FXUS63 KPAH 252052
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
249 PM CST WED NOV 25 2009

.SHORT TERM... /TONIGHT THROUGH SATURDAY/
MAIN CONCERN CONTINUES TO BE SMALL CHANCES OF PRECIPITATION THROUGH 
THURSDAY EVENING.

AN UPPER-LEVEL IMPULSE WILL SWEEP EASTWARD THROUGH THE QUAD STATE 
LATE THIS AFTERNOON THROUGH EARLY THIS EVENING...THEN LATE TONIGHT 
THROUGH THURSDAY EVENING...THE PRIMARY UPPER-LEVEL LOW/TROUGH WILL 
PIVOT THROUGH THE REGION.

THE 12Z MODELS ARE IN FAIRLY GOOD AGREEMENT ON THESE FEATURES...BUT 
THE TIMING OF ASSOCIATED CLOUD COVER AND ANY CHANCE OF PRECIPITATION 
IS UP FOR DEBATE. TRIED TO LOOK UPSTREAM AS MUCH AS POSSIBLE FOR 
NEAR TERM TRENDS WITH THE INITIAL IMPULSE. A BAND OF MID-LEVEL 
CLOUDS SHOULD SHIFT EASTWARD THROUGH THE REGION VERY SOON...BUT THE 
LOWER RAIN-PRODUCING CLOUDS CURRENTLY REMAIN NORTHWEST OF KSTL. FEEL 
THAT ANY MEASURABLE PRECIPITATION IS LIKELY TO REMAIN NORTH OF OUR 
AREA THROUGH THIS EVENING...BUT LEFT A SLIGHT CHANCE OF RAIN IN 
NORTHERN PORTIONS OF SOUTHERN ILLINOIS JUST TO FIT IN 
COLLABORATION-WISE. 

THERE SHOULD BE A BRIEF PERIOD OF CLEARING TOWARD MIDNIGHT BEFORE 
THE MORE SOLID CLOUD SHIELD ASSOCIATED WITH THE MAIN LOW/TROUGH 
BEGINS TO SPREAD SOUTHWARD INTO THE AREA TOWARD MORNING. ALL BUT 
WESTERN PORTIONS OF SOUTHEAST MISSOURI SHOULD SEE OVERCAST/BROKEN 
CONDITIONS BY LATE MORNING THURSDAY. 

AN EVALUATION OF 12Z NAM AND GFS SOUNDINGS INDICATES A PERIOD OF 
LIFT...RESULTING IN NEAR SATURATION THROUGH A SIGNIFICANT DEPTH OF 
THE TROPOSPHERE...SWEEPING EASTWARD ALONG THE I-64 CORRIDOR FROM 
MID-MORNING INTO THE MID AFTERNOON HOURS THURSDAY. THE LIFT IS NOT 
TERRIBLY STRONG OR LONG-LIVED...AND TRUE SATURATION IS 
QUESTIONABLE...SO DO NOT FEEL SIGNIFICANT POPS ARE WARRANTED. IT MAY 
END UP BEING A FLURRY/SPRINKLE EVENT...RATHER THAN MEASURABLE RAIN 
OR SNOW. 

THE SOUNDINGS INDICATE THAT SNOW SHOULD COME CLOSE TO REACHING THE 
GROUND...WITH MELTING DEPENDING ON HOW MUCH WARMING THERE WILL BE AT 
THE SURFACE. WITH CLOUDS EXPECTED ALL DAY LONG IN THE NORTH...LITTLE 
WARMING IS LIKELY...WITH SOME AREAS POSSIBLY NOT REACHING 40 
DEGREES. THEREFORE...WILL MENTION RAIN OR SNOW...BUT GROUND 
TEMPERATURES WILL BE TOO WARM FOR ANY ACCUMULATIONS...IF A LITTLE 
SNOW BURST DOES OCCUR. ALL MODEL GUIDANCE INDICATES THAT THE LIFT 
SHOULD BE EAST OF THE AREA BY 00Z FRIDAY...WHETHER OR NOT SKIES HAVE 
CLEARED BY THEN. THEREFORE HAVE REMOVED ALL PRECIPITATION FOR 
THURSDAY EVENING.

AS FOR NEAR TERM TEMPERATURES...TRIED TO STAY ON THE WARM SIDE 
TONIGHT WITH PERIODIC CLOUDS...AND WEST WINDS. COLD ADVECTION WILL 
NOT TAKE READINGS MUCH BELOW 40 IN MOST PLACES. AS PREVIOUSLY 
STATED...HAVE GONE ON THE COLD SIDE FOR HIGHS TOMORROW. WILL LIKELY 
HAVE A FREEZE THURSDAY NIGHT...SO IT WILL BE RATHER COLD FOR THOSE 
HEARTY BLACK FRIDAY SHOPPERS. SOUTH WINDS DEVELOP FRIDAY...AS 
SURFACE HIGH PRESSURE SETTLES SOUTH OF THE AREA. SO A NICE WARM UP 
WILL BEGIN FRIDAY.

