Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 240831 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 431 AM EDT TUE MAR 24 2015 .SHORT TERM...(TODAY THROUGH WEDNESDAY) ISSUED AT 409 AM EDT TUE MAR 24 2015 SURFACE HIGH PRESSURE IS CURRENTLY CENTERED ACROSS SOUTHEAST CANADA...WITH LOW PRESSURE MOVING FROM THE FRONT RANGE OF THE ROCKIES INTO THE HIGH PLAINS. A QUASI-STATIONARY FRONT EXTENDS EAST FROM THE LOW...BECOMING MORE ILL-DEFINED CLOSER TO TN/KY...ALTHOUGH THE TEMPERATURE GRADIENT IS PRETTY STOUT WITH 30S IN NORTHERN KY/SOUTHERN OH...AND 50S IN TENNESSEE. ALOFT...AN UPPER LEVEL TROUGH IS MOVING THROUGH THE ROCKIES...WITH RIDGING ACROSS THE PLAINS. THE MODELS ARE IN GOOD AGREEMENT THAT A LEAD SHORT WAVE TROUGH WILL EJECT OUT OF THE ROCKIES TROUGH AND BECOME NEGATIVELY TILTED AS IT MOVES ACROSS THE PLAINS LATER TODAY...EVENTUALLY MOVING INTO THE OHIO VALLEY/GREAT LAKES BY WEDNESDAY. THE SURFACE LOW WILL FOLLOW SUIT...INITIALLY ALLOWING A WARM FRONT TO MOVE NORTH INTO THE OHIO VALLEY LATER TONIGHT...BEFORE A COLD FRONT QUICKLY FOLLOWS FOR WEDNESDAY...ALTHOUGH THE SOUTHERN PORTION OF THE FRONT WILL BE WEAKENING AS THE UPPER LEVEL FORCING SAILS OFF TO THE NORTH AND EAST. FOR EASTERN KENTUCKY...TODAY WILL FEATURE QUITE A BIT OF VARIATION WITH THE HIGH TEMPERATURES...AS LOCATIONS NORTH OF I-64 WILL REMAIN CLOUDIER AND COOLER WITH READINGS IN THE LOW 50S...WHILE SOME SUNSHINE AND SOUTHWEST FLOW HELP PUSH HIGHS TO AROUND 70 ALONG AND SOUTH OF THE HAL ROGERS AND HIGHWAY 80 CORRIDORS. A MODEST LOW LEVEL JET NOSING IN FROM THE WEST WILL ALLOW FOR SOME SHOWERS TO THREATEN...MAINLY NORTH OF THE MOUNTAIN PARKWAY THIS AFTERNOON INTO EARLY THIS EVENING. A LULL IN THE POPS WILL OCCUR LATER THIS EVENING AS THE WARM FRONT LIFTS NORTH...HOWEVER AS THE COLD FRONT APPROACHES FROM THE WEST OVERNIGHT INTO WEDNESDAY...POP CHANCES WILL INCREASE ONCE AGAIN...WITH HIGHER VALUES NORTHWEST...AND LOWER ONES SOUTHEAST. ELEVATED INSTABILITY OUT AHEAD OF THE COLD FRONT CONTINUES TO BE SHOWN IN THE MODELS...SO WILL MAINTAIN SLIGHT CHANCES FOR THUNDER. .LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY) ISSUED AT 431 AM EDT TUE MAR 24 2015 WE BEGIN THE PERIOD WITH FIRST FRONTAL BOUNDARY AND LOW PRESSURE SYSTEM PUSHING EAST AND NE OF THE REGION. RIGHT NOW THE GFS WANTS TO KEEP QPF SIGNALS ALONG THE BAROCLINIC ZONE...HOWEVER IT SEEMS TO BE THE ODD MODEL OUT AT THIS POINT. CONSEQUENTLY LEANED TOWARD PREVIOUS FORECAST AND MODEL BLENDS FOR THIS PERIOD. THIS KEEPS SLIGHT POPS IN BETWEEN THESE TWO UPPER LEVEL INDUCED SYSTEMS. OPTED TO KEEP SLIGHT CHANCE THUNDER GIVEN REASONABLE ELEVATED INSTABILITY IN PLACE. THE SECOND LOW PRESSURE WILL BEGIN FORMING ACROSS THE CENTRAL PLAINS WEDNESDAY NIGHT AND WILL BE THE NEXT MORE SUBSTANTIAL WEATHER MAKER IN THE PERIOD. THIS FEATURE WILL MOVE NE ALONG THE BAROCLINIC ZONE AS LONG WAVE TROUGH PROGRESSES EAST. EVENTUALLY SWINGING A STRONG COLD FRONT