Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 200619 AAC AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 219 AM EDT MON APR 20 2015 .UPDATE... ISSUED AT 140 AM EDT MON APR 20 2015 HOURLY GRIDS HAVE BEEN UPDATED BASED ON RECENT RADAR...OBSERVATION AND SATELLITE TRENDS. SOME SCATTERING OUT OF THE LOW CLOUDS HAS BEEN OBSERVED IN THE SOUTHWESTERN COUNTIES PER AWOS AND ASOS DATA. IN FACT...SOME EASTERN VALLEY LOCATIONS IN THE EAST APPEAR TO BE DECOUPLED WITH LOW DEWPOINT DEPRESSIONS. KI35 HAS BEEN REPORTING 2SM VIS LIKELY FROM SOME LIGHT FOG. DESPITE THE GRADIENT IN PLACE...SEVERAL ADDITIONAL EASTERN VALLEY LOCATIONS ANY ALSO HAVE SOME PATCHY FOG DEVELOPMENT OVER THE NEXT 3 TO 5 HOURS...BEFORE CLOUDS INCREASE IN ADVANCE OF WHAT IS LEFT OF CONVECTION NOW TO OUR WEST AND SOUTHWEST. ATTM...HELD WITH THE PREVIOUS SLIGHT CHANCE POPS FOR THIS AND THE PREVIOUS TIMING. FOR THE MAIN ISSUANCE WE WILL CONSIDER WHETHER OR NOT THUNDER WILL NEED TO BE INCLUDED WITH THIS VERSUS JUST SHOWERS. UPDATE ISSUED AT 1044 PM EDT SUN APR 19 2015 AN AREA OF CONVECTION HAS BEEN WORKING ITS WAY EAST THROUGH THE REGION THIS EVENING...AND A COUPLE OF UPDATES HAVE BEEN SENT TO PROVIDE UPDATES ON TIMING. HAVE ALSO UPDATED FOR TIMING OF POP ON MONDAY. 18Z GFS AND NAM WERE IN GOOD AGREEMENT FOR MONDAY...AND THE 00Z NAM STILL SEEMS TO SUPPORT THE PREVIOUS RUN. REMNANTS OF CONVECTION CURRENTLY EXITING ARKANSAS WILL PROVIDE A SMALL CHANCE IN THE MORNING...BUT THE GREATER PROSPECT FOR RAIN LOOKS TO BE LATE IN THE DAY. DIURNAL DESTABILIZATION COUPLED WITH A WEAK SHORTWAVE TROUGH ROTATING THROUGH THE LARGER SCALE SYNOPTIC SCALE TROUGH AND GENERAL COOLING ALOFT SHOULD RESULT I200N SCATTERED TO NUMEROUS SHOWERS DEVELOPING IN THE AFTERNOON...AND POSSIBLY A FEW MORE THUNDERSTORMS. && .SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT) ISSUED AT 359 PM EDT SUN APR 19 2015 LATEST SURFACE MAP FEATURES BROAD LOW PRESSURE ACROSS IL/IN/KY WITH A WARM FRONT EXTENDING ESE INTO OUR SOUTHWEST COUNTIES. FURTHER WEST ACROSS THE PLAINS...A COLD FRONT EXTENDS NORTH TO SOUTH. ALOFT...AN AMPLIFIED PATTERN IS IN PLACE ACROSS THE HEART OF THE CONUS...WITH AN UPPER LEVEL LOW WITHIN THE NORTHERN STREAM LOCATED ACROSS CENTRAL MANITOBA. MEANWHILE...A COUPLE OF WELL DEFINED SHORT WAVE TROUGHS ARE CHURNING EASTWARD WITHIN THE SOUTHERN STREAM...ONE CURRENTLY LOCATED ACROSS KS/OK...AND THE OTHER SWINGING NORTHEAST THROUGH NORTHERN MS/AL. PLENTY OF CONVECTION IS FIRING UP THIS AFTERNOON...WITH SHOWERS AND THUNDERSTORMS INITIATING ACROSS WESTERN KY/TN OUT AHEAD OF THE APPROACHING SHORT WAVE TROUGH AS WELL AS WITHIN THE VICINITY OF THE SURFACE LOW. THE MAIN PRECIPITATION SHIELD THAT BROUGHT MORE STEADY