FXUS61 KCTP 261205
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
705 AM EST THU NOV 26 2009
.SYNOPSIS...
AREAS OF CLEARING...ALONG WITH LIGHT WIND AND CONSIDERABLE LOW LEVEL
MOISTURE...WILL MAINTAIN AREAS OF DENSE FOG ACROSS MUCH OF CENTRAL
PENNSYLVANIA AND THE SUSQUEHANNA VALLEY THROUGH ABOUT 9 AM TODAY. A
STRONG COLD FRONT WILL CROSS THE REGION LATE THIS THANKSGIVING
AFTERNOON AND EVENING...ACCOMPANIED BY NUMEROUS RAIN SHOWERS. MUCH
COLDER AIR WILL PUSH INTO THE REGION AND COMBINE WITH A POTENT UPPER
AIR DISTURBANCE TO CHANGE THE RAIN SHOWERS TO SNOW SHOWERS LATER
TONIGHT. WINDY AND COLD CONDITIONS WITH SCATTERED MOUNTAIN SNOW
SHOWERS WILL OCCUR THROUGH MUCH OF SATURDAY. A RIDGE OF HIGH
PRESSURE WILL BRING FAIR BUT CHILLY WEATHER FOR MUCH OF SUNDAY
BEFORE ANOTHER COLD FRONT BRINGS A CHANCE FOR RAIN AND SNOW SHOWERS
EARLY NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
IR IMAGERY EARLY THIS MORNING INDICATES A PERSISTENT WEDGE OF CLEAR
SKIES DOWNSTREAM OF THE ALLEGHENIES. THIS CLEARING COMBINED WITH LGT
SFC FLOW AND CONSIDERABLE LLVL MOISTURE HAS RESULTED IN AREAS OF
FG...WITH PATCHY DENSE FG ESP IN THE VALLEYS. SEVERAL SITES HAVE
HOVERED AROUND 1/4SM...AND GIVEN IMPACT TO TRAVEL THIS MORNING HAVE
HOISTED A DENSE FG ADV THRU 9AM. MECHANICAL MIXING WILL REMAIN LOW
THRU 14Z...THEN GRADUALLY INCREASE SWSTRLY FLOW AND SHUD SCOUR OUT
FG IMPROV VSBYS FOR THE SECOND HALF OF THE MORNING. A FEW VALLEYS
COULD SEE PROLONGED REDUCTIONS TO VSBYS AS SOUNDINGS SUGGEST A WEAK
INVERSION THRU 18Z. ELSEWHERE EXPECT MOSTLY CLOUDY WITH A FEW PEAKS
OF SUN BTWN 14-17Z...HOWEVER VERY FEW LOCATIONS AND TIMING IS A
CHALLENGE.
POPS APPEAR TO BE LOW THRU MIDDAY...HOWEVER EXPECT AS FRONTAL BNDRY
APPROACHES FROM THE WEST...PATCHY DZ/LGT SHRA PUSH INTO PORTIONS OF
THE NW CWFA. THEN SLT CHC FOR ALLEGHENIES EARLY THIS AFTN. INCREASED
MOISTURE SLUG ARRIVES AFT 18Z AS TROUGH AXIS SLOWLY PROGRESSES EAST.
MUCH OF THE CWFA WILL REMAIN MILD THRU THE MORNING...TEMPS ACROSS
THE NW PLATEAU SHUD HOVER IN THE M/U 40S. ELSEWHERE EXPECT
L50S...POSSIBLY M50S FOR PORTIONS OF THE LOWER SUSQ.
TONIGHT...
CHALLENGES FOR TONIGHT RESIDE ARND COVERAGE OF PRECIP AND TIMING OF
P-TYPE BECOMING MIXED RASN. 850MB THERMAL TROUGH ARRIVES LATE THIS
AFTN...HOWEVER IT DOESN/T APPEAR TO BE COOL ENUF UNTIL AFT 06Z FRI
WHEN TEMPS OF -5 TO -7 DEG C ARE PROGGED. AS TROUGH AXIS SLOWLY
PIVOTS TOWARDS CENTRAL PA...FLOW TURNS W/NWSTRLY AND INCREASES
UPSLOPE EFFECT SHUD DEVELOP FOR THE ALLEGHENIES. COASTAL LOW WILL
CONTINUE TO DEVELOP AND SLIDE NORTH OFF THE NJ COAST...PUSHING A
SLUG OF PRECIP INTO THE SUSQ-VALLEY.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY/...
