Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 211450 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 1050 AM EDT THU AUG 21 2014 .UPDATE...
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ISSUED AT 1050 AM EDT THU AUG 21 2014 14Z SFC ANALYSIS SHOW GENERAL LOW PRESSURE NORTH OF THE OHIO RIVER WITH HIGHER PRESSURE FOUND TO THE SOUTH. A STATIONARY BOUNDARY EXISTS THROUGH THE NORTHERN PORTIONS OF THE OHIO VALLEY AND WESTERN PARTS OF THIS FRONT...CONNECTED BACK TO DEEPER LOW PRESSURE OVER THE NORTHERN PLAINS...HAS BEEN A GENESIS REGION FOR RECENT MCS ACTIVITY. THIS ACTIVITY IS ALSO SUPPORTED BY A STREAM OF MID LEVEL ENERGY RIDING ALONG THE NORTHERN FRINGE OF A DEVELOPING RIDGE TO THE SOUTHWEST OF KENTUCKY. THIS WOULD TEND TO SUPPORT CONVECTION WORKING SOUTHEAST FROM THE UPPER MIDWEST TO THE CENTRAL APPALACHIANS PASSING BY JUST TO OUR NORTHEAST. HOWEVER...INSTABILITY BUILDING WITH THE RECENT ARRIVAL OF SUMMER TIME HEAT AND HUMIDITY ACROSS KENTUCKY WILL BE ENOUGH TO KEEP A THREAT OF THE STORMS AND THEIR OUTFLOW BOUNDARIES SNEAKING INTO NORTHEAST PORTIONS OF THE CWA AND PERHAPS FURTHER TO THE SOUTHWEST IN THE AFTERNOON. THE CURRENT RADAR HAS A HEALTHY CLUSTER OF STORMS CROSSING FROM INDIANA INTO OHIO WITH A GROWING SOUTHERN EXTENT TRACKING THROUGH NORTHERN KENTUCKY. EXPECT THIS TO BRUSH INTO NORTHERN PARTS OF THE FORECAST AREA THROUGH THE NEXT SEVERAL HOURS. THE HRRR KEEPS THIS FIRST WAVE JUST NORTH OF THE CWA...WHILE THE 12Z NAM12 DIPS THE CONVECTION DEEPER INTO EAST KENTUCKY. FOR THIS UPDATE HAVE SPLIT THE DIFFERENCE BETWEEN THESE TWO SCENARIOS AND PEAKED POPS IN THE NORTHEAST THROUGH THE AFTERNOON WITH SOME SMALL TO MODERATE POPS EVEN DOWN INTO THE CUMBERLAND VALLEY BY EVENING. HIGH PWS AND THE RAINS OF THE PAST SEVERAL DAYS WILL MEAN A THREAT OF FLASH FLOODING FOR PLACES THAT SEE REPEATED STORMS... PARTICULARLY THROUGH THE MID SECTION OF THE CWA. SPC HAS PLACED EASTERN PARTS OF THE AREA...ALONG THE PREVIOUSLY DISCUSSED STORM TRACK...IN A SLIGHT RISK FOR SEVERE WEATHER...MAINLY DAMAGING WINDS AND LARGE HAIL. THIS APPEARS REASONABLE GIVEN THE HIGH CAPE...LOW LIS...AND LACK OF A MID LEVEL CAP. ACCORDINGLY THIS CONCERN WILL CONTINUE TO BE HIGHLIGHTED IN THE HWO ALONG WITH A MENTION OF THE HEAT AND HUMIDITY...TEMPS NEAR 90 AND DEWPOINTS IN THE 70S...THROUGH THE WEEKEND. HAVE ALSO FINE TUNED THE T AND TD GRIDS PER THE LATEST OBS...TRENDS...AND CONSSHORT GUIDANCE. THESE UPDATES HAVE BEEN SENT TO THE NDFD AND WEB SERVERS WITH NEW HWO AND ZONES ON THEIR WAY. UPDATE ISSUED AT 757 AM EDT THU AUG 21 2014 THE FORECAST REMAINS ON TRACK THIS MORNING. FRESHENED UP THE HOURLY TEMPERATURES...DEW POINTS...AND SKY COVER TO ACCOUNT FOR THE LATEST TRENDS IN THE OBSERVATIONS.
