Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 011745 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 145 PM EDT WED JUL 1 2015 .UPDATE... ISSUED AT 145 PM EDT WED JUL 1 2015 FRONTAL ZONE IS DRAPED ACROSS EASTERN/CENTRAL KENTUCKY...FROM NEAR BIG SANDY...BACK TOWARDS STANTON...TO JUST SOUTH OF LEXINGTON. SURFACE OBS SHOW A NICE CONVERGENCE ZONE ASSOCIATED WITH THIS FRONT. OUTFLOW FROM OVERNIGHT CONVECTION CONTINUES TO PUSH ACROSS SOUTH CENTRAL KENTUCKY WITH A BAND OF SHOWERS AND THUNDERSTORMS. THIS LINE IS EXPECTED TO PUSH ON THROUGH AREAS MAINLY SOUTH OF WHERE THE FRONTAL ZONE IS LOCATED THIS AFTERNOON. EXPECT JUST A QUICK ROUND OF RAIN BEFORE DRIER WEATHER WORKS BACK IN BEHIND THIS LINE. AS IT APPEARS NOW...WEATHER MAY TURN QUIET AGAIN THIS EVENING BEFORE AN MCS DROPS IN FROM THE NORTHWEST LATE TONIGHT. MODELS STILL UNCERTAIN ON PLACEMENT OF ANY MCS LATE TONIGHT...SO CONFIDENCE REMAINS LOW ON THE FORECAST FOR LATE TONIGHT. WHAT DOES APPEAR MORE CERTAIN...IS WIND AND HAIL THREAT IS GREATLY DIMINISHED WITH ONGOING CLOUD COVER PUTTING THE CLAMPS ON MORE SIGNIFICANT INSTABILITY. THUS...OUTSIDE OF A STRAY 30 MPH WIND GUST...SHOULD BE A MUCH QUIETER AFTERNOON. UPDATE ISSUED AT 1132 AM EDT WED JUL 1 2015 UPDATED TO REFINE POPS BASED ON THE LATEST TRENDS. ONLY A FEW ECHOES SHOWING UP ACROSS SOUTHEAST KENTUCKY THIS MORNING...SO WILL MAINTAIN SOME ISOLATED SHOWERS ACROSS THE SOUTH. BOUNDARY FROM OVERNIGHT CONVECTION CONTINUES TO PUSH EAST INTO CENTRAL KENTUCKY WITH A FEW SHOWERS ALONG THIS BOUNDARY MOVING EAST. WOULD EXPECT ACTIVITY TO EXPAND AS THIS BOUNDARY PUSHES ACROSS THE AREA THIS AFTERNOON WITH MODEST INSTABILITY ALREADY IN PLACE ACROSS THE AREA. STILL LOTS OF CLOUD COVER IN PLACE THIS MORNING...SO THIS WILL LIKELY KEEP INSTABILITY FROM GETTING ALL THAT HIGH. REGARDLESS...THE HIGHEST CHANCES FOR RAIN WILL REMAIN SOUTH OF I-64 THROUGH THE DAY. UPDATE ISSUED AT 805 AM EDT WED JUL 1 2015 UPDATED GRIDS TO BRING IN LINE WITH HOURLY TRENDS. MCS CURRENTLY PLOWING THROUGH THE BOOTHEEL OF MO. MODELS SHOW COLD POOL FROM THIS COMPLEX OF STORMS SPREADING RAPIDLY SOUTH AND EAST THROUGH THE DAY. CONSEQUENTLY STILL EXPECT CONVECTION ASSOCIATED WITH THIS SYSTEM TO AFFECT AT LEAST PART OF OUR CWA LATER THIS AFTERNOON. ALSO UPDATED THE HWO TO HIGHLIGHT AN INCREASING POTENTIAL FOR LOCALLY HEAVY RAINFALL THROUGH THE NEXT SEVERAL DAYS. NEARLY STATIONARY FRONTAL ZONE WILL HAVE SEVERAL DISTURBANCES PASS ALONG THE BOUNDARY PRODUCING ROUNDS OF SHOWERS AND THUNDERSTORMS. CONSIDERING RECENT RAINFALL...LOCALLY HEAVY RAIN MAY LEAD TO SOME NUISANCE FLOODING... ESPECIALLY WHERE THUNDERSTORMS PASS REPEATEDLY OVER THE SAME AREAS. && .SHORT TERM...