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

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000 FXUS64 KMRX 112034 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 334 PM EST THU FEB 11 2016 .SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)... MOSTLY CLEAR SKIES THIS EVENING WILL BECOME MOSTLY CLOUDY BY MIDNIGHT AS A JET STREAK AND VORT MAX OVER THE DAKOTAS THIS AFTERNOON TRACKS SOUTHEAST. ADEQUATE LIFT FROM QG FORCING WITH THE LEFT EXIT REGION OF THE JET AND PVA WILL MOVE INTO OUR AREA LATE TONIGHT...LIKELY NEAR OR A LITTLE BEFORE SUNRISE. THE COLUMN MOISTENS FROM THE TOP DOWN AS MODELS SHOW AN INITIAL NEAR-SURFACE DRY LAYER. ALTHOUGH THE NAM SOUNDINGS SHOW A SMALL ABOVE-FREEZING LAYER FRIDAY MORNING...EVAPORATIVE COOLING WITHIN THIS LAYER SHOULD MAKE ANY CHANCE MIXED P-TYPES VERY LOW. THE PERIOD OF BEST SNOW ACCUMULATION LOOKS TO BE FROM SUNRISE TO NOON...WITH LOCATIONS NORTH OF I-40 SEEING A HALF INCH TO ONE INCH DURING THAT TIME FRAME. FOR AREAS SOUTH OF I-40...THE WINDOW OF ADEQUATE MOISTURE DEPTH APPEARS TOO NARROW FOR ANY ACCUMULATION...PLUS A LOW LEVEL SW FLOW WILL WARM TEMPERATURES INTO THE 40S BY LATE MORNING/EARLY AFTERNOON. DURING THE AFTERNOON...THE 850-500 MB TROUGH AXIS MOVES THROUGH...TURNING WINDS FROM SW TO A MORE W-NW DIRECTION. COLD ADVECTION ALOFT CREATING STEEPENING LAPSE RATES AND A 30 KT NW 925-850 MB WIND SHOULD KEEP SNOW SHOWERS GOING INTO FRIDAY EVENING IN SW VA AND NE TN...WITH THE GREATEST ACCUMULATIONS IN THE MOUNTAINS FROM UPSLOPE ENHANCEMENT. THE NW FLOW PORTION OF THIS EVENT COULD PRODUCE AN ADDITIONAL 1-2 INCHES IN HIGHER ELEVATIONS FOR A STORM TOTAL OF 2- 3 INCHES. AS A RESULT...A WINTER WEATHER ADVISORY WILL BE ISSUED FOR SW VA AND THE NE TN MOUNTAINS FROM FRIDAY MORNING THROUGH LATE FRIDAY NIGHT. WIND CHILLS WILL BE A CONCERN FRIDAY NIGHT IN THE MOUNTAINS...BUT AT THIS TIME CONFIDENCE IS NOT HIGH ENOUGH ABOUT THIS TO GO WTIH A THIRD PERIOD ADVISORY. .LONG TERM...(SATURDAY THROUGH THURSDAY)... ARCTIC HIGH PRESSURE SETTLES OVER THE FORECAST AREA SATURDAY AND SUNDAY WITH VERY COLD TEMPERATURES SATURDAY AND SATURDAY NIGHT FOLLOWED BY SLIGHT WARMING SUNDAY AND INCREASING CLOUDS AHEAD OF NEXT SYSTEM SUNDAY NIGHT. A FEW SNOW SHOWERS EARLY SATURDAY MORNING ACROSS SOUTHWEST VIRGINIA BUT ELSEWHERE SKIES CLEARING WITH NORTHWEST WINDS KEEPING THE WIND CHILL TEMPERATURE DOWN IN THE SINGLE DIGITS AND TEENS DURING THE DAY AND AROUND ZERO OR BELOW AT NIGHT AS TEMPERATURES DROP BACK TO THE SINGLE DIGITS AND TEENS. ACTUAL HIGHS SATURDAY IN THE TEENS MOUNTAINS AND MOST OF SW VIRGINIA WITH 20S ELSEWHERE EXCEPT LOWER 30S