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

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000 FXUS64 KMRX 241920 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 320 PM EDT FRI APR 24 2015 .SHORT TERM (TONIGHT THROUGH SATURDAY NIGHT)...VERY ACTIVE PERIOD WITH A SIGNIFICANT SEVERE WEATHER OUTBREAK POSSIBLE SATURDAY AFTERNOON AND EVENING. SURFACE RIDGING WILL CONTINUE TO MOVE EAST OF THE AREA WITH INCREASING SOUTHERLY FLOW ALOFT. THE INCREASING SOUTHERLY FLOW/ISENTROPIC LIFT AND JET MOVING THROUGH ENHANCING DIVERGENCE ALOFT WILL SPREAD SHOWERS INTO THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS OVERNIGHT. WARM FRONT WILL MOVE INTO THE AREA SATURDAY MORNING...THEN PROGRESS SLOWLY WEST-EAST THROUGH THE AREA DURING THE DAY. AS UPPER TROUGH MOVES TOWARD THE REGION SATURDAY...FORCING WILL INCREASE WITH CYCLO-GENESIS MOVING THROUGH THE LOWER OHIO VALLEY. END RESULT WILL BE INCREASING INSTABILITY AND SHEAR. CAPES IN THE WARM SECTOR WILL INCREASE TO 1500-2000 J/KG WITH SOUNDINGS SHOWING FAIRLY LARGE HAIL CAPES. ALSO...SHEAR WILL BE IMPRESSIVE...ESPECIALLY ALONG AND NEAR THE WARM FRONT WITH 0-1KM SHEAR OF 25KTS/0-1KM SRH OF 250-300 M2/S2. THE 0-6KM SHEAR WILL ALSO BE FAVORABLE FOR SUPERCELL DEVELOPMENT OVER 40KTS. EXACT EVOLUTION OF STORM DEVELOPMENT IS STILL UNCERTAIN...BUT CURRENT THINKING IS ISOLATED-SCATTERED SUPERCELL DEVELOPMENT ALONG THE WARM FRONT EARLY AFTERNOON ACROSS THE PLATEAU...THEN MOVING INTO THE CENTRAL/SOUTHERN VALLEY. ISOLATED TORNADOES ARE POSSIBLE. MODELS CONTINUE TO SHOW A MCS DEVELOPING ACROSS KENTUCKY...THEN MOVING EAST SOUTHEAST INTO THE REGION FOLLOWING WARM FRONT. THERE COULD BE A SQUALL LINE ASSOCIATED WITH THE MCS. FORECAST SOUNDINGS SHOW STRONG INDICATIONS OF STRONG DAMAGING HIGH WINDS. GOOD MID- LEVEL DRY AIR ENHANCING DOWNBURSTS STRENGTH AND LOW-LEVEL JET OF 40-50KTS...PRODUCES DERECHO COMPOSITE PARAMETERS IN THE VERY FAVORABLE RANGE OF 2 TO 4. THE MAIN SEVERE CONCERN WILL BE DAMAGING WINDS IN EXCESS OF 70KTS...LARGE HAIL OF GOLFBALL OR LARGER...ISOLATED TORNADOES AND LOCALLY HEAVY RAINFALL. STRONG CONVECTION WILL MOVE OUT OF THE AREA BY LATE EVENING WITH RESIDUAL SHOWERS LEFT. .LONG TERM (SUNDAY THROUGH FRIDAY)...THE COLD FRONT WILL SAG SOUTH OF THE REGION ON SUNDAY...BUT LINGERING POST FRONTAL SHOWERS AND CLOUD COVER WILL STILL BE POSSIBLE THROUGH THE MORNING HOURS/EARLY AFTERNOON HOURS /ESPECIALLY ACROSS SW VA/NE TN AND EAST TENNESSEE MOUNTAINS/. BY SUNDAY NIGHT...GOOD CLEARING WILL OCCUR AND RESULT IN A SUNNY BUT COOL DAY ON MONDAY. TUESDAY WILL BE FAIRLY SIMILAR TO MONDAY...WITH SOME MORE CLOUD COVER MOVING IN LATE AHEAD OF A EASTWARD MOVING LOW PRESSURE SYSTEM. THIS STORM SYSTEM WILL MAINTAIN THE COOLER CONDITIONS DURING THE MIDDLE PART OF THE WEEK...AND SOME DECENT OPPORTUNITIES FOR SHOWERS TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...BEFORE TAPERING THINGS OFF THURSDAY MORNING. THEREAFTER ...UPPER-RIDGING LOOKS TO BUILD BACK INTO THE REGION FOR FRIDAY INTO THE NEXT WEEKEND. THIS WILL BRING FAIR WEATHER AND DRY CONDITIONS TO KICK OFF THE FIRST WEEKEND OF MAY. && .PRELIMINARY POINT TEMPS/POPS... CHATTANOOGA AIRPORT, TN 55 75 61 76 / 90 80 40 20 KNOXVILLE MCGHEE TYSON AIRPORT, TN 52 71 60 70 / 80 80 70 30 OAK RIDGE, TN 52 71 59 69 / 80 80 70 20 TRI CITIES AIRPORT, TN 45 67 54 63 / 50 80 70 60 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$

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