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

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638 FXUS64 KMRX 130908 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 408 AM EST SAT FEB 13 2016 .SHORT TERM...
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(TODAY AND TONIGHT)...COLD NORTHWEST FLOW WILL CONTINUE INTO TODAY...BUT WILL GRADUALLY WEAKEN THIS AFTERNOON. CLOUDS AND A FEW SNOW SHOWERS/FLURRIES WILL LINGER EARLY IN THE PERIOD ESPECIALLY NORTH AND MOUNTAINS...AND WILL DIMINISH FROM SOUTHWEST TO NORTHEAST DURING THE DAY. HIGH/MID CLOUDS WILL INCREASE OVERNIGHT AS MOISTURE BEGINS TO RETURN AGAIN WELL AHEAD OF NEXT SYSTEM. WIND CHILL ADVISORY STILL LOOKS GOOD AS IS...SO NO CHANGES THERE AT THIS TIME. MAV TEMPS GENERALLY LOOK REASONABLE AND WILL STAY CLOSE. .LONG TERM...(SUNDAY THROUGH FRIDAY)...MORE ACTIVE WEATHER IN STORE DURING AT LEAST THE FIRST HALF OF THE EXTENDED PERIOD WITH SOME COLD AIR IN PLACE ON SUNDAY AND AN ATMOSPHERE THAT WANTS TO GENERATE A STRENGTHENING TROUGH PATTERN OVER THE CENTER OF THE NATION. AS WEAK SHORT WAVE ENERGY SWINGS THROUGH THE LAKES/MIDWEST ON SUNDAY THE RESPONSE WILL BE WINDS BECOMING SOUTHWESTERLY ALOFT. THIS WILL LEAD TO PROBLEMS AS THE WARM AND MOISTENING FLOW RIDES ISENTROPICALLY OVER THE LARGELY SUB-FREEZING AIRMASS ACROSS THE FORECAST AREA (THE EXCEPTION BEING THE LOWER ELEVATIONS OF SOUTHEAST TENNESSEE). SO THE LOW LEVELS WILL PROBABLY BE TOO COLD OVER MOST OF THE AREA WHEN THE RISING...MILDER AIR BECOMES SATURATED AND FALLS TO THE SURFACE IN THE FORM OF SNOW SUNDAY AFTERNOON THROUGH SUNDAY NIGHT. THROUGH THE SUNDAY NIGHT INTO MONDAY MORNING PERIOD A SHORT WAVE SYSTEM WILL BE DEEPENING OVER THE LOWER MISSISSIPPI VALLEY AND DRIVING EAST. THIS IS THE OLD SCENARIO WHERE THE ATMOSPHERE WANTS TO WARM BECAUSE OF THE STRENGTHENING SOUTHERLY FLOW AHEAD OF THE 85H AND SURFACE LOW PRESSURE CENTERS WHICH APPEAR TO PASS DIRECTLY OVER THE FORECAST AREA MONDAY NIGHT. THEREFORE IN THIS SCENARIO...SNOWFALL WOULD ACCUMULATE LATE SUNDAY NIGHT THROUGH MONDAY MORNING OVER MUCH OF THE FORECAST AREA WITH THE GREATEST IMPACT PERHAPS BEING ALONG THE I-40 CORRIDOR AND POINTS NORTH INTO SOUTHWEST VIRGINIA. OF COURSE STAYED WITH THE BEST POSSIBILITY OF ACCUMULATING SNOW OVER THE CUMBERLAND PLATEAU EAST NORTHEAST THROUGH NORTHEAST TENNESSEE AND SOUTHWEST VIRGINIA WHERE SNOWFALL AMOUNTS COULD RANGE FROM TWO TO FOUR INCHES. THE FORECAST GETS COMPLICATED WITH THE SNOW TO RAIN TRANSITION LATER SUNDAY NIGHT INTO MONDAY WITH THE APPROACHING SURFACE LOW AS SNOW MIXES WITH SLEET FOR A PERIOD BEFORE CHANGING ENTIRELY TO RAIN. THE INITIAL SHORT WAVE MOVES AWAY TO THE EAST MONDAY NIGHT INTO TUESDAY MORNING WHERE PRECIPITATION TYPE WILL BE DIFFICULT AGAIN AS SOME COLDER AIR SPILLS INTO THE BACK SIDE OF THIS FEATURE CHANGING PRECIP BACK INTO SNOW LEADING TO THE POSSIBILITY OF SOME LIGHT ACCUMULATION ACROSS THE FORECAST AREA ONCE AGAIN. YET ANOTHER COMPACT LITTLE WAVE IS DEPICTED BY THE MODELS TO RIP SOUTHEAST ACROSS THE SOUTHERN APPALACHIANS TUESDAY AFTERNOON THROUGH TUESDAY NIGHT WITH TEMPERATURE STRUCTURE KEEPING PRECIPITATION IN THE FORM OF LIGHT RAIN DURING THE DAY WITH A LIKELY CHANGEOVER TO SNOW AT NIGHT AS SOME CHILLY AIR BUILDS INTO THE BACK OF THIS UPPER TROUGH. KEPT SOME LIGHT SNOW SHOWERS GOING WITH SMALL POPS ON WEDNESDAY...MAINLY IN THE HIGHER TERRAIN AREAS ACROSS THE NORTHERN PART OF THE FORECAST AREA AS NORTHWESTERLY WINDS GENERATE OROGRAPHIC SNOWFALL. FINALLY WEDNESDAY NIGHT THROUGH FRIDAY DAYTIME PERIOD SHOULD BE DRY WITH A MUCH WELCOMED WARMING TREND AS THE MORE ACTIVE STORM TRACK THANKFULLY SHIFTS FARTHER NORTH ACROSS THE UPPER MIDWEST.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 34 21 40 35 / 0 0 20 60 KNOXVILLE MCGHEE TYSON AIRPORT, TN 30 18 34 31 / 10 0 30 70 OAK RIDGE, TN 29 18 34 31 / 0 0 40 70 TRI CITIES AIRPORT, TN 25 13 30 26 / 10 0 30 70
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&& .MRX WATCHES/WARNINGS/ADVISORIES...
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NC...NONE. TN...WIND CHILL ADVISORY UNTIL NOON EST TODAY FOR BLOUNT SMOKY MOUNTAINS-COCKE SMOKY MOUNTAINS-JOHNSON-SEVIER SMOKY MOUNTAINS-SOUTHEAST CARTER-SOUTHEAST GREENE-SOUTHEAST MONROE-UNICOI. VA...WIND CHILL ADVISORY UNTIL NOON EST TODAY FOR RUSSELL-WASHINGTON- WISE.
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&& $$

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