Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 231157 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 757 AM EDT SAT AUG 23 2014 .UPDATE... ISSUED AT 716 AM EDT SAT AUG 23 2014 LINGERING MOISTURE FROM LAST NIGHT/S RAINFALL HAS CAUSED AREAS OF FOG ACROSS PORTIONS OF EASTERN KY. GIVEN THE AMOUNT OF MOISTURE...EXPECT THIS FOG TO STICK AROUND FOR THE NEXT COUPLE OF HOURS BEFORE SLOWLY LIFTING AND BURNING OFF WITH DAYTIME HEATING BY MID MORNING. AS SUCH...ADJUSTED THE WEATHER GRIDS TO ACCOUNT FOR THE MORNING FOG ACROSS THE AREA. ALSO...UPDATED THE POP GRIDS TO BETTER ACCOUNT FOR THE LATEST MODEL DATA AND THOUGHTS FOR RAIN POTENTIAL OVER THE NEXT SEVERAL HOURS...PUSHING BACK ISOLATED POPS BY 1 TO 2 HOURS...AND KEEPING LOWER END IN A COUPLE HOURS LONGER. AS IT NOW STANDS...UPDATED FORECAST INTRODUCES ISOLATED POPS THIS MORNING...WHICH IS STILL AN HOUR OR TWO SOONER THAN SOME OF THE SURROUNDING OFFICES. WHILE THIS MIGHT BE TOO QUICK...THE FACT THAT MOISTURE IS SO ABUNDANT...AND THERE ARE A FEW POP UP SHOWERS ALREADY SHOWING UP ACROSS SOUTHERN HALF OF THE CWA...FELT MORE CONFIDENT WITH INCLUDING POPS THAN NOT INCLUDING THEM. REGARDLESS...AS DAYTIME HEATING ENSUES...EXPECT THINGS TO BEGIN DEVELOPING BY EARLY AFTERNOON. LOADED IN THE LATEST OBSERVATIONAL DATA TO MAKE SURE TEMPS...DEW POINTS...AND WINDS WERE WELL REFLECTED IN THE ONGOING NEAR TERM FORECAST. && .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 421 AM EDT SAT AUG 23 2014 WHILE 500MB HEIGHTS CONTINUE TO PUSH A STRONG RIDGING PATTERN INTO THE LOWER MISSISSIPPI RIVER VALLEY AND DEEP SOUTH...TROUGHING CONTINUES TO LINGER ALONG THE NEW ENGLAND SEABOARD. EASTERN KY/S POSITION IN THE TRANSITION ZONE WILL CONTINUE TO MAKE US SUSCEPTIBLE TO SHORTWAVE ACTIVITY THROUGH THE SHORT TERM. AT THE SURFACE...A STATIONARY BOUNDARY PARKED JUST NORTH OF THE OHIO RIVER YESTERDAY WAS THE FOCAL POINT FOR A STRONG PULL OF WAA AND UNSTABLE MOIST AIR FROM THE GULF. AS TEMPS ROSE DURING THE AFTERNOON...THE ATMOSPHERE BECAME MORE UNSTABLE...AND THE FRONT PROVIDED THE LIFT NEEDED TO INITIATE STRONG SHOWERS AND THUNDERSTORMS CAPABLE OF PRODUCING TORRENTIAL RAINS. THESE STORMS THEN MOVED S AND SE INTO EASTERN KY THROUGHOUT THE EVENING AND OVERNIGHT...CAUSING FLASH FLOODING ACROSS MANY LOCATIONS. FOR TODAY...THIS FRONTAL BOUNDARY WILL SHIFT ONLY SLIGHTLY...BECOMING MORE N/S ORIENTED ALONG THE ERN KY BORDER ACCORDING TO THE LATEST GFS ANALYSIS. GIVEN THE SIMILAR SET UP TO YESTERDAY...EXPECT A NEAR REPEAT OF EVENTS...WITH THE BEST CONVECTION EXPECTED MORE OVER THE WRN AND SWRN PORTIONS OF THE CWA. THIS WILL NOT LIMIT OTHER SCATTERED CONVECTION FROM DEVELOPING ELSEWHERE ACROSS THE CWA AS WELL. PWAT VALUES ARE STILL AROUND/ABOVE 2 INCHES DURING THE AFTERNOON AND EVENING...WITH STORM MOTION AND 0-6KM WINDS GENERALLY 10-12 KNOTS OR LESS. SLOW MOVING HEAVY RAINERS WILL BE THE STORY ONCE MORE. WHILE THUNDERSTORMS ARE DEFINITELY POSSIBLE...GENERALLY NE FLOW AND SOME MID LEVEL CAPPING MAY BE ENOUGH TO KEEP SEVERE POTENTIAL AT BAY FOR THE MOST PART. BIGGEST CONCERN WILL OBVIOUSLY BE THE FLASH FLOODING POTENTIAL...ESPECIALLY GIVEN THE ONGOING SATURATED/ABOVE SATURATED CONDITIONS ACROSS EASTERN KY. BY THIS