ACROSS THE REGION THURSDAY. THIS WILL GIVE BEST CHANCES FOR POPS THROUGH THE PERIOD WITH THUNDER POSSIBLE ALONG AND NEAR THE FRONT. ONCE AGAIN DECENT INSTABILITY WITH LAPSE RATES AOA 6.5C PER KM EARLY ON THURSDAY MAKES THIS SEEM REASONABLE. THINK THE THUNDER WILL DROP OFF THROUGH THE DAY AS STRONG COLD FRONT WILL USHER IN COLDER AIR BEHIND IT. THEREFORE DID OPT TO LEAN TOWARD A NON DIURNAL CURVE THURSDAY WITH TEMPS DROPPING FROM NW TO SE THROUGH THE LATE AFTERNOON. THIS FRONT WILL PROGRESS EAST THURSDAY NIGHT AND THE BEST PRECIP CHANCES WILL GO WITH THE FRONT. SOME QUESTIONS REMAIN FOR FRIDAY ON HOW MUCH MOISTURE WILL BE LEFT OVER AS ENERGY ASSOCIATED WITH THE UPPER LEVEL TROUGH SWINGS ACROSS THE OHIO VALLEY. DID LEAN TOWARD THE BLEND WHICH DOES KEEP SLIGHT TO CHANCE POPS FROM SW TO NE. SOME SLIGHT CHANCE POPS LINGER INTO FRIDAY NIGHT SUPPORTED BY THE GFS AND GEM. GIVEN THAT FORECAST SOUNDINGS SUPPORT MIX TO SOME WET FLAKES HAVE TRANSISTIONED TO THIS OVERNIGHT. OTHERWISE IN THE WAKE OF THIS STRONG COLD FRONT A CANADIAN HIGH IS FORECAST TO DROP SOUTHEAST. THIS WILL SET THE STAGE FOR CLEARING SKIES AND MUCH COLDER TEMPS ACROSS EASTERN KENTUCKY MOVING INTO THE WEEKEND. WHILE FRIDAY NIGHT WILL FEATURE COLD TEMPERATURES WITH LOWS IN THE MID TO UPPER 20S. CLOUDS WILL SLOWLY CLEAR OUT OVERNIGHT AND THE HIGH WILL STILL BE NOSING INTO THE REGION. SATURDAY WILL FEATURE SUNNY SKIES AS DRIER AND COOLER AIR CONTINUE TO FILTER INTO THE REGION. BEST CHANCE FOR RADIATIONAL COOLING AND CLEAR SKIES WILL BE SATURDAY NIGHT...AS HIGH PRESSURE MOVES RIGHT OVER EASTERN KENTUCKY. THERE IS STILL A FAIR AMOUNT OF UNCERTAINTY ON SURFACE HIGH PLACEMENT...AND THESE TEMPS COULD NEED TO BE BUMPED DOWN FROM THE LOW TO MID 20S THAT ARE IN THE GRIDS DEPENDING ON HOW THIS PLAYS OUT. THIS AREA OF HIGH PRESSURE WILL SHIFT SE OF THE REGION SUNDAY LEADING TO RETURN FLOW. HIGH TEMPS WILL BOUNCE BACK INTO THE LOW TO MID 50S. MODELS BECOME QUITE DIVERGENT BY SUNDAY NIGHT INTO MONDAY AS ANOTHER UPPER LEVEL WAVE DROPS SOUTHEAST. RIGHT NOW THE GFS IS MUCH MORE PROGRESSIVE BRINGING A COLD FRONT SOUTH BY SUNDAY NIGHT...WHILE THE ECMWF BRINGS THIS FEATURE DOWN LATER MONDAY. STUCK WITH BLEND AT THIS POINT GIVEN THE GREATER UNCERTAINTY. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT) ISSUED AT 230 AM EDT TUE MAR 24 2015 EXPECT VFR CONDITIONS TO HOLD THROUGH THE PERIOD ACROSS THE AREA. MAINLY MID-LEVEL CLOUDS WILL BE SEEN THROUGH DAWN. A WEAK WARM FRONT WILL THEN DEVELOP DURING THE DAY...ALLOWING FOR SOME SHOWER ACTIVITY AS WELL AS LOWER CEILINGS...ALTHOUGH STILL VFR. THE BOUNDARY WILL EVENTUALLY LIFT NORTH OF EASTERN KENTUCKY LATER TUESDAY NIGHT. WINDS WILL BE OUT OF THE ENE AT 5 TO 10 KTS INITIALLY AND THEN LIGHTEN AND VEER AROUND TO THE SE LATE IN THE PERIOD. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GEOGERIAN LONG TERM...DJ AVIATION...GEOGERIAN

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