Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 301817 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 217 PM EDT TUE JUN 30 2015 .UPDATE...
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ISSUED AT 216 PM EDT TUE JUN 30 2015 INSTABILITY HAS BEEN ON THE INCREASE THROUGH THE AREA THIS AFTERNOON AND SHOWERS AND THUNDERSTORMS HAVE DEVELOPED QUITE QUICKLY IN CENTRAL KY AND FINALLY INTO EASTERN KENTUCKY. THE AREA REMAINS DIVIDED INTO TWO AREAS WHERE THE NORTHERN PORTION OF KENTUCKY HAS A BIT MORE SHEAR AND THE SOUTH HAVING A BIT MORE CAPE. OVERALL...THIS ACTIVITY BEARS SOME RESEMBLANCE TO YESTERDAYS CONVECTION BUT WITH QUITE A BIT LESS SHEAR. HOWEVER SOME CORES HAVE SHOWN SOME GOOD DEVELOPMENT ACROSS THE AREA WITH THE FORECAST VALUES FOR CAPE SHOWING NEAR THE 2000 J/KG RANGE WITH SOME STRONG TO SEVERE STORMS THIS AFTERNOON. THEREFORE...SPC HAS ISSUED A SEVERE THUNDERSTORM WATCH THROUGH 9PM ACROSS THE AREA. HAVE ISSUED AN UPDATE WITH THIS ADDED INFORMATION AND A NEW ZFP. UPDATE ISSUED AT 1020 AM EDT TUE JUN 30 2015 CONDITIONS ACROSS THE AREA FEATURE FOG OVER THE VALLEYS FINALLY DISSIPATING AND HAVE TAKEN IT OUT OF THE FORECAST FOR THIS MORNING. AS WELL...LINGERING SHOWERS AND A FEW STORMS HAVE ALSO DISSIPATED AND THIS WILL REMAIN THE CASE BASED UPON A WEAK INVERSION STILL IN PLACE. WILL RAMP UP POPS AFTER NOON AND BRING THUNDER INTO THE FORECAST DURING THIS TIME. AS STATED BY THE NIGHT SHIFT...THIS ACTIVITY TODAY STILL LOOKS RATHER MINIMAL...POSSIBLY LESS THAN YESTERDAY. THE HI RES MODELS SUGGEST THIS BUT BASED UPON THE FACT THE ACTIVITY YESTERDAY TOOK SOME TIME TO STRENGTHEN...THE SLIGHT RISK TODAY SEEMS RELEVANT FOR THIS AFTERNOON. A NEW ZFP HAS BEEN SENT WITH THE GRIDS SENT TO THE WEB. UPDATE ISSUED AT 718 AM EDT TUE JUN 30 2015 LIGHT RAIN HAS FINALLY EXITED THE SOUTHEASTERN PORTIONS OF OUR AREA. HAVE SEEN SOME LOW STRATUS AND PATCHY DENSE FOG FORM... MAINLY WHERE SKIES HAVE CLEARED ACROSS OUR WESTERN AND NORTHERN MOST COUNTIES. REMOVED HIGHER POPS IN OUR SOUTHEAST FOR THE EARLY MORNING TIME FRAME. ALSO BEEFED UP THE FOG IN THE ZONES AND BROUGHT GRIDS IN LINE WITH HOURLY OBS.
