FXUS63 KJKL 061850
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
250 PM EDT SAT SEP 6 2008
.SHORT TERM.../TONIGHT THROUGH MONDAY/...UPDATED
LOW CLOUDS WILL BE SLOW TO DISSIPATE THROUGH THE REST OF THE
AFTERNOON AND EVENING HOURS... AND WILL LIKELY HOLD ON OR REDEVELOP
SOME LATE TONIGHT OVER SOUTHEAST KENTUCKY WITH PLENTIFUL LOW LEVEL
MOISTURE IN PLACE. DRIER AIR WILL GRADUALLY ADVECT IN THROUGH TIME
BUT WITH INCREASING SUBSIDENCE ALOFT OVERNIGHT... THIS SEEMS LIKE A
GOOD SETUP FOR AREAS OF FOG TO DEVELOP... LIKELY BECOMING LOCALLY
DENSE IN OUR RIVER VALLEYS. OTHERWISE... THE ISOLATED SHOWER
ACTIVITY NOW PRESENT SHOULD CONTINUE TO DIMINISH... ESPECIALLY AFTER
THE SUN SETS... AND DO NOT PLAN TO CARRY A FIRST PERIOD POP AT THIS
TIME.
STRONG UPPER LEVEL RIDGE OF HIGH PRESSURE OVER THE WESTERN ATLANTIC
WILL PUSH WESTWARD SOME SUNDAY THROUGH MONDAY AS HURRICANE IKE
SLIDES BY UNDERNEATH. A SHORTWAVE WILL RACE BY TO OUR NORTH ON
SUNDAY COMPLETE WITH A WEAK SURFACE COLD FRONTAL PASSAGE DURING THE
DAY. THE ATMOSPHERE IS TOO DRY FOR ANY RAINFALL WITH THE FEATURE
HOWEVER. SURFACE HIGH PRESSURE WILL THEN BRING FAIR SKIES SUNDAY
NIGHT AND MONDAY.
TEMPS TONIGHT SHOULD REMAIN A LITTLE ABOVE GUIDANCE... ESPECIALLY
WHERE THE CLOUDS HANG ON THE LONGEST OVER SOUTHEAST KENTUCKY. WE
EXPECT LOWS TO REMAIN NEAR SEASONAL NORMS THOUGH TONIGHT AND AGAIN
SUNDAY NIGHT. THE MERCURY WILL JUMP BACK ABOVE NORMAL FOR DAYTIME
HIGHS SUNDAY AND MONDAY AS HEIGHTS RISE ALOFT. HELD EXPECTED HIGHS
UNDER THE WARMEST GFS NUMBERS TOMORROW EXPECTING A LITTLE BIT OF A
SLOW START WITH THE FOG AROUND EARLY. THIS SHOULD BE LESS OF A
HINDRANCE MONDAY AND WITH 850 MB TEMPS APPROACHING 20C... WE SHOULD
HEAD TOWARD 90.
.LONG TERM.../MONDAY NIGHT THROUGH SATURDAY/...UPDATED
COULD BE A RATHER ACTIVE TIME PERIOD...WITH A NUMBER OF SYSTEMS
AFFECTING THE REGION. BUT...IT ALSO COMES WITH A FAIR DEGREE OF
UNCERTAINTY...ESPECIALLY LATE IN THE PERIOD.
EARLY ON...MODELS AGREE ON A COLD FRONT APPROACHING THE REGION FROM
THE NW ON MONDAY NIGHT...AND THEN EXITING TO THE SE TUESDAY EVENING.
THERE LOOKS TO BE ENOUGH MOISTURE AND INSTABILITY ALONG THE FRONT TO
WARRANT AT LEAST CHANCE POPS...WITH THE GREATEST LIKELIHOOD BEING
DURING THE DAY TUESDAY.
