FXUS63 KPAH 100004 AAA
AFDPAH

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PADUCAH KY
604 PM CST WED DEC 9 2009

.UPDATE...
DISCUSSION FOR 00Z THURSDAY ROUTINE TAF ISSUANCE. NO UPDATE TO
PUBLIC DISCUSSION SECTION.

&&

.DISCUSSION...
MAIN CONCERNS ARE WIND CHILLS TONIGHT...AND THEN POP POTENTIAL
FRIDAY THROUGH TUESDAY.

DEEP SURFACE LOW PULLING AWAY FROM THE REGION THIS AFTERNOON...AND 
WINDS HAVE DROPPED TO BELOW ADVISORY CRITERIA...SO THE WIND ADVISORY 
WILL BE ALLOWED TO EXPIRE AS SCHEDULED AT 3 PM. WINDS WILL CONTINUE 
TO BE QUITE STRONG AND GUSTY TONIGHT...AS SURFACE HIGH PRESSURE 
BUILDS IN TO OUR SOUTHWEST. COLD...DRY ADVECTION WILL CONTINUE 
THROUGH THE NIGHT AND MUCH OF THURSDAY. GENERALLY FOLLOWED THE 
COLDER MET NUMBERS TONIGHT AND THURSDAY. RESULTANT WIND CHILLS IN 
THE 09Z-15Z TIMEFRAME WILL BOTTOM OUT FROM ZERO TO 10 ABOVE 
THROUGHOUT THE AREA. WILL CONTINUE TO HIGHLIGHT THIS COLDEST AIR OF 
THE SEASON IN THE HWO AND ONLINE. 

THURSDAY NIGHT WILL SEE THE SURFACE HIGH SETTLE OVER THE QUAD STATE 
REGION. SO GOOD RADIATIONAL COOLING WITH A VERY DRY AIRMASS IN PLACE 
WOULD TYPICALLY LEAD TO THE COLDEST NIGHT OF THIS COLD 
OUTBREAK...BUT GUIDANCE IS HARDLY COLDER THAN TONIGHT. WILL LEAN 
TOWARD COOLER MET GUIDANCE...BUT WILL NOT BE SURPRISED IF IT ENDS UP 
BEING COLDER THAN ALL GUIDANCE.

FOR FRIDAY THROUGH TUESDAY...THE FLOW ALOFT BECOMES NEARLY 
ZONAL...BUT REMAINS QUITE FAST. A PAIR OF DISTURBANCES WILL IMPACT 
THE AREA...ONE SATURDAY INTO SUNDAY...AND THE OTHER STRONGER ONE 
MONDAY INTO TUESDAY. THE ECMWF AND GFS SEEM TO BE TRENDING DRIER AND 
FASTER WITH THE SECOND SYSTEM. HOWEVER...WITH THE ARCTIC AIRMASS IN 
PLACE...IT WILL BE DIFFICULT TO GET DECENT MOISTURE RETURN AHEAD OF 
EITHER ONE. THE MODELS ARE SPITTING OUT LOTS OF LIGHT QPF THROUGHOUT 
THE PERIOD FROM SATURDAY NIGHT THROUGH MONDAY NIGHT. 

COULD EASILY SPREAD 20-30 POPS THROUGHOUT THE AREA FROM SATURDAY 
THROUGH TUESDAY...BUT TRIED TO CONFINE POPS TO 2 DISTINCT PERIODS. 
GENERALLY FOLLOWED THE 12Z GFS...WHICH SATURATES THE LOWEST 6-9KFT 
OVER MUCH OF THE AREA IN RETURN FLOW BY SATURDAY AFTERNOON...AND 
THEN KEEPS IT IN PLACE THROUGH THE NIGHT AND INTO SUNDAY MORNING. 
MODEL SOUNDINGS INDICATE THAT THE TEMPERATURES WOULD BE ABOVE 
FREEZING THROUGHOUT THE UNSATURATED LAYER...SO WARM RAIN PROCESSES 
WOULD LEAD TO OVERGROWN DRIZZLE...IF IT HAPPENS AT ALL. KEPT 
PRECIPITATION ALL RAIN FOR NOW...WITH LOWS SATURDAY NIGHT MAINLY IN 
THE MIDDLE 30S.

THE OTHER POP PERIOD IS FROM MONDAY INTO TUESDAY. BOTH THE ECMWF AND 
GFS INDICATE A SHARPER SYSTEM MOVING THROUGH THE REGION MONDAY. THE 
GFS HAS ANOTHER ARCTIC AIRMASS COMING IN BEHIND THE ASSOCIATED COLD 
FRONT...WHILE THE ECMWF DOES NOT. DESPITE THIS DIFFERENCE...THEY 
BOTH BRING THE FRONT THROUGH THE REGION MONDAY. THERE WILL BE LITTLE 
MOISTURE FOR THIS SYSTEM TO WORK WITH...SO WILL KEEP POPS IN THE 
20-30 RANGE. 

TUESDAY WILL PROBABLY BE DRY...BUT WILL KEEP THE POPS JUST TO MAKE 
SURE THE MODELS ARE CONSISTENT. MENTIONED SOME RAIN OR SNOW IN THE 
NORTH FOR LATE MONDAY NIGHT AND TUESDAY...WHEN SOME SUB-FREEZING AIR 
COULD REACH THE AREA. HOWEVER...FEEL THAT MOST OF THE 
PRECIPITATION...IF THERE IS ANY...WILL BE RAIN AND WILL BE OUT OF 
THE WAY BEFORE THE FREEZING AIR ARRIVES.

&&

.AVIATION...
KCGI AND KPAH TAF SITES WILL SEE VFR CONDITIONS THROUGHOUT THE
FORECAST PERIOD. THE MAIN IMPACT THROUGH 06Z THURSDAY WILL BE A
COMBINATION OF A NARROW CIRRUS DECK MOVING EAST-NORTHEAST FROM
AR/TN...AND A BRIEF INTRUSION OF A STRATOCUMULUS DECK WORKING
SOUTHWARD FROM SRN IL. ONCE THE MIXING LAYER DROPS BELOW 2KFT AGL
LATER TONIGHT...WIND GUSTS SHOULD BE MINIMIZED AT THE
SURFACE...ALONG WITH THE LOSS OF ANY CLOUDS.

FOR KEVV AND KOWB...KEPT HIGH MVFR CEILINGS IN PLACE THROUGH THE
FIRST 12-14 HOURS OF THE FORECAST PERIOD...ALONG WITH A
CORRESPONDING WIND GUSTS. ONCE THE WINDS SHIFT SLIGHTLY TO THE
SOUTHWEST THURSDAY MORNING...WIND SPEED/GUSTS SHOULD DIMINISH
SIGNIFICANTLY ALONG WITH THE LOSS OF CLOUD COVER AS WARM AIR
ADVECTION MOVES OVER THE AREA.

FOR NOW...LIGHT SNOW/FLURRIES SHOULD REMAIN JUST NORTH OF THE
KEVV/KOWB TAF SITES THIS EVENING...SO NO MENTION WAS INCLUDED IN
THE TAFS AT THIS TIME.

&&

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

$$

SMITH