Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 132242
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
642 PM EDT SAT SEP 13 2014

.UPDATE...
ISSUED AT 457 PM EDT SAT SEP 13 2014

BASED ON TRENDS IN SATELLITE IMAGERY...HAVE SLOWED THE DECREASE IN
CLOUDS OVER OUR SE COUNTIES THIS EVENING.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 342 PM EDT SAT SEP 13 2014

A DISTURBANCE MOVING ACROSS THE LOWER GREAT LAKES HAS RESULTED IN A
COLD FRONT EXPANDING DOWN ALONG THE ATLANTIC COAST. MOISTURE
ASSOCIATED WITH THIS SYSTEM LED TO WIDESPREAD CLOUD COVERAGE ACROSS
MUCH OF THE EASTERN US...INCLUDING THE OHIO RIVER VALLEY THROUGH THE
MORNING HOURS. AN AREA OF STRONG SUBSIDENCE/DRY AIR IS CURRENTLY
SHOWING UP ON WATER VAPOR AND VISIBLE IMAGERY FLOWING IN FROM THE
CENTRAL PLAINS AND INTO THE OHIO RIVER VALLEY THIS AFTERNOON.
CURRENTLY...CLOUDS ARE BREAKING UP ACROSS LMK/S CWA...WITH JKL
EXPECTED TO FOLLOW SUIT LATE THIS AFTERNOON AND EVENING. CLOUD COVER
KEPT HIGH TEMPS AT BAY TODAY...BUT SOME BRIEF CLEARING /ESPECIALLY IN
THE NORTH/ BEFORE SUN DOWN COULD BE ENOUGH TO BOOST TEMPS UP ANOTHER
COUPLE DEGREES BEFORE ALL IS SAID AND DONE.

SURFACE HIGH PRESSURE...AND ZONAL FLOW WILL TAKE HOLD FOR THE
REMAINDER OF THE SHORT TERM. UNLIKE LAST NIGHT...CLEARING SKIES WILL
LEAD TO OPTIMAL RADIATIONAL COOLING /ESPECIALLY IN THE NORTH WHERE
CLEARING IS EXPECTED TO OCCUR FIRST/ AND ALLOW TEMPS TO DROP TO WELL
BELOW NORMAL FOR THIS TIME OF YEAR. OVERNIGHT LOWS COULD VERY
POSSIBLY DROP INTO THE UPPER 40S ACROSS THE NORTHERN HALF OF THE
CWA...AND LOW TO MID 50S ACROSS THE SOUTHERN HALF. FOR
TOMORROW...CONVECTION FROM THE STATIONARY FRONT NEAR THE ATLANTIC
WILL EXPAND DURING THE DAY. UNLIKE PREVIOUS DAYS...LATEST MODEL RUNS
ARE STILL SUPPORTING THERE NOT BEING QUITE ENOUGH FORCING FOR THIS
MOISTURE TO MAKE IT BACK INTO FAR SE KY. SO KEPT WITH PREVIOUS
FORECAST/S IDEA OF LEAVING OUT ANY MENTION OF PRECIP HERE.
OTHERWISE...DRY AIR AND HIGH PRESSURE WILL PREVAIL...WITH WRLY WINDS
ALOFT AND NRLY WINDS AT THE SURFACE CONTINUING TO ADVECT IN COLDER
AIR. HIGHS TOMORROW WILL BE SLIGHTLY WARMER THAN TODAY JUST GIVEN
THE FACT THAT THE SUN WILL PLAY MORE OF AN INFLUENCE. HOWEVER...THEY
WILL STILL BE QUITE BELOW NORMAL...ONLY REACHING THE LOW TO MID 70S
ACROSS THE REGION.

AS FAR AS FOG IS CONCERNED OVERNIGHT...SEVERAL FACTORS LED TO THIS
NOT BEING INCLUDED IN THE FORECAST. FIRST IS JUST THE STRONG
SUBSIDENCE THAT IS MOVING INTO THE REGION. NORMALLY THIS MAY LEAD TO
THE ENTRAPMENT OF MOISTURE NEAR THE SURFACE AND ACTUALLY PROMOTE FOG
DEVELOPMENT. HOWEVER...IN THIS CASE THERE IS JUST NOT MUCH MOISTURE
TO WORK WITH. THERE IS SOME DISCREPANCY IN THE LATEST FORECAST
SOUNDINGS. WHILE THE GFS IS POINTING TOWARDS POSSIBLE FOG...THE NAM
IS LEANING MORE TOWARDS A LOW STRATUS DECK...BOTH WITH VERY LITTLE
MOISTURE TO SUPPORT. MORE THAN LIKELY IF ANYTHING DOES
DEVELOP...FAVOR MORE THE LOW STRATUS DECK SOLUTION...BUT EVEN THAT
SHOULD BE PATCHY IF EXISTENT AT ALL. ALSO...THE WIND DIRECTION NEAR
THE SURFACE WILL BE NRLY SHIFTING TO MORE NERLY. THIS DIRECTION IS
GENERALLY NOT VERY CONDUCIVE TO FOG DEVELOPMENT IN THE REGION.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 200 PM EDT SAT SEP 13 2014

