Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 031110 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 710 AM EDT MON AUG 3 2015 .UPDATE... ISSUED AT 645 AM EDT MON AUG 3 2015 THE CLUSTER OF STORMS JUST NORTHWEST OF THE CWA IS HOLDING TOGETHER A BIT BETTER THAN MODELED. IT LOOKS LIKE IT WILL BRUSH INTO AT LEAST FLEMING COUNTY. HAVE UPDATED THE GRIDS TO REFLECT THIS AND ALSO TO MATCH UP THE LATEST OBS AND TRENDS FOR T/TD GRIDS. HAVE UPLOADED THESE TO THE NDFD AND WEB SERVERS...ALONG WITH AN UPDATED ZFP ISSUANCE. && .SHORT TERM...(TODAY THROUGH TUESDAY) ISSUED AT 345 AM EDT MON AUG 3 2015 07Z SFC ANALYSIS SHOWS HIGH PRESSURE STILL HOLDING ON OVER SOUTHERN KENTUCKY AHEAD OF A COLD FRONT OFF TO THE NORTHWEST. SKIES ARE CLEAR THROUGH THE CWA AND THIS HAS RESULTED IN A GOOD NIGHT OF RADIATIONAL COOLING. ACCORDINGLY...SHELTERED VALLEYS ARE RUNNING NEARLY 10 DEGREES COOLER THAN THE RIDGES WITH LOWER 60S FOUND IN THE HOLLOWS COMPARED TO THE LOW 70S ON THE HILL TOPS. DEWPOINTS...MEANWHILE...ARE GENERALLY IN THE LOW TO MID 6OS ACROSS EASTERN KENTUCKY WITH LIGHT TO CALM WINDS. NO SIGN OF ANY FOG YET...BUT DO ANTICIPATE SHALLOW AND LOCALLY DENSE FOG IN THE RIVER VALLEYS TOWARD DAWN AGAIN THIS MORNING. THE MODELS ARE IN FAIRLY GOOD AGREEMENT ALOFT AS THEY SHOW THE SOUTHWARD SHIFT IN THE BROAD AND UNSEASONABLY DEEP LOW CURRENTLY OVER EAST CENTRAL CANADA. THIS MOVEMENT WILL SERVE TO TIGHTEN UP THE MID LEVEL GRADIENT THROUGH THE OHIO VALLEY LATER TODAY AND THROUGH THE REST OF THE SHORT TERM. EAST KENTUCKY WILL BE IN NORTHWEST FLOW WITH RIPPLES OF MINOR WAVES PASSING THROUGH INTO MID WEEK. OF NOTE...A MORE PROGRESSIVE WAVE WILL MOVE EAST FROM THE PLAINS AND TO THE MID MISSISSIPPI VALLEY BY LATE TUESDAY WITH SOME LOCALIZED HEIGHT RISES FOR EASTERN KENTUCKY. THE MODEL SPREAD IS A BIT LARGER WITH THIS KEY FEATURE AS THE NAM LAGS BEHIND THE ECMWF AND GFS IN BRINGING THE ENERGY WITH THIS WAVE INTO KENTUCKY LATER TUESDAY NIGHT. HAVE FAVORED THE HRRR AND NAM12 EARLY ON IN THE FORECAST GIVEN THEIR HIGHER RESOLUTION...BEFORE GOING WITH MORE OF A BLEND LATER AS UNCERTAINTY WITH THE DETAILS INCREASE. SENSIBLE WEATHER WILL FEATURE ONGOING STORMS TO THE NORTH...OUT AHEAD OF THE APPROACHING COLD FRONT...LIKELY FADING AS THEY CLOSE IN ON THE OHIO RIVER. THIS WILL PROBABLY SEND A BOUNDARY OR TWO INTO NORTHEASTERN KENTUCKY LATER THIS MORNING AND IT COULD BECOME A FOCUS FOR CONVECTIVE DEVELOPMENT FOR OUR AREA THROUGH THE AFTERNOON. THIS WILL TAKE PLACE IN AN ENVIRONMENT INCREASINGLY SUPPORTIVE OF STRONG CONVECTION GIVEN AFTERNOON CAPES FORECAST TO BE NEAR 3K J/KG...SOME MID LEVEL DRYING...AND STEEP LAPSE RATES. THE WINDS ALOFT WILL BE MORE FAVORABLE FOR ORGANIZED DEVELOPMENT...TOO...BUT THE SHEAR IS NOT THAT IMPRESSIVE. COMBINED WITH THE APPROACH OF THE MAIN FRONT...THOUGH THIS SHOULD BE ENOUGH FOR AT LEAST SCATTERED STRONG THUNDERSTORMS TO DEVELOP WITH STRONG TO SEVERE ONES POSSIBLE OVER THE NORTHERN PORTION OF THE CWA LATE IN THE DAY. WITH A RELATIVELY LOW WET BULB ZERO LEVEL AND DCAPES APPROACHING 1500 J/KG LARGE HAIL AND DAMAGING WIND GUSTS WILL BE THE MAIN THREAT. SPC HAS PLACED A LARGE CHUNK OF THE NORTHERN PARTS OF OUR AREA IN A SLIGHT RISK FOR THIS CONCERN. WILL HIGHLIGHT THIS IN THE WX STORY...VIA A WEB HEADLINE...AND IN THE HWO. THE THREAT OF SHOWERS AND STORMS WILL THEN CONTINUE THROUGH THE NIGHT AS THE FRONT SETTLES SOUTH ACROSS EAST KENTUCKY. THE CLOUDS AND BOUNDARY SHOULD BE ENOUGH TO KEEP TEMPERATURES WARMER AND MORE UNIFORM MONDAY NIGHT. STORM CHANCES WILL CONTINUE ON TUESDAY WITH THE FRONT OVER THE AREA AND THE APPROACH OF