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&& .SHORT TERM...(TODAY THROUGH WEDNESDAY) ISSUED AT 440 AM EDT TUE JUN 30 2015 AMPLIFIED PATTERN REMAINS IN PLACE WITH RIDGING ACROSS THE WESTERN CONUS AND TROUGHING ACROSS THE EASTERN CONUS. SHORT WAVES CONTINUE TO ROTATE THROUGH THE BASE OF THE EASTERN TROUGH...BEING THE MAIN DRIVER OF OUR WEATHER THROUGH THE SHORT TERM. MODELS CONTINUE TO SHOW GOOD AGREEMENT WITH OVERALL PATTERN...WITH ONLY DIFFERENCES SHOWING UP WITH RESPECT TO TIMING AND STRENGTH OF PASSING SHORT WAVES. AREA OF CONVECTION HAS STALLED OUT ACROSS CENTRAL AND EASTERN TN. THERE HAS ALSO BEEN SOME PERSISTENT LIGHT RAIN NORTH OF THE TN STATE LINE JUST INSIDE OUR CWA AS WELL. RECENT RUN OF THE HRRR HAS THIS AREA OF CONVECTION LIFTING BACK UP TO THE NE THIS MORNING...CATCHING A PORTION OF OUR CWA. RADAR TRENDS APPEAR TO BE TRENDING IN THAT DIRECTION THOUGH NOT AS STRONGLY AS THE HRRR WOULD SUGGEST. ADDED SOME HIGHER POPS AND REINTRODUCED SOME ISOLD THUNDER FOR THE FAR SOUTHEAST TO ACCOUNT FOR THIS POSSIBILITY. ANOTHER IN THE CURRENT SERIES OF DISTURBANCES WILL DROP INTO THE REGION LATER TODAY...PRODUCING ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS. BASED ON CURRENT FORECAST SOUNDINGS...MARGINAL TO AT BEST MODEST SHEAR AND SFC BASED INSTABILITY SUGGESTS THE POTENTIAL FOR A FEW SEVERE STORMS THIS AFTERNOON AND EARLY THIS EVENING...SIMILAR TO MONDAY. IN ADDITION...SPC CONTINUES TO CARRY OUR AREA IN A SLIGHT RISK FOR SEVERE THUNDERSTORMS TODAY. AS SUCH WILL MENTION THE POTENTIAL THREAT IN OUR HWO. .LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY) ISSUED AT 344 AM EDT TUE JUN 30 2015 LONG RANGE MODELS ARE STILL IN VERY GOOD AGREEMENT STARTING OUT THURSDAY WITH A DEEP LONGWAVE TROUGHING PATTERN SETTING UP ACROSS MUCH OF THE EASTERN CONUS AND REMAINING IN PLACE THROUGH MUCH OF THE WEEKEND...WHILE SLOWLY DAMPENING. THIS PULL OF NORTHERLY AIR WILL KEEP TEMPERATURES BELOW NORMAL THROUGH THE WEEKEND AS WELL. MULTIPLE SHORTWAVES WILL TRAVERSE THE LONGWAVE TROUGH...WHICH WILL LIKELY AFFECT MUCH OF THE OHIO RIVER VALLEY...BRINGING ENHANCED AREAS OF LIFT FOR SHOWERS AND THUNDERSTORMS...AND EVEN SOME MCS POTENTIAL. A STRONG UPPER LEVEL LOW WILL GAIN STRENGTH AS IT MOVES SOUTH INTO SOUTHERN CANADA SUNDAY INTO MONDAY. THIS WILL DAMPEN THE TROUGH ACROSS THE EASTERN CONUS...BUT WILL KEEP A WEAK NW FLOW REGIME ACROSS THE OHIO RIVER VALLEY. THE UPPER LEVEL LOW WILL THEN SHIFT EASTWARD MONDAY NIGHT INTO TUESDAY...DIRECTLY IMPACTING THE UPPER GREAT LAKES. EXPECT ENERGY FROM THIS SYSTEM TO IMPACT AS FAR SOUTH AS KENTUCKY TO END OUT THE FORECAST PERIOD. CONFIDENCE REMAINS LOW...HOWEVER...FOR THIS LATE WEEKEND/EARLY WORK WEEK SYSTEM...AS THE GFS AND ECMWF