FLATTENS OUT AGAIN CHRISTMAS EVENING IN TIME FOR THE ARRIVAL OF ANOTHER FAST MOVING UPPER TROUGH AND ASSOCIATED SURFACE COLD FRONT WHICH MAY BRING SOME LIGHT RAIN ON FRIDAY.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 49 33 53 41 / 10 0 10 60 KNOXVILLE MCGHEE TYSON AIRPORT, TN 47 31 51 38 / 20 0 10 40 OAK RIDGE, TN 46 30 50 38 / 20 0 10 30 TRI CITIES AIRPORT, TN 45 29 48 34 / 40 10 0 50
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$

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