EVENING/OVERNIGHT...THE FRONTAL BOUNDARY WILL MAKE A QUICK PUSH SW ACROSS THE CWA. THIS...AND LOSS OF DIURNAL HEATING AND INSTABILITY WILL QUICKLY REDUCE POPS ACROSS THE REGION...THOUGH LATEST NAM12 SOUNDINGS ARE STILL SHOWING PWAT VALUES BETWEEN 1.75 AND 2.0 IN. OVERNIGHT SATURDAY NIGHT AS WELL. IN OTHER WORDS...EXPECT COVERAGE AND THUNDER POTENTIAL TO LESSON SUBSTANTIALLY...THOUGH ANY STORMS THAT DO PERSIST WILL CONTINUE TO PUT DOWN HEAVY RAIN WHILE EXPERIENCING A SLOWING STORM MOTION. FLASH FLOODING THREATS...THEREFORE...WILL CONTINUE INTO THE OVERNIGHT HOURS. THE FRONTAL BOUNDARY WILL SHIFT OFF TO OUR SW FOR THE FORECAST SUNDAY...WITH THE UPPER LEVEL RIDGE ENCOMPASSING MUCH OF THE OHIO RIVER VALLEY. DIURNAL DRIVEN INSTABILITY WILL CONTINUE...AS A WEAK SURFACE DISTURBANCE SETS UP ACROSS THE SOUTH CENTRAL PORTION OF THE STATE. THIS WILL BE THE PRIMARY EPICENTER FOR STORM DEVELOPMENT...HOWEVER ANYTHING STRONG IS HIGHLY UNLIKELY GIVEN THE UNSUPPORTED WEAK WIND PROFILE. PWAT VALUES WILL SHOW A LESSENING TREND...BUT ARE STILL STICKING AROUND THE 1.75 IN. RANGE WITH LITTLE TO NO STORM MOTION. WOULDN/T BE SURPRISED TO SEE SOME MORE GOOD HEAVY SOAKERS THIS DAY AS WELL. CHANCES FOR SHOWERS WILL QUICKLY DROP OFF WITH LOSS OF DAYTIME HEATING IN THE EVENING. GIVEN THE CONTINUED BUILDING HEIGHTS ACROSS THE REGION...AND A MORE TROPICAL AIRMASS MOVING INTO THE OHIO RIVER VALLEY...TEMPS WILL CONTINUE TO CLIMB TO JUST BELOW THE 90 DEGREE MARK TODAY AND TOMORROW...WITH HIGH HUMIDITY VALUES MAKING IT FEEL CLOSER TO 100 DEGREES. CLOUDS AND THE POTENTIAL FOR SHOWERS WILL KEEP TEMPS FROM REACHING EVEN HIGHER. MIN TEMPS WILL REMAIN WELL ABOVE NORMAL UNDER THIS WARM AIRMASS...ONLY DIPPING DOWN INTO A HUMID UPPER 60S AND LOW 70S. .LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) ISSUED AT 458 AM EDT SAT AUG 23 2014 BY SUNDAY NIGHT...THE UPPER LEVEL AND SURFACE HIGH WILL BE WELL IN PLACE THROUGH THE END OF THE PERIOD. WITH THIS TYPE OF PATTERN...THE DAYS WILL BE FAIRLY WARM AND MOIST AND THERE WILL PRETTY MUCH BE A SLIGHT CHANCE TO A CHANCE FOR THUNDERSTORMS EVERY AFTERNOON AND EVENING. WITH THE HIGH PRESSURE IN PLACE...THE AIR WILL ONLY BE MOIST IN THE LOWER LAYERS. THIS WILL ALLOW FOR A LITTLE BREAK FROM THE FLASH FLOODING THREAT THAT HAS BEEN SO PREVALENT DURING THIS VERY MOIST AUGUST. SO FAR THIS AUGUST...JACKSON HAS RECEIVED 6.28 INCHES OF RAIN...WITH 3.69 INCHES BEING THE NORMAL RAINFALL FOR AUGUST. FOR TEMPERATURES...WENT WITH THE MODEL BLEND AND THEN NUDGED THEM TOWARD THE 00 GMT RAW ECMWF. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING) ISSUED AT 756 AM EDT SAT AUG 23 2014 LOTS OF VLIFR CONDITIONS AROUND EASTERN KENTUCKY THIS MORNING...ESPECIALLY NEAR AREAS THAT RECEIVED HEAVY RAIN YESTERDAY AFTERNOON AND EVENING. EXPECTING THE FOG TO START LIFTING BETWEEN 12Z AND THEN RETURNING TO VFR BY 14 -15Z. EXPECTING ISOLATED TO SCATTERED THUNDERSTORMS AGAIN THIS AFTERNOON STARTING BETWEEN 18 TO 21Z. FOG AND MIST WILL BE FORMING AGAIN TONIGHT...ESPECIALLY IN VALLEYS AND LOCATIONS THAT RECEIVE HEAVY RAIN TODAY. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JMW SHORT TERM...JMW LONG TERM...JJ AVIATION...JJ

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