Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 121716 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 116 PM EDT SAT JUL 12 2014 .UPDATE... ISSUED AT 116 PM EDT SAT JUL 12 2014 ISOLATED CONVECTION MAINLY TIED TO TERRAIN IS EXPECTED TO REMAIN TO OUR SOUTHEAST THIS AFTERNOON AND WILL NOT ADD ANY ISOLATED SHOWERS OR THUNDERSTORMS AT THIS TIME. HOWEVER WILL NEED TO CONTINUE TO MONITOR THE HIGHER MOUNTAIN TERRAIN NEAR THE VA BORDER FOR ANY DEVELOPMENT. THE AREA OF SHOWERS AND THUNDERSTORMS OVER WESTERN INDIANA IS AHEAD OF NEARLY STATIONARY WARM FRONTAL BOUNDARY THAT REPRESENTS THE LEADING EDGE OF 70 PLUS DEWPOINT TEMPERATURES OVER IL...MO AND WESTERN KY. SATELLITE...RADAR AND LIGHTNING TRENDS ALL SHOW CONTINUING WEAKENING OF CONVECTION OVER INDIANA. THE SHORT RANGE RAP AND HRRR ALSO SHOW CONTINUING DECAY OF THIS CONVECTION...AND ONLY IMPACT ON OUR AREA WILL BE SOME INCREASE IN HIGH LEVEL CLOUDS. QUITE DRY HERE IN EASTERN KY EARLY THIS AFTERNOON WITH DEWPOINTS AS LOW AS THE LOWER 50S. WILL BE UPDATING NDFD FOR LATEST OBSERVATIONAL TRENDS. UPDATE ISSUED AT 935 AM EDT SAT JUL 12 2014 NDFD AND ASSOCIATED PRODUCTS HAVE BEEN UPDATED FOR LATEST OBSERVATIONAL TRENDS. THE MENTION OF EARLY MORNING VALLEY FOG HAS BEEN REMOVED FROM THE ZFP. UPDATE ISSUED AT 748 AM EDT SAT JUL 12 2014 HOURLY GRIDS WERE FRESHENED UP BASED ON RECENT OBSERVATIONS AND SATELLITE IMAGERY. OTHERWISE...THE CURRENT FORECAST IS ON TRACK. SFC AND UPPER LEVEL RIDGING SHOULD BRING TO A WARM AND DRY DAY TO ALL AREAS ONCE VALLEY FOG LIFTS AND DISSIPATE. && .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 405 AM EDT SAT JUL 12 2014 EARLY THIS MORNING...UPPER LEVEL RIDGING WAS CENTERED OVER THE PLAINS STATES WITH RIDGING EAST INTO THE SOUTHEASTERN STATES AND ALSO WEST AND NORTHWEST INTO THE DESERT SOUTHWEST AND NORTH INTO PARTS OF THE INTER MOUNTAIN WEST. AN UPPER LEVEL LOW WAS CENTERED JUST WEST OF THE HUDSON BAY REGION WITH SOME BROAD TROUGHING TO ITS SOUTH ACROSS PARTS OF CENTRAL CANADA SOUTH INTO THE NORTH CENTRAL US AND NORTHERN GREAT LAKES REGIONS. AT THE SFC...HIGH PRESSURE WAS CENTERED ALONG THE MID ATLANTIC SEABOARD WITH THE RIDGE AXIS EXTENDING SOUTH INTO THE SOUTHEASTERN STATES. EXTENDING SOUTH FROM SFC LOW PRESSURE OVER CENTRAL CANADA WAS A COLD FRONT THAT DOWN SOUTH AND SOUTHWEST ACROSS WESTERN LAKE SUPERIOR AND THEN FURTHER WEST AND SOUTHWEST INTO THE NORTHERN PLAINS. MEANWHILE...THE REMNANTS OF A BOUNDARY THAT CROSSED THE AREA EARLIER IN THE WEST EXTENDED FROM SFC LOW PRESSURE NEAR THE LEE OF THE ROCKIES FIRST