RAINS ACROSS EASTERN KENTUCKY THIS MORNING HAS MOVED OFF TO THE NORTHEAST AND EAST. THE MODELS ARE IN GOOD AGREEMENT THROUGH THE SHORT TERM...WITH CONVECTION LIKELY FIRING UP ACROSS EASTERN KENTUCKY IN THE FORM OF CLUSTERS AND LINE SEGMENTS THROUGH THE REST OF THIS AFTERNOON. THE SHEAR REMAINS AMPLE...HOWEVER INSTABILITY STILL LOOKS MARGINAL GIVEN THE PERSISTENT CLOUD COVER. STILL...THERE IS A LITTLE THINNING TO THE CLOUDS ACROSS CENTRAL TN/KY AND THIS MAY WORK EAST THROUGH THE REST OF THE AFTERNOON...ALLOWING FOR JUST ENOUGH INSTABILITY TO SUPPORT A FEW STRONGER STORMS. LOCALLY HEAVY RAINFALL ALSO REMAINS A CONCERN GIVEN THE SLOWER EASTWARD MOVEMENT TO THE LINES. THIS ACTIVITY WILL WIND DOWN FROM SOUTHWEST TO NORTHEAST THROUGH THE REST OF THIS EVENING...AS THE SHORT WAVE TROUGH EXITS TO THE NORTHEAST AND DAMPENS. THERE WILL BE A RELATIVE LULL IN THE CONVECTION OVERNIGHT...BEFORE THE MAIN COLD FRONT AND ANOTHER SHORT WAVE TROUGH APPROACH TOWARDS DAWN. ANOTHER FAIRLY STOUT LOW LEVEL JET WILL ENGAGE LATE TONIGHT INTO MONDAY MORNING ACROSS THE OHIO AND TENNESSEE VALLEYS AS THE UPPER LEVEL TROUGH AMPLIFIES AND SURFACE LOW PRESSURE DEEPENS AS IT HEADS NORTH INTO THE GREAT LAKES. DEPENDING ON THE TIMING OF THE COLD FRONT ON MONDAY...THERE REMAINS A MARGINAL THREAT FOR STRONG TO SEVERE STORMS...WITH DAMAGING WINDS BEING THE MAIN THREAT GIVEN THE MORE UNIDIRECTIONAL FLOW. WILL CONTINUE TO MENTION THIS IN THE HWO. HAVE GONE WITH CATEGORICAL POPS FOR MONDAY...AS A FEW ROUNDS OF SHOWERS AND STORMS SHOULD EVENTUALLY HIT MOST LOCATIONS THROUGHOUT THE DAY...WITH THE COLD FRONT AS WELL AS A COUPLE OF PASSING SHORT WAVE TROUGHS. SCATTERED SHOWERS WILL WIND DOWN ACROSS THE SOUTHEAST LATE MONDAY NIGHT...WITH TEMPERATURES COOLING OFF TO THE 40S BY DAWN TUESDAY. .LONG TERM...(TUESDAY THROUGH SUNDAY) ISSUED AT 345 PM EDT SUN APR 19 2015 THE EXTENDED PORTION OF THE FORECAST WILL ALTERNATE BETWEEN COOL AND DRY PERIODS AND COOL AND WET PERIODS. THE BEGINNING THE EXTENDED WILL BE MARKED BY RIDGE OF HIGH PRESSURE THAT WILL BE SLOWLY RETREATING SOUTHEASTWARD AHEAD OF AN APPROACHING COLD FRONT. BOTH THE GFS AND ECMWF MODELS WERE IN GOOD AGREEMENT ON THIS. THE CONSENSUS IS FOR TUESDAY AND TUESDAY TO BE DRY AHEAD OF THE FRONT...WITH ISOLATED TO SCATTERED RAIN SHOWERS OVERSPREADING THE AREA TUESDAY NIGHT AS THE FRONT MOVES THROUGH. BASED ON THE EAST WEST ORIENTATION OF THE FRONT...AND THE NEARLY ZONAL FLOW ALONG IT...IT APPEARS THE FRONT WILL GET HUNG UP A BIT AS IF MOVES OUT OF THE OHIO VALLEY AND INTO THE TENNESSEE VALLEY. THIS WOULD LEAD TO SCENARIO WHERE THE FRONT REMAINS IN PLACE THROUGH WEDNESDAY EVENING...BEFORE FINALLY PUSHING OFF TO THE SOUTHEAST ONCE THE WINDS BEHIND