000
FXUS63 KPAH 271731
AFDPAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
1130 AM CST MON DEC 27 2010
.UPDATE...
UPDATED AVIATION SECTION FOR 18Z TAF ISSUANCE WHICH PRIMARILY
INVOLVES CLEARING TRENDS THIS AFTERNOON INTO THIS EVENING. PUBLIC
PRODUCTS HAVE ALREADY BEEN UPDATED WITH SIMILAR THINKING.
&&
.DISCUSSION...
AS THE LARGE EASTERN U.S. VERTICALLY STACKED CLOSED LOW RAPIDLY
MOVE EAST NORTHEAST ALONG THE WESTERN ATLANTIC/NORTHEASTERN U.S.
COASTLINE TODAY THROUGH TUESDAY NIGHT...THE UPPER LEVEL PATTERN
WILL QUICKLY MOVE FROM A SHARPLY AMPLIFIED SHORTWAVE RIDGE TO
ZONAL FLOW ACROSS THE WFO PAH FORECAST AREA.
BY LATE TUESDAY NIGHT INTO WEDNESDAY...BOTH OF THE LATEST RUNS OF
THE DETERMINISTIC GFS/ECMWF NUMERICAL GUIDANCE INTRODUCE A MINOR
PROGRESSIVE SHORTWAVE IN THE CENTRAL AND SOUTHERN PLAINS /KS TO
SWRN TX/. WITH SOUTHERLY FLOW EXPECTED TO ALREADY BE IN PLACE AT
THE SURFACE AND ALOFT STARTING IN THE WEST /SERN MO/ LATER THIS
AFTERNOON...A SLOW INFLUX OF MOISTURE WILL BE IN PLACE WITH THE
AFOREMENTIONED SHORTWAVE TO BE LIFTED TO SATURATION FOR AT LEAST A
SMALL CHANCE FOR PRECIPITATION BY WEDNESDAY MORNING.
THE IMPACT OF INSOLATION /SUNSHINE/...TERRESTRIAL RADIATION AND WARM
AIR ADVECTION TODAY AND INTO TUESDAY WILL BE TEMPERED BY THE
ENERGY THAT WILL BE REQUIRED TO MELT AND EVAPORATE THE EXISTING
SNOW COVER. HOWEVER...GROUND/AIR TEMPERATURES WILL STILL BE COLD
ENOUGH BY TUESDAY NIGHT TO STILL SUPPORT A BRIEF /ALBEIT SMALL/
PERIOD OF MIXED PRECIPITATION THROUGH AT LEAST 10-11 AM CST ON
WEDNESDAY. IN ADDITION...ENOUGH SATURATION WILL BE IN PLACE THAT
THERE MAY BE SOME ADVECTION FOG NORTH OF THE DEVELOPING
PRECIPITATION EARLY WEDNESDAY MORNING. THIS WILL NEED TO BE
MONITORED IN LATER FORECASTS. ANY PRECIPITATION THAT FALLS BY
WEDNESDAY AFTERNOON SHOULD BE ALL RAIN.
THE PERSISTENT CYCLONIC VORTEX THAT HAS HAS BEEN OFF THE GULF OF
ALASKA/NORTHWEST U.S. COASTLINE DURING THE PAST WEEK WILL MOVE
ONSHORE AND BECOME A DOMINANT...BUT SLOWLY PROGRESSIVE THROUGH
FROM WEDNESDAY THROUGH AT LEAST MIDDAY SUNDAY /PER THE LATEST
GFS/ECMWF GUIDANCE/. THIS WILL KEEP THE WFO PAH FORECAST AREA IN A
PERSISTENT AND MOIST SOUTHWESTERLY FLOW UNTIL LATE FRIDAY
NIGHT...WITH A SURFACE COLD FRONT FINALLY MOVES THROUGH ON
SATURDAY...LEADING TO THE INFLUX OF COLDER AIR AT LOW LEVELS AND
BRINGS A RETURN TO A SMALL CHANCE FOR MIXED PRECIPITATION AND
EVENTUALLY A SMALL CHANCE FOR SNOW BEFORE ENDING SATURDAY NIGHT.
THE UPPER LEVEL AND SURFACE FLOW WILL BE PREDOMINATELY
PARALLEL...SO AS THE LEADING EDGE OF THE WESTERN U.S. TROUGH MOVES
INTO THE WFO PAH FORECAST AREA DURING THE LATTER HALF OF THE
WEEK...THE LOCAL AREA WILL EXPERIENCE PERIODIC WAVES OF SHOWERS.
INSTABILITY WILL BE LIMITED...DEPENDING ON THE MINOR SHORTWAVES
TRANSVERSING ALONG THE EASTERN EDGE OF THE TROUGH. WHERE THE
INSTABILITY IS THE GREATEST...A SMALLER CHANCE OF THUNDERSTORMS
/MAINLY ELEVATED/ WERE MAINTAINED IN THE FORECAST.
TO SUM IT UP...THE WFO PAH FORECAST AREA WILL WARM UP TO NEAR OR
ABOVE NORMAL BY MIDWEEK...BUT BECOME INCREASINGLY WET TOWARD THE
END OF THIS YEAR AND THE BEGINNING OF THE NEW YEAR.
&&
.AVIATION...
AT 17Z...THE THICKEST CLOUD COVER APPEARS TO RUN FROM SOUTHERN
ILLINOIS SOUTHWARD THROUGH THE PURCHASE AREA...WITH MORE SOLID LOW
MVFR CLOUDS SPREADING BACK SOUTHEAST OVER THE EVANSVILLE TRI STATE
AS WELL. SATELLITE IMAGERY IS FINALLY SHOWING SOME CLEARING TRYING
TO DEVELOP OVER SOUTHEAST MISSOURI...BUT THE 925MB FLOW FROM THE
BLOOMFIELD MISSOURI PROFILER HAS SHIFTED FROM NEARLY DUE WEST BACK
TO NORTH...WHICH MAY BE AN INDICATION THAT THE CLEARING WILL INDEED
TAKE A BIT LONGER TO PUSH EAST THROUGH THE REGION. DECIDED TO HOLD
MVFR CEILINGS IN AT KCGI UNTIL 20Z...AND NOT CLEAR OUT KOWB UNTIL
02Z.
WINDS WILL BE LIGHT AND VARIABLE THIS AFTERNOON WITH SURFACE HIGH
PRESSURE SETTLING OVER THE AREA. A LIGHT SOUTH OR SOUTHWEST WIND
WILL GRADUALLY DEVELOP OVER ALL AREAS EXCEPT WEST KENTUCKY
TONIGHT...AS THE SURFACE HIGH SHIFTS SOUTHEAST. SOUTH TO SOUTHWEST
WINDS WILL DEVELOP THROUGHOUT THE AREA TUESDAY MORNING...BUT SPEEDS
WILL BE UNDER 10KTS.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
MO...NONE.
IL...NONE.
IN...NONE.
&&
$$
AVIATION....DRS
PUBLIC......SMITH
