Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 181525 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
1025 AM EST THU DEC 18 2014

.UPDATE...
ISSUED AT 1025 AM EST THU DEC 18 2014

14Z SFC ANALYSIS SHOWS A VERY WEAK AREA OF LOW PRESSURE SLIDING BY TO
THE SOUTH OF EASTERN KENTUCKY. THE PRECIPITATION WITH THIS...MAINLY
FLURRIES...IS FADING FAST WITH MOSTLY VIRGA LEFT. TEMPERATURES ARE
GENERALLY IN IN THE UPPER 20S AND LOWER 30S THROUGH THE AREA WITH
DEWPOINTS IN THE MID AND UPPER 20S...WHILE WINDS ARE LIGHT. SATELLITE
SHOWS A FEW BREAKS OUT THERE BUT CIGS ARE MAINLY IN THE LOW MVFR
RANGE NORTH AND VFR SOUTH. HAVE UPDATED THE FORECAST TO DIMINISH THE
POPS QUICKLY THROUGH MIDDAY IN CONJUNCTION WITH THE 12Z NAM12 AND
LATEST HRRR. ALSO FINE TUNED HIGH TEMPERATURES AND THE HOURLY T/TD
GRIDS PER THE LATEST OBS...TRENDS...AND CONSSHORT GUIDANCE. THESE
HAVE BEEN SENT TO THE NDFD AND WEB SERVERS ALONG WITH AN UPDATE TO
THE HWO AND ZONES.

UPDATE ISSUED AT 552 AM EST THU DEC 18 2014

THERE IS A FAIR AMOUNT OF RADAR RETURNS MAKING IT INTO SOUTHEAST
KY...UNLIKE WHAT MANY OF THE HI RES MODELS WERE SHOWING EARLIER.
DESPITE THE DRY AIR IN PLACE AT THE SURFACE...DEW POINT DEPRESSIONS
HAVE LESSENED TO 0 IN SOME OF OUR SOUTHWESTERN COUNTIES. AND WITH
SNOW AND SLEET BEING REPORTED ONLY A FEW COUNTIES OVER...DECIDED IT
WAS TIME TO GO AHEAD AND EXPAND THE CHANCES FOR PRECIP THIS MORNING.
AS IT IS NOW...IT LOOKS LIKE ALL OF THE COUNTIES ALONG THE TENNESSEE
BORDER...AS WELL AS THE NEXT TIER OF COUNTIES NORTHWARD WILL LIKELY
BE AFFECTED BY LIGHT SNOW AND POTENTIAL SLEET THIS MORNING. LATEST HI
RES MODELS...INCLUDING THE HRRR AND NAM 12 ARE SHOWING THE SYSTEM
LOSING INTENSITY VERY QUICKLY THIS MORNING...AND CUTTING OFF PRECIP
CHANCES ACROSS OUR CWA WITHIN THE NEXT FEW HOURS. HOWEVER...GIVEN THE
LEVEL OF UNCERTAINTY...AND THE ONGOING STRONG REFLECTIVITIES...ERRED
ON THE PESSIMISTIC SIDE AND KEPT MENTION OF SNOW AND ICE IN UNTIL MID
MORNING. ALSO...WENT AHEAD AND ISSUED A SPECIAL WEATHER STATEMENT
THROUGH 15Z FOR THE AFFECTED COUNTIES SINCE ANY PRECIP WILL LIKELY
ACCUMULATE ON SURFACES DURING THE MORNING COMMUTE.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 358 AM EST THU DEC 18 2014

