Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 171241
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
741 AM EST WED DEC 17 2014

.UPDATE...
ISSUED AT 722 AM EST WED DEC 17 2014

OVER THE LAST FEW HOURS...LATEST IR IMAGERY HAS SHOWN SOME COLDER
CLOUD TOPS ADVECTING EASTWARD INTO THE REGION. THIS...IN ADDITION TO
MORNING TEMPERATURES IN THE LOW TO MID 30S ACROSS PORTIONS OF EASTERN
KY...HAS LED TO SOME ISOLATED FLURRY REPORTS. EXPECT THESE COLDER
CLOUDS CONTINUE MOVING ACROSS EASTERN KY. THE COMBINATION OF
ONGOING DRIZZLE THIS MORNING...LOWERING TEMPS ALOFT...AND LOW TO MID
30S SURFACE TEMPS EXPECTED TO STICK AROUND FOR SEVERAL HOURS
LONGER...WARRANTED THE BELIEF THAT A GOOD PORTION OF THE AREA COULD
SEE SOME FLURRY POTENTIAL...EVEN IF ONLY A SLIGHT CHANCE. WENT AHEAD
AND COMBINED ISOLATED FLURRY POTENTIAL WITH THE ONGOING AREAS OF
DRIZZLE IN THE WEATHER GRIDS. THIS WILL HAVE THE FLURRIES ENDING
ALONG WITH THE DRIZZLE AS DRY AIR FINALLY MIXES DOWN TO THE SURFACE
BY LATE MORNING/EARLY AFTERNOON.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 426 AM EST WED DEC 17 2014

A WEAK BOUNDARY PASSING THROUGH THE REGION OVERNIGHT HAS PROMPTED A
SLIGHT INCREASE IN MOISTURE...WHICH HAS RESULTED IN LIGHT RAIN SHOWERS
ACROSS A GOOD PORTION OF THE NORTHERN HALF OF THE CWA. AS THE
BOUNDARY /WHICH IS IN THE FORM OF A WEAK COLD FRONT CONNECTED TO LOW
PRESSURE CURRENTLY TRACKING ACROSS THE LOWER GREAT LAKES/ CONTINUES
EASTWARD OUT OF KY...EXPECT SHOWERS TO COME TO AN END FROM W TO E
THROUGH 11Z. FORECAST SOUNDINGS ARE STILL SUPPORTING DRIZZLE HANGING
AROUND MUCH OF THE AREA THROUGH MID MORNING TO EARLY AFTERNOON AS A
STRONG SUBSIDENCE INVERSION KEEPS LOW LEVEL MOISTURE IN PLACE.
BETWEEN 15 AND 18Z...DRY AIR WILL FINALLY BEGIN TO MIX DOWN...AND LOW
CLOUDS WILL BREAK. UNFORTUNATELY...HIGH CLOUDS WILL BE BUILDING IN
AROUND THE SAME TIME AS THE NEXT SYSTEM APPROACHES THE REGION. WENT
ABOVE GUIDANCE ON CLOUD COVER...KEEPING BKN CLOUDS ACROSS MUCH OF THE
CWA AS THIS TRANSITION OCCURS.