(TODAY THROUGH THURSDAY) ISSUED AT 417 AM EDT WED JUL 1 2015 A WET PERIOD WILL BE IN STORE. WE WILL START OFF THIS MORNING WITH A LARGE LONGWAVE TROUGH CONTINUING ACROSS THE REGION. THE SHORTWAVE WHICH SPARKED RAIN AND STORMS YESTERDAY WILL BEGIN SHIFTING NORTHEAST AND OUT OF THE REGION WHILE ANOTHER SMALLER SHORTWAVE BEGINS TO TAKE FORM UPSTREAM OF EASTERN KY. THE GFS...NAM...AND ECMWF ARE ALL IN GOOD AGREEMENT THAT AN MCS WILL FROM AS A RESULT OF THIS SHORTWAVE...SETTLING ACROSS MISSOURI BY 12Z THIS MORNING /AS CAN ALREADY BE SEEN ON IR/. WITH NW FLOW STILL IN PLACE...EXPECT SOME OF THE MOISTURE FROM THIS SYSTEM TO ADVECT INTO KY...IN CONJUNCTION WITH ANY LEFT OVER MOISTURE FROM YESTERDAY/S SYSTEM...AS THE MCS BECOMES COLD POOL AND SHEER DRIVEN. AS WE BEGIN HEATING THROUGH THE DAY...THIS MOISTURE WILL BEGIN RISING AND SCT SHOWERS AND THUNDERSTORMS TO START DEVELOPING ACROSS THE REGION. WHILE A WEAK FRONTAL BOUNDARY WILL BE POSITIONED ALONG THE OHIO RIVER VALLEY...IT SEEMS AS THOUGH THE BEST STORM POTENTIAL WILL BE SPARKED ACROSS THE SOUTHERN CWA...CLOSER TO THE TN BORDER AND THE COLD POOL DRIVEN OUTFLOW BOUNDARY. ACCORDING TO SOUNDINGS ACROSS THE SW CWA...THE LAST TWO RUNS OF THE NAM12 MODEL HAVE BEEN IN GOOD AGREEMENT WITH SHOWING CAPE VALUES TOPPING OUT NEAR 4000 J/KG BETWEEN 18 AND 21Z...A STRONG FAT CAPE...AND DRYING ALOFT WHICH MAY PROMOTE SOME DECENT HAIL POTENTIAL. LI/S WILL EVEN BE TOPPING OUT AROUND -9 AT KSME AND KLOZ...SUPPORTING THE IDEA FOR UNSTABLE CONDITIONS CONDUCIVE TO STRONG THUNDERSTORM DEVELOPMENT. THAT BEING SAID...AS YOU HEAD FARTHER NORTH...INSTABILITY AND WIND SHEAR DROPS SIGNIFICANTLY AS YOU LOSE INFLUENCE FROM THE COLD POOL OF THE UPSTREAM MCS. THIS CORRELATES WELL TO THE MRG AND SLIGHT RISK AREAS OF THE SPC DAY 1 CONVECTIVE OUTLOOK. THE ECMWF MAY ACTUALLY HAVE THE BEST HANDLE ON THIS SYSTEM DURING THE OVERNIGHT PERIOD...AS IT IS SHOWING A STRONG HANDLE ON THE MESOSCALE FEATURES AND HAS VERY GOOD INITIALIZATION SO FAR THIS MORNING. CURRENTLY...IT IS SHOWING A WELL DEFINED LLVL JET BELOW THE NOCTURNAL INVERSION FEEDING THE MCS AS IT MOVES INTO