.LONG TERM... /SATURDAY NIGHT THROUGH WEDNESDAY/
THE FORECAST FROM LATE THANKSGIVING WEEKEND INTO EARLY NEXT WEEK 
REMAINS CHALLENGING GIVEN THE MYRIAD OF OPERATIONAL MODEL SOLUTIONS. 
THE PERIOD WILL START WITH DEVELOPING SOUTHWESTERLY FLOW AHEAD OF AN 
ELONGATED TROUGH EXTENDING FROM THE NORTHERN PLAINS INTO THE DESERT 
SOUTHWEST. AS THIS TROUGH PROGRESSES EAST...RETURN MOISTURE DRAWN 
NORTHWARD FROM THE GULF WILL LEAD TO AN INCREASING CHANCE OF RAIN ON 
SUNDAY. 

DIFFERENCES IN THE GFS/ECMWF GUIDANCE EMERGE EARLY NEXT WEEK IN 
THEIR HANDLING OF THIS TROUGH. SOME SOLUTIONS SPLIT THE TROUGH... 
CLOSING OFF A LOW IN THE SOUTHERN STREAM WHILE KEEPING THE NORTHERN 
STREAM MUCH MORE PROGRESSIVE. OTHERS ARE MORE PROGRESSIVE WITH THE 
ENTIRE TROUGH...QUICKLY SHIFTING IT TO THE EAST OF THE AREA BY MID 
WEEK. THE MOST RECENT HANDFUL OF OPERATIONAL GFS RUNS HAVE BEEN 
ABYSMALLY INCONSISTENT WITH THE EVOLUTION OF THIS PATTERN...AND A 
LOOK AT THE INDIVIDUAL ENSEMBLE MEMBERS ONLY FURTHER UNDERSCORES 
THIS. ON THE OTHER HAND...THE RUN-TO-RUN CONSISTENCY OF THE ECMWF IS 
MUCH BETTER...AND ACTUALLY HAS SOME SUPPORT IN THE GFS ENSEMBLE MEAN.

AS A RESULT...WE HAVE LEANED HEAVILY ON THE 00Z AND 12Z ECMWF FOR 
THIS FORECAST PACKAGE. CONSEQUENTLY...THE BEST CHANCE OF RAIN STILL 
APPEARS TO BE SUNDAY NIGHT AND MONDAY AS A COLD FRONT WORKS ITS WAY 
EAST ACROSS THE REGION. DWINDLING MOISTURE BEHIND THE FRONT WILL 
RESULT IN DECREASING RAIN CHANCES MONDAY NIGHT...WITH ONLY SLIGHT 
CHANCES LINGERING OVER MAINLY THE PENNYRILE REGION ON TUESDAY. HIGH 
PRESSURE SHOULD TAKE HOLD BY THE MIDDLE OF NEXT WEEK...RESULTING IN 
DRY CONDITIONS TO ROUND OUT THE SEVEN DAY FORECAST PERIOD.

&&

.AVIATION...
WILL SEE A COUPLE OF SWATHS OF LOW VFR/MVFR CEILINGS ROTATE EASTWARD 
THROUGH THE AREA OVER THE NEXT 24 HOURS. THE FIRST WILL BE CENTERED 
ABOUT 00Z...AND SHOULD GENERALLY STAY VFR. NOT CONFIDENT ON THE 
SOUTH/SOUTHWESTWARD EXTENT OF THE CLOUD BAND...BUT IT SHOULD BE OF 
LITTLE CONCERN TO AVIATION. 

THE SECOND WILL MOVE THROUGH THURSDAY MORNING INTO THE AFTERNOON 
HOURS. THIS WILL BE THE STRONGER IMPULSE AND COULD RESULT IN MVFR 
CEILINGS...ESPECIALLY IN THE NORTH. SOME VERY LIGHT RAIN COULD ALSO 
RESULT IN THE NORTH INCLUDING THE KEVV TAF. 

SHOULD SEE SOME NICE MIXING BOTH THIS AFTERNOON AND THURSDAY 
MID-MORNING ON. GUSTS MAY APPROACH 20KTS THURSDAY...BUT THEY SHOULD 
BE LOWER AND LESS PREVALENT THIS AFTERNOON.

&&

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

$$

SHORT TERM......DRS
LONG TERM.......RP
AVIATION........DRS