Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 251525 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
1025 AM EST TUE NOV 25 2014

.UPDATE...
ISSUED AT 1025 AM EST TUE NOV 25 2014

14Z SFC ANALYSIS SHOWS HIGH PRESSURE BRIEFLY BUILDING INTO EAST
KENTUCKY THIS MORNING BRINGING SUNNY SKIES AND A DRIER AIR MASS. THE
EARLIER HIGH CLOUDS HAVE SLID OFF TO THE EAST OF THE STATE AND WINDS
ARE LIGHT AND VARIABLE. TEMPERATURES ARE IN THE LOW TO MID 40S IN
MOST PLACES ACROSS THE CWA NOW THAT THE COLDER VALLEYS ARE STARTING
TO MIX OUT. DEWPOINTS ARE CURRENTLY IN THE LOW 30S...BUT WITH DRIER
AIR OFF THE SFC THESE ARE EXPECTED TO MIX DOWN INTO THE 20S THROUGH
MID AFTERNOON. FIRST GLANCE OF THE LATEST NAM12 SHOWS THE SOUTHEAST
LOW A BIT FURTHER EAST FROM THE MORE AGGRESSIVE 06Z RUN. HOWEVER...IT
STILL HAS A SIGNIFICANT AMOUNT OF PCPN FALLING TONIGHT INTO WEDNESDAY
MORNING IN AND NEAR THE VIRGINIA BORDER COUNTIES WHERE MUCH OF IT
WILL LIKELY WET BULB TO SNOW. SOME ACCUMULATIONS APPEAR LIKELY...
PARTICULARLY IN THE HIGHER ELEVATIONS AND ON GRASSY/ELEVATED SFCS
ELSEWHERE. THE SPS CONTINUES BUT MAY NEED TO BE UPGRADED TO AN
ADVISORY LATER THIS AFTERNOON DEPENDING ON HOW THE OTHER MODELS COME
IN. FOR THIS UPDATE...HAVE MAINLY FINE TUNED T AND TD GRIDS INTO THE
AFTERNOON PER THE LATEST OBS...TRENDS...AND CONSSHORT GUIDANCE. THESE
HAVE BEEN SENT TO THE NDFD AND WEB SERVERS.

UPDATE ISSUED AT 621 AM EST TUE NOV 25 2014

06Z NAM AND GFS ARE NOW IN AND BOTH ARE A LITTLE MORE ROBUST WITH
PRECIPITATION AND BOTH A TAD FARTHER WEST WITH THE EXTENT. IN
FACT...THE NAM SNOWFALL ALGORITHM IS SUGGESTING AS MUCH AS 5 INCHES
OF SNOW COULD FALL OVER FAR SOUTHEAST KENTUCKY. HOWEVER...THIS IS THE
FIRST RUN SUGGESTING THIS HIGH OF QPF AND WILLING TO CONSIDER IT AN
OUTLIER FOR NOW...BUT THE 12Z MODEL GUIDANCE WILL HAVE TO BE WATCHED
FOR POSSIBLE TRENDS TOWARDS THE HIGHER SNOWFALL AMOUNTS TONIGHT.
ALREADY SEEING SOME COOLER CLOUD TOPS DEVELOPING ACROSS EAST
TEXAS...SO AS MENTIONED...MAY NEED TO WATCH FOR A FARTHER WEST EXTENT
TO THE PRECIPITATION.

ALSO SOMETHING ELSE TO CONSIDER...DRY AIR MIX DOWN ACROSS SOUTHEAST
KENTUCKY THIS AFTERNOON MAY BRING DOWN SOME AWFULLY LOW
DEWPOINTS...WHICH WOULD SET THE STAGE FOR GOOD WET BULB COOLING AS
PRECIPITATION MOVES IN TONIGHT. THUS...IF LOWER DEWPOINTS
MATERIALIZE...THEY MAY HELP DISTINGUISH BETWEEN WHO GETS MORE
SNOW...VERSES MORE RAIN. LOWER DEWPOINTS WOULD ALLOW FOR A FASTER
TRANSITION TO SNOW...AND THUS...MORE SNOWFALL ACCUMULATION. FOR
NOW...WILLING TO SIT ON THIS AND LET DAY-SHIFT RE-EVALUATE THE NEED
FOR ANY CHANGES. IF MODELS CONTINUE TO HOLD COURSE...IT LOOKS LIKE AT
A MINIMUM A WINTER WEATHER ADVISORY WOULD BE NEEDED FOR A PORTION OF
THE AREA.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 307 AM EST TUE NOV 25 2014

