Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 230539
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
139 AM EDT WED JUL 23 2014

.UPDATE...
ISSUED AT 139 AM EDT WED JUL 23 2014

CONDITIONS ACROSS THE AREA REFLECT THE CURRENT FORECAST QUITE WELL.
PERHAPS SOME LESSENING OF THE CLOUD COVER IS IN ORDER AS THE MORE
WIDE SPREAD COVER IS STILL UP STREAM. OTHERWISE...THE CURRENT
FORECAST REMAINS ON TRACK AND HAVE UPLOADED THE CURRENT OBS INTO THE
GRIDS.

UPDATE ISSUED AT 1040 PM EDT TUE JUL 22 2014

THE SHOWERS HAVE DRIED UP ACROSS THE ENTIRE AREA BESIDES A SMALL CELL
OVER NORTHERN PULASKI COUNTY. THIS WILL DIMINISH THROUGH 11
PM...LEAVING MOSTLY CLEAR TO PARTLY CLOUDY SKIES OVERHEAD FOR THE
MAJORITY OF THE OVERNIGHT. EXPECT MOISTURE TO INCREASE BETWEEN 4 AND
8 AM...WITH PERHAPS A SMALL UPTICK IN CONVECTIVE ACTIVITY THREATENING
ALONG THE SOUTHEAST TERRAIN. THE LATEST HRRR IS SUGGESTING SOME
ACTIVITY MAKING IT IN FROM THE NORTHWEST BEFORE DAWN...HOWEVER THE
CONVECTIVE OUTCOME LOOKS A BIT QUICK ACCORDING TO THE LATEST
SATELLITE TRENDS...SO STUCK WITH THE INHERITED DRY POPS IN THE
BLUEGRASS FOR NOW. BALMY LOWS OF AROUND THE 70 DEGREE MARK FOR MOST
LOCATIONS STILL LOOK ON TARGET. DID INCORPORATE THE LATEST HOURLY
OBSERVATIONS INTO THE DIURNAL DROP OFF FOR THE REST OF THE NIGHT.
UPDATES HAVE BEEN SENT.

UPDATE ISSUED AT 817 PM EDT TUE JUL 22 2014

CONVECTION IS ON THE DECLINE WITH THE LOSS OF HEATING. WILL HANG ONTO
ISOLATED SHOWERS AND A RUMBLE OF THUNDER FOR ANOTHER HOUR OR TWO...
BEFORE A LULL IS THEN EXPECTED INTO THE OVERNIGHT. AS WEAKER
SOUTHWEST FLOW ENGAGES IN TH LOW LEVELS TOWARDS DAWN...THERE MAY BE A
SMALL INCREASE IN CONVECTION ONCE AGAIN...WHICH THE CURRENT FORECAST
ALREADY HAS WELL IN HAND. UPDATES HAVE BEEN SENT.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 420 PM EDT TUE JUL 22 2014

AS OF LATE AFTERNOON...AN UPPER LEVEL LOW IS MEANDERING ALONG THE
GULF COAST WHILE THE EASTERN EXTENT OF AN UPPER LEVEL RIDGE CENTERED
NEAR THE FOUR CORNERS REGION EXTENDS INTO THE LOWER OH VALLEY REGION.
A SHORTWAVE IS ROTATING ACROSS THE NORTHERN GREAT LAKES AND ONTARIO
WITH ANOTHER UPSTREAM ENTERING NORTHWEST ONTARIO.

THE SHORTWAVES WILL COMBINE TO HELP FORM AN EASTERN CONUS TROUGH
THROUGH THE PERIOD WHILE THE RIDGE AMPLIFIES ACROSS THE ROCKIES. A
SFC LOW ASSOCIATED WITH THE DEVELOPING TROUGH WILL TRACK FROM JUST
NORTH OF THE NORTHERN GREAT LAKES AND INTO THE MARITIMES THROUGH WED
NIGHT WITH THE DEVELOPING TROUGH AND NORTHWEST FLOW PUSHING THE
TRAILING COLD FRONT INTO THE OH VALLEY LATE TONIGHT INTO THE DAY ON
WED. THIS FRONT WILL GRADUALLY CROSS THE REGION LATE ON WED AFTERNOON
INTO WED EVENING.

