Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 222027
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
327 PM EST MON DEC 22 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 325 PM EST MON DEC 22 2014

TODAY HAS BROUGHT PARTLY TO MOSTLY CLOUDY SKIES ACROSS EASTERN KY
TODAY. THIS WILL CONTINUE TO BE THE TREND BEFORE MORE SUBSTANTIAL
CLOUD COVER PROGRESSES NORTHEAST ACROSS THE REGION TONIGHT. CURRENTLY
WE ARE TRACKING SHOWERS ACROSS MIDDLE TN THIS AFTERNOON...HOWEVER
MESOSCALE MODELS DO WEAKEN THIS AND KEEPS MUCH OF THE SHOWERS WEST.
THIS WILL NEED TO CONTINUE TO BE MONITORED. HOWEVER DID OPT TO AT
LEAST INTRODUCE SLIGHT POPS ACROSS THE REGION THIS EVENING INTO
TONIGHT. THE MODELS DO EVENTUALLY INTRODUCE MORE PRECIP OVERNIGHT
ALONG MORE OF A WARM FRONTAL BOUNDARY THAT SURGES NORTH. A TROUGH
ACROSS THE CENTRAL US WILL CONTINUE TO DIG SE AND AID IN DEVELOPING A
SURFACE LOW ACROSS THE LOWER MS RIVER VALLEY. THERE IS EXPECTED TO BE
A TRANSITION IN LIFTING MECHANISMS TUESDAY AS LOW ACROSS THE UPPER
MIDWEST BECOMES VERTICALLY STACKED AND ENERGY/LIFT MOVES NE WITH THE
DEVELOPING LOW. ALSO THERE COULD BE SOME REASONABLE HELP FROM
DOWNSLOPING DURING THIS PERIOD. THEREFORE WILL KEEP BETTER CHANCES OF
PRECIP ACROSS WESTERN PORTIONS OF THE CWA TUESDAY. ANOTHER TRICKY
PART OF THIS WILL BE HOW MUCH CLOUD COVER WILL BE ACROSS THE EAST AND
HOW THAT WILL AFFECT TEMPS. RIGHT NOW GOING WITH TEMPS GENERALLY IN
THE UPPER 50S TO LOWER 60S ACROSS THE CWA...HOWEVER IF SOME CLEARING
IS SEEN YOU COULD SEE HIGHER TEMPS. THE LOW PRESSURE ACROSS THE MS
RIVER VALLEY IS EXPECTED TO TRACK NORTH AND EAST ACROSS THE TN/OH
VALLEYS OVERNIGHT TUESDAY. THIS WILL LEAD TO WIDESPREAD SHOWERS
ACROSS THE CWA LATER TUESDAY INTO TUESDAY NIGHT.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 315 AM EST MON DEC 22 2014

THE FOCUS OF THE EXTENDED PERIOD WILL BE THE TUESDAY NIGHT THROUGH
CHRISTMAS MORNING TIME FRAME. A POWERFUL STORM SYSTEM IS EXPECTED TO
FORM OVER THE SOUTHERN MISSISSIPPI RIVER VALLEY TUESDAY NIGHT INTO
WEDNESDAY...AS A STREAK IN THE POLAR JET PHASES WITH A SOUTHERN
STREAM JET STREAK OVER THE LOUISIANA MISSISSIPPI REGION. THIS
SOUTHERN STORM SYSTEM IS EXPECTED TO PUSH ACROSS THE TENNESSEE AND
OHIO VALLEY REGIONS AS A LARGE TROUGH OF LOW PRESSURE ALOFT MAKES
ITS WAY ACROSS THE NORTHERN PLAINS AND GREAT LAKES REGION. BOTH THE
ECMWF AND GFS MODELS WERE IN GOOD AGREEMENT WITH THE TIMING OF THIS
LARGE WEATHER SYSTEM...ALONG WITH THE EVOLUTION OF PRECIPITATION
ASSOCIATED WITH IT AND THE EASTWARD PROGRESSION OF THE SYSTEM.
TEMPERATURES WILL BE QUITE WARM TO BEGIN THE PERIOD...WITH READINGS
IN 50S EXPECTED BOTH TUESDAY NIGHT AND WEDNESDAY. PRECIPITATION WILL
START OUT AS PERSISTENT MODERATE TO AT TIMES LOCALLY HEAVY RAIN
SHOWERS. THIS RAIN WILL LAST THROUGHOUT CHRISTMAS EVE DAY. ONCE THE
UPPER LOW MOVES OFF TO THE EAST...WINDS WILL SHIFT TO THE WEST
CHRISTMAS EVE NIGHT INTO EARLY CHRISTMAS DAY. THIS WILL ALLOW SOME
COLDER AIR TO FILTER INTO THE BEHIND THE DEPARTING WEATHER SYSTEM.
AS A RESULT...THE RAIN WILL GRADUALLY MIX WITH SNOW LATE WEDNESDAY
NIGHT INTO EARLY THURSDAY MORNING. THE LATEST MODEL SOUNDINGS ARE
SUGGESTING THAT ICE CRYSTAL GROWTH ALOFT WILL BE LACKING...THEREFORE
MAKING FOR ONLY VERY MEAGER AMOUNTS OF SNOW OCCURRING ACROSS THE
AREA. BASED ON THAT...AND THAT FACT THE GROUND WILL BE QUITE
WARM...VERY LITTLE IF ANY SNOW ACCUMULATION IS EXPECTED.