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&& .SHORT TERM...
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(TODAY THROUGH FRIDAY) ISSUED AT 357 AM EDT THU AUG 21 2014 THE LATEST SURFACE MAP FEATURES HIGH PRESSURE ACROSS THE GULF COAST STATES...WITH LOW PRESSURE ACROSS THE PLAINS STATES. A STATIONARY BOUNDARY EXTENDS EAST FROM THE PLAINS INTO THE GREAT LAKES/OHIO VALLEY REGION. ALOFT...AN UPPER LEVEL LOW CONTINUES TO SPIN ACROSS THE NORTHERN GREAT LAKES...WITH AN UPPER LEVEL RIDGE CENTERED NEAR THE NORTHERN GULF OF MEXICO...AND MORE TROUGHING FEATURED ACROSS THE NORTHERN ROCKIES. SEVERAL COMPLEXES OF THUNDERSTORMS HAVE BEEN GENERATING AND THEN RIDING SOUTHEAST ON THE PERIPHERY OF THE UPPER LEVEL RIDGE OVER THE PAST FEW DAYS. CURRENTLY...EASTERN KENTUCKY REMAINS QUIET AS ONLY A WEAKENING SMALLER COMPLEX OF THUNDERSTORMS IS SLOWLY MOVING THROUGH SOUTHEAST ILLINOIS AND SOUTHWEST INDIANA. THE NEXT MORE ORGANIZED COMPLEX IS CURRENTLY MOVING THROUGH MINNESOTA. THE MODEL GUIDANCE HAS BEEN ALL OVER THE PLACE WITH THE TIMING OF THE MORE ORGANIZED CONVECTION AS OF LATE. AS SUCH...HAVE USED A GENERAL BLEND OF THE GUIDANCE AND THE INHERITED FORECAST. AS THE UPPER LEVEL RIDGE SLOWLY BUILDS INTO THE REGION THROUGH FRIDAY...IT WILL GENERALLY NUDGE THE MCS TRACK FURTHER NORTHEAST...HOWEVER SINCE THERE WILL BE PLENTY OF FUEL FOR THE STORMS AND A WEAK SYNOPTIC PATTERN IN PLACE...CAN NOT RULE OUT OUTFLOW INFLUENCE FURTHER SOUTHWEST. SOME STORMS COULD APPROACH SEVERE LIMITS...AND ISOLATED FLASH FLOODING WILL ALSO BE A POSSIBILITY...ESPECIALLY WHERE STORMS CAN MOVE PARALLEL TO ANY ESTABLISHED OUTFLOW BOUNDARIES. WILL HIGHLIGHT THESE THREATS IN THE HWO. POPS WILL GENERALLY PEAK IN THE AFTERNOON HOURS TODAY AND FRIDAY...WITH LESSER CHANCES DURING THE OVERNIGHT HOURS. HIGHS TODAY WILL AVERAGE IN THE 85 TO 90 DEGREE RANGE...WITH AROUND 90 DEGREES EXPECTED FOR MOST LOCATIONS ON FRIDAY. .LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY) ISSUED AT 357 AM EDT THU AUG 21 2014 THE EXTENDED PORTION OF THE FORECAST BEGINS ON FRIDAY NIGHT WITH A WELL DEVELOPED MID LEVEL RIDGE CENTERED OVER THE MID WEST AND LONGWAVE TROUGH ENTERING THE NORTHWEST WITH AN EXITING TROUGH OVER THE NORTHEAST. THE MID LEVEL RIDGE AXIS EVENTUALLY SHIFTS EAST OVER THE OH VALLEY BY MONDAY AS IT WEAKENS A BIT WITH THE APPROACHING TROUGH OVER THE NORTHERN PLAINS AND THE TROUGH OVER THE NORTHEAST EXITING INTO THE ATLANTIC. THIS PATTERN BASICALLY KEEPS THE RIDGE OVER EASTERN KENTUCKY THROUGH