NORTH AND NORTHEAST INTO THE MID MS VALLEY AND THEN SOUTH AND THEN SOUTHEAST ACROSS PARTS OF THE SOUTHEASTERN STATES. EARLY TODAY...MAINLY RIVER VALLEY FOG SHOULD GRADUALLY LIFT AND BEGIN TO DISSIPATE WITHIN AND HOUR OR TWO AFTER SUNRISE. OVERALL...VIS REDUCTIONS WITH THIS SHOULD BE LESS THAN ON FRIDAY AM. TODAY AND TONIGHT...THE UPPER LEVEL LOW WILL DROP SOUTH AND THEN SOUTHEAST INTO NORTHWESTERN ONTARIO BY DAWN ON SUNDAY. THIS WILL PUSH THE INITIAL SFC COLD FRONT EAST MORE QUICKLY THAN SOUTH A RIDGING WILL REMAIN IN PLACE FROM THE ROCKIES INTO THE SOUTHERN PLAINS AND SOUTHEASTERN CONUS. THE SOUTHWESTERN PART OF THE BOUNDARY SHOULD EVENTUALLY MERGE WITH THE OLD BOUNDARY ACROSS THE CENTRAL PLAINS AS A SFC WAVE WORKS NORTHEAST FROM THE CENTRAL CONUS AND INTO THE GREAT LAKES. THIS WILL ALSO SEND WHAT IS LEFT OF THE OLD BOUNDARY NORTHEAST ACROSS THE AREA AS A WARM FRONT TONIGHT. THIS WILL USHER IN A RETURN OF MUCH DEEPER MOISTURE LATE TONIGHT AND ESPECIALLY INTO SUNDAY. THE UPPER LEVEL LOW SHOULD MOVE FURTHER SOUTH BY THE END OF TH PERIOD AND LEAD TO FURTHER HEIGHT FALLS ACROSS THE GREAT LAKES AND LOCALLY. DURING THIS PERIOD THE INITIAL COLD FRONT SHOULD REACH NEAR THE OH RIVER BY THE END OF THE PERIOD. HOWEVER...A MORE POTENT FRONT WILL ALSO DROP SOUTH INTO THE GREAT LAKES AND MIDWEST ALSO BY THE END OF THE PERIOD. THE MOST ACTIVE WEATHER WITH THE LOWERING HEIGHTS AND SHORTWAVES WORKING THROUGH THE FLOW SHOULD BE AFTER THE PERIOD. HOWEVER... WITH INCREASING MOISTURE AND SOME SFC HEATING THE ATMOSPHERE WILL BEGIN TO BECOME UNSTABLE ON SUNDAY AHEAD OF THE SLOW MOVING BOUNDARY. THERE WILL ALSO BE SOME SLIGHT HEIGHT FALLS DURING SUNDAY AFTERNOON AS WELL. SOME ISOLATED TO POSSIBLY SCATTERED CONVECTION IS ANTICIPATED AT THAT POINT. SHEAR SHOULD BE GREATEST ACROSS THE FAR NORTHWEST...BUT MODELS DIFFER IN THE DEGREE OF INSTABILITY. SPC HAS PLACE THE FAR NORTHWEST CWA IN A SLIGHT RISK OF SEVERE THUNDERSTORMS AND PENDING ON CONVECTIVE EVOLUTION THE SOUTHWEST END OF A PREFRONTAL LINE OF STORMS MIGHT REACH THE FAR NORTHWEST CWA LATE IN THE PERIOD. THE DEGREE OF INSTABILITY IN PLACE ACROSS THE NORTHWEST PART OF THE AREA...WHEN A LINE POSSIBLY ARRIVES LATE ON SUNDAY WOULD DETERMINE WHETHER ANY STRONG TO SEVERE STORMS WITH GUSTY WINDS BEING THE MAIN THREAT WOULD OCCUR. IT WOULD SEEM HOWEVER IF ENOUGH INSTABILITY CAN BE REALIZED THAT MONDAY WOULD BE THE DAY DURING THE ENTIRE FORECAST PERIOD WHERE STRONG TO SEVERE THUNDERSTORMS WOULD BE MOST PROBABLE...AHEAD OF A SHARPER FRONT AND STRONGER MID LEVEL