Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 170926
AFDJKL

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

.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 THROUGH TUESDAY)
ISSUED AT 245 PM EST TUE DEC 16 2014

PROGRESSIVE PATTERN WILL CONTINUE THROUGH THE EXTENDED. THE PERIOD
WILL START AS A MID LEVEL TROUGH CROSSES INTO THE OHIO RIVER VALLEY
ON THURSDAY. MODELS HAVE TRENDED MORE AGGRESSIVE WITH THIS FEATURE
WITH THE 12Z SUITE OF MODELS WITH GFS EVEN SHOWING SOME MODEST LIFT
ABOVE 850MB. THE MAIN LIMITING FACTOR FOR PRECIPITATION ON THURSDAY
WILL BE THE LOW LEVEL DRY AIR. HOWEVER...GIVEN THE DEEP MOISTURE
STARTING AROUND 5KFT...THIS SHOULD BE ENOUGH TO AT LEAST WARRANT A
CHANCE OF MEASURABLE PRECIPITATION REACHING THE GROUND.
HOWEVER...THIS PRECIPITATION MAY DRY UP AS IT TRIES TO PUSH
NORTHWARD THROUGH THE DAY. THUS...PLAN TO GO WITH CHANCE POPS ACROSS
THE SOUTH...TRAILING OFF TO SLIGHT CHANCE IN THE NORTH. ALL OF THIS
PRECIPITATION AS EXPECTED WILL REMAIN LIGHT...BUT SOME SNOWFLAKES
COULD MIX IN AT TIMES THROUGH THE DAY. HIGH PRESSURE WILL PROVIDE
DRY WEATHER THURSDAY NIGHT THROUGH FRIDAY.

THE WEATHER TURNS MORE INTERESTING BY FRIDAY NIGHT THROUGH SATURDAY
AS A SOUTHERN STREAM SHORTWAVE PUSHES EAST ACROSS THE SOUTHERN TIER
OF THE US. THIS SYSTEM IS NOT EXPECTED TO GET MUCH HELP FROM THE
NORTHERN STREAM...AND THUS...NOT MUCH COLD AIR IS EXPECTED TO GET
WORKED INTO THIS SYSTEM. THIS FACT...COMBINED WITH A WEAKENING AREA
OF LOW PRESSURE TRACKING ACROSS THE GULF COAST STATES WILL LIKELY
YIELD VERY LITTLE SNOW POTENTIAL. HOWEVER...WE ARE ON THE NORTH SIDE
OF THIS SYSTEM...WHICH WOULD BE THE BEST SPOT FOR ANY SNOW.
PRECIPITATION IS EXPECTED TO SPREAD INTO THE AREA LATE FRIDAY NIGHT
AND CONTINUE THROUGH SATURDAY. BEST SNOW POTENTIAL MAY BE AT THE
ONSET FRIDAY NIGHT...BUT AGAIN...PRECIPITATION RATES MAY BE FAIRLY
LIMITED...KEEPING SNOW AMOUNTS FROM BEING ALL THAT HIGH. IN
FACT...WE COULD SEE A MIX OF RAIN/SNOW RIGHT THROUGH SATURDAY WITH
VERY LITTLE SNOW ACCUMULATION FOR MUCH OF THE AREA. THE ECMWF
REMAINS THE COLDER OF THE MODELS SUGGESTING BETTER SNOW
POTENTIAL...WHILE THE GFS HAS MAINTAINED ITS ALL RAIN FORECAST.
GOING WITH A COMPROMISE ON HIGHS ON SATURDAY WOULD BE TEMPERATURES
AROUND 40 BY THE AFTERNOON ACROSS MUCH OF THE AREA. ITS POSSIBLE
SOME COOLER READINGS IN THE 30S COULD KEEP MORE SNOW GOING A BIT
LONGER ACROSS THE NORTHERN PORTION OF THE AREA...BUT WITH WEAK
PRECIP RATES...COMBINED WITH ABOVE FREEZING TEMPERATURES...SHOULD
REALLY CUT INTO ANY SNOWFALL POTENTIAL EVEN WITH THE COLDER ECMWF
SOLUTION. PRECIPITATION WILL WIND DOWN BY SATURDAY NIGHT GOING OVER
TO A PERIOD OF LIKELY DRIZZLE.

DRY WEATHER WILL RETURN FOR SUNDAY AND PERSIST INTO THE EARLY PART
OF NEXT WEEK. TEMPERATURES ARE EXPECTED TO REMAIN FAIRLY SEASONABLE
THROUGH THE END OF THE FORECAST PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 127 AM EST WED DEC 17 2014

WHILE AREAS OF DRIZZLE ARE ONGOING ACROSS MUCH OF EASTERN KY...THE
NORTHEAST PORTION OF THE STATE /GENERALLY AREAS NORTH OF THE MOUNTAIN
PARKWAY/... HAVE ACTUALLY SEEN A INCREASE FROM DRIZZLE TO LIGHT RAIN
SHOWERS. EXPECT THIS RAIN TO HAVE LITTLE DIFFERENCE IN IMPACTS TO
THAT OF THE DRIZZLE...SO WILL JUST CONTINUE WITH DRIZZLE MENTION AT
THIS TIME IN TAFS...ESPECIALLY GIVEN THAT THE RAIN SHOWERS SHOULD
TAPER OFF AT KSYM...KJKL...AND KSJS OVER THE NEXT COUPLE HOURS.
MEANWHILE...CIGS SHOULD REMAIN BETWEEN IFR AND MVFR THROUGH THE
REMAINDER OF THE NIGHT...THEN MVFR THROUGH A MAJORITY OF THE DAY
TOMORROW...AT LEAST UNTIL DRY AIR IS FINALLY ABLE TO MIX DOWN TO THE
SURFACE...CUTTING OFF DRIZZLE POTENTIAL...AND SLOWLY BREAKING THE LOW
CLOUD DECK. LATEST GFS FORECAST SOUNDINGS ARE SHOWING THIS OCCURRING
SOMETIME BETWEEN 18 AND 21Z...WHILE THE NAM TRIES TO HOLD ON TO THE
MOISTURE A BIT LONGER. LEANED MORE TOWARDS THE GFS SOLUTION AT THIS
TIME.


&&

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

$$

SHORT TERM...JMW
LONG TERM...KAS
AVIATION...JMW





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