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

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000 FXUS64 KMRX 290711 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 311 AM EDT WED JUL 29 2015 .SHORT TERM...
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(TODAY AND TONIGHT)...AREAS OF DENSE FOG WILL BE POSSIBLE THROUGH EARLY MORNING AS WE CURRENTLY HAVE A LOW TEMP/DEWPOINT SPREADS ACROSS THE AREA COMBINED WITH FEW CLOUDS AND CALM WINDS. FOG WILL CLEAR A FEW HOURS AFTER SUNRISE. PLEASE USE CAUTION WHILE TRAVELING THROUGH AREAS OF DENSE FOG AS VISIBILITY MAY SUDDENLY DECREASE. TODAY WILL BE SIMILAR TO YESTERDAY IN TERMS OF AFTERNOON CONVECTION. UPPER RIDGE TO OUR WEST WILL ALLOW US TO BE IN A MOSTLY UNCAPPED ENVIRONMENT BY THE AFTERNOON HOURS. COVERAGE EXPECTED TO BE ISO/SCT. A FEW STORMS COULD BE STRONG WITH ONE OR TWO POSSIBLY BECOMING SEVERE DUE TO CAPES RANGING FROM 2000 TO 3000 J/KG ACROSS THE AREA. THESE WILL BE PULSE STORMS DUE TO THE LACK OF SHEAR SO THEY WILL BE SHORT LIVED. THE MAIN THREATS WILL BE HEAVY RAINFALL AND ISO DAMAGING WIND GUSTS. TEMPS WILL RANGE FROM THE LOW TO MID 90S FOR MOST OF THE AREA WITH HEAT INDICES RANGING FROM THE MID 90S TO NEAR 100. THOUGH THESE VALUES DON`T MEET ADVISORY CRITERIA PERSONS SHOULD STILL EXERCISE CAUTION WHILE PERFORMING ANY OUTDOOR ACTIVATES DURING THE AFTERNOON HOURS. STORMS WILL LINGER INTO THE EVENING HOURS IN ADVANCE OF AN APPROACHING COLD FRONT. STORMS WILL EVENTUALLY WAIN IN COVERAGE THE FURTHER WE GET INTO THE NIGHT. OVERNIGHT LOWS WILL BE A FEW DEGREES ABOVE NORMAL WITH LOWS IN THE LOW TO MID 7OS. .LONG TERM...(THURSDAY THROUGH TUESDAY)...MODELS REALLY NOT IN VERY GOOD AGREEMENT ON TIMING OF THE COLD FRONT ON THURSDAY...WITH NAM ZIPPING THE COLD FRONT THROUGH OUR FORECAST AREA BY 12Z THURSDAY. THIS RESULTS IN LESS THAN 10 PERCENT POPS FROM THE NAM MOS FOR THURSDAY. I HAVE OPTED FOR NOW TO STAY CLOSER TO THE SIMILAR GFS/ECMWF TIMING...WHICH SUPPORTS OUR PREVIOUS POP/WX GRIDS FOR THURSDAY WITH CHANCE POPS. HOWEVER...BOTH THE GFS/ECMWF FRONTAL TIMING WOULD ALLOW THE DROPPING OF POPS BY OR BEFORE 04Z FRIDAY. TRENDED OUR GRIDS THAT WAY AND ALLOWED POPS TO DROP FROM THE NW BY THURSDAY AFTERNOON...THEN JUST KEPT SLIGHT CHANCE POPS IN ERN MOST COUNTIES THROUGH THURSDAY EVENING. WE THEN SEE NW FLOW ALOFT ESTABLISHED AS THE UPPER RIDGE RETROGRADES WESTWARD AND TROUGHING DEVELOPS OVER THE ERN THIRD OF THE NATION. SURFACE RIDGING AT THE SAME TIME LOOKS TO SET UP ACROSS THE SE STATES AND SRN APPALACHIANS FOR FRIDAY THROUGH THE WEEKEND. THIS MADE THE SUPERBLEND 20 TO 30 PERCENT POPS ON SUNDAY AND MONDAY QUITE SUSPECT...SINCE SURFACE WINDS STAY LIGHT AND VARIABLE DUE TO THE RIDGE. DAYTIME HEATING ALONE LOOKS INSUFFICIENT TO CREATE MUCH IN THE WAY OF SHOWERS OR THUNDERSTORMS...WITH VERY LIMITED LOW LEVEL MOISTURE CONVERGENCE. GFSX AND ECMWX POPS FOR FRIDAY THROUGH MONDAY WERE WELL BELOW CLIMO...SO I KEPT OUR GRIDS DRY UNTIL MONDAY AFTERNOON TO TUESDAY NIGHT. FOR TEMPS...WENT A LITTLE COOLER THAN GFS FOR THURSDAY MAXES GIVEN THE POTENTIAL FOR MORNING AND AFTERNOON CONVECTION. THE GFS MOS TEMPS LOOKED VERY GOOD FOR THURSDAY NIGHT AND FRIDAY. THE SUPERBLEND MINS/MAXES WERE CLOSELY FOLLOWED FOR THE REST OF THE LONG TERM... WITH A SLIGHT ADJUSTMENT TO GIVE MORE OF A RANGE IN MINS IN THE MTNS.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 94 75 92 71 / 30 30 50 10 KNOXVILLE MCGHEE TYSON AIRPORT, TN 92 73 89 69 / 30 30 40 10 OAK RIDGE, TN 92 74 90 67 / 30 30 40 10 TRI CITIES AIRPORT, TN 90 70 88 63 / 30 30 50 20
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SR/TG

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