Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 180545
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1245 AM EST THU DEC 18 2014

.UPDATE...
ISSUED AT 1050 PM EST WED DEC 17 2014

HOURLY GRIDS HAVE BEEN UPDATED BASED ON RECENT TRENDS IN OBSERVATIONS
AND SATELLITE IMAGERY. STRATOCU HAS REDEVELOPED OVER THE SOUTHEASTERN
COUNTIES AND IS SPREADING BACK SOUTH ACROSS NORTHEASTERN KY AS WELL.
AS THE MID AND HIGH CLOUDS GRADUALLY ADVANCE IN FROM THE SOUTHWEST
CONFIDENCE IN THIS LOW DECK IS NOT EXTREMELY HIGH...BUT CLOUDS WILL
GRADUALLY INCREASE. WITH THE CLOUD FORECAST BEING LOW CONFIDENCE...IT
ALSO LEADS TO A TRICKY HOURLY TEMPERATURE FORECAST. MANY VALLEY
LOCATIONS THAT ARE CLOUD FREE ARE IN THE MID AND UPPER 20S AND MAY
DROP A COUPLE MORE DEGREES DURING BREAKS IN THE CLOUDS AND WHERE
CLOUDS DO NOT INCREASE FOR A FEW MORE HOURS. RECENT HRRR RUNS SUPPORT
A SLIGHTLY HIGHER CHANCE FOR LIGHT PRECIPITATION IN THE SOUTHWEST
REACHING THE GROUND NEAR DAWN AND OVERCOMING DRY AIR CENTERED NEAR
850 MB. THIS WOULD PROBABLY FALL AS ALL SNOW DUE TO WETBULBING. THIS
WOULD MAINLY BE FOR THE LAKE CUMBERLAND REGION COUNTIES OF WAYNE AND
MCCREARY AND POSSIBLY EXTENDING INTO ADJACENT PARTS OF SOUTHERN
PULASKI... SOUTHWEST LAUREL AND WESTERN WHITLEY COUNTIES.
OTHERWISE...THE LOW LEVELS SHOULD REMAIN TOO DRY FOR ANYTHING MORE
THAN VIRGA OR SOME STRAY FLURRIES OR SPRINKLES ON THU...BUT THERE
WILL BE PLENTY OF CLOUDS.

UPDATE ISSUED AT 815 PM EST WED DEC 17 2014

HOURLY GRIDS HAVE BEEN ADJUSTED TO ACCOUNT FOR THE CLEARING SOUTH OF
THE INTERSTATE 64 CORRIDOR AND HOURLY TEMPERATURE TRENDS. SOME
LOCATIONS SUCH AS JKL AND SME AS WELL AS VALLEY LOCATIONS ARE RUNNING
BELOW THE PREVIOUS FORECAST SO THE FIRST FEW HOURS WERE TRENDED
ACCORDINGLY ALTHOUGH MIN T FOR THE REST OF THE NIGHT WAS UNCHANGED FOR
MOST LOCATIONS. LIGHT PRECIP OR VIRGA WILL APPROACH THE SW PART OF THE
CWA TOWARD DAWN...BUT WILL BE STRUGGLING TO OVERCOME SIGNIFICANT LOW
LEVEL DRY AIR.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 310 PM EST WED DEC 17 2014

19Z SFC ANALYSIS SHOWS HIGH PRESSURE STARTING TO MORE EFFECTIVELY
MOVE INTO THE AREA. THIS IS BEGINNING TO BREAK UP THE LOW LEVEL CLOUD
COVER ACROSS AT LEAST THE SOUTHERN HALF OF THE CWA. THESE CLOUDS HAVE
KEPT TEMPERATURES IN CHECK SO FAR TODAY WITH READINGS GENERALLY IN
THE MID TO UPPER 30S NORTH AND IN THE LOWER 40S IN THE SOUTHEAST
WHERE SOME EARLY SUNSHINE IS MAKING ITS PRESENCE FELT. DEWPOINTS HAVE
DRIED OUT THROUGH THE DAY AND ARE NOW IN THE UPPER 20S TO LOWER 30S.
WINDS HAVE BEEN RELATIVELY LIGHT GENERALLY FROM THE WEST AT 5 TO 10
KTS TODAY.

THE MODELS ARE NOW IN PRETTY GOOD AGREEMENT ALOFT THROUGH THE SHORT
TERM PORTION OF THE FORECAST. THEY ALL DEPICT THE CLOSED...BUT
PROGRESSIVE...UPPER LOW THAT WILL SKIRT EAST THROUGH THE LOWER GREAT
LAKES THIS EVENING AND OVERNIGHT. A BRIEF PERIOD OF RIDGING WILL
FOLLOW INTO THURSDAY MORNING FOR EASTERN KENTUCKY BEFORE A RATHER
DAMPENED WAVE MOVES THROUGH LATER IN THE DAY AND THAT NIGHT WITH
SOME WEAK MID-LEVEL ENERGY FLOWING INTO THE CONFLUENCE ZONE EAST OF
THE AREA. WITH THE GENERAL MODEL AGREEMENT HAVE FOLLOWED THE HIGH
RESOLUTION NAM12 AND HRRR MOST CLOSELY FOR WEATHER DETAILS.

