FXUS63 KPAH 080001 AAA
AFDPAH

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PADUCAH KY
601 PM CST MON DEC 7 2009

.UPDATE...
AVIATION DISCUSSION FOR 00Z TUESDAY ROUTINE TAF ISSUANCE. 

NO CHANGE TO PUBLIC SECTION WITH THIS ISSUANCE.

&&

.DISCUSSION...
/LAST ISSUED 203 PM CST MON DEC 7 2009/
AFTER A BRIEF REPRIEVE TODAY FROM ANY WEATHER...OUR NEXT SYSTEM
WILL BE QUICK ON ITS HEELS. MODELS HAVE BEEN ADVERTISING FOR A FEW
DAYS THAT TONIGHT WILL BE DRY...BUT NOW IT APPEARS WITH THE LATEST
RUNS...WE COULD SEE PRECIPITATION CREEP INTO OUR SOUTHERN COUNTIES
SOMETIME AFTER MIDNIGHT TONIGHT...MOST LIKELY DURING THE PREDAWN
HOURS. MOISTURE ADVECTION/ISENTROPIC LIFT WILL COMMENCE LATER
TONIGHT TO OUR SOUTH...AND AFFECT OUR REGION AFTER MIDNIGHT
TONIGHT. WE COULD SEE SOME SLEET IN SOUTHEAST MISSOURI AS THE
PRECIPITATION BEGINS...AS SOUNDINGS LOOK SIMILAR TO WHAT HAPPENED
LAST NIGHT.

IN THE MEANTIME...A STRONG SFC LOW PRESSURE SYSTEM WILL BE
ORGANIZING OVER THE CENTRAL ROCKIES AND MOVING EAST ACROSS THE
CENTRAL PLAINS ON TUESDAY. AS THIS OCCURS...WE WILL SEE OCCASIONAL
RAIN SHOWERS PRETTY MUCH ALL DAY. LOOKING AT SOUNDINGS...WE COULD
SEE SOME SLEET ACROSS PARTS OF SOUTHEAST MISSOURI AND SOUTHWEST
ILLINOIS FOR A FEW HOURS IN THE MORNING...BUT AFTER ABOUT 15Z...IT
SHOULD BE ALL RAIN. 

AS THE SFC LOW HEADS NORTHEAST INTO THE UPPER MIDWEST TUESDAY
NIGHT...OUR CHANCES FOR RAIN WILL BEGIN TO TAPER OFF FROM WEST TO
EAST RATHER QUICKLY. BY 12Z WEDNESDAY...THE SFC LOW IS POSITIONED
OVER LAKE MICHIGAN...SO WE SHOULD BE FREE OF ANY HEAVY
PRECIPITATION AFTER MIDNIGHT ON TUESDAY. THEREFORE...THE LOWER
CHANCES WE ALREADY HAVE GOING FOR THE OVERNIGHT PERIOD STILL LOOK
GOOD. 

THE COLD AIR REALLY STARTS COMING IN WITH A VENGEANCE BY 12Z
WEDNESDAY AND CONTINUES THROUGHOUT THE DAY AND THE PRESSURE
GRADIENT REALLY TIGHTENS AS WELL. WINDS OF 20 TO 30 MPH WILL BE
COMMON WITH HIGHER GUSTS. THEREFORE...WE WILL PROBABLY NEED A WIND
ADVISORY FOR WEDNESDAY. OUR HIGH TEMPERATURE WILL OCCUR IN THE
MORNING...WITH TEMPS DROPPING THROUGHOUT THE DAY. WE BELIEVE THERE
IS NOT ENOUGH MOISTURE TO WARRANT ANY PRECIPITATION DURING THE
DAY...ALTHOUGH COULD NOT RULE OUT A FEW FLURRIES...BUT WILL
CONTINUE WITH A DRY FORECAST AT THIS TIME. BY 00Z THURSDAY...H85
TEMPS DROP DOWN TO -8 TO -13 DEG C ACROSS THE AREA FROM SOUTH TO
NORTH. THEREFORE...IT WILL BE A VERY COLD NIGHT ACROSS THE
HEARTLAND WEDNESDAY NIGHT...AND THURSDAY LOOKS TO BE A DAY SIMILAR
TO LAST FRIDAY...WHEN WE BARELY REACHED THE MID 30S.

FOR THE PERIOD THURSDAY NIGHT THROUGH MONDAY. A BLEND OF THE 12Z
GFS...AND 00Z/12Z RUNS OF THE ECMWF WERE USED FOR THE FORECAST. A
LARGE AREA OF HIGH PRESSURE IS FORECAST TO COVER MUCH OF THE
NATION EAST OF THE MISSISSIPPI RIVER FRIDAY THROUGH SUNDAY. A WEAK
MID TROP SYSTEM IS FORECAST TO MOVE IN FROM THE CENTRAL U.S. LATE
FRIDAY...AND ACROSS THE AREA SATURDAY. PRECIP LOOKS LESS LIKELY
FRIDAY...BUT A SMALL CHANCE STILL EXISTS FRIDAY NIGHT INTO
SATURDAY. KEPT WITH THE LIGHT RAIN OR SNOW/LIGHT SNOW THEME BASED
ON THERMAL PROFILES AND UNCERTAINTY. POPS ARE ONLY 20 PERCENT AS
WELL...BUT MAY NEED TO BE A LITTLE HIGHER SATURDAY. SUNDAY AND
BEYOND...KEPT THE FORECAST DRY. A REINFORCING HIGH PRESSURE AXIS
IS PROGGED TO DEVELOP SOUTHEAST FROM CANADA AND COVER MUCH OF THE
NATION EAST OF THE ROCKIES. THE HIGH WILL MOVE EAST BY LATE MONDAY
WHICH MAY ALLOW A FRONTAL BOUNDARY TO APPROACH. AGAIN...NOT ENOUGH
CONFIDENCE TO INCLUDE ANY POPS YET.

&&

.AVIATION...
VERY DIFFICULT FORECAST WITH THIS ISSUANCE IN TERMS OF DETERMINING
TRANSITION FROM VFR/MVFR CATEGORY TO IFR CATEGORY FOR KCGI/KPAH
TAF SITES THROUGH 09Z TUESDAY. RAPID MOISTURE RETURN UNDER THE LOW
LEVEL INVERSION...IN ADVANCE OF INVERTED TROUGH...WILL COMPLICATE
THINGS ONCE PRECIPITATION RETURNS TO THE TAF SITES BEFORE DAYBREAK
AT KCGI/KPAH...AND CLOSER TO 14Z AT KEVV/KOWB. 

ANY BREAKS IN THE LOW LEVEL CLOUD COVER AT THE BEGINNING OF THE
FORECAST PERIOD SHOULD FILL IN QUICKLY AFTER 09Z AT
KCGI/KPAH. THESE BREAKS SHOULD BE EVIDENT BRIEFLY BETWEEN 09-14Z
AT KEVV/KOWB.

ONCE THE RAIN BEGINS...CEILINGS SHOULD REMAIN AT IFR/LIFR LEVELS
THROUGH 00Z WEDNESDAY AT KCGI/KPAH...AND AT LOW MVFR CEILINGS AT
KEVV/KOWB. DESPITE LIGHT EASTERLY SURFACE WINDS...VISIBILITIES DUE
TO THE RAIN WILL DROP TO IFR LEVELS AT KCGI/KPAH...AND MVFR LEVELS
AT KEVV/KOWB.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
MO...NONE.
IL...NONE.
IN...NONE.
&&

$$

AVIATION...SMITH