IN THE MEANTIME...ISOLATED SHOWERS AND POSSIBLY A STRAY THUNDERSTORM
WILL REMAIN POSSIBLE MAINLY UNTIL NEAR SUNSET AND DAYTIME HEATING IS
LOST. THERE WILL BE SOME MINOR HEIGHT FALLS OVERNIGHT AND WITH A
MOIST AIR MASS IN PLACE...A STRAY SHOWER CANNOT BE RULED OUT
OVERNIGHT...BUT THIS WOULD BE FEW AND FAR BETWEEN OTHERWISE...THE
CONSECUTIVELY DRIVEN CU SHOULD DISSIPATE OVERNIGHT AND PATCHY RIVER
VALLEY FOG IS AGAIN ANTICIPATED.

MORE ORGANIZED CONVECTION IS ANTICIPATED AS THE FRONT APPROACHES AND
CROSSES THE REGION AND THE UPPER LEVEL TROUGH DEVELOPS OVER THE
EASTERN CONUS. THIS FRONT AND UPPER LEVEL FORCING FROM THE DEVELOPING
TROUGH WILL INTERACT WITH A MOIST PREFONTAL AIR MASS TO BRING MORE
ORGANIZED CONVECTION TO THE REGION FROM WED AFTERNOON INTO WED NIGHT.
MORNING HEATING WILL BE DE PENDANT ON HOW MUCH CLOUD COVER THERE IS IN
THE AM AND THIS WILL ULTIMATELY DETERMINE INSTABILITY. MODERATE
INSTABILITY IS ANTICIPATED WITH TEMPS IN THE MID 80S TO AROUND 90 AND
DEWPOINTS IN THE UPPER 60S TO AROUND 70. THE LOW LEVEL GRADIENT WILL
BE RATHER WEAK AND SO WILL THE WINDS WHILE THE UPPER LEVEL WINDS WILL
NOT BE ALL THAT STRONG SO SHEAR WILL BE WEAK. PWS IS PROGGED TO CLIMB
1.5 TO 1.8 INCH RANGE FROM MIDDAY WED INTO WED NIGHT...SO STORMS
SHOULD BE ABLE TO PRODUCE LOCALLY HEAVY RAIN. A STRONGER STORM OR TWO
MIGHT ALSO BE ABLE TO PRODUCE STRONG WIND GUSTS. ONCE THE FRONT
CROSSES THE REGION...INSTABILITY WILL DIMINISH AND THE THREAT FOR
THUNDER SHOULD ALSO DIMINISH LATE WED NIGHT.

TEMPS WILL CONTINUE TO BE ABOVE NORMAL THROUGH THE PERIOD...BUT A
COLDER AND DRIER AIR MASS WILL ALREADY BE STARTING TO ADVECT INTO THE
AREA LATE IN THE PERIOD.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 348 AM EDT TUE JUL 22 2014

THE MODELS ARE IN ONLY FAIR AGREEMENT ALOFT THROUGH THE EXTENDED
PORTION OF THE FORECAST. WHILE THEY ALL DEPICT THE ABNORMAL PATTERN
OF A STRONG FOUR CORNERS REGION RIDGE AND DEEP TROUGHING IN THE EAST
CONTINUING THROUGH THE END OF THE WEEK AND INTO THE START OF THE
NEXT WEEK...THEY DIFFER ON THE MAGNITUDE AND TIMING OF THE EVOLVING
EASTERN TROUGH...PARTICULARLY OVER THE WEEKEND AND INTO MONDAY.
SPECIFICALLY...FALLING HEIGHTS OVER KENTUCKY WILL BE THE RULE INTO
THURSDAY NIGHT AS THE RETROGRADING LOW TO THE SOUTH PULLS AWAY AND
THE NORTHERN STREAM SENDS A SERIES OF SHORTWAVES THROUGH THE AREA IN
NORTHWEST FLOW. THIS EASTERN TROUGH PULLS AWAY TO START THE WEEKEND
WITH HEIGHTS CLIMBING TEMPORARILY BEFORE THEY FALL AGAIN IN THE FACE
OF A NODE OF THE LARGE NORTHEAST TROUGH GEARING UP FOR A DIVE INTO
THE UPPER MIDWEST AND OHIO VALLEY. THE 00Z GFS IS MOST AGGRESSIVE
WITH THIS EVOLUTION WHILE THE 12 ECMWF KEEPS ITS CORE WAVE FURTHER
TO THE NORTHWEST AND LAGS THE GFS DEVELOPMENT. HOWEVER...THE LATEST
CMC AND ECMWF ARE TRENDING MORE TOWARD THE GFS. REGARDLESS...
NORTHWEST FLOW WILL DOMINATE THE LOCAL PATTERN AS HEIGHTS FALL INTO
MONDAY MORNING. EVENTUALLY...THE ECMWF CATCHES UP...WITH THE DEEPER
AND MORE WESTERN TROUGH IDEA OF THE GFS BUT SOME SIGNIFICANT
DIFFERENCES REMAIN WITH THE PATTERN OVER THE OHIO VALLEY TO CLOSE
OUT THE WEEK. THE BETTER AGREEMENT EARLIER IN THE EXTENDED SUPPORTS
A BLENDED SOLUTION WHILE THE LARGER SPREAD LATER ON LOWERS
CONFIDENCE SO THAT THE ENSEMBLES AND A SLIGHT LEAN TOWARD THE GFS
ARE PREFERRED SOLUTIONS.

