FXUS63 KJKL 280117
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
817 PM EST FRI NOV 27 2009

.SHORT TERM.../THE REST OF TONIGHT/...UPDATED

UPDATED THE FORECAST TO SLIGHTLY LOWER THE TEMPERATURES ON THE
RIDGES FOR TONIGHT BASED ON CURRENT OBSERVATIONAL TRENDS. NO FURTHER
UPDATES ARE ANTICIPATED.

THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...

/TONIGHT THROUGH SUNDAY/

LOW CLOUDS ASSOCIATED WITH A DEPARTING WEATHER SYSTEM LINGERED OVER
THE NE PART OF THE FORECAST AREA DURING THE AFTERNOON. THEY WILL
CONTINUE TO THIN OUT...WITH MAINLY CLEAR SKIES BY 00Z. SURFACE HIGH
PRESSURE COUPLED WITH RIDGING BUILDING IN ALOFT WILL THEN PROVIDE
CLEAR OR MOSTLY CLEAR SKIES THROUGH SATURDAY NIGHT. LIGHT WINDS AND A
RETURN OF WARM AIR ADVECTION WILL BRING RIDGE/VALLEY LOW TEMP
DIFFERENCES...ESPECIALLY ON SATURDAY NIGHT.

THE UPPER RIDGE WILL BE FLATTENING TOWARD THE END OF THE PERIOD AS AN
UPPER TROUGH DROPS SE ACROSS THE CONUS. ITS ASSOCIATED SURFACE COLD
FRONT WILL APPROACH FROM THE NW ON SUNDAY. CLOUDS WILL INCREASE
DURING THE DAY. THE WRF MOS SHOWS 20 PERCENT POP IN OUR FAR WESTERN
AREAS ON SUNDAY...WITH LOWER POPS IN THE GFS MOS. WITH AN INHERITED
30 PERCENT POP IN WESTERN COUNTIES...WILL ONLY BACK OFF TO THE
HIGHER WRF POPS AT THIS POINT...WAITING FOR SUBSEQUENT MODEL RUNS TO
SEE IF STILL LOWER POPS ARE WARRANTED.

.LONG TERM.../SUNDAY NIGHT THROUGH FRIDAY/

SPLIT STREAM FLOW ALOFT AT THE START OF THE PERIOD WILL ALLOW FOR A 
POSITIVE TILT TROUGH OVER THE UPPER MIDWEST TO SWING A POTENT COLD 
FRONT THROUGH SUNDAY NIGHT AND MONDAY. MEANWHILE...CUTOFF LOW HANGS 
OUT OVER THE SOUTHWEST CONUS BEFORE EJECTING EASTWARD. WENT WITH 70 
POPS JUST BEFORE DAWN ON MONDAY...HOWEVER IF MODELS REMAIN CONSTANT 
FOR ANOTHER FORECAST CYCLE OR TWO WILL PROBABLY END UP GOING 
CATEGORICAL. THE SYSTEM QUICKLY EXITS THE AREA BY MONDAY NIGHT WITH 
A BRIEF PERIOD OF UPSLOPE FLOW KEEPING SOME POPS LINGERING IN THE 
SOUTHWEST. MOISTURE IS SHALLOW AT THIS POINT...BUT FEEL THAT THERE 
COULD BE JUST ENOUGH TO SQUEEZE OUT A FEW MEASURABLE AREAS OF RAIN 
EARLY MONDAY NIGHT. 

EAST KENTUCKY REMAINS IN NO MAN/S LAND TUESDAY NIGHT THROUGH THE 
FIRST HALF OF WEDNESDAY BEFORE THE CLOSED LOW MENTIONED ABOVE BEGINS 
TO EJECT EASTWARD. HAD HOPES THAT TODAY WOULD BRING A SWING TOWARD 
AGREEMENT ON HOW THIS SYSTEM EVOLVES FOR LATE IN THE FORECAST PERIOD
...HOWEVER THE OPPOSITE HAS OCCURRED WITH RESPECTED MODELS STICKING 
TO THEIR GUNS. GFS TRIES TO SHUNT THE SYSTEM FAR TO THE SOUTH AND 
EAST WITH SURFACE LOW RIDING UP THE SOUTHEAST AND THEN EAST COAST. 
EVENTUALLY THE SOUTHERN SYSTEM PHASES WITH THE NORTHERN STREAM AND 
CREATES A FULL LATITUDE TROUGH AND WOULD MEAN COLDER TEMPERATURES AT 
THE END OF THE FORECAST PERIOD AND BEYOND. THE EURO HAS BEEN 
CONSISTENT IN EJECTING THE SOUTHERN STREAM SYSTEM MORE TO THE 
NORTHEAST WITH A SURFACE LOW RIDING SOMEWHERE NEAR THE CWA. THIS IS 
A WARMER/WETTER SOLUTION FOR THE AREA. FOR NOW WILL CONTINUE TO 
COMPROMISE...WITH AN EMPHASIS ON THE ECMWF CONSISTENCY AND BETTER 
OVERALL PERFORMANCE IN THE LONG TERM. THE ONE THING THAT I CAN HAVE 
CONFIDENCE IN IS THAT MODELS HANDLING OF THE MORE ACTIVE SUBTROPICAL 
JET IS REALISTIC. THE SOUTHERN OSCILLATION INDEX HAS BEEN NEGATIVE 
OVER THE PAST COUPLE OF WEEKS...AND WITH A GENERALLY 10-14 DAY LAG 
BETWEEN NEGATIVE VALUES AND A RAMP UP...ACTIVITY SHOULD CONTINUE. 
INTERACTION BETWEEN THE POLAR AND SUBTROPICAL JETS...POSSIBLE 
PHASING...SHOULD BE THE END RESULT AS TO WHERE THE SURFACE LOW 
DEVELOPS TRACKS.

WITH THE EURO SOLUTION...WILL CONTINUE TO HAVE A PERIOD OF DOWNSLOPE 
DRYING IN THE SOUTHEAST AS POPS INCREASE OVERALL FROM SOUTH TO NORTH 
ON WEDNESDAY. OTHERWISE...WILL GO CHANCE POPS FOR NOW WITH LOW END 
CHANCE IN THE NORTH AND HIGH END CHANCE IN THE SOUTH UNTIL DETAILS 
BECOME MORE CLEAR.

AS FAR AS TEMPERATURES ARE CONCERNED...DID NOT CHANGE MUCH FROM 
PREVIOUS FORECAST AS UNCERTAINTY REMAINS...ESPECIALLY IN THE 
WEDNESDAY THROUGH FRIDAY TIME FRAME. HIGH TEMPERATURES SHOULD STAY 
IN THE UPPER 40S TO AROUND 50 MONDAY THROUGH WEDNESDAY AFTERNOONS AS 
THE MERCURY STRUGGLES TO RECOVER EACH AFTERNOON AFTER COLD FRONTAL 
PASSAGE. COULD SEE SOME LOW TEMPERATURES AROUND AND BELOW FREEZING 
IN THE VALLEYS ON MONDAY AND TUESDAY NIGHTS...WITH RIDGES STAYING IN 
THE UPPER 30S TO AROUND 40 ON TUESDAY NIGHT.
&&

.AVIATION.../00Z TO 24Z/...UPDATED

MAINLY CLEAR SKIES AND UNRESTRICTED VISIBILITY ARE EXPECTED
THROUGHOUT THE PERIOD AS HIGH PRESSURE DOMINATES. 

&&

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

&&

$$

SHORT TERM...HAL/JJ
LONG TERM....SCHOETTMER
AVIATION...JJ