SURFACE HIGH PRESSURE CONTINUES TO BE IN CHARGE FOR THE OHIO RIVER
VALLEY AND MANY POINTS TO OUR NORTH AND SOUTH. STRONG SUBSIDENCE
TRAPPING LOW LEVEL MOISTURE ACROSS THE NE PORTION OF THE CWA HAS LED
TO CONTINUED MVFR CLOUDS...WHICH ACCORDING TO THE LATEST FORECAST
SOUNDINGS...SHOULDN/T BE BUDGING UNTIL SOMETIME EARLY THIS
AFTERNOON. MEANWHILE...ALOFT...A SHORTWAVE IS CONTINUING TO DAMPEN
AS IT TRACKS EASTWARD...AND SHOULD BE POISED TO REACH THE
MISSISSIPPI RIVER VALLEY BETWEEN 12 AND 18Z TODAY. SO FAR...THIS
SYSTEM HAS BROUGHT LIGHT PRECIP ACROSS FAR SW KY...AS IT CONTINUES
TO SHIFT EASTWARD TOWARDS OUR SW CWA DURING THE EARLY MORNING HOURS.
THE AMOUNT OF LOW LEVEL DRY AIR IS STILL A CONCERN IN THIS AREA OF
THE CWA...AND WHETHER OR NOT THE PRECIP CAN OVERCOME IT. EXPECTING
BEST CHANCES FOR WEATHER ACROSS WAYNE AND MCCREARY COUNTIES GIVEN
THE LATEST HI RES MODEL DATA...INCLUDING THE HRRR AND ECMWF.
FORECAST SOUNDINGS ARE SHOWING BELOW FREEZING SURFACE TEMPS AT THESE
LOCATIONS...BUT WITH THE POTENTIAL FOR A SLIGHT WARM NOSE TEETERING
ALONG THE FREEZING LINE SEVERAL THOUSAND FEET ABOVE GROUND THROUGH
18Z. AS SUCH...WENT AHEAD AND MENTIONED SOME ICE PELLETS ALONG WITH
A CHANCE OF SNOW IN THESE TWO COUNTIES...WITH A SLIGHT CHANCE OF
LIGHT SNOW EVENTUALLY MIXING WITH RAIN AFTERWARDS ELSEWHERE IN THE
SW CWA.

THE SHORTWAVE WILL EVENTUALLY FLATTEN AND SHIFT EAST OF KY BY 06Z
FRIDAY ELIMINATING ANY FURTHER PRECIP CONCERNS FOR THE SHORT TERM.
THE ONE CAVEAT WILL BE THE EXISTENCE OF THE MID LEVEL CLOUDS WITH
MUCH OF THE TEMPERATURE PROFILE /INCLUDING SURFACE TEMPS/ DROPPING
BELOW FREEZING BY THIS EVENING AND THROUGHOUT THE OVERNIGHT. A FEW
FLURRIES MAY GET SQUEEZED OUT ACROSS THE CWA DURING THE EVENING. IN
FACT...MAY NOT HAVE EXTENDED THE FLURRY POTENTIAL FAR ENOUGH ACROSS
THE CWA. BUT THE CONFIDENCE IS STILL QUITE LOW ON THIS SUBJECT.

CONTINUED TO GO ABOVE GUIDANCE FOR CLOUD COVER OVER THE NEXT 36
HOURS AS MID/LOW LEVEL CLOUDS LOOK TO STICK AROUND THROUGH
FRIDAY...BEFORE ANOTHER ROUND OF HIGH CLOUDS WORKS INTO THE CWA.
THIS MAY INHIBIT SOME OF THE BEST RIDGE VALLEY SPLIT POTENTIAL
TONIGHT. OVERALL...TEMPERATURES SHOULD/T DEVIATE MUCH FROM WHAT WAS
SEEN IN THE PREVIOUS 24 HOURS. HIGHS TODAY WILL GENERALLY BE IN THE
UPPER 30S AND LOW 40S...WITH OVERNIGHT LOWS TONIGHT DROPPING DOWN
INTO THE UPPER 20S. WINDS AT THE SURFACE WILL REMAIN QUITE LIGHT AND
VARIABLE THROUGH THE SHORT TERM...WHILE ABOVE THE CONTINUED MID
LEVEL SUBSIDENCE INVERSION...THEY WILL INCREASE RAPIDLY THANKS TO A
WEST TO EAST ORIENTED JET STREAK WHICH IS CURRENTLY PUSHING ALONG
AND SOUTH OF KY.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 358 AM EST THU DEC 18 2014

