Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 180859
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
359 AM EST THU DEC 18 2014

.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 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1245 AM EST THU DEC 18 2014

HIGH PRESSURE OVERHEAD IS KEEPING A STRONG SUBSIDENCE INVERSION IN
PLACE ACROSS MUCH OF THE NORTHERN HALF OF THE CWA...TRAPPING LOW LEVEL
MOISTURE AND RESULTING IN OVC MVFR CIGS...INCLUDING AT KSJS AND KSYM
/AND IMPOSING ON KJKL FAIRLY QUICKLY/. MEANWHILE...A WEAK UPPER LEVEL
DISTURBANCE IS MOVING INTO THE MISSISSIPPI RIVER VALLEY...SPREADING
AN AREA OF HIGH CLOUDS OUT AHEAD OF IT. EXPECT THE SOUTHWARD
PROGRESSION OF THE LOW CLOUDS TO BE STOPPED BY THE INCOMING
DISTURBANCE...AND MVFR CIGS TO SIT IN PLACE OVER THE AFFECTED TAF
SITES THROUGH THE REMAINDER OF THE NIGHT. MODELS ARE STILL SHOWING
THIS DISTURBANCE BRINGING A CHANCE OF LIGHT PRECIP TO KSYM AND KLOZ.
HOWEVER...GIVEN THE STRONG SURGE OF LOW LEVEL DRY AIR IN THIS AREA /WHERE
LOW LEVEL CLOUD COVER HAS NOT BEEN A FACTOR/...IT WILL BE HARD FOR
ANY PRECIP TO REACH THE GROUND. MAY NOT RULE OUT SOME SPRINKLES OR
FLURRIES AS CIGS LOWER TO AROUND 5 TO 7K FT BETWEEN 10 AND 14Z THIS
MORNING...BUT GIVEN LOW CONFIDENCE AND MINIMAL IMPACTS...DID NOT
INCLUDE IN TAFS AT THIS TIME. ANY LINGERING LOW LEVEL CLOUDS LOOK TO
BREAK BETWEEN 15 AND 18Z TODAY. OTHERWISE...WHILE WESTERLY WINDS
ALOFT CONTINUE TO BE VERY STRONG...EXPECT LIGHT AND VARIABLE WINDS
WITHIN THE FIRST FEW THOUSAND FEET AGL.


&&

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

$$

SHORT TERM...JMW
LONG TERM...AR
AVIATION...JMW





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