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

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972 FXUS64 KMRX 041912 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 312 PM EDT WED MAY 4 2016 .SHORT TERM /TONIGHT AND THURSDAY/... A SHARP COLD FRONT IS QUICKLY MOVING THROUGH SOUTHERN KENTUCKY AND NORTHERN MIDDLE TENNESSEE...AND TRACKING TOWARD THE PLATEAU... EASTERN TENNESSEE VALLEY AND THE SOUTHERN APPALACHIANS. ALONG/AHEAD OF THE FRONT...A LINE OF SHOWERS AND EMBEDDED THUNDERSTORMS CONTINUES TO PROGRESS TOWARD THE AREA AS WELL...MAKING INTO THE PLATEAU BETWEEN 19-20Z...AND SPREADING ACROSS THE MRX CWA BETWEEN 21-03Z. GIVEN THE VERY STEEP LAPSE RATES IN PLACE /7 TO 7.5 DEG C PER KM/...AND THE COLD AIR ALOFT...SOME SMALL HAIL IS LIKELY TO ACCOMPANY THIS ACTIVITY...ALONG WITH SOME BREEZY TO GUSTY GRADIENT WNW WINDS. AFTER SUNSET...COLD AIR ADVECTION WILL TAKE PLACE IN WAKE OF THE INITIAL FRONTAL PASSAGE AS THE UPPER-PARENT LOW ROTATES SOUTH INTO THE SOUTHERN APPALACHIANS. THE HEIGHT OF THE MELTING LEVEL WILL DROP TO AROUND 4000-4500 FEET OVERNIGHT...TRANSITIONING ANY LINGERING SHOWERS ALONG THE SMOKY MOUNTAINS TO SNOW LATER TONIGHT. IT IS NOT OUT OF THE REALM OF POSSIBILITY FOR SOME 1 TO 2 INCH SNOWFALL TO OCCUR AT THE VERY TOP OF THE MOUNTAINS /ABOVE 5000 FEET/...SO HAVE A SPECIAL WEATHER STATEMENT TO ACCOUNT FOR THIS VERY LOCALIZED TERRAIN DRIVEN SNOWFALL. A BREAK IN THE PRECIPITATION SHOULD OCCUR LATE TONIGHT INTO THURSDAY MORNING. THEN...ANOTHER ROUND OF LIGHT SHOWERS AND DENSE CLOUD COVER WILL MOVE IN...THANKS TO ANOTHER SHORTWAVE LOBE OF COLD AIR...ROTATING INTO THE REGION. THIS ACTIVITY WILL BE FAIRLY LIGHT...BUT THE PRECIPITATION...COLD AIR ADVECTION AND THE CLOUD COVER WILL KEEP HIGHS 15 TO 25 DEGREES BELOW NORMAL IN THE 55 TO 60 DEGREE RANGE. .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... EASTERN U.S. UPPER LOW SHIFTS VERY SLOWLY EAST FROM THE SOUTHERN APPALACHIANS TO THE MIDDLE ATLANTIC COAST AT THE START OF THE EXTENDED PERIOD TO A POSITION OVER THE MIDDLE ATLANTIC COAST BY SATURDAY MORNING. STILL A FAIR AMOUNT OF MOISTURE AND SOME SHORT WAVE LIFT IN A SLIGHTLY UNSTABLE ENVIRONMENT THROUGH THIS EARLY PART OF THE FORECAST FOR A FEW MORE SHOWERS AND SOME THUNDERSTORMS...MAINLY ACROSS SOUTHWEST VIRGINIA AND NORTHEAST TENNESSEE. THE CHANCE FOR A SHOWER OR THUNDERSTORM GRADUALLY INCREASES FROM NORTHERN SECTIONS INCLUDING SOUTHWEST VIRGINIA AND NORTHEAST TENNESSEE THROUGH CENTRAL EAST TENNESSEE SATURDAY INTO SUNDAY AS A SHORT WAVE DRIVES SOUTHEAST FROM THE GREAT LAKES ACROSS THE NORTHEASTERN STATES. A COOL FRONTAL BOUNDARY WILL SLIP FARTHER SOUTH INTO THE FORECAST AREA SATURDAY NIGHT INTO SUNDAY REQUIRING THE ADJUSTMENT TO MEDIUM CHANCE POPS. THIS BOUNDARY PRESSES BACK TO THE NORTH OF THE FORECAST AREA SUNDAY NIGHT INTO MONDAY AS ANOTHER UPPER TROUGH AMPLIFIES OVER THE MIDDLE OF THE NATION. THERE SHOULD BE A RELATIVE MIN IN PROBABILITY OF PRECIP SUNDAY NIGHT INTO MONDAY NIGHT. HOWEVER...THE AMPLIFIED TROUGH MOVES THROUGH THE MISSISSIPPI VALLEY TUESDAY INTO WEDNESDAY DRIVING ANOTHER SURFACE FRONTAL SYSTEM THROUGH THE MID SOUTH. THE CHANCE FOR CONVECTION WILL RAMP UP AHEAD OF THIS BOUNDARY WITH THE HIGHEST POPS ON WEDNESDAY AS THE SYSTEM COLD FRONT MOVES INTO THE FORECAST AREA. && .PRELIMINARY POINT TEMPS/POPS... CHATTANOOGA AIRPORT, TN 46 62 49 72 / 50 20 10 0 KNOXVILLE MCGHEE TYSON AIRPORT, TN 44 57 47 68 / 80 50 30 20 OAK RIDGE, TN 44 58 47 69 / 80 50 30 10 TRI CITIES AIRPORT, TN 42 55 45 61 / 90 70 60 30 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ AMP/TH

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