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

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000 FXUS64 KMRX 171923 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 320 PM EDT FRI APR 17 2015 .SHORT TERM (TONIGHT AND SATURDAY)...UPPER LOW WILL CONTINUE TO WEAKEN AS IT MOVES ACROSS THE SOUTHERN APPALACHIANS LATER THIS EVENING. LIGHT PRECIPITATION ACROSS SOUTHERN MRX CWA WILL SHIFT EAST OF THE AREA BY MIDNIGHT. UPPER RIDGING WILL BUILD INTO THE AREA TONIGHT AND MUCH OF SATURDAY. SURFACE HIGH PRESSURE OVER THE AREA WILL SLOWLY WEAKEN SATURDAY AS AN INVERTED SURFACE TROUGH BEGINS TO BUILD NE INTO THE TN VALLEY SATURDAY AFTERNOON. TEMPERATURES WILL BE WARM TONIGHT WITH PATCHY FOG POSSIBLE. DIURNALLY DRIVEN CONVECTION POSSIBLE BY SATURDAY AFTERNOON AS CONVECTIVE TEMPERATURE IS REACHED FAVORING HIGHER ELEVATIONS. .LONG TERM (SATURDAY NIGHT THROUGH FRIDAY)...THERE COULD STILL BE A FEW ONGOING DIURNAL SHOWERS AND STORMS AT THE START OF SATURDAY EVENING (00Z SUNDAY) BUT SHOULD MAINLY BE FOCUSED ACROSS THE HIGHER TERRAIN. THESE SHOWERS AND STORMS SHOULD DISSIPATE WITH SUNSET. MODELS HAVEN`T CHANGED TOO DIFFERENTLY FROM YESTERDAY`S LONGTERM FORECAST FOR THE SATURDAY NIGHT/SUNDAY TIME PERIOD. THE BIGGEST CHANGE IS THE MODELS HAVE SLOWED THE ARRIVAL OF PRECIP CLOSER TO THE SUNDAY MORNING TIME FRAME INSTEAD OF OVERNIGHT SATURDAY. SATURDAY NIGHT HIGH PRESSURE IS SLIDING EAST AS A CLOSED LOW OVER THE CENTRAL/SOUTHERN PLAINS IS GETTING ABSORBED INTO A TROUGH DROPPING DOWN OUT OF CANADA. AT THIS POINT IN TIME...THE FLOW IS QUICKLY TURNING SOUTHERLY IN RESPONSE TO THE APPROACHING TROUGH THUS PUMPING SUBSTANTIAL MOISTURE UP INTO THE SOUTHERN APPALACHIAS AS THE SUB- TROPICAL JET TAPS INTO THE GULF OF MEXICO. BY SUNDAY MORNING PWS RANGE FROM 1.4 TO 1.6 ACROSS THE AREA...PUTTING US WELL INTO THE 90TH PERCENTILE FOR THIS TIME OF YEAR. 12Z SUNDAY MODELS STILL SHOWING AREA OF LOW PRESSURE OVER WEST TN TAKING A SHARP TURN NORTH TOWARD THE GREAT LAKES SUNDAY AFTERNOON AND EVENING. AS THIS LOW SWINGS NORTH ACROSS THE WESTERN PORTION OF THE STATE IT WILL BRING IN MODERATE TO LOCALLY HEAVY PRECIP ACROSS THE AREA DUE TO STRONG LIFT AND HIGH PWS. THE SOUTHERN/CENTRAL VALLEY COULD SEE UP TO ONE INCH OF RAIN ON BY LATE SUNDAY AFTERNOON WHILE NETN AND SWVA COULD SEE UP TO HALF AN INCH. INSTABILITY STILL LOOKS RATHER WEAK...ONLY A FEW HUNDRED J/KG OF ELEVATED CAPE. SO WHILE THUNDERSTORMS STILL LOOK POSSIBLE IT DOESN`T APPEAR THAT WE WILL SEE MUCH IN THE WAY OF SEVERE. BIGGEST THING TO WATCH ON SUNDAY IS FOR LOCALIZED FLOODING DUE TO PREVIOUS RAINFALL OVER THE PAST SEVERAL DAYS. MAIN AREA OF CONCERN IS FOR OUR COUNTIES DOWN IN THE SOUTHERN VALLEY. BULK OF THE PRECIP HAS LIFTED NORTH OF THE AREA BY SUNDAY EVENING. ANOTHER QUICK SHOT OF PRECIP SUNDAY NIGHT INTO MONDAY AS THE COLD FRONT ASSOCIATED WITH THE LONGWAVE TROUGH ROLLS THROUGH. MONDAY`S QPF LOOKS RATHER LIGHT AS THERE WON`T BE A TON OF MOISTURE AVAILABLE. WE MAY BEGIN TO SEE CLEARING AS EARLY AS MONDAY AFTERNOON/EVENING...BUT DEFINITELY BY MONDAY NIGHT AS MUCH DRIER AIR QUICKLY INFILTRATES INTO THE REGION. TUESDAY LOOKS LIKE A VERY NICE DAY WITH MOSTLY SUNNY SKIES AND HIGHS IN THE IN THE MID TO UPPER 60S. TUESDAY NIGHT INTO WEDNESDAY WE ARE BACK TO A ZONAL FLOW. WITH ZONAL FLOW ON WEDNESDAY WE SEE AN A SLIGHT CHANCE FOR PRECIP ACROSS THE NORTHERN AREAS AS A WEAK IMPULSE RACES THROUGH THE FLOW BUT MAIN IMPACT WILL BE INCREASED CLOUD COVER COMPARED TO TUESDAY. MODELS STILL NOT IN BEST AGREEMENT ON NEXT SYSTEM THAT MOVES IN ON THURSDAY/FRIDAY. THE GFS CONTINUES TO TO BRING IN MOISTURE WHILE THE ECMWF IS STILL SLOWER AND DRIER. WILL CONTINUE WITH LOW WIDESPREAD POPS UNTIL BETTER MODEL AGREEMENT. && .PRELIMINARY POINT TEMPS/POPS... CHATTANOOGA AIRPORT, TN 58 78 63 74 / 20 30 90 90 KNOXVILLE MCGHEE TYSON AIRPORT, TN 57 78 60 73 / 10 20 90 90 OAK RIDGE, TN 59 79 60 73 / 10 20 90 90 TRI CITIES AIRPORT, TN 52 78 54 69 / 10 10 60 90 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SON/SR

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