ARE STILL SHOWING SOME DISAGREEMENT ON TIMING AND PLACEMENT. AS FOR SENSIBLE CONDITIONS...THE NW FLOW AND SHORTWAVES WILL PRODUCE A SERIES OF FRONTAL BOUNDARIES AND SPARKS FOR SHOWERS AND THUNDERSTORMS. THE FIRST OF THESE BOUNDARIES WILL HAVE MOVED INTO THE OHIO VALLEY REGION TO START OFF THE EXTENDED PERIOD...AND WILL OSCILLATE NORTH AND SOUTH BUT REMAIN OVERALL RATHER STATIONARY THROUGH THE FIRST PART OF THE WEEKEND. MEANWHILE...NUMEROUS LOCALIZED SURFACE LOW PRESSURE SYSTEMS WILL BE DRIVEN BY UPPER LEVEL SHORTWAVES AND GENERALLY PUSH ACROSS SOUTHERN KY AND TN. THIS IS WHERE THE BULK OF THE MOISTURE AND MCS POTENTIAL WILL LIE. BY FRIDAY...THE SHORTWAVE MOVING THROUGH WILL PASS ACROSS THE NORTHERN PORTION OF THE STATE...AND THE LOCAL SURFACE BOUNDARY WILL ALIGN ITSELF ALONG THE OHIO RIVER. THIS TIME AROUND...EXPECT BEST MOISTURE /RAIN AND THUNDER POTENTIAL/ TO MOVE ACROSS THE ENTIRE STATE...CONTINUING THROUGH MUCH OF THE WEEKEND BUT PEAKING DURING THE AFTERNOON AND EARLY EVENING HOURS. IF THE ECMWF MODEL HOLDS TRUE...THE STRENGTHENING UPPER LEVEL LOW MOVING SE ACROSS CANADA WILL BRING A MUCH STRONGER COLD FRONT ACROSS THE NORTHERN MISSISSIPPI RIVER VALLEY MONDAY AND INTO THE OHIO RIVER VALLEY AND POINTS NORTHWARD MONDAY NIGHT INTO TUESDAY. CONFIDENCE ON TIMING AND THE EXACT FRONTAL LOCATION IS STILL QUITE LOW HOWEVER...GIVEN THE DISCREPANCIES IN THE GFS AND ECMWF THIS FAR OUT IN THE FORECAST /AS MENTIONED ABOVE/. STUCK WITH A BLEND OF THESE MODELS...WHICH LED TO JUST A MENTION OF CHANCE POPS DURING THIS TIME PERIOD. HOWEVER...THIS SYSTEM COULD BRING ANOTHER STRONG DOSE OF STRONG SHOWERS AND THUNDERSTORMS /PWATS 2 INCHES AN ABOVE/...AND POTENTIALLY SOME STRONG WINDS WITH 25 TO 30 KNOTS EXPECTED JUST ABOVE THE SURFACE AND THROUGH THE MID LEVELS ACCORDING TO THE LATEST GFS40. && .AVIATION...
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(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON) ISSUED AT 216 PM EDT TUE JUN 30 2015 CLOUD COVER ACROSS THE AREA HAS BEGUN TO CLEAR OUT AND CIGS LIFTING WITH CU DEVELOPMENT ON THE INCREASE. WITH THIS...SHOWERS AND THUNDERSTORMS WILL BE ON THE INCREASE. OUTSIDE ANY THUNDERSTORMS...VFR CONDITIONS WILL PREVAIL THROUGH THE EVENING. WINDS WILL MAINLY BE OUT OF THE WEST UP TO 10 KNOTS IN SOME PLACES. AFTER THUNDERSTORM ACTIVITY THROUGH THE AFTERNOON...LOCATIONS THAT HAVE RECEIVED RAINFALL WILL LIKELY BEGIN FOG AGAIN TONIGHT...ESPECIALLY WITH THE MORE MOIST AIR MASS IN PLACE. AND SO HAVE PUT SOME IFR AND BELOW LINES IN THE TAFS FOR ALL THE TAF SITES.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...SHALLENBERGER SHORT TERM...RAY LONG TERM...JMW AVIATION...SHALLENBERGER

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