Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 242053 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 453 PM EDT SUN MAY 24 2015 .SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT) ISSUED AT 347 PM EDT SUN MAY 24 2015 UPPER LEVEL RIDGING HAS BEEN SHIFTING EASTWARD ACROSS THE OHIO RIVER VALLEY THROUGHOUT THE DAY AS BROAD TROUGHING AND AN UPPER LEVEL CLOSED LOW CONTINUE TO EXPAND ACROSS THE WESTERN HALF OF THE CONUS. MUCH OF WESTERN KY AND THE MISSISSIPPI RIVER VALLEY IS FINDING ITSELF WEDGED IN BETWEEN THE TWO PATTERNS WITH INCREASING PRESSURE GRADIENTS...RESULTING IN SOME BREEZY CONDITIONS ACROSS MUCH OF THE WESTERN AND CENTRAL PORTION OF THE STATE. HERE IN EASTERN KY...RIDGING IS STILL TRYING TO HOLD ON FOR THE NEXT FEW HOURS...BUT EXPECT HEIGHTS TO BE ON A SLOW DECLINE THROUGHOUT THE NIGHT AND INTO THE DAY TOMORROW AS THE UPPER LEVEL TROUGHING BEGINS TO CROSS OVER THE MISSISSIPPI RIVER VALLEY. A RIVER OF MOISTURE IS CURRENTLY STREAMING FROM THE GULF OF MEXICO UPWARDS THROUGH THE MISSISSIPPI RIVER VALLEY AND THEN WRAPPING ITSELF INTO THE STRONG LOW CURRENTLY COVER THE NORTHERN PLAINS...OR EASTWARD UP AND ALONG THE NORTHWARD EXTENT OF THE UPPER LEVEL RIDGE. THIS IS RESULTING IN A LARGE AMOUNT OF CLOUD COVER ACROSS THESE ABOVE MENTIONED AREAS. WHILE A FEW CLOUDS HAVE FOUND THEIR WAY INTO EASTERN KY...WE ARE GENERALLY MOSTLY SUNNY WITH STRONG BUT DRY SOUTHERLY FLOW AS OF 1930Z. AS THE RIDGE CONTINUES TO BREAK DOWN OVERNIGHT...AND THE UPPER LEVEL TROUGH NEARS CLOSER...EXPECT THESE CLOUDS TO EXPAND ACROSS KY...GENERALLY OF THE HIGH VARIETY...THOUGH SOME MID AND LOWER CLOUDS MAY BEGIN MOVING IN AS EARLY AS TOMORROW MORNING. ALONG WITH THESE CLOUDS...THERE WILL CONTINUE TO BE AN UPTICK IN MOISTURE AND TEMPERATURES FOR THE DAY TOMORROW. A SHORTWAVE MOVING UP AND ALONG THE EXITING RIDGE WILL PROVIDE A STRONG ENOUGH TRIGGER TO ALLOW SCATTERED SHOWERS AND THUNDERSTORMS TO BEGIN DEVELOPING TOMORROW DURING THE DAY...INCREASING IN COVERAGE AND INTENSITY AS WE HEAD INTO THE AFTERNOON HOURS WITH PEAK HEATING AND INSTABILITY. AS THE RIDGE CONTINUES TO BREAK DOWN OVER THE EAST...EXPECT THIS CONVECTION TO SPREAD ACROSS THE ENTIRE CWA DURING THE DAY. LOSS OF DAYTIME HEATING AND FUEL WILL ALLOW DIMINISHED COVERAGE OVERNIGHT MONDAY NIGHT...BUT CONTINUED LOWERING HEIGHTS AND MORE SHORTWAVE INFLUENCE WILL ALLOW FOR SHOWERS AND THUNDERSTORMS TO QUICKLY BEGIN RAMPING UP AGAIN BY