A FAIRLY ACTIVE PATTERN IN STORE FOR THE EXTENDED PORTION OF THE
FORECAST. THE MODELS AREA IN PRETTY GOOD AGREEMENT WITH THE LARGE
SCALE UPPER LEVEL FLOW PATTERN THROUGH MID WEEK. THREE SYSTEMS ARE
FORECAST TO AFFECT EASTERN KENTUCKY...THE FIRST BEING A WEAK AREA OF
LOW PRESSURE THAT IS FORECAST TO FORM OVER THE SOUTHERN PLAINS AND
THEN PROGRESS EASTWARD ACROSS THE GULF COAST FRIDAY NIGHT THROUGH
SATURDAY NIGHT. THE SECOND AND THIRD WEATHER SYSTEMS TO AFFECT THE
REGION...SHOULD THE MODELS PAN OUT...WOULD COME MONDAY THROUGH
WEDNESDAY OF NEXT WEEK. THE FIRST OF THESE LATE PERIOD SYSTEMS IS
PROGGED TO ORIGINATE OVER THE GULF OF MEXICO AND MOVE UP THE EASTERN
SLOPES OF THE APPALACHIAN MOUNTAINS MONDAY AND MONDAY NIGHT. THE
SECOND WEATHER SYSTEM IN THIS SCENARIO IS FORECAST TO TAKE SHAPE
OVER THE NORTHERN PLAINS TO BEGIN THE NEW WORK WEEK. THIS SECOND
SYSTEM WOULD COME IN THE FORM OF A LARGE SCALE AND MUCH DEEPER
TROUGH THAN EITHER OF THE SOUTHERN STREAM SYSTEMS. THIS AREA OF LOW
PRESSURE WOULD PROVIDE THE SOURCE OF COLD AIR THAT COULD BRING SUB
FREEZING TEMPERATURES AND SNOW NEXT WEDNESDAY NIGHT.

THE UNCERTAINTY WITH THIS WEEKENDS WEATHER WILL REVOLVE AROUND HOW
MUCH COLD AIR WILL BE ABLE TO FILTER INTO THE AREA AS THE SOUTHERN
PLAINS LOW MAKES ITS NORTHEASTERN TURN FRIDAY NIGHT. BASED ON THE
LATEST MODEL SOUNDINGS AND TIME HEIGHTS...THERE IS SOME UNCERTAINTY
AS TO HOW FAR SOUTH THE COLD AIR WILL PENETRATE FRIDAY NIGHT INTO
SATURDAY MORNING. BASED ON THIS...DECIDED TO CONFINE ANY
ACCUMULATING SNOW TO THE AREA NORTH OF THE MOUNTAIN PARKWAY BETWEEN
6 AND 12Z FRIDAY NIGHT. THE SNOW SHOULD THEN TRANSITION TO A RAIN
SNOW MIX EARLY SATURDAY MORNING...AND THEN TO ALL RAIN BY EARLY
SATURDAY AFTERNOON. ANY SNOW ACCUMULATIONS THAT DO OCCUR WOULD
LIKELY BE CONFINED TO GRASSY AREAS AND ELEVATED SURFACES. OUR FAR
EASTERN COUNTIES COULD SEE ANOTHER SHOT OF RAIN SNOW MIX OR ALL SNOW
FOR A BRIEF PERIOD SATURDAY NIGHT AS THE LOW EXITS THE AREA AND
WINDS SHIFT TO THE NORTH NORTHEAST. A WEAK RIDGE OF HIGH PRESSURE
ALOFT SHOULD PROVIDE A BRIEF RESPITE FROM THE WINTRY WEATHER LATE
SATURDAY NIGHT THROUGH MID MORNING ON SUNDAY. THE MODELS ONCE AGAIN
OFFER UP SOME UNCERTAINTY AS TO EXACTLY WHEN PRECIPITATION ONSET
WILL BE ON SUNDAY...WITH THE GFS MODEL HOLDING OFF A LOT LONGER THAN
THE ECMWF. BASED ON THIS...WENT WITH A BLEND BETWEEN THE TWO MODELS
FOR PRECIP ONSET ON SUNDAY ACROSS OUR EASTERN COUNTIES...WITH LIGHT
RAIN AFFECTING THE SOUTHEASTERN TWO THIRDS OF THE AREA AS MOISTURE
FROM THE GULF LOW BEGINS TO MOVE NORTHWARD INTO THE AREA. THE BETTER
SHOT OF PRECIPITATION WILL COME FROM MONDAY NIGHT THROUGH WEDNESDAY
EVENING...AS A MUCH STRONGER AND WETTER WEATHER SYSTEM DIVES OUT OF
THE NORTHERN PLAINS AND PHASES WITH WHAT EVER ENERGY IS LEFT OVER
FROM THE GULF OF MEXICO WEATHER SYSTEM. MOST OF THE PRECIPITATION
WITH THIS THIRD WEATHER SYSTEM LOOKS TO BE IN THE FORM OF RAIN BASED
ON THE TEMPERATURE PROFILES SEEN IN THE LATEST MODEL DATA. COULD SEE
SOME MORE SNOW WITH THIS FINAL WEATHER SYSTEM AS WINDS SHIFT TO THE
WEST AND NORTHWEST BEHIND THE LOW AS IT MOVES INTO NEW ENGLAND AND
COLDER AIR SPILLS INTO THE REGION.