SENSIBLE WEATHER WILL FEATURE A BRIEF TIME OF CLEARING THIS EVENING
AND INTO TONIGHT THAT SHOULD ALLOW FOR SOME DECENT RADIATIONAL
COOLING AND RIDGE TO VALLEY TEMPERATURE DIFFERENCES THROUGH MIDNIGHT.
THEREAFTER...HIGH AND MID LEVEL CLOUDS WILL RETURN TO THE AREA FROM
WEST TO EAST AND PUT A CAP ON THE COOLING...LIMITING FURTHER TERRAIN
DIFFERENCES FOR THE REST OF THE NIGHT. THESE CLOUDS WILL ATTEMPT TO
BRING SNOW TO THE SOUTHWESTERN PARTS OF THE AREA BEFORE DAWN...BUT IT
WILL HAVE TO OVERCOME THE DRYING TAKING PLACE ATTM. ACCORDINGLY...
HAVE UNDERCUT QPF AND POPS FROM THE NAM/MET FOR LATE TONIGHT INTO
THURSDAY MORNING. THE AREA OF LOW PRESSURE RESPONSIBLE FOR THE PCPN
THREAT WILL DAMPEN THROUGH THE MORNING AND FADE OUT BY AFTERNOON. FOR
THIS...HAVE LIMITED THE PCPN THREAT TO JUST FLURRIES AND SPRINKLES
FOR THE SECOND HALF OF THE DAY. ADDITIONAL MOISTURE WILL PASS BY TO
THE NORTH LATER THAT EVENING AND A FEW FLURRIES WILL BE POSSIBLE FROM
THIS ALONG WITH ANOTHER COOL NIGHT.

AGAIN USED THE BCCONSSHORT AS A STARTING POINT FOR THE T/TD/WIND
GRIDS FOR THE FIRST 20 HOURS OR SO BEFORE POPULATING WITH THE
SUPERBLEND THEREAFTER. MINOR ADJUSTMENTS WERE MADE FOR TERRAIN
EFFECTS BOTH TONIGHT AND THURSDAY NIGHT. AS FOR POPS...ENDED UP A BIT
UNDER THE MET NUMBERS AND CLOSER TO THE DRIER MAV ONES FOR TONIGHT
AND THURSDAY GIVEN THE DRY AIR THAT WILL BE IN PLACE.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 340 PM EST WED DEC 17 2014

FORECAST MODELS ARE IN GOOD AGREEMENT ON AN ACTIVE WEATHER PATTERN
WITH AT LEAST TWO SYSTEMS TO AFFECT US THROUGH THE PERIOD.

THE FIRST STORM OVER THE WEEKEND CONTINUES TO LOOK RATHER WEAK. A
LIGHT RAIN/SNOW MIX WILL MOVE INTO THE AREA OVERNIGHT FRIDAY NIGHT.
THIS WILL CHANGE TO ALL RAIN DURING THE DAY ON SATURDAY...FOLLOWED
BY PERHAPS BY A LITTLE MORE SNOW AS THE PRECIPITATION ENDS SATURDAY
NIGHT. THERE IS JUST NOT A LOT OF COLD AIR IN PLACE AND
PRECIPITATION LOOKS LIGHT SO ANY SNOW ACCUMULATIONS WILL BE VERY
LIGHT WITH THIS SYSTEM...IF ANY OCCUR AT ALL.

A MUCH MORE IMPRESSIVE STORM SYSTEM IS SHOWING UP IN THE COMPUTER
MODELS FOR THE MIDDLE OF NEXT WEEK...WITH DECENT AGREEMENT ON AN
IMPACTFUL SYSTEM JUST IN TIME FOR PEAK HOLIDAY TRAVEL. AN UPPER
LEVEL TROUGH WILL DIG IN OVER THE PLAINS EARLY IN THE WEEK AND
BECOME NEGATIVELY TILTED OVER THE OHIO VALLEY MID WEEK. THIS CAUSES
EXPLOSIVE DEEPENING OF A SURFACE LOW PRESSURE WHICH IS PROGGED TO
DEVELOP AND TRACK OVER US OR VERY CLOSE TO US ON ITS WAY NORTH TO
THE GREAT LAKES. THIS SYSTEM IS STILL WAY TOO FAR OUT IN THE FUTURE
TO PINPOINT EXACTLY WHAT TYPE OF WEATHER WE WILL BE DEALING
WITH...BUT RAIN...WIND AND SNOW ARE ALL ON THE TABLE FROM TUESDAY
THROUGH WEDNESDAY...AND POTENTIALLY BEYOND.

&&

.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.
&&

$$

UPDATE...JP
SHORT TERM...GREIF
LONG TERM...ABE
AVIATION...JMW





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