Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 261842 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 242 PM EDT SAT JUL 26 2014 .SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT) ISSUED AT 242 PM EDT SAT JUL 26 2014 DYNAMIC SITUATION UNFOLDING OVER THE NEXT 24 TO 36 HOURS AS A DEEP TROUGH ALOFT DIVES INTO THE OHIO VALLEY. A STRONG COLD FRONT WILL DROP SOUTHEAST INTO THE REGION SUPPLANTING WHAT WILL BECOME A VERY WARM AND VERY MOIST AIRMASS IN PLACE ACROSS OUR REGION. THIS COMBINATION OF A SPRING-TIME SETUP ALOFT COMBINED WITH SUMMER-TIME HEAT AND HUMIDITY WILL CREATE CONDITIONS FAVORABLE FOR A SIGNIFICANT SEVERE WEATHER OUTBREAK ON SUNDAY. MODELS CONTINUE TO INDICATE A THUNDERSTORM COMPLEX WILL ORGANIZE TO OUR WEST THIS AFTERNOON AND EVENING. THIS APPEARS TO BE HAPPENING OVER MISSOURI AT THIS TIME. THESE STORMS SHOULD MARCH EASTWARD INTO THE OVERNIGHT HOURS LIKELY ENDING UP SOMEWHERE OVER SOUTHERN INDIANA AND NORTHERN KENTUCKY BY OR SHORTLY AFTER MIDNIGHT. THIS COMPLEX SHOULD BE WEAKENING AS IT ENTERS OUR FORECAST AREA AFTER MIDNIGHT...BUT CANNOT RULE OUT THE THREAT FOR DAMAGING WINDS AS IT CROSSES THE REGION. THIS THREAT WOULD BE GREATEST FROM JKL AND POINTS TO THE NORTH. THE GREATER SEVERE WEATHER THREAT CONTINUES TO BE THE ANTICIPATED SECOND ROUND OF THUNDERSTORMS EXPECTED TO ERUPT OVER US OR JUST TO OUR NORTH SUNDAY AFTERNOON. PROVIDED EARLY MORNING CONVECTION GETS OUT OF THE WAY IN TIME AND ATMOSPHERE DESTABILIZES AS PROJECTED... THESE STORMS COULD BE QUITE STRONG. SOUNDINGS TOMORROW AFTERNOON ARE IMPRESSIVE. STORM RELATIVE HELICITY VALUES EXCEED 300 M2/S2 COMBINED WITH CAPE PROGGED TO EXCEED 3000 J/KG AND LCLS AROUND 3000 FT MSL. IF THESE CONDITIONS VERIFY...A RARE JULY TORNADO OUTBREAK COULD OCCUR. STILL...LOTS OF UNCERTAINTY WITH HOW TONIGHTS ACTIVITY WILL PAN OUT AND HOW THIS WILL AFFECT OUR CONDITIONS ON SUNDAY BUT WILL CONTINUE TO PLAY UP THE SEVERE WEATHER POTENTIAL IN OUR SUITE OF PRODUCTS. IN ADDITION TO THE SEVERE WEATHER CONCERNS...ISOLATED FLASH FLOODING IS A CONCERN PRIMARILY ON SUNDAY. MOISTURE POOLING IN ADVANCE OF THE FRONT WILL PUSH SURFACE DEWPOINTS INTO THE LOW TO MID 70S AND PWATS WILL JUMP TO 1.75 INCHES AND ABOVE. STORM MOTIONS LOOK FAST ENOUGH TO PRECLUDE A WIDESPREAD FLASH FLOODING THREAT...BUT AGAIN THAT WILL DEPEND LARGELY ON HOW PRIMED WE GET BY TONIGHTS CONVECTION. NO FLASH FLOOD WATCH WILL BE ISSUED AT THIS TIME...BUT THAT MAY NEED TO BE REVISITED SHOULD THE INITIAL ROUND OF CONVECTION SATURATE THE GROUND TONIGHT. .LONG TERM...