TUESDAY MORNING. FOR TEMPERATURES...STRONG SOUTHERLY FLOW ACROSS THE REGION ALLOWED TEMPS TO MAKE IT INTO THE LOW AND MID 80S THIS AFTERNOON. WITH INCREASING MOISTURE...CONTINUED STRONG SOUTHERLY FLOW...AND THE POTENTIAL FOR AN UPTICK IN CLOUD COVER OVERNIGHT...EXPECT OVERNIGHT TEMPERATURES TO BE MUCH WARMER THAN NIGHTS PREVIOUS. GENERALLY UPPER 50S TO MID 60S ARE EXPECTED. WE COULD STILL SEE SOME DECENT RIDGE TO VALLEY TEMPERATURE DIFFERENCES...BUT EXPECT THAT GIVEN THE ABOVE MENTIONED FACTORS...THE BEST POTENTIAL FOR THIS TO OCCUR WILL BE IN THE TERRAIN ACROSS THE FAR EASTERN PORTION OF THE CWA...AWAY FROM THE BEST CLOUD COVER AND WIND INFLUENCES. TEMPERATURES COULD FALL AS LOW AS THE LOW TO MID 50S IN SOME OF THESE VALLEYS OVERNIGHT. BY TOMORROW...TWO THINGS WILL COME INTO PLAY. FIRST...STRONGER SOUTHERLY FLOW ACROSS THE REGION WHICH WOULD PROMOTE A CONTINUED WARM UP ACROSS THE REGION. HOWEVER...THIS MAY BE OFFSET BY ENCROACHING CLOUD COVER AND THE POSSIBILITY FOR RAIN. AS SUCH...EXPECT SIMILAR TEMPS OVERALL TO THAT OF TODAY...GENERALLY IN THE LOW TO MID 80S. TEMPERATURES WILL OBVIOUSLY LIKELY FLUCTUATE AS RAIN SHOWERS/THUNDERSTORMS PASS OVER. FINALLY...BY TOMORROW NIGHT...THE INCREASING CLOUDS AND MOISTURE WILL WORK TO ALLEVIATE THE LARGE RIDGE VALLEY DIFFERENCES...AND WILL KEEP TEMPS GENERALLY MILD ACROSS THE REGION...IN THE LOW TO MID 60S FOR OVERNIGHT LOWS. .LONG TERM...(TUESDAY THROUGH SUNDAY) ISSUED AT 453 PM EDT SUN MAY 24 2015 A WARM AND RELATIVELY HUMID AIR MASS WILL BE IN PLACE AS THE PERIOD STARTS...AS HIGH PRESSURE AT THE SURFACE AND ALOFT OFF THE EAST COAST TRANSPORTS DEEP MOISTURE NORTH AND NORTHEAST OVER THE FORECAST AREA. A LARGE CHUNK OF THE CURRENT SOUTHWEST CONUS LARGE SCALE TROUGH WILL LIFT OUT TO THE NORTHEAST AS A SHORTWAVE TROUGH... CROSSING THE MIDWEST ON TUESDAY. THIS SHOULD LEND UPPER SUPPORT FOR PRECIP LOCALLY. SUFFICIENT SHEAR WILL BE PRESENT FOR ORGANIZED CONVECTION ON TUESDAY. THE DEGREE OF INSTABILITY WHICH WILL DEVELOP REMAINS IN QUESTION. IF THERE IS TOO MUCH ONGOING CLOUD COVER AND PRECIP DURING THE DAY TUESDAY...IT WILL LIMIT OUR DESTABILIZATION AND THE THREAT OF STRONG CONVECTION. BUT...IF ENOUGH HEATING OCCURS...THERE IS A CONCERN FOR SEVERE WEATHER. AFTER THE TUESDAY SYSTEM PASSES...BROAD FLOW OUT OF THE WEST SOUTHWEST WILL PERSIST FROM HERE NORTHWESTWARD. MODELS SHOW ANOTHER SHORTWAVE TROUGH APPROACHING IN THE FLOW ALOFT LATE