BEHIND THIS FRONT...DRIER AIR TRIES TO MOVE IN. THERE IS SOME
CONFLICT BETWEEN THE ECMWF AND GFS AS TO HOW EFFECTIVELY OUR AIR
DRIES OUT. THE GFS IS CONSISTENT RUN TO RUN IN BRINGING CLEARING
SKIES AND DRY WEATHER LATE TUESDAY NIGHT THROUGH WEDNESDAY...AND IS
ALSO BACKED BY ITS 00Z ENSEMBLE. THE ECMWF IS MORE MOIST...SHOWING
THE DRY AIR HAVING A HARD TIME PENETRATING ANY FURTHER SOUTH THAN
KY. HOWEVER...IT DID TREND DRIER FROM THE 12Z FRI RUN TO THE 00Z SAT
RUN. HAVE OPTED FOR A DRIER FORECAST AT THIS TIME WITHOUT ANY PRECIP
ON WED.
WITH SURFACE HIGH PRESSURE QUICKLY SKIRTING BY TO OUR NORTH...WARM
AIR ADVECTION SHOULD RETURN ALREADY WEDNESDAY NIGHT. IT IS NOT CLEAR
HOW SOON WE WILL HAVE ENOUGH MOISTURE PRESENT IN THE WARM AIR
ADVECTION/ISENTROPIC LIFT TO SUPPORT PRECIP. HAVE USED A LONG PERIOD
OF 20 PERCENT POP AT THIS POINT FROM WED NIGHT THROUGH THURSDAY
NIGHT...BUT THAT NUMBER COULD EASILY GO UP OR DOWN IN ANY OF THE
THREE PERIODS.
MODELS ALL BRING ANOTHER UPPER TROUGH AND ASSOCIATED COLD FRONT TO
THE AREA LATE IN THE WEEK...ALTHOUGH THE EXACT TIMING IS STILL
QUESTIONABLE. AT THIS TIME...THE FRONT IS EXPECTED TO MAKE IT SE OF
US LATE FRIDAY OR FRIDAY NIGHT ALLOWING FOR DRIER AIR TO ARRIVE.
HOWEVER...JUST HOW FAR IT GOES AND HOW LONG DRIER AIR STAYS IN PLACE
ARE THE NEXT BIG QUESTIONS. THE ANSWERS TO THESE APPEAR TO LIE WITH
HURRICANE IKE AND ITS EVENTUAL TRACK AND TIMING. IT IS TOO EARLY TO
HAVE ANY KIND OF CONFIDENCE IN THE TROPICAL SYSTEM. HAVE LEFT LOW
POPS IN THROUGH SATURDAY BECAUSE OF THE POTENTIAL INFLUENCE OF IKE.
FOR TEMPS...SAW NO REASON TO STRAY FAR FROM MEX GUIDANCE. IT WAS
NEAR SEASONAL AVERAGES...EXCEPT MAYBE A BIT ABOVE NORMAL FOR LOWS.
&&
.AVIATION.../18Z TO 18Z/
LOW CLOUDS ARE BEGINNING TO LIFT BUT MVFR CIGS WILL LIKELY PERSIST
UNTIL AT LEAST 20Z AT THE TAF SITES... AND LONGER FOR EASTERN
LOCATIONS SUCH AS JKL... PBX AND K22. PLENTIFUL LOW LEVEL MOISTURE
WILL REMAIN IN PLACE TONIGHT AND EXPECT DETERIORATING CONDITIONS
WITH FOG/STRATUS DEVELOPMENT LATE. WILL FOLLOW ALL THE NOW
INCREASINGLY PESSIMISTIC GUIDANCE AND TREND FORECAST CONDITIONS
DOWNWARD AT OUR TAF SITES WITH A TEMPO VLIFR PERIOD FOR SEVERAL
HOURS LATE TONIGHT/EARLY SUNDAY MORNING. SOME DRIER AIR MAY KEEP
CONDITIONS SLIGHTLY BETTER NORTH OF JKL. OTHERWISE... VFR EXPECTED
ONCE FOG BURNS OFF SUNDAY MORNING.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...ABE
LONG TERM...HAL
AVIATION...ABE
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