EXTREME SOUTHERN VALLEY AND SW NORTH CAROLINA LOWER ELEVATIONS. ON SUNDAY SLIGHTLY WARMER IN THE 20S SW VIRGINIA AND HIGHER ELEVATIONS TO 30S ELSEWHERE. BEGINNING SUNDAY EVENING MODELS BRINGING ANOTHER SYSTEM INTO THE TN VALLEY SUNDAY NIGHT AND EARLY MONDAY FROM THE NW WITH LIGHT SNOW THEN A MUCH STRONGER SYSTEM APPROACHING FROM THE WEST AND SOUTH LATE MONDAY AND MONDAY NIGHT THROUGH TUESDAY. THE FORECAST FOR THIS PERIOD IS STILL UNCERTAIN AS THEIR ARE MODEL DIFFERENCES IN TIMING...THE VERTICAL TEMPERATURE PROFILE...AND PRECIPITATION TYPE AND DURATION FOR THIS EVENT. MODELS GENERALLY SHOW THE PRECIPITATION STARTING AS ALL SNOW WITH THE FIRST WEAK SYSTEM SUNDAY NIGHT INTO EARLY MONDAY...FOLLOWED BY WARMING TEMPERATURES MONDAY SO THAT THE SNOW CHANGES OVER TO RAIN OVER MUCH OF THE AREA. THEN AS THE SYSTEM DEEPENS AND MOVES NE MONDAY NIGHT AND TUESDAY CHANGES BACK TO ALL SNOW SOMETIME BETWEEN MONDAY NIGHT AND TUESDAY NIGHT. THERE STILL LOOKS LIKE A POTENTIAL FOR MIXED PRECIPITATION MONDAY DEPENDING ON THE TRACK OF THE SYSTEM. THE ECMWF...CANADIAN AND GFS ALL SHOW A SURFACE LOW OVER THE LOWER MS VALLEY MONDAY THAT MOVES EAST ACROSS THE SOUTHEAST STATES TO NEAR OR JUST SOUTH OF THE FORECAST AREA BY LATE MONDAY NIGHT OR JUST EAST OF THE APPALACHIANS TUESDAY MORNING AND DEEPENS BEFORE MOVING NE ALONG THE ATLANTIC COAST TUESDAY. THE STRENGTH AND TRACK OF THIS SYSTEM WILL GREATLY INFLUENCE THE AMOUNT OF WARMING AND PRECIPITATION TYPES MONDAY THROUGH TUESDAY. AS COLDER AIR WORKS IN TUESDAY INTO WEDNESDAY MORE SNOWFALL IS LIKELY. ESPECIALLY MOUNTAINS AND NORTHEAST. HAVE KEPT LOWS AND HIGHS BELOW GUIDANCE FOR MONDAY THROUGH WEDNESDAY BUT CURRENT FORECAST MAY NOT BE LOW ENOUGH. PLEASE STAY WEATHER AWARE THIS WEEKEND...AND MONITOR THE LATEST FORECAST INFORMATION FROM THE NATIONAL WEATHER SERVICE REGARDING THIS STORM SYSTEM...ESPECAILLY IF YOU HAVE TRAVEL PLANS! IN WAKE OF THIS SYSTEM...THURSDAY MODELS SHOW A WARMER PATTERN RETURNING WITH TEMPERATURES REBOUNDING TO THE 50S AS UPPER-LEVEL HIGH PRESSURE BUILDS INTO THE TENNESSEE VALLEY. && .PRELIMINARY POINT TEMPS/POPS... CHATTANOOGA AIRPORT, TN 30 50 25 34 / 10 10 10 0 KNOXVILLE MCGHEE TYSON AIRPORT, TN 28 41 22 27 / 20 40 20 10 OAK RIDGE, TN 27 40 21 28 / 40 50 10 0 TRI CITIES AIRPORT, TN 21 35 16 24 / 30 70 40 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...WINTER WEATHER ADVISORY FROM 6 AM FRIDAY TO 4 AM EST SATURDAY FOR JOHNSON-SOUTHEAST CARTER-UNICOI. VA...WINTER WEATHER ADVISORY FROM 6 AM FRIDAY TO 4 AM EST SATURDAY FOR LEE-RUSSELL-SCOTT-WASHINGTON-WISE. && $$ DGS/TD

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