SURFACE RIDGING CONTINUES TO BUILD INTO EASTERN KENTUCKY THIS MORNING
WITH SKIES GENERALLY CLEAR TO MOSTLY CLEAR. THIS WILL HOLD THROUGH
THE DAY...PROVIDING A COOLER...BUT STILL RELATIVELY PLEASANT DAY. IN
FACT...WITH THE HELP OF THE SUNSHINE AND TEMPERATURES IN SOME PLACES
ALREADY IN THE 40S THIS MORNING...WE SHOULD HAVE NO PROBLEM
SURPASSING THE 50 DEGREE MARK THIS AFTERNOON. WITH AN ABUNDANCE OF LOW
LEVEL DRY AIR JUST OFF THE SURFACE...RAP AND HRRR ARE SUGGESTING
FAIRLY LOW DEWPOINTS THIS AFTERNOON...ESPECIALLY ACROSS SOUTHEAST
KENTUCKY. IT MIGHT BE A STRETCH TO FALL INTO THE TEENS...BUT
CERTAINLY DEWPOINTS DOWN INTO THE MID 20S WILL BE POSSIBLE. THIS WILL
PUT US CLOSE TO THE 25 PERCENT RH`S THIS AFTERNOON. I WOULDN`T BE
SURPRISED TO SEE A FEW SPOTS ACTUALLY REACH THIS VALUE...ESPECIALLY
IN SOUTHEAST KENTUCKY.

CLOUDS WILL BE ON THE INCREASE THIS EVENING AND ESPECIALLY TONIGHT.
MODELS HAVE AN AREA OF LOW PRESSURE DEVELOPING OVER FLORIDA AND
TRACKING NORTHWARD ALONG THE COAST TONIGHT. NEARLY ALL MODELS ARE IN
SUPPORT OF MOISTURE AND LIFT ASSOCIATED WITH THIS SYSTEM DEVELOPING
ACROSS FAR SOUTHEAST AND EAST KENTUCKY OVERNIGHT INTO WEDNESDAY
MORNING. GIVEN THE ABUNDANCE OF DRY AIR IN PLACE...WET BULB
TEMPERATURES WILL BE FAIRLY LOW. ASSUMING WE GET PRECIP RATES THAT
SUPPORT IT...WE SHOULD SEE PRIMARILY SNOW LATE TONIGHT INTO WEDNESDAY
MORNING...BUT SOME RAIN MAY BE POSSIBLE FARTHER INTO EASTERN KENTUCKY
WHERE PRECIP RATES MAY NOT BE AS HIGH. REGARDLESS...WE SHOULD SEE
TEMPERATURES COOL ENOUGH TO SUPPORT SOME LIGHT SNOW ACCUMULATION
ACROSS SOUTHEAST KENTUCKY. AT THIS TIME...THE HIGHEST AMOUNTS SHOULD
BE ABOVE 2500 FEET...WHERE 2 TO 3 INCHES OF SNOW MAY BE POSSIBLE.
LIGHTER AMOUNTS IN THE LOWER ELEVATIONS UP TO AN INCH WILL BE
POSSIBLE FOR AREAS SOUTHEAST OF A LINE FROM INEZ TO HAZARD...TO
BARBOURVILLE. WHILE SNOW IS EXPECTED ACROSS SOUTHEAST KENTUCKY...THE
REST OF EASTERN KENTUCKY MAY NOT SEE MUCH MORE THAN INCREASED CLOUD
COVER. PLAN TO GO AHEAD AND ISSUE AN SPS FOR OUR SOUTHEAST COUNTIES
TO ADDRESS THE POTENTIAL SNOWFALL. GIVEN THE EXPECTED CLOUD COVER
INTO WEDNESDAY...WENT WITH A PRETTY GOOD GRADIENT IN TEMPERATURES
FROM WEST TO EAST...WITH READINGS AROUND 50 IN THE WEST TO LOW AND
MID 30S IN THE EAST. PRECIPITATION WILL DEPART BY MIDDAY
WEDNESDAY...WITH TEMPORARY BREAK IN PRECIPITATION EXPECTED THROUGH
THE AFTERNOON AND EVENING.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 307 AM EST TUE NOV 25 2014