WEDNESDAY AND WEDNESDAY EVENING...JUSTIFYING ANOTHER PERIOD OF ELEVATED POP. ONCE THIS PASSES...FLOW ALOFT RELAXES AND GEOPOTENTIAL HEIGHTS RISE...SUPPORTING A LOWER POP LATE IN THE WEEK. HOWEVER...THERE WILL BE NO SUBSTANTIAL CHANGE IN SURFACE AIR MASS...AND WITH WARM AND MOIST AIR LINGERING...THE POP WILL NOT GO AWAY ENTIRELY. FINALLY...ANOTHER SYSTEM COULD AFFECT THE REGION OVER THE WEEKEND. THE GFS AND ECMWF DO START TO SHOW MORE PATTERN DIFFERENCES BY THEN...BUT BOTH SHOW SOME SEMBLENCE OF THE SYSTEM AFFECTING US. THE GFS HAS A COLD FRONT DROPPING IN FROM THE NORTH FASTER THAN THE ECMWF...BUT BOTH EVENTUALLY SHOW THE FRONT IN OUR VICINITY BY SUNDAY...WITH OUR AREA POSITIONED ON THE EASTERN SIDE OF AN UPPER LEVEL TROUGH. WITH DISAGREEMENT FOR SATURDAY...HAVE STAYED WITH FAIRLY LOW POPS...BUT WENT UP TO HIGH CHANCE FOR SUNDAY WHEN BOTH MODELS SHOW A MORE FAVORABLE ENVIRONMENT. THROUGHOUT THE LONG TERM PERIOD...DIURNAL HEATING WILL LIKELY PLAY A ROLE IN TIMING OF PRECIP COVERAGE ON THE LARGE SCALE...AND HAVE TIMED PEAK POP LOCALLY DURING THE LATE AFTERNOON AND EVENING HOURS EACH DAY. THIS MAY BE ABLE TO BE FURTHER REFINED AS TIME PASSES AND CONFIDENCE GROWS IN HANDLING OF SMALLER SCALE FEATURES. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON) ISSUED AT 137 PM EDT SUN MAY 24 2015 VFR CONDITIONS WILL CONTINUE AT THE TAF SITES OVER THE NEXT 24 HOURS. SOME PATCHY RIVER VALLEY FOG IS EXPECTED AGAIN TONIGHT...BUT SHOULD NOT IMPACT TAF SITES. OTHERWISE...EXPECT SOME THIN HIGH CLOUDS AND OCCASIONAL PATCHES OF MID LEVEL CLOUDS TO DRIFT ACROSS THE AREA FROM TIME TO TIME TODAY AND TONIGHT. SOUTH WINDS HAVE BEGUN RAMPING UP ACROSS CENTRAL KENTUCKY THIS AFTERNOON...SO INCLUDED MENTION OF HIGHER WINDS AND POTENTIAL GUSTS FOR KSME/KLOZ/AND KSME BEFORE TAPERING THEM OFF AFTER 00Z MONDAY. SOME MID/LOWER CLOUDS WILL BEGIN TO MOVE INTO THE REGION BY LATE TONIGHT AND INTO THE DAY TOMORROW...MAINLY AT THE ABOVE MENTIONED TAF SITES CLOSER TO THE CENTRAL AND NORTHERN PORTION OF THE STATE. THESE CIGS SHOULD GENERALLY REMAIN IN THE LOW END VFR CATEGORY. EXPECT ANY RAIN CONCERNS TO HOLD OFF UNTIL AFTER 18Z...THOUGH DID GO AHEAD AND INCLUDE VCSH FOR THE FAR MOST WESTERN TAF SITE /KSME/ IN CASE THINGS BEGIN MOVING IN AN HOUR OR TWO FASTER THAN PREDICTED. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JMW LONG TERM...HAL AVIATION...JMW

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