THE MODELS ARE IN PRETTY GOOD AGREEMENT ALOFT RIGHT ON THROUGH THE
EXTENDED. FOR THE BULK OF THE TIME...A TROUGH WILL BE PRESENT
THROUGH THE EASTERN HALF OF THE NATION WITH MAINLY WEAK SHORTWAVES
PASSING ABOVE THE OHIO VALLEY IN NORTHWEST FLOW. HOWEVER...AT THE
START OF THE EXTENDED ONE OF THE STRONGER WAVES WILL MOVE THROUGH
JUST NORTH OF OUR AREA MONDAY NIGHT. THE TROUGH FLATTENS OUT A BIT
IN THE WAKE OF THIS WAVE DURING THE MIDDLE PART OF THE WEEK. THE
NEXT CONCENTRATED BATCH OF ENERGY WILL PASS THROUGH THE OHIO VALLEY
TO CLOSE OUT THE WEEK BRINGING SOME BRIEF RESURGENCE TO THE TROUGH.
THE MODEL AGREEMENT DOES START TO BREAKDOWN HEADING INTO THE WEEKEND
WITH THE GFS ERASING THE TROUGH QUICKER THAN THE ECMWF IN RESPONSE
TO STRONGER TROUGHING BUILDING THROUGH THE ROCKY MOUNTAIN STATES.
SLIGHT RIDGING THEN FOLLOWS OVER THE AREA THROUGH THE DAY SATURDAY.
HOWEVER...THERE IS SOME QUESTION CONCERNING THE STABILITY OF THE
DEEPER WESTERN TROUGH SOLUTION FROM THE ECMWF THAT ALSO CASTS DOUBT
ON THE STRENGTH OF THE DOWNSTREAM RIDGE OVER OUR REGION. HOWEVER...
GIVEN THE SIMILARITIES IN THE MODELS...HAVE FAVORED A MODEL BLEND
SOLUTION THROUGH THE FORECAST PERIOD.

SENSIBLE WEATHER WILL FEATURE ONE AREA OF COOL HIGH PRESSURE MOVING
OFF TO THE EAST DURING THE DAY MONDAY WHILE ANOTHER HEADS THIS WAY
FROM THE NORTHERN PLAINS. BETWEEN THESE TWO HIGHS ANOTHER WEAK COLD
FRONT WILL SLIP THROUGH THE OHIO VALLEY AND INTO EAST KENTUCKY
MONDAY NIGHT INTO TUESDAY MORNING. DRIER AIR WILL PRESS SOUTH DEEPER
INTO KENTUCKY DURING THE DAY TUESDAY AND INTO WEDNESDAY. ANOTHER
COOL AREA OF HIGH PRESSURE THEN DESCENDS THROUGH THE GREAT LAKES AND
SETTLES INTO THE OHIO VALLEY ON THURSDAY WITH A LIKELY DRY FRONT AT
ITS LEADING EDGE. THIS HIGH THEN DRIFTS TO THE EAST BEFORE STARTING
TO MODERATE LATER FRIDAY AND INTO THE DAY SATURDAY. ALTHOUGH NONE OF
THESE HIGHS WILL PARK DIRECTLY OVER EAST KENTUCKY...THEY SHOULD BE
STRONG ENOUGH TO KEEP ANY THREAT OF SHOWERS TO A MINIMUM.

THE CR GRID LOAD PROVIDED A GOOD START TO THE FORECAST FOR THE
EXTENDED...THOUGH DID ADJUST THE POPS A TAD TOWARD MORE OF A DIURNAL
TREND EACH DAY AND ALSO TO GO A BIT DRIER LATTER IN THE PERIOD. DID
TWEAK THE LOW TEMPERATURE GRIDS A BIT EACH NIGHT TO REFLECT SOME
MINOR RIDGE AND VALLEY DIFFERENCES THAT WILL PROBABLY BE LARGEST ON
THURSDAY AND FRIDAY NIGHTS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 642 PM EDT SAT SEP 13 2014

EARLY THIS EVENING AN MVFR AND LOW VFR OVERCAST PERSISTED SOUTHEAST
OF A LINE FROM KSME TO KSJS. TO THE NORTHWEST...CLOUDS DECREASED
RAPIDLY...WITH GENERALLY VFR CONDITIONS IN PLACE. THE DECREASE IN
CLOUDS WILL MOVE SOUTHEAST TONIGHT...WITH MOST CEILINGS EXPECTED TO
EXIT INTO VA BY ABOUT 06Z. MOSTLY VFR SHOULD THEN PERSIST THROUGH
THE REMAINDER OF THE PERIOD. SOME DENSE VALLEY FOG MAY DEVELOP
OVERNIGHT...BUT IT WOULD LIKELY BE LIMITED IN COVERAGE TO THE DEEPER
VALLEYS. WINDS WILL NOT BE SIGNIFICANT.

&&

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

$$

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






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