THE REST OF THE EXTENDED. WITH THIS PATTERN IN PLACE THROUGH SUNDAY...EASTERN KENTUCKY REMAINS IN NORTHWEST FLOW WITH STILL A FEW MCS/S LIKELY POISED TO TRACK SOUTHEAST INTO THE AREA FOR THIS WEEKEND. WHILE MODELS INHERENTLY WILL HAVE TROUBLE TRACKING THEM...THE FIRST ONE SHOULD BE MOVING THROUGH FRIDAY NIGHT WITH THE NEXT ONE POSSIBLY SATURDAY NIGHT. BY SUNDAY...THE RIDGE AXIS REALLY BEGINS TO SET IN AND ADDITIONAL STRONG CONVECTION MAY BE LESS LIKELY AND MAY BE MORE TIED TO DIURNAL PROCESSES WITH A STATIONARY BOUNDARY ALONG THE EASTERN PORTION OF THE CWA. BY MONDAY AND THROUGH WEDNESDAY...THE MID LEVEL RIDGE AXIS MOVES OVER THE AREA WHICH SHOULD EFFECTIVELY CUT OFF CONVECTION...AT LEAST DEEP CONVECTION. SOME AFTERNOON SHOWERS AND POSSIBLY A STORM OR TWO MAY DEVELOP UNDER THE RIDGE. THE SOLUTION OF THE ALL MODEL BLEND WOULD SUGGEST SOME UNCERTAINTY THERE WITH THE BEST CHANCE OF PRECIP FRIDAY NIGHT THROUGH SUNDAY. THIS IS IN GOOD AGREEMENT WITH THE GFS AND EURO AS WELL. OVERALL THE BROAD BRUSH OF POPS THROUGH THE FIRST 3 DAYS OF THE EXTENDED SEEMS NEEDED DUE TO THE NATURE OF THE MODELS HAVING TROUBLE DEPICTING THE COMPLEXES MOVING THROUGH BUT DID GO WITH SOME DIURNAL CHARACTERISTICS. BY THE END OF THE EXTENDED...THE MODELS SEEM TO HINT AT THE RIDGE MOVING FARTHER EAST AS A STRONG SHORTWAVE AND ASSOCIATED COLD FRONT SEEMS POISED TO MOVE THROUGH THE MS RIVER VALLEY AND INTO THE OH VALLEY. IN ADDITION...THE WARM AND MUGGY WEATHER STILL LOOKS TO BE ON TAP THROUGH THE WEEKEND WITH HIGHS AROUND 90 THROUGH MONDAY AND DEW POINTS AROUND 70. THE END OF THE EXTENDED DOES SHOW SOME RELIEF FROM THE WARM AND HUMID WEATHER WITH THE APPROACH OF THE AFOREMENTIONED COLD FRONT.
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&& .AVIATION...
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(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING) ISSUED AT 757 AM EDT THU AUG 21 2014 IFR OR WORSE FOG/STRATUS WILL DISSIPATE BY AROUND 13Z. SCATTERED TO NUMEROUS CONVECTION WILL LIKELY THREATEN ONCE AGAIN FROM 16Z THROUGH EARLY THIS EVENING. TIMING THIS ACTIVITY CONTINUES TO BE VERY CHALLENGING SO WILL KEEP VCTS WORDING ONLY AT THIS TIME. SOME MVFR OR WORSE FOG WILL LIKELY BE SEEN ONCE AGAIN AFTER 04Z TONIGHT. WINDS OF AROUND 5 KTS OR LESS WILL REMAIN OUT OF THE SOUTHWEST THROUGH THE PERIOD AS WELL.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...GEOGERIAN LONG TERM...SHALLENBERGER AVIATION...GEOGERIAN

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