CONCERNING THE APPROACHING SYSTEM...A SHORTWAVE IS EXPECTED TO
DEVELOP ALONG THE LEEWARD SIDE OF AN UPPER LEVEL TROUGH WHICH WILL
BE SITTING ALONG THE PACIFIC COAST TODAY. AS THIS SHORTWAVE RACES
OUT AHEAD OF THE TROUGH...IT WILL CREATE A DISTURBANCE WHICH WILL
BEGIN PULLING MOISTURE IN FROM THE GULF COAST AS IT REACHES THE
MISSISSIPPI RIVER VALLEY WEDNESDAY NIGHT/THURSDAY MORNING. ALL
MODELS ARE SHOWING PRECIP REACHING WESTERN AND SOUTH CENTRAL KY
BETWEEN 6 AND 12Z THURSDAY. HOWEVER...DIGGING A LITTLE DEEPER...THIS
SYSTEM IS NOT ALL THAT IS APPEARS. FIRST OFF...KY WILL BE UNDER THE
INFLUENCE OF A STRONG HIGH PRESSURE SYSTEM AT THE SURFACE. FURTHER
MORE...FORECAST SOUNDINGS ARE SHOWING A STRONG LAYER OF DRY AIR NEAR
THE SURFACE IN RESPONSE TO THE SURFACE HIGH. WHAT MOISTURE
ACCOMPANIES THIS SHORTWAVE WILL BE SHALLOW...AND WILL HAVE TO FALL
THROUGH A FAIRLY SUBSTANTIAL AMOUNT OF LOW LEVEL DRY AIR. AFTER
COLLABORATION WITH SURROUNDING OFFICES...DECIDED TO SUBSTANTIALLY
DROP POPS FROM GUIDANCE. SINCE MODELS WERE PLACING THE BEST
POTENTIAL FOR PRECIP ACROSS OUR SW COUNTIES IN THE CWA...DID KEEP
SLIGHT CHANCES HERE. HOWEVER FOR EVERYWHERE ELSE...WILL MORE THAN
LIKELY SEE A SPRINKLE/FLURRY EVENT BASED ON THE GFS AND NAM
SOUNDINGS. THE SHORTWAVE WILL QUICKLY PHASE OUT ACROSS KY...WITH ANY
LINGERING PRECIP EXPECTED TO END THURSDAY EVENING...THOUGH SOME MID
LEVEL CLOUDS WILL LIKELY STICK AROUND.

FAIRLY ZONAL FLOW AND ABUNDANT CLOUD COVER ACROSS THE REGION WILL
WORK TO KEEP FAIRLY STEADY TEMPS IN THE FORECAST FOR THE NEXT 36 TO 48
HOURS. HIGHS WILL BE IN THE UPPER 30S AND LOW 40S...WITH A FAIRLY
SMALL DIURNAL DROP TO THE UPPER 20S TO AROUND 30 DURING THE
OVERNIGHT.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 441 AM EST WED DEC 17 2014

THE MODELS ARE IN GOOD AGREEMENT WITH A PROGRESSIVE LONG WAVE PATTERN
TO HOLD ON THROUGH THE END OF THE WEEK...FOLLOWED BY STRONGER
AMPLIFICATION INTO EARLY NEXT WEEK. SMALL SCALE FEATURES WITHIN THE
LONG WAVE PATTERN HAVE COME INTO BETTER AGREEMENT THROUGH THE
WEEKEND...WITH MUCH LESS AGREEMENT INTO EARLY NEXT WEEK. THE BLENDED
GUIDANCE OFFERED A GOOD COMPROMISE AND STUCK FAIRLY CLOSE TO IT.

A DAMPENING SHORT WAVE TROUGH WILL BE EXITING ACROSS THE OHIO VALLEY
EARLY IN THE PERIOD...WITH A FEW FLURRIES/SPRINKLES LINGERING IN THE
NORTHEAST KENTUCKY EARLY THURSDAY EVENING. MEANWHILE...THE MAIN SOUTHERN
STREAM TROUGH WILL BE MOVING ALONG THE GULF COAST AND THEN EVENTUALLY
SWING MORE TOWARDS THE SOUTHERN APPALACHIANS THROUGH THE END OF THE
WEEKEND. THE ASSOCIATED SURFACE LOW TRACK HAS CONTINUED FURTHER
SOUTH. THERE HAS ALSO BEEN A WEAKER TREND WITH THIS SYSTEM. THE ECMWF
AND GFS CONTINUE TO STICK TO THEIR DIFFERING THERMAL PROFILES...WITH
THE ECMWF COLDER AND SUPPORTIVE OF AT LEAST A LITTLE SNOWFALL UP
NORTH...WHILE THE GFS MAINTAINS ITS MAINLY ALL RAIN SOLUTION. AS
SUCH...WILL KEEP A GENERAL BLEND OF BOTH SOLUTIONS GOING...ALLOWING
FOR A LITTLE SNOW GENERALLY NEAR AND NORTH OF THE MOUNTAIN PARKWAY.