(MONDAY THROUGH SATURDAY) ISSUED AT 242 PM EDT SAT JUL 26 2014 AN ANOMALOUS LARGE AND DEEP UPPER TROUGH WILL PERSIST OVER THE EASTERN CONUS THROUGH THE PERIOD. THE SURFACE COLD FRONT MARKING THE LEADING EDGE OF THE UNSEASONABLY COOL AIR MASS UNDER THE TROUGH WILL BE WELL TO OUR SOUTHEAST ALREADY AS THE PERIOD STARTS...BUT RESIDUAL LOW LEVEL MOISTURE WILL STILL BE MIXING VERTICALLY INTO THE NEW AIR MASS AS COOLING ALOFT OCCURS. THIS MAY RESULT IN A FEW SHOWERS OR THUNDERSTORMS MONDAY AFTERNOON OR EVENING...ESPECIALLY IN OUR NE COUNTIES WHERE COOLER MID LEVEL TEMPS ARE EXPECTED. ON TUESDAY...DRIER SURFACE AIR AND A MID LEVEL CAP SHOULD KEEP CONVECTIVE CURRENTS BELOW ABOUT 10K FEET. SOME LIQUID COULD STILL TRY TO FALL OUT OF THE CLOUDS...BUT WITH LIMITED CLOUD DEPTH AND DRIER AIR...WILL ONLY MENTION SPRINKLES IN THE FORECAST. A COOL AND DRY AIR MASS FIRMLY IN PLACE...COUPLED WITH A CESSATION OF COOLING ALOFT...WILL ALLOW FOR MAINLY CLEAR SKIES FROM TUESDAY NIGHT THROUGH THURSDAY NIGHT. NEAR RECORD LOW TEMPS WILL BE A POSSIBILITY. AS THE HIGHLY AMPLIFIED UPPER TROUGH WEAKENS AT THE END OF THE WEEK...MODELS AGREE ON ITS AXIS RETROGRADING TO THE WEST AS A LOW CLOSES OFF. WITH THE LOW/TROUGH AXIS SLIPPING TO OUR WEST...WE WILL RETURN TO ITS EAST SIDE WHICH IS SYNOPTICALLY MORE FAVORABLE FOR PRECIP. FLOW FROM THE GULF OF MEXICO WILL STILL BE CUT OFF AND LOW LEVEL MOISTURE WILL BE SLOW TO INCREASE...SO WILL ONLY USE LOW POPS. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 146 PM EDT SAT JUL 26 2014 VFR CONDITIONS ARE ANTICIPATED THROUGH THE FIRST HALF OF THE TAF PERIOD WITH LIGHT WINDS. AFTER MIDNIGHT TONIGHT...A COMPLEX OF THUNDERSTORMS WILL LIKELY PUSH EASTWARD TOWARD THE AREA FROM THE WEST. DETAILS ARE STILL UNCERTAIN...BUT THE GREATEST THREAT FOR A DIRECT IMPACT FROM THESE STORMS LIES FROM JKL...SJS AND POINTS TO THE NORTH WHERE A PERIOD OF AT LEAST MVFR CONDITIONS ARE LIKELY BETWEEN 07Z AND 11Z. THERE IS A SLIGHT RISK THAT THESE STORMS WILL BE SEVERE CONTAINING DAMAGING WIND GUSTS. TO THE SOUTH...THERE IS A SMALLER THREAT FOR A DIRECT IMPACT AND WILL SIMPLY ADVERTISE A GENERIC VCTS MENTION IN THE TAFS FOR LOZ AND SME. ONCE THE FIRST ROUND OF THUNDERSTORMS PASSES THROUGH...THERE WILL LIKELY BE A LULL IN THE SHOWER AND THUNDERSTORM ACTIVITY BEFORE ANOTHER ROUND MOVES THROUGH SUNDAY AFTERNOON AND EVENING. THIS SECOND ROUND WILL CARRY A GREATER RISK OF SEVERE WEATHER. SOUTHWEST WINDS WILL INCREASE ALOFT THROUGH THE NIGHT...BUT REMAIN BELOW LLWS THRESHOLDS. THESE WINDS WILL SURFACE DURING THE DAY ON SUNDAY WITH GUSTS UP TO 20 KTS LIKELY AFTER 15Z. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...ABE LONG TERM...HAL AVIATION...ABE

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