Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 241224 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
824 AM EDT TUE MAR 24 2015

.UPDATE...
ISSUED AT 824 AM EDT TUE MAR 24 2015

FRESHENED UP THE HOURLY TEMPERATURES...DEW POINTS AND SKY COVER TO
BETTER JIVE THE LATEST TRENDS IN OBSERVATIONS...OTHERWISE THE
FORECAST REMAINS ON TRACK.

&&

.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
TRANSITIONED 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 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 824 AM EDT TUE MAR 24 2015

EXPECT VFR CONDITIONS TO HOLD ON THROUGH THE PERIOD ACROSS THE
AREA. 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 TONIGHT...BEFORE A COLD FRONT
APPROACHES FROM THE WEST TOWARD DAWN WEDNESDAY MORNING...
THREATENING MAINLY THE I-64 CORRIDOR WITH SHOWERS AND PERHAPS A
RUMBLE OF THUNDER. WINDS WILL BE OUT OF THE ENE AT 5 TO 10 KTS
INITIALLY AND THEN LIGHTEN UP TOWARDS DUSK. WINDS WILL THEN BECOME
OUT OF SOUTH AT 5 TO 10 KTS BETWEEN 08 AND 12Z.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEOGERIAN
SHORT TERM...GEOGERIAN
LONG TERM...DJ
AVIATION...GEOGERIAN



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