SENSIBLE WEATHER WILL FEATURE AN APPROACHING COLD FRONT SERVING AS A
FOCUSING MECHANISM FOR SHOWERS AND THUNDERSTORMS WEDNESDAY NIGHT
INTO THURSDAY. COOLER AND DRIER AIR WILL FILTER INTO THIS PART OF
THE STATE LATER IN THE DAY THURSDAY PUTTING AN END TO THE CONVECTIVE
CHANCES FROM NORTHWEST TO SOUTHEAST. DRY AND RELATIVELY COOL WEATHER
FOLLOWS INTO THE START OF THE WEEKEND THANKS TO A BRIEF VISIT OF
HIGH PRESSURE. HOWEVER...THE COLD FRONT THAT BROUGHT THE DRIER
WEATHER WILL START TO SURGE NORTH OVER THE WESTERN PARTS OF THE
REGION AND BRING WARMTH...MOISTURE...AND BETTER CONVECTIVE CHANCES
BACK INTO THE AREA ON SATURDAY. A SERIES OF SHORT WAVES AT MID
LEVELS...THE DEVELOPING TROUGH...AND THE SFC FRONTAL STRUCTURE OVER
THE OHIO VALLEY KEEP SHOWER AND THUNDERSTORM CHANCES GOING INTO
SUNDAY AND MONDAY.

THE CR GRID LOAD PROVIDED A DECENT START TO THE FORECAST FOR THE
EXTENDED...THOUGH DID ADJUST THE POPS TO ADD A TINGE OF DIURNAL TO
THE TIMING OF THE CONVECTION. ALSO...TWEAKED THE LOW TEMPERATURE
GRIDS A TAD TO REFLECT RIDGE AND VALLEY DIFFERENCES WEDNESDAY AND
THURSDAY NIGHT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 139 AM EDT WED JUL 23 2014

SKIES ARE CLEARING OUT ACROSS THE AREA AND WITH SOUTHWESTERLY FLOW
BRINGING IN MOIST AIR...SOME FOG WILL DEVELOP IN THE MORNING HOURS.
TAF SITES SHOULD GO DOWN TO AT LEAST MVFR IF NOT SOME IFR TOWARDS
DAWN. JKL IS MORE LIKELY TO SOME VALLEY FOG ADVECTED IN ON STATION.
HEADING INTO THE DAY...CLOUD COVER WILL BE ON THE INCREASE AS A COLD
FRONT MOVES THROUGH. HAVE PUT THUNDER IN THE TAF SITES AND ON STATION
BY 19Z AS THE BEST CHANCE FOR THUNDERSTORMS WILL BE DURING THE
AFTERNOON TOWARDS THE EVENING WITH THE FRONT APPROACHING AS WELL.
MOST LOCATIONS SHOULD GO DOWN TO IFR CONDITIONS WITH THIS DURATION OF
PRECIP. CEILINGS SHOULD THEN BE IFR THROUGH THE REST OF THE TAF
PERIOD AS WELL. WINDS SHOULD BR LIGHT BUT INCREASE OUT OF THE WEST
WITH THE FRONT.

&&

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

$$

UPDATE...SHALLENBERGER
SHORT TERM...JP
LONG TERM...GREIF
AVIATION...SHALLENBERGER





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