SYSTEM. .LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) ISSUED AT 326 AM EDT SAT JUL 12 2014 THE MODELS WERE IN GENERAL AGREEMENT IN THE EXTENDED PERIOD. THE WEATHER OF THE UPCOMING WEEK WILL FEATURE WIDESPREAD SHOWERS AND STRONG TO POSSIBLY SEVERE THUNDERSTORMS SUNDAY NIGHT THROUGH MONDAY EVENING. THE MODEL DATA ALL SUGGEST DECENT INSTABILITY...GOOD LOW LEVEL MOISTURE FEED FROM THE SOUTH...AND SOME WIND SHEAR DURING THE DAY ON MONDAY. THE TRIGGER FOR ALL THE EXPECTED SHOWER AND STORM ACTIVITY WILL BE A SLOW MOVING AND FAIRLY POTENT COLD FRONT. SHOWERS AND STORMS WILL BE MOST NUMEROUS AND STRONGEST DURING FRONTAL PASSAGE MONDAY AFTERNOON AND EVENING...SHOULD THE LATEST MODEL SOLUTIONS PAN OUT THAT IS. THE FRONT IS EXPECTED TO STALL OUT ALONG THE SPINE OF THE APPALACHIANS MONDAY NIGHT...KEEPING A CHANCE OF RAIN IN THE FORECAST THROUGH THE END OF THE DAY ON TUESDAY. MUCH COOLER AND DRIER AIR WILL FILTER INTO THE REGION BEHIND THE FRONT BEGINNING TUESDAY NIGHT. THIS NEW AIR MASS WILL CONTRIBUTE TO WELL BELOW NORMAL TEMPERATURES FOR THIS TIME OF YEAR...WITH HIGHS TOPPING OUT IN THE VERY COMFORTABLE MID TO UPPER 70S TUESDAY WEDNESDAY AND THURSDAY. OVERNIGHT LOWS TUESDAY NIGHT AND WEDNESDAY NIGHT SHOULD EASILY DROP INTO THE MID TO UPPER 50S ACROSS THE AREA BENEATH PARTLY CLOUD SKIES. THE MERCURY SHOULD BE ABLE TO CLIMB A BIT HIGHER TO END THE WEEK AS THE AIRMASS MODIFIES...WITH HIGHS REACHING THE LOWER 80S ON FRIDAY. AFTER A DRY PERIOD DURING THE MIDDLE OF THE WEEK...ANOTHER SHOT OF RAIN MIGHT BE IN THE OFFING TOWARD THE END OF THE WEEK...AS A WEATHER SYSTEM PASSES BY TO OUR SOUTH THURSDAY NIGHT THROUGH FRIDAY NIGHT. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 116 PM EDT SAT JUL 12 2014 SCATTERED CUMULUS AROUND 5K TO 6K FEET WITH LIGHT WINDS CAN BE EXPECTED THIS AFTERNOON AS HIGH PRESSURE CONTINUES TO CONTROL THE LOCAL WEATHER. ISOLATED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO REMAIN JUST OUTSIDE OF THE FORECAST AREA THIS AFTERNOON IN THE HIGHER TERRAIN OF SW VA...TN AND NC. THERE WAS LESS FOG THIS MORNING THAN YESTERDAY MORNING AND EXPECT THAT TREND TO CONTINUE. AS SUCH WILL LEAVE FOG OUT OF TAFS FOR THIS FORECAST. VFR CONDITIONS WILL PREVAIL AGAIN ON SUNDAY...BUT SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE BY SUNDAY NIGHT AHEAD OF A COLD FRONT DROPPING SOUTH ACROSS OH AND INDIANA. .JKL WATCHES/WARNINGS/ADVISORIES... && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...SBH SHORT TERM...JP LONG TERM...AR AVIATION...SBH

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