Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 200004 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 804 PM EDT TUE AUG 19 2014 .UPDATE... ISSUED AT 804 PM EDT TUE AUG 19 2014 UPDATED THE FORECAST TO END THE PRECIPITATION FOR THE LATE AFTERNOON AND THEN TO TIME IN THE NEXT BATCH OF SHOWERS AND THUNDERSTORMS INTO THE AREA DURING THE OVERNIGHT. HAVE VERY LOW CONFIDENCE IN THE MODELS DUE TO THE BIG DIFFERENCES IN TIMING. WENT WITH A MIX OF THE HRRR ...EXTRAPOLATION AND A MODEL CONSENSUS TO TRY AND TIME A BAND OF SHOWERS AND THUNDERSTORMS INTO THE AREA TONIGHT ASSOCIATED WITH A SHORT WAVE WHICH WILL BE MOVING INTO THE AREA FROM THE WEST TONIGHT. THE 0 TO 6 KM MEAN FLOW IS ONLY AROUND 12 MPH AND THE PRECIPITABLE WATER IS AROUND 1.6 INCHES TONIGHT...SO WILL NEED TO KEEP AN EYE ON THE PRECIPITATION AMOUNTS FOR POTENTIAL HYDRO ISSUES. THE INSTABILITY IS CLEARLY SUFFICIENT FOR ANY CONVECTION TO RESULT IN THUNDER. FEEL PRETTY CONFIDENT THAT THERE WILL BE A LINE MOVING THROUGH THE AREA TONIGHT...HOWEVER DO NOT HAVE GOOD CONFIDENCE IN THE TIMING. && .SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT) ISSUED AT 258 PM EDT TUE AUG 19 2014 ISOLATED DIURNALLY DRIVEN CONVECTION OVER THE SOUTHEAST PART OF THE FORECAST AREA CONTINUES TO WANE. EXPECT A CONTINUED DECREASING TREND THROUGH THE REMAINDER OF THE DAY AND WILL CARRY ONLY ISOLATED SHOWERS...NO THUNDER...FOR THE EVENING PORTION OF THE FORECAST. OVER THE NEXT 36 HOURS SHORT WAVES WILL CONTINUE TO ROTATE AROUND THE PARENT UPPER LOW WHICH IS SITUATED OVER THE GREAT LAKES. THIS KEEPS A NEARLY CONSTANT THREAT OF SHOWERS AND THUNDERSTORMS IN THE FORECAST. THE FIRST WAVE WILL AFFECT THE AREA TONIGHT...AND A SECOND WAVE LOOKS TO IMPACT THE AREA WEDNESDAY NIGHT. AT THE SURFACE A WEAK COLD FRONT IS ADVANCING ESE ACROSS IL. SHOWERS AND THUNDERSTORMS OUT AHEAD OF THIS FEATURE WILL CONTINUE TO MOVE TOWARDS EAST KY THROUGH THE REST OF THE AFTERNOON AND EVENING. THERE IS CONSIDERABLE UNCERTAINTY HOW LONG THE SHOWERS AND THUNDERSTORMS WILL MAINTAIN THEMSELVES AFTER SUNSET AS THE BEST FORCING LOOKS TO REMAIN NORTH OF OUR AREA TONIGHT...AND MODEL DATA SUPPORTS A WEAKENING TREND WITH ANY CONVECTION THAT MOVES INTO OUR AREA LATER TONIGHT. EVEN SO WILL STILL NEED TO CARRY SHOWER AND THUNDERSTORM CHANCES LATER TONIGHT...WITH THE BEST CHANCES IN THE NORTHWEST AND LOWEST CHANCES IN THE SOUTHEAST. ON WEDNESDAY THE FRONT WILL STALL IN OUR VICINITY...AND MORE CONVECTION WILL BE POSSIBLE ESPECIALLY IN THE AFTERNOON. AS ANOTHER WAVE APPROACHES WEDNESDAY NIGHT AND THE FRONT BEGINS LIFTING NORTHEAST SHOWER AND THUNDERSTORM CHANCES WILL CONTINUE. THE MUGGY WEATHER WILL PERSIST AS THERE WILL BE LITTLE CHANGE IN DAILY TEMPERATURE TRENDS AND DEWPOINTS WILL CONTINUE TO RUN IN THE UPPER 60S TO LOWER 70S. .LONG TERM...