MISSOURI. AS WE HEAD INTO THE DAY...THE MCS WILL LIKELY BECOME MORE COLD POOL AND SHEER DRIVEN...SHIFTING SE AND AWAY FROM THE LLVL JET AS THE INVERSION AND WINDS BREAK DOWN. BY 0Z TONIGHT...THE ECMWF CLEARLY SHOWS THE LLVL JET REESTABLISHING ITSELF ACROSS MISSOURI AND REENERGIZING THE MCS ACROSS MISSOURI...WHILE THE STRONGEST CONVECTION OVER OUR CWA BEGINS TO DISSIPATE WITH LOSS OF DAYTIME HEATING/FORCING. BY THURSDAY...THE MCS WILL FOLLOW THE SHORTWAVE AND ROUND THE LONGWAVE TROUGH AXIS. IN THIS SCENARIO...WOULD TEND THE LEAN TOWARDS THE ECMWF AND THE NAM 12...SINCE THE GFS SEEMS TO BE PULLING THE TROUGH AXIS MUCH FURTHER SOUTHWARD...AND THEREBY PRODUCING A STRONGER SYSTEM...COMPLETE WITH A DEVELOPING SURFACE LOW TRACKING UP THE OHIO RIVER. THIS PEGS THE HIGHEST QPF ACROSS THE NORTHERN CWA AND ALONG AND NORTH OF THE OHIO RIVER VALLEY...WHICH IS OUT OF AGREEMENT WITH EVERY OTHER MODEL...AND WAS HIGHLIGHTED BY THE WPC MODEL DIAGNOSTIC DISCUSSION AS BEING UNREALISTIC. INSTEAD...EXPECT THE MCS AND BEST MOISTURE TO RIDE ALONG THE TIGHTEST THICKNESS PATTERN...WITH BEST INSTABILITY AND QPF THEREFORE LOCATED ACROSS OUR SOUTHERN CWA AND IN THE TN VALLEY. CONCERNING THE AMOUNT OF MOISTURE...PWATS IN THE 1.75 TO 2.00 INCH RANGE ARE POSSIBLE THROUGH THE DAY THURSDAY...WITH WPC PEGGING AROUND AN INCH OF PRECIP OVER A 6 HOUR PERIOD DURING THE DAY NEAR THE TN BORDER. SOME OF THE HEAVIER STORMS/SHOWERS MAY PRODUCE LOCALLY HIGHER AMOUNTS AS WELL. THIS MAY CREATE SOME PROBLEMS AS WE HEAD INTO THURSDAY NIGHT AND THE HEART OF THE MCS TRAVELS ACROSS EASTERN KY AND BRINGS WIDESPREAD HEAVY RAINFALL. EXPECT FLASH FLOODING TO BE A CONCERN...ESPECIALLY ACROSS THE SOUTHERN CWA WHERE PWATS ARE EXPECTED TO TOP OUT BETWEEN 2.1 AND 2.25 INCHES. AFTER SOME DISCUSSION WITH MRX ABOUT WHETHER OR NOT TO GO AHEAD AND ISSUE A FLASH FLOOD WATCH...ULTIMATELY DECIDED TO HOLD OFF UNTIL DURING THE DAY TOMORROW. THE PRIMARY REASON BEING THAT THE MODELS ARE STILL SHOWING SOME DISAGREEMENT AND EACH ONE HAS SOME UNREALISTIC SCENARIOS...NOT TO MENTION THIS LATEST RUNS OF THE ECMWF SHOWED SOME INCONSISTENCIES COMPARED TO THE PREVIOUS RUN. WOULD HOPE THAT IN THE NEXT ONE TO TWO RUNS...AS THE MCS GETS GOING TODAY...THE MODELS WILL START TO GET A BETTER HANDLE ON THE UPCOMING SITUATION...AS WELL AS HOW FAR NORTH INTO OUR CWA FLASH FLOODING MIGHT BE OF CONCERN. .LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY) ISSUED