FXUS63 KLMK 040456
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1156 PM EST THU DEC 3 2009
...UPDATED AVIATION DISCUSSION...
.SHORT TERM (TONIGHT AND FRIDAY)...
HIGH PRESSURE OVER THE NORTHERN ROCKIES WILL DROP INTO THE SOUTHERN
PLAINS FRIDAY AND WILL HAVE A RIDGE AXIS EXTENDING NORTHEAST UP THE
OHIO RIVER VALLEY. ALOFT AREA WILL CONTINUE UNDER SOUTHWESTERLY FLOW
AS UPPER LOW OVER THE UPPER MS RIVER VALLEY SHIFTS SOUTH AND OPENS
UP.
LOW CLOUDS WILL SLOWLY ERODE THIS EVENING...BUT THEN GIVE WAY TO A
MID/UPPER DECK ROTATING IN AROUND THE LOW. MAY HAVE SOME SPOTS GO
CLEAR...BUT NOT EXPECTING THIS TO LAST FOR LONG. ALSO...WILL HAVE
STEADY ENOUGH WINDS OVERNIGHT TO PREVENT IDEAL RADIATIONAL COOLING.
STILL GIVEN THE COLD AIRMASS BUILDING IN TODAY...EXPECT READINGS TO
FALL TO NEAR THE LOWEST OF THE SEASON SO FAR. KBWG WILL HAVE TROUBLE
GETTING DOWN TO THE 25 THEY HAD TUESDAY MORNING...BUT REST OF THE
SITES WILL BE CLOSE.
FRIDAY SHOULD END UP MOSTLY SUNNY OVER OUR SOUTHERN INDIANA COUNTIES
BUT MID CLOUDS SHOULD CONTINUE ACROSS KENTUCKY...AND WILL WORD AS
PARTLY SUNNY. WITH THE CLOUDS...TEMPERATURES WILL STRUGGLE TO REACH
THE UPPER 30S FOR HIGHS ACROSS THE REGION. PRESSURE GRADIENT WILL
LOOSEN WITH THE RIDGING ACROSS THE AREA...AND EXPECT LIGHTER WEST TO
NORTHWEST WINDS THAN TODAY.
.LONG TERM (FRIDAY NIGHT - THURSDAY)...
FRIDAY NIGHT THROUGH MONDAY NIGHT...
SHORT/MED RANGE MODELS CONTINUE TO BE IN VERY GOOD AGREEMENT WITH
THE FIRST SYSTEM TO AFFECT OUR REGION LATE FRIDAY NIGHT AND EARLY
SATURDAY MORNING. OVERALL TRENDS IN THE MODEL DATA ARE MORE
DECIDEDLY EAST IN THEIR SURFACE TRACK RESULTING IN LESS
PRECIPITATION FOR OUR FORECAST AREA. SFC LOW PRESSURE SYSTEM IS
FORECAST TO MOVE ACROSS THE NORTHERN GULF OF MEXICO AND OFF THE
SOUTHEAST COAST BY SATURDAY MORNING. CYCLONIC CIRCULATION AROUND
THE SYSTEM SHOULD BRING MOSTLY CLOUDY SKIES TO THE EASTERN 2/3RDS OF
OUR REGION FRIDAY NIGHT AND EARLY SATURDAY. PRECIPITATION SHIELD ON
THE LATEST MODEL RUNS ARE EAST OF THE 03/00Z AND 03/06Z RUNS WITH
ONLY A HANDFUL OF OUR SE COUNTIES PERHAPS SEEING A FEW SNOW SHOWERS
WITH THIS SYSTEM. OVERALL...FCST FOR THIS SYSTEM IS VERY SIMILAR TO
THE ONGOING FCST WHERE WE HAVE LOW CHC POPS FOR THE SE SECTIONS. AS
IT STANDS RIGHT NOW...BEST CHANCES OF ANY SNOW WILL BE EAST OF A
LINE FROM TOMPKINSVILLE UP TO RUSSELL SPRINGS. PRECIPITATION IS
EXPECTED TO BE LIGHT AND WITH TEMPS DOWN IN THE UPPER 20S...A VERY
LIGHT ACCUMULATION OF SNOW WILL BE POSSIBLE...MOSTLY AN HALF INCH OR
LESS. BETTER SNOW CHANCES WILL BE LOCATED JUST TO OUR EAST ACROSS
THE HILLS OF EASTERN KY. SYSTEM IS FORECAST TO QUICKLY PULL EAST
WITH SUBSTANTIAL CLEARING TAKING PLACE DURING THE DAY ON SATURDAY.
HIGHS WILL WARM INTO THE MID-UPPER 30S WITH OVERNIGHT LOWS IN THE
LOWER-MID 20S.