THE OTHER ISSUE OF NOTE WITH THIS SYSTEM WILL BE THE WIND. AS THE
UPPER LOW PRESSES EASTWARD AND STRENGTHENS...THE SURFACE WINDS WILL
RESPOND IN KIND ACROSS EASTERN KENTUCKY. WINDS WILL BEGIN TO PICK UP
QUITE A BIT DURING THE AFTERNOON HOURS ON WEDNESDAY...WITH SOUTHERLY
WINDS OF 10 TO 20 MPH POSSIBLE. THE WINDS COULD GUST AS HIGH AS 30
TO 40 MPH FROM TIME TO TIME...PARTICULARLY AS THE UPPER LOW AND ITS
ATTENDANT SURFACE COLD FRONT MOVE PAST THE AREA.

TEMPERATURES TO BEGIN THE PERIOD WILL BE WELL ABOVE NORMAL...WITH
READINGS TOPPING OUT IN THE MID TO UPPER 50S ON WEDNESDAY AND NIGHT
TIME LOWS IN THE MID 30S WEDNESDAY NIGHT. AFTER THAT...THINGS WILL
RETURN TO NORMAL AS THE COLD AIR SETTLES OVER THE REGION. HIGHS EACH
DAY FROM CHRISTMAS DAY THROUGH THE WEEKEND ARE EXPECTED TO AT OR
SLIGHTLY BELOW NORMAL. THE EXCEPTIONS TO THIS COULD BE FRIDAY AND
FRIDAY NIGHT...WHEN ANOTHER WEATHER SYSTEM TRAVERSES THE REGION.
TEMPERATURES ON FRIDAY COULD WARM INTO THE LOWER 50S AS WINDS SHIFT
TO THE SOUTH AHEAD OF THE APPROACHING WEATHER SYSTEM. THE PERIOD OF
THE FORECAST...HOWEVER...IS WHERE THINGS GET A BIT OUT OF SORTS. THE
ECMWF MODEL HAS A LARGE...ROBUST...AND VERY MOIST WEATHER SYSTEM
MOVING ACROSS THE REGION DURING THE WEEKEND...WHILE THE GFS IS
FORECASTING A MUCH WEAKER AN NEARLY PRECIPITATION FREE WEATHER
SYSTEM DURING THIS SAME PERIOD OF TIME. FINALLY DECIDED TO INCLUDE A
SLIGHT CHANCE OF RAIN FOR THE SATURDAY SUNDAY TIME FRAME TO ACCOUNT
FOR THE FACT THAT BOTH MODELS ARE PRODUCING SOME SORT OF
PRECIPITATION FOR EASTERN KENTUCKY...WHILE AT THE SAME TIME
ACCOUNTING FOR THE ENORMOUS DIFFERENCES BETWEEN THE TWO MODELS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 110 PM EST MON DEC 22 2014

CLOUDS HAVE GENERALLY BEEN VFR MUCH OF THE DAY TODAY. THERE HAVE BEEN
PATCHES OF MVFR AT TIMES AS CLOUDS CONTINUE TO INCREASE TODAY ACROSS
THE SW. RIGHT NOW THINKING THAT MORE IN THE WAY OF SOME MVFR CEILINGS
HAVE BEEN MOVING CLOSER TO THE SW PORTIONS OF THE REGION THIS
AFTERNOON. OPTED TO GO AHEAD WITH MVFR CEILINGS AT SME AND SLOWLY
PROGRESS NORTH THROUGH THE NIGHT. ALSO ADDED THE MENTION OF VCSH
OVERNIGHT GIVEN THAT MODELS KEEP TRENDING TOWARD SOME SLIGHT SHOWERS
FOR MUCH OF THE REGION. OTHERWISE TAFS AREA WIDE ARE EXPECTED TO
CONTINUE TO TREND TOWARD MVFR CEILINGS.


&&

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

$$

SHORT TERM...DJ
LONG TERM...AR
AVIATION...DJ





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