432
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
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