THE OTHER WEATHER CONCERN OF NOTE FOR THE END OF THE EXTENDED PERIOD
WILL BE WINDS...PARTICULARLY FROM WEDNESDAY ONWARD. THE MODELS ALL
AGREE THAT A WELL DEVELOPED PRESSURE GRADIENT WILL ACCOMPANY THE
GREAT PLAINS WEATHER SYSTEM AS IT MOVES EAST. SUSTAINED WEST TO
NORTHWEST WINDS OF 10 TO 15 MPH...WITH GUSTS OF 20 TO 25 MPH...WILL
NOT BE OUT OF THE QUESTION. TEMPERATURES THROUGHOUT THE EXTENDED
PERIOD LOOK TO BE AT OR SLIGHTLY ABOVE NORMAL FROM SUNDAY THROUGH
WEDNESDAY. THE WARMEST STRETCH DURING THAT TIME WOULD BE MONDAY AND
TUESDAY...AS WINDS SHIFT TO THE SOUTH AHEAD OF THE MID WEEK WEATHER
SYSTEM. HIGHS ON EACH OF THOSE DAYS ARE EXPECTED TO TOP OUT IN THE
UPPER 40S AND LOWER 50S RESPECTIVELY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 656 AM EST THU DEC 18 2014

AN UPPER LEVEL DISTURBANCE IS BRINGING MOISTURE ACROSS SOUTHERN
KENTUCKY THIS MORNING. SURFACE HIGH PRESSURE...HOWEVER...IS MAKING
IT HARD FOR THE MAJORITY OF THIS MOISTURE TO MAKE IT THROUGH THE
LAYER OF DRY AIR AT THE SURFACE. IT IS POSSIBLE FOR KSME AND KLOZ TO
SEE A FEW SPURTS OF SNOW AND POSSIBLY SLEET AS WE HEAD INTO THE MID
MORNING. HOWEVER...THE LIGHT AND ISOLTED NATURE OF THIS PRECIP IS
NOT LIKELY TO CAUSE VIS RESTRICTIONS...SO CONTINUED TO KEEP MENTION
OF PRECIP OUT OF THE TAF. FOR THE REMAINING TAF SITES...LESS
INFLUENCE FROM THIS UPPER LEVEL DISTURBANCE HAS LEFT HIGH PRESSURE TO
RULE THE SKIES. THIS HAS RESULTED IN A STRONG SUBSIDENCE
INVERSION...TRAPPING LOW LEVEL MOISTURE AND CREATING A MVFR CIG DECK.
EXPECT BOTH THE LLVL CLOUD DECK...AND ANY REMAINING PRECIP
CHANCES...TO DISSIPATE AS WE HEAD INTO THE LATE MORNING/EARLY
AFTERNOON. WHILE WINDS WILL REMAIN LIGHT NEAR THE SURFACE...A WEST TO
EAST ORIENTED UPPER LEVEL JET STREAK WILL KEEP STRONG WESTERLY WIND
FLOW ABOVE THE HIGH PRESSURE INVERSION /AROUND 6K FT AGL/ FOR THE
NEXT 24 HOURS.

&&

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

$$

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



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