THE MID LEVEL WAVE FROM THE WEST. AGAIN STARTED WITH THE SHORTBLEND MODEL FOR THE T/TD/WIND GRIDS THROUGH THE DAY FOLLOWED BY THE SUPERBLEND FOR TONIGHT AND TUESDAY. DID MAKE SOME ADJUSTMENTS TO TEMPERATURES THIS MORNING AND...TO A LESSER EXTENT...TONIGHT WITH RESPECT TO RIDGE AND VALLEY DIFFERENCES. AS FOR POPS...WENT A BIT HIGHER THAN GUIDANCE THROUGH THE PERIOD GIVEN THE FRONT HANGING OVER THE AREA...DESPITE IT BEING RATHER MOISTURE STARVED. .LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY) ISSUED AT 358 AM EDT MON AUG 3 2015 THE UPPER LEVEL PATTERN CONTINUES TO FEATURE A WESTERN CONUS RIDGE AND A TROUGH OVER THE EAST WITH AN ACTIVE JET STREAM. THIS BRINGS ACTIVE WEATHER TO THE REGION WITH A SERIES OFF SHORTWAVES RIDING OVER THE WESTERN RIDGE AND INTO THE OH VALLEY. DESPITE SUBTLE SHIFTS IN THE WESTERN RIDGE WITH AN ACTIVE JET STREAM INTO THE WEST COAST...THE GFS AND EURO SEEM TO AGREE ON THE LONGWAVE PATTERN. THOUGH BESIDES THE WEDNESDAY AND THURSDAY FEATURES...TIMING WILL STILL POSE QUITE A PROBLEM. DETAILS CLOSER TO THE SURFACE WILL FEATURE A LINGERING SURFACE BOUNDARY BEING QUASI/STATIONARY DRAPED ACROSS KY AND THE LOWER OH VALLEY AS SEVERAL SHORTWAVES TRACK EAST SOUTHEAST FROM THE FRONT RANGE OF THE ROCKIES THROUGH THE PLAINS AND INTO THE OH VALLEY. HEADING FURTHER INTO THE PERIOD...A GOOD DEAL OF UPPER LEVEL SUPPORT IN THE FORM OF A STRONG JET STREAK ENTERS THE WEST COAST OVER CENTRAL CA AND THROUGH THE ROCKIES WEAKENING THE RIDGE A BIT. THIS PUSHES A EVEN BETTER WELL DEFINED WAVE THROUGH THE PLAINS AND INTO THE OH VALLEY BY WEDNESDAY NIGHT. MODELS HAVE BEEN HINTING AT THIS FEATURE FOR QUITE A FEW RUNS THAT SEEM TO BRING A WELL DEFINED SYSTEM THROUGH KY WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. THE SUPER BLEND AGREES WITH THIS REASONING AS WELL...ADVERTISING WELL ABOVE LIKELY POPS THROUGH THE WEDNESDAY AND THURSDAY NIGHT PERIOD. THIS PERIOD WILL PROVE TO BE THE MOST INTERESTING AND ACTIVE PORTION OF THE EXTENDED. AS MENTIONED EARLIER...THE GFS AND EURO DIVERGE IN SOLUTIONS HEADING INTO THE WEEKEND WITH THE UPPER LEVEL PATTERN FLATTENING IN THE GFS BUT REMAINING A BIT MORE AMPLIFIED IN THE EURO. THUS...A STALLED BOUNDARY OVER THE TN VALLEY AND ALONG THE APPALACHIANS AND A CONTINUED ACTIVE BUT SUBTLE UPPER LEVEL PATTERN WILL KEEP SHOWER AND THUNDERSTORM CHANCES THROUGH THE LAST FEW DAYS OF THE EXTENDED BUT LACKING CONFIDENCE...WOULD BE MORE INCLINED TO STAY WITH AND JUST BELOW THE SOLUTION OF THE SUPER BLEND. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING) ISSUED AT 710 AM EDT MON AUG 3 2015 FOG AND LOW CIGS WILL STILL BE POSSIBLE BROUGHT SOME IFR OR LOWER VIS/CIG INTO THE SME AND SJS SITES WITH MVFR VIS POSSIBLE AT SME BEFORE LIFTING AND CLEARING BY 1230Z WITH VFR CONDITIONS THROUGH THE REST OF THE TAF PERIOD FOR MOST SITES. HOWEVER...OUTFLOW BOUNDARIES FROM EARLIER STORMS OFF TO OUR NORTH AND WEST WILL SPREAD SOUTH INTO NORTHEAST KENTUCKY THIS MORNING. THIS WILL COMBINE WITH THE APPROACH OF A COLD FRONT TO MAKE STRONG THUNDERSTORMS A POSSIBILITY IN THE LATE AFTERNOON AND EVENING... MAINLY NORTH OF INTERSTATE 64. FOR THIS...WILL CONTINUE MENTION OF VCTS IN THE SYM TAF AFTER 21Z. AS FOR WINDS...EXPECT THEM TO REMAIN LIGHT AND VARIABLE THROUGH MOST OF THE TAF PERIOD AT ALL THE SITES...THOUGH LATER THIS AFTERNOON WE COULD SEE SOME GUSTS OF 10 TO 15 KTS OUT OF THE WSW AHEAD OF THE FRONT IN THE AS IT DROPS TOWARD THE FAR NORTH. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...GREIF LONG TERM...SHALLENBERGER AVIATION...GREIF

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