Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 170627
AFDJKL

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

.UPDATE...
ISSUED AT 116 AM EST WED DEC 17 2014

WITHIN THE LAST COUPLE OF HOURS...DRIZZLE HAS PICKED UP SIGNIFICANTLY
ACROSS THE NORTHERN HALF OF THE CWA...TRANSITIONING TO MORE OF A
SCATTERED RAIN SHOWER EVENT WITH EMBEDDED AREAS OF DRIZZLE. THERE
DOES SEEM TO BE A BACK EDGE TO THIS HEAVIER PRECIP...WHICH IS
CURRENTLY MOVING EASTWARD INTO OUR CWA. AS SUCH...HEIGHTENED WORDING
FROM DRIZZLE TO SCATTERED RAIN SHOWERS...DIMINISHING FROM WEST TO
EAST OVER THE NEXT 6 HOURS AND TRANSITIONING BACK TO DRIZZLE WITH A
FEW ISOLATED AREAS OF HEAVIER RAINFALL POSSIBLE THROUGH 12Z. ALSO
FRESHENED UP THE NEAR-TERM FORECAST FOR TEMPS...DEW POINTS...AND
WINDS...BASED ON THE 5Z OBSERVATIONS.

UPDATE ISSUED AT 1105 PM EST TUE DEC 16 2014

DRIZZLE AND SOME EMBEDDED SHOWERS CONTINUE ACROSS EASTERN KENTUCKY.
THE HOURLY POPS HAVE BEEN INCREASED TO ISOLATED FOR THE NORTH AND
EAST INTO EARLY ON THU. HOURLY TEMPERATURES HAVE BEEN FRESHENED UP
BASED ON RECENT OBSERVATIONS. NO SIGNIFICANT CHANGES WERE NEEDED AT
THIS TIME.

UPDATE ISSUED AT 745 PM EST TUE DEC 16 2014

HOURLY GRIDS HAVE BEEN UPDATED BASED ON RADAR AND OBSERVATION TRENDS.
THIS LED TO LOWERING TEMPERATURES IN THE HIGHEST TERRAIN INITIALLY
ABOVE 2500 FEET. MODEL PLAN VIEW DATA ALSO SUGGESTED SLIGHTLY LOWER
MIN T IN THE HIGHER TERRAIN NEAR BLACK MTN. RAIN SHOWERS CONTINUE
ACROSS THE EASTERN PART OF THE CWA...WITH SOME DRIZZLE FURTHER TO THE
WEST. MODEL DATA SUGGESTS SUFFICIENT MOISTURE FOR DRIZZLE TO LINGER
THROUGH THE NIGHT AND INTO EARLY ON WED. THE HIGHEST TERRAIN SHOULD
COOL ENOUGH FOR CHANCES OF FREEZING DRIZZLE ABOVE 2000 FEET. THIS
THREAT WILL BEGIN FIRST...IN THE NEXT HOUR OR TWO ON TOP OF BLACK MTN
AND THEN GRADUALLY SPREAD TO PINE MOUNTAIN AND POSSIBLY THE LOG
MOUNTAINS.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 315 PM EST TUE DEC 16 2014

19Z SFC ANALYSIS SHOWS A FAIRLY DEEP AREA OF LOW PRESSURE LIFTING
NORTHEAST THROUGH THE EASTERN GREAT LAKES. THE COLD FRONT ASSOCIATED
WITH THIS SYSTEM IS NOW THROUGH EASTERN KENTUCKY AND AS A RESULT
GUSTY WEST WINDS ARE BRINGING IN A COLDER AIR MASS. AS IT DOES SO...
IT IS ALSO GENERATING A SUBSTANTIAL AREA OF DRIZZLE AND LOWER CIGS.
TEMPERATURES VARY FROM THE LOW 40S WEST TO NEAR 50S EAST ACROSS THE
CWA WITH DEWPOINTS IN THE UPPER 30S TO LOWER 40S.