HIGH PRESSURE IS THEN FCST TO BUILD INTO THE REGION FOR SUNDAY WITH
MOSTLY SUNNY SKIES EXPECTED. HIGHS WILL SLOWLY MODERATE A BIT WITH
READINGS RANGING FROM THE UPPER 30S TO THE LOWER 40S IN THE NORTH
WITH MAINLY LOWER 40S ACROSS THE SOUTHERN HALF. CLOUDS WILL BE ON
THE INCREASE SUNDAY NIGHT WITH LOWS DROPPING DOWN INTO THE LOWER-MID
30S.
SECOND SYSTEM OF THE PERIOD LOOKS TO QUICKLY SCOOT THROUGH THE AREA
LATE SUNDAY NIGHT AND MONDAY MORNING. EARLIER MODEL RUNS SEEMED A
BIT TOO FAR SOUTH GIVEN THE JET STRUCTURE FORECAST. HOWEVER IT
APPEAR THAT THE 03/12Z EURO AND GFS WANT TO INCREASE THE LOW-LEVEL
JET A BIT AND GET SOME ISENTROPIC LIFT INTO THE REGION LATE SUN
NIGHT. SFC TEMPS LOOK TO STAY CLOSE TO FREEZING WITH CRITICAL
THICKNESSES REMAINING JUST WARM ENOUGH FOR A RAIN SNOW MIX. WHILE
ITS A LOW PROBABILITY AT THIS POINT...THERE ARE SOME INDICATIONS
THAT IF WE STAY COLDER AT THE SURFACE THAN WHAT IS CURRENTLY
FORECAST...WE COULD BE LOOKING AT A PERIOD OF FREEZING RAIN MONDAY
MORNING. SOMETHING TO WATCH OVER THE COMING DAYS FOR SURE...BUT THE
SETUP FROM A CONCEPTUAL MODEL APPROACH CERTAINLY SUPPORTS THIS.
PRECIPITATION LOOKS TO MOVE QUICKLY TO EAST WITH MUCH OF THE AREA
GOING DRY BY MON AFTERNOON. PREVIOUS FCST HIGHS LOOKED GOOD HERE
AND BASICALLY ADJUSTED THEM SLIGHTLY BASED ON THE COMBO OF GFS AND
EURO 2M TEMPS WITH HIGHS IN THE LOWER 40S IN THE NORTH AND MID 40S
IN THE SOUTH. MONDAY NIGHT LOWS SHOULD COOL INTO THE UPPER 20S IN
THE NORTH AND LOWER 30S IN THE SOUTH.
TUESDAY THROUGH THURSDAY...
LONG RANGE MODEL SOLUTIONS CONTINUE TO SHOW SOME SPREAD IN THEIR
SOLUTIONS ALOFT THROUGH THIS PERIOD. MAIN FORECAST CHALLENGE WILL
BE THE NEG TILTED TROF DEVELOPING OVER THE PACIFIC NW AS LARGE
POSITIVE HEIGHT ANOMALY DEVELOPS OVER THE GULF OF AK. AS THE JET
DIVES INTO THE PAC NW...CLOSED H5 LOW DEVELOPS OVER IDAHO AND THEN
ROLLS EASTWARD ACROSS THE NORTHERN PLAINS. THE GFS IS MORE PHASED
THAN THE EURO HERE RESULTING IN MORE OF A FULL WAVE TROUGH MOVING
ACROSS THE CONUS AND A SFC LOW TRACK THAT IS A BIT TO THE SE AND E
OF THE EURO. FOR NOW WE HAVE TRENDED THE FCST CLOSER TO THE 03/12Z
EURO AND THE 00Z EURO ENSEMBLES. WITH THAT SAID...CLOUDS WILL
INCREASE MONDAY NIGHT WITH PRECIP MOVING INTO THE REGION EARLY TUE
MORNING. THERMAL PROFILES ARE SUGGESTIVE OF RAIN AND/OR SNOW MIX AT
ONSET...BUT QUICKLY CHANGING TO RAIN AS SOUTHERLY WINDS AT THE SFC
AND ALOFT PUSH TEMPERATURES UP INTO THE LOWER-MID 40S BY AFTERNOON.
GOOD DOSE OF PRECIPITATION WILL BE TUE NIGHT AND WED AS SFC LOW GOES
TO OUR NORTHWEST. WE'LL BE ON THE WARM SIDE OF THE SYSTEM WITH A
GENERAL COLD RAIN. PRECIPITATION WILL GRADUALLY DIMINISH WED NIGHT
WITH A CHANGEOVER TO SNOW BEFORE ENDING. DRY CONDITIONS ARE
EXPECTED FOR THU AS ZONAL FLOW BECOMES ESTABLISHED ACROSS MUCH OF
THE COUNTRY.
&&
.AVIATION (06Z TAF ISSUANCE)...
QUIET WEATHER IN THE TAFS WITH HIGH PRESSURE IN CONTROL. SCT-BKN AC
STREAMING UP FROM THE SOUTHWEST SHOULD BE ABOUT THE ONLY CLOUD TYPE.
WINDS WILL BE FROM THE WEST AND NORTHWEST AROUND 4 TO 7 KNOTS.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
SHORT TERM........RJS
LONG TERM.........MJ
AVIATION..........13