AT 515 AM EDT WED JUL 1 2015 SEEING MORE SIGNIFICANT DIFFERENCES IN THE DETERMINISTIC ECMWF AND GFS THROUGH THE EXTENDED. OVERALL UPPER LEVEL PATTERN BECOMES LESS AMPLIFIED THROUGH THE PERIOD. GFS IS MORE AMPLIFIED... STRONGER WITH SHORT WAVE ENERGY DROPPING INTO THE MID-MISSISSIPPI AND OHIO VALLEY AT THE START OF THE EXTENDED...FRI INTO SAT. NATIONAL GUIDANCE SUGGEST THE OPERATIONAL GFS IS TOO STRONG WITH THIS SYSTEM CONSIDERING UPSTREAM ENERGY AND ITS INFLUENCE ON EVOLUTION OF THE WAVE THROUGH THE OHIO VALLEY. A BLEND OF SOLUTIONS/GUIDANCE APPEARS TO BE THE BEST APPROACH FOR THE EXTENDED PORTION OF THE FORECAST...PERHAPS WITH A NUDGE TOWARDS THE DETERMINISTIC ECMWF. SENSIBLE WEATHER STILL LOOKS UNSETTLED WITH AT LEAST A CHANCE OF RAIN EACH DAY. BAROCLINIC...OR FRONTAL ZONE APPEARS TO STALL OUT ACROSS THE REGION. MODELS ARE SHOWING SUBTLE DIFFERENCES IN THE EXACT LOCATION OF THIS ZONE OF UNSETTLED WEATHER. MOST LIKELY LOCATION APPEARS TO BE SOUTH OF THE OHIO RIVER BUT NORTH OF THE TENN VALLEY. THE WEATHER WILL BE QUITE ACTIVE WITHIN THIS SECTOR WHICH INCLUDES THE COMMONWEALTH. CONSIDERING THE RECENT RAINFALL WE HAVE EXPERIENCED OVER THE LAST FEW DAYS...HYDRO ISSUES COULD BECOME A CONCERN AS MULTIPLE DISTURBANCES TRACK THROUGH THE AREA. TEMPERATURES WILL PROBABLY TREND A BIT CLOSER TO NORMAL THROUGH THE PERIOD...ESPECIALLY TOWARDS THE END OF THE FORECAST WINDOW. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON) ISSUED AT 145 PM EDT WED JUL 1 2015 WHILE VFR CONDITIONS HAVE RETURNED TO THE AREA THIS AFTERNOON...CIGS WILL LIKELY COME BACK DOWN TONIGHT AS A FRONTAL ZONE REMAINS DRAPED ACROSS EASTERN KENTUCKY. THUS...EXPECT CLOUDS TO LOWER THROUGH THE NIGHT FALLING BACK TO IFR BY LATE TONIGHT. ITS POSSIBLE STRATUS COULD BUILD DOWN ONTO THE RIDGES...CREATING SOME POCKETS OF DENSE FOG FOR AIRPORTS ON THE RIDGES. WILL HAVE TO MONITOR THAT TONIGHT. A BAND OF SHOWERS/STORMS WILL PUSH EAST ACROSS SOUTHERN KENTUCKY THIS AFTERNOON...BUT THEN UNCERTAINTY INCREASES TONIGHT AS A POTENTIAL MCS ORGANIZES UPSTREAM. DEPENDING ON WHERE THIS FEATURE TRACKS...WE MAY GET MORE RAIN/STORMS LATE TONIGHT INTO TOMORROW MORNING. HOWEVER...TOO MUCH UNCERTAINTY AT THIS TIME TO JUMP ON THIS IDEA. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KAS SHORT TERM...JMW LONG TERM...RAY AVIATION...KAS

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