THE BOUNDARY SHIFT TO THE NORTHWEST. IN SPITE OF THE LINGERING NATURE OF THE FRONT...THE ONE ISSUE WITH THE SET UP WILL BE LACK OF MOISTURE OFF THE GULF AND GOOD LIFT ALONG THE FRONT. THEREFORE...THE FORECAST AT THIS TIME WILL FEATURE SCATTERED RAIN SHOWERS ALONG THE FRONT AND NO THUNDER DUE TO LACK OF INSTABILITY. DUE TO UPLIFT AND LINGERING MOISTURE BEHIND THE FRONT...WE COULD SEE RAIN SHOWERS IN THE AREA THROUGH THURSDAY AFTERNOON BEFORE EXITING OUR FAR SOUTHEASTERN COUNTIES. ANOTHER RIDGE OF HIGH PRESSURE IS THEN PROGGED TO SETTLE OVER THE REGION THURSDAY NIGHT AND MOST OF FRIDAY...BEFORE ANOTHER WEATHER SYSTEM MOVES IN FROM THE SOUTHWEST LATE FRIDAY AFTERNOON. ONCE AGAIN ONLY RAIN SHOWERS ARE EXPECTED DUE TO LACK OF INSTABILITY AND COOL TEMPERATURES. THIS SECOND AROUND OF PRECIPITATION WILL LAST A COUPLE OF DAYS AS WELL...WITH THE LAST RAIN SHOWERS EXITING THE AREA EARLY SUNDAY MORNING...SHOULD THE GFS HOLD TRUE TO ITS CURRENT LATE PERIOD SOLUTION ANYWAY. TEMPERATURES DURING THE UPCOMING WORK WEEK WILL LIKELY BE WELL BELOW NORMAL FOR EVERYDAY BUT WEDNESDAY...DUE TO THE PRESENCE OF COOLER THAN NORMAL AIR...CLOUD COVER AND THE TWO ROUNDS OF RAIN SHOWERS. HIGHS EACH DAY ARE FORECAST TO MAX OUT IN THE UPPER 50S AND LOWER 60S FOR MOST LOCATIONS EACH DAY BUT WEDNESDAY. ON WEDNESDAY A PERIOD OF SOUTHERLY TO SOUTHWESTERLY FLOW MAY BE ENOUGH TO ALLOW TEMPERATURES TO PEAK NEAR NORMAL VALUES SOUTH OF THE MOUNTAIN PARKWAY. OVERNIGHT LOWS WILL GENERALLY BE IN THE 40S. THE EXCEPTION MAY BE FRIDAY NIGHT...WHEN MOSTLY CLEAR TO PARTLY CLOUDY SKIES AND LIGHT NORTHWEST WINDS MAY ALLOW MIN TEMPS TO DIP INTO THE UPPER 30S ACROSS THE AREA. WE MIGHT EVEN SEE SOME PATCHY FROST IN THE DEEPER AND MORE SHELTERED VALLEYS IN OUR EAST AND NORTHEAST BY EARLY SATURDAY MORNING. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT) ISSUED AT 200 AM EDT MON APR 20 2015 SOME SCATTERING OUT OF THE LOW CLOUDS HAS OCCURRED AND SHOULD TRANSLATE NORTHEAST ACROSS THE AREA FOR SOME TIMES OF VFR OVER THE NEXT 3 TO 5 HOURS AT THE TAF SITES. AFTER THAT...ANOTHER ROUND OF SHOWERS AND POSSIBLY A STRAY THUNDERSTORM MAY MOVE THROUGH FROM WEST TO EAST BETWEEN ABOUT 09Z AND 14Z. A BETTER SHOT AT SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL COME GENERALLY BETWEEN 18Z TO 00Z. ANY OF THE STRONGER SHOWERS OR THUNDERSTORMS WILL BE CAPABLE OF DROPPING CONDITIONS BELOW MVFR AT LEAST FOR A TIME. OTHERWISE...MAINLY VFR OR MVFR IS EXPECTED THROUGH THE PERIOD. WINDS WILL PICK UP OUT OF THE WEST AROUND 16Z AND AFTER...WITH SOME GUSTS TOPPING 20 KTS. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GEOGERIAN LONG TERM...AR AVIATION...JP

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