THE MODELS BEGIN THE PERIOD IN PRETTY GOOD AGREEMENT...WITH A LARGE
SCALE UPPER LEVEL TROUGH OF LOW PRESSURE EJECTING OUT OF THE
NORTHERN PLAINS AND ACROSS THE OHIO AND TENNESSEE VALLEY REGIONS
WEDNESDAY NIGHT THROUGH FRIDAY. IT APPEARS THAT THIS INITIAL SYSTEM
WILL BE FAIRLY PROGRESSIVE...SO ANY PRECIPITATION ASSOCIATED WITH IT
SHOULD BE SHORT LIVED AND NOT VERY HEAVY. A SHOT OF COLD AIR WILL
SPILL INTO THE REGION AS THE SYSTEM DEPARTS...WITH HIGHS ON THURSDAY
ONLY TOPPING OUT AROUND 40 DEGREES...AFTER MORNING LOWS IN THE UPPER
20S AND LOWER 30S. A RIDGE OF HIGH PRESSURE IS THEN PROGGED TO
BECOME ESTABLISHED ACROSS THE REGION TO BEGIN THE WEEKEND...WITH
WARMER TEMPERATURES AND PARTLY CLOUDY SKIES ON TAP FOR FRIDAY NIGHT
AND SATURDAY. SATURDAY COULD MARK THE START OF A SIGNIFICANT WARMING
TREND...WITH HIGHS POSSIBLY TOPPING OUT IN THE LOW TO MID 50S. THE
REGION IS EXPECTED TO WARM EVEN MORE ON SUNDAY AND MONDAY...AS THE
MERCURY CLIMBS INTO THE MID TO UPPER 50S FOR MOST LOCATIONS BOTH
DAYS. OVERNIGHT LOWS SATURDAY AND SUNDAY NIGHT WILL FEEL ALMOST
BALMY IF THEY IN FACT ONLY DROP INTO THE LOW TO MID 40S EACH NIGHT.

ENOUGH COLD AIR WILL LIKELY SPILL INTO THE REGION TO BEGIN THE
PERIOD TO ALLOW FOR SOME SNOW TO MIX WITH RAIN EARLY WEDNESDAY NIGHT
INTO THURSDAY MORNING ACROSS THE AREA. LITTLE IF ANY SNOW
ACCUMULATION IS EXPECTED. THE NEXT ROUND OF PRECIPITATION IS
EXPECTED TO MOVE ACROSS THE AREA BEGINNING SATURDAY NIGHT...AS A
WEAK FRONTAL BOUNDARY MOVES INTO AND STALLS OUT ACROSS THE AREA. THE
MODELS KEEP THE FRONT IN PLACE...AND THEREFORE THE THREAT OF
PRECIPITATION...THROUGH THE END OF THE DAY ON MONDAY. TEMPERATURES
DURING THIS PERIOD WILL REMAIN WARM ENOUGH FOR ANY PRECIPITATION
THAT OCCURS TO REMAIN IN LIQUID FORM. DUE TO SOME SMALL TIMING
DIFFERENCES BETWEEN THE MODELS REGARDING PRECIPITATION
ONSET...DURATION...AND AREAL COVERAGE...DECIDED TO GO WITH ONLY
CHANCE POPS AT THIS TIME. BASED ON THE LATEST MODEL DATA...THE FRONT
COULD EITHER REMAIN STALLED ACROSS THE AREA...ECMWF...OR DRIFT
SLOWLY NORTH AS A WEAK WARM FRONT...GFS...DURING THE MONDAY INTO
MONDAY NIGHT TIME FRAME. ONLY TIME WILL TELL.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 621 AM EST TUE NOV 25 2014

VFR CONDITIONS WILL CONTINUE THROUGH THIS EVENING AS HIGH PRESSURE
PUSHES EAST ACROSS THE AREA. A DEVELOPING LOW PRESSURE SYSTEM WILL
SPREAD MOISTURE BACK INTO EASTERN KENTUCKY LATE TONIGHT...WITH CIGS
LOWERING. AS OF RIGHT NOW...LOOKS LIKE WE SHOULD SEE A GRADIENT IN
THE LOWER CIGS WITH THE LOWEST (IFR/MVFR) IN THE EAST...TRAILING
BACK TO VFR IN THE WEST. WE WILL ALSO SEE PRECIPITATION SPREAD INTO
THE AREA...MAINLY ACROSS SOUTHEASTERN KENTUCKY...WITH A MIX OF RAIN
AND SNOW...LIKELY BECOMING ALL SNOW. THIS WILL RESTRICT VISIBILITIES
BY LATE TONIGHT AS WELL...MAINLY AT KJKL AND KSJS.

&&

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

$$

UPDATE...GREIF
SHORT TERM...KAS
LONG TERM...AR
AVIATION...KAS




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