(THURSDAY THROUGH TUESDAY) ISSUED AT 258 PM EDT TUE AUG 19 2014 AN UPPER LEVEL DOME OF HIGH PRESSURE WILL BUILD OVER THE SOUTHEAST CONUS NORTHWARD INTO THE OHIO VALLEY DURING THE PERIOD AS A TROUGH PERSISTS ALONG THE EAST COAST. MODELS ARE FAIRLY CONSISTENT WITH THIS SCENARIO...ALTHOUGH THE ECMWF IS A BIT MORE BULLISH WITH THE STRENGTH OF THE UPPER RIDGE OVER OUR REGION LATE IN THE PERIOD. THE NET RESULT WILL BE INCREASING TEMPERATURES SLOWLY THROUGH TIME. TEMPERATURES OFFERED BY MOS GUIDANCE AND EVEN OUR STANDARD MODEL BLEND MAY BE A BIT TOO WARM THOUGH CONSIDERING HOW WET MOST OF OUR FORECAST AREA HAS BEEN RECENTLY AND ESPECIALLY CONSIDERING DEWPOINTS WILL BE AROUND 70 OR IN THE LOW 70S MUCH OF THE TIME. NEVERTHELESS...THE LONG TERM PERIOD WILL LIKELY FEATURE SOME OF THE WARMEST WEATHER WE HAVE EXPERIENCED THIS SUMMER...OR AT LEAST EQUAL TO WHAT WAS OBSERVED JULY 10TH THROUGH THE 13TH. WITH THE WARM AND MUGGY AIRMASS IN PLACE...ALONG WITH A DIFFUSE QUASI-STATIONARY FRONTAL BOUNDARY OVERHEAD OR JUST TO OUR EAST... THERE WILL BE A DAILY CHANCE OF THUNDERSTORMS. POPS WILL BE HIGHEST OVER OUR NORTHEAST COUNTIES THURSDAY AND FRIDAY...CLOSER TO THIS BOUNDARY...BUT THEN GRADUALLY DECREASE EACH DAY SATURDAY THROUGH TUESDAY AS THE UPPER RIDGE BEGINS TO EXERT MORE INFLUENCE OVER OUR REGION. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING) ISSUED AT 800 PM EDT TUE AUG 19 2014 THIS IS A VERY DIFFICULT FORECAST. EXPECT SOME VALLEY FOG TO FORM TONIGHT AND ALSO EXPECT A LINE OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO MOVE ACROSS THE AREA AS A SHORT WAVE APPROACHES FROM THE WEST. THE INTERACTION OF THE RAIN SHOWERS AND THE VALLEY FOG IS VERY DIFFICULT TO PREDICT. SOMETIMES THE SHOWERS MIX OUT THE FOG AND OTHER TIMES THEY MAKE IT WORSE DEPENDING ON HOW HARD IT RAINS. IF THE SHOWERS DO NOT MAKE IT INTO THE AREA...THEN THE FOG MAY BE WORSE THAN WHAT WAS CURRENTLY IN THE TAFS. SORT OF HEDGED A BIT AND PUT A TEMPO WITH SOME LOW VISIBILITY IN THE FORECAST AND INCLUDED BOTH THUNDER AND MIST. THE 6Z TAF WILL MOST LIKELY HAVE A BETTER HANDLE ON THE TIMING. AFTER MORNING CLEARING...EXPECT SOME SHOWERS AND THUNDERSTORMS TO FORM AGAIN TOMORROW AFTERNOON. JUST PUT A VCTS INTO THE FORECAST DUE TO UNCERTAINLY OF THE TIMING FOR THE STORMS. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JJ SHORT TERM...SBH LONG TERM...ABE AVIATION...JJ

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