THE MODELS ARE IN DECENT ENOUGH AGREEMENT ALOFT THROUGH THE SHORT
TERM PORTION OF THE FORECAST AS THEY ALL DAMPEN OUT THE CURRENT
TROUGH OVER THE AREA WHILE ABSORBING IT INTO THE MAIN MID LEVEL LOW
OVER THE UPPER MIDWEST. THIS WILL KEEP FAST...WEST TO EAST...FLOW
ABOVE EASTERN KENTUCKY INTO THE DAY WEDNESDAY...THOUGH MODEL
DIFFERENCES START TO MAGNIFY BY DAWN. THE ECMWF IS SLOWER MOVING
THIS MIDWEST LOW EAST COMPARED TO THE GEM AND GFS WHICH WILL ALSO
SERVE TO KEEP OUR HEIGHTS SLIGHTLY SUPPRESSED INTO WEDNESDAY EVENING.
DESPITE THIS...THE PREFERRED ECMWF DOES NOT LAG IN BRINGING THE NEXT
BATCH OF ENERGY INTO THE REGION FROM A QUICK MOVING WAVE PASSING OUT
OF THE SOUTHERN PLAINS. THIS WILL SEEP INTO OUR SOUTHWEST PARTS BY
THURSDAY MORNING. FOR THE FORECAST...FOLLOWED A BLEND OF THE HIGHER
RESOLUTION HRRR AND NAM12 WITH SOME ADJUSTMENT TOWARD THE MAIN
FEATURES IN THE LATEST ECMWF.

A DREARY EVENING AND OVERNIGHT IS ANTICIPATED THROUGH EASTERN
KENTUCKY AS LOW CIGS AND DRIZZLE WILL DOMINATE UNDER A SUBSIDENCE
INVERSION...PARTICULARLY OVER THE NORTHERN HALF THE CWA. THERE IS A
CONCERN THAT THE HIGHER POINTS OF EASTERN KENTUCKY FALL TO
FREEZING...OR A COUPLE OF DEGREES BELOW...BY DAWN GIVEN THE CAA
OVERNIGHT. COMBINED WITH THE AREAS OF DRIZZLE STILL AROUND...THERE
WILL BE A THREAT OF FREEZING DRIZZLE GENERALLY ABOVE 2000 FEET. FOR
THIS...WILL ISSUE AN SPS FROM LATE TONIGHT INTO THURSDAY MORNING FOR
OUR SOUTHEASTERN-MOST COUNTIES WITH THAT HIGHER TERRAIN. THE LOW
CLOUDS WILL PROBABLY HOLD TOUGH INTO THE FIRST PART OF THE DAY
WEDNESDAY BUT THERE COULD BE SOME BREAKUP MAKING FOR A BRIEF PERIOD
OF SUNSHINE DURING THE AFTERNOON AHEAD OF THE NEXT BATCH OF HIGHER
CLOUDS DUE IN HERE LATER THAT EVENING. THESE NEXT CLOUDS WILL QUICKLY
INCREASE AND LOWER THROUGH THE NIGHT WITH EVEN SOME LIGHT RAIN OR
SNOW POSSIBLE BY DAWN THURSDAY...THOUGH TEMPERATURES WILL BE MILDER
THAN TONIGHT IN MOST PLACES.

USED THE BCCONSSHORT AS A STARTING POINT FOR THE T/TD/WIND GRIDS FOR
THE FIRST 20 HOURS BEFORE POPULATING WITH THE SUPERBLEND THEREAFTER.
THESE WERE THEN SUBJECTED TO MINOR ADJUSTMENTS FOR TERRAIN EFFECTS
MAINLY TONIGHT AND WEDNESDAY NIGHT. AS FOR POPS...ENDED UP JUST ABOVE
THE HIGHER MET MOS GUIDANCE TONIGHT GIVEN THE LOW QPF BUT MODERATE
POPS WITH EXTRA EMPHASIS ON DRIZZLE AS PTYPE. ALSO...FOR LATE
WEDNESDAY WENT A BIT HIGHER THEN GUIDANCE IN THE SOUTHWEST GIVEN THE
FAST FLOW REGIME.

.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.
&&

$$

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






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