AFTER A DRY FRIDAY...PRECIPITATION WILL MOVE INTO EASTERN KENTUCKY LATE
FRIDAY NIGHT INTO SATURDAY FROM SOUTHWEST TO NORTHEAST...BEFORE
DIMINISHING INTO SATURDAY NIGHT. SUNDAY INTO MONDAY LOOK DRY AS HIGH
PRESSURE AT THE SURFACE TAKES HOLD. DEEP TROUGHING WILL THEN TAKE
SHAPE ACROSS THE CENTRAL CONUS. THERE IS DISAGREEMENT IN THE
EVOLUTION AND TIMING OF A LIKELY STRONGER SURFACE SYSTEM TO CONTEND
WITH FROM LATE MONDAY NIGHT ONWARD. STUCK CLOSE TO THE BLENDED
GUIDANCE GIVEN THE LOWER CONFIDENCE THIS FAR OUT...WITH CHANCES OF
SHOWERS RETURNING TO THE FORECAST FOR MONDAY NIGHT AND TUESDAY.

TEMPERATURES WILL AVERAGE BELOW NORMAL THROUGH THE WEEKEND...BEFORE
MODIFYING TO NEAR NORMAL THROUGH EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 739 AM EST WED DEC 17 2014

LOW LEVEL MOISTURE REMAINS TRAPPED BY A STRONG SUBSIDENCE INVERSION
AS WE HEAD INTO THE MORNING HOURS ACROSS EASTERN KY. AREAS OF DRIZZLE
AND EVEN SOME ISOLATED FLURRIES ARE POSSIBLE TO START OFF THE TAF
PERIOD. WHILE MOST TAF SITES CONTINUE TO FLUCTUATE BETWEEN IFR AND
MVFR CIGS...KJKL HAS DROPPED TO AROUND 300FT DUE TO SOME HEAVIER
PRECIP THAT IS CURRENTLY MOVING ACROSS THE TAF SITE. IN
GENERAL...EXPECT DRY AIR TO FINALLY MAKE IT TO THE SURFACE DURING THE
LATE MORNING/EARLY AFTERNOON HOURS...ALLOWING PRECIP TO END...BUT BKN
MVFR CLOUDS TO CONTINUE. BY THIS EVENING...MODELS ARE SHOWING THE LOW
CLOUDS FINALLY SCATTERING OUT. ANOTHER DISTURBANCE WILL THEN MOVE
INTO THE REGION OVERNIGHT TONIGHT...BRINGING THE POTENTIAL FOR SOME
LIGHT SNOW LATE TONIGHT/EARLY TOMORROW MORNING FOR KSME AND
KLOZ. HOWEVER...LOW LEVEL DRY AIR WILL MAKE IT HARD FOR THE PRECIP TO
ACTUALLY REACH THE SURFACE. THEREFORE CONFIDENCE IS TOO LOW TO
MENTION IN TAFS AT THIS TIME. FINALLY...STRONG WINDS ALOFT MAY BE OF
CONCERN OVER THE NEXT 24 HOURS. AN UPPER LEVEL JET HAS SET UP ACROSS
KY...AND WILL BRING CONTINUED STRONG WESTERLY FLOW IN THE MID AND
UPPER LEVELS. THE STRONG SUBSIDENCE INVERSION IN PLACE SHOULD KEEP
WINDS LIGHT WITHIN THE FIRST FEW THOUSAND FEET AGL.

&&

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

$$

UPDATE...JMW
SHORT TERM...JMW
LONG TERM...GEOGERIAN
AVIATION...JMW






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