THE FIRST SHOT FOR TRUE (THOUGH QUITE ELEVATION DEPENDENT) LAKE
EFFECT/OROGRAPHIC SNOW ACROSS THE NORTHWEST MOUNTAINS AND LAUREL
HIGHLANDS WILL BE ONGOING FRIDAY AS A SHARP AND SLIGHTLY NEG TILT
UPPER TROUGH MOVES ACROSS PENN AND HELPS TO RAPIDLY INTENSIFY LOW
PRESSURE OFF THE MID ATLANTIC/SRN NEW ENGLAND COAST.
AS THIS LOW "BOMBS OUT" (BY 16-18 MB/12 HOURS) EAST OF CAPE COD
LATER FRIDAY...WEST TO NORTHWEST WINDS WILL QUICKLY INCREASE TO
SUSTAINED SPEEDS OF 15 TO 20 MPH WITH GUSTS OF 30 TO 35 MPH TWD
EVENING. DEEPENING MIXED LAYER HEIGHT WILL TAP SOME 40 MPH WINDS
(SEVERAL KFT AGL) FRIDAY NIGHT MAKING IT EVEN MORE WINDY...THANKS TO
THE TOGHT PRESSURE GRADIENT TO THE WEST OF THE 974 MB...POWERHOUSE
OF A LOW THAT WILL BE LIFTING SLOWLY NORTH TWD THE MOUTH OF THE ST
LAWRENCE BY THE MIDDAY HOURS ON SAT.
STILL A BRISK...15 TO 20 MPH SUSTAINED WIND IS ANTICIPATED FOR MUCH
OF SATURDAY ACROSS THE NE HALF OF THE CWA. WINDS WILL BE DIMINISHING
AND BACKING TO A MORE WEST/SW DIRECTION IN THE AFTERNOON ACROSS THE
WRN MTNS.
MADE VERY LITTLE CHANGE FROM PREVIOUS FEW SETS OF GRIDS AND ZONE
PACKAGES WITH RESPECT TO THE POPS...QPF...AND INDIVIDUAL/12 HOUR
SNOW TOTALS. STORM TOTAL SNOW ACCUMULATION OF A FEW INCHES STILL
APPEAR LIKELY ACROSS THE NRN AND WRN MTNS...WITH LOCALIZED 4-5 INCH
AMOUNTS POSSIBLE ON THE RIDGE TOPS AS THE SUBSIDENCE INVERSION LIFTS
TWD 10 KFT AGL...THEN VANISHES FOR ABOUT 6-10 HOURS FRIDAY. BECAUSE
OF THE RATHER STRONG ELEVATION DEPENDENCY OF THE ACCUMULATIONS...THE
EXTENDED 12+ HOUR PERIOD OF SNOWFALL...AND RATHER ISOLATED 4-5 INCH
SNOW TOTALS...WILL REFRAIN FROM ISSUING A WINTER WEATHER (OR LES)
ADVISORY AT THIS POINT.
TEMPS WILL BE SLIGHTLY BELOW NORMAL ACROSS THE VALLEYS OF CENTRAL
PENN AND THE SUSQ REGION FRIDAY AND SATURDAY...EQUATING TO HIGHS
MAINLY IN THE LOWER TO MID 40S. HIGHS ACROSS THE MTNS WILL BE IN THE
LOWER TO MID 30S FRIDAY...AS A RESULT OF THE EXTENSIVE
CLOUDS/WIDESPREAD SNOW SHOWERS/AND THE POCKET OF COLDEST 850 MB
TEMPS OF -5 TO -6C MOVING OVER THE ALLEGHENY
PLATEAU.
LOWS BOTH FRIDAY NIGHT AND SAT NIGHT WILL BE IN THE U20S TO MID
30S...WHICH IS A FEW DEG F ABOVE NORMAL. SNOW SHOWERS AREAL COVERAGE
WILL GRADUALLY DIMINISH DURING THIS PERIOD...WITH JUST ISOLATED SNOW
SHOWERS AND FLURRIES LIMITED TO THE FAR NW ZONES BY SAT
NIGHT.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
SFC RIDGING WILL BUILD NEWD SAT NIGHT/SUN...PROVIDING IMPROVING
CONDS AND MODERATING TEMPS AS LLVL FLOW BACKS AROUND TO THE SW.
LINGERING SNOW SHOWERS/FLURRIES POSSIBLE THROUGH ABOUT DAYBREAK
SUNDAY ACROSS WARREN/MCKEAN COUNTIES WITH THE MEAN 925-850 WIND FROM
280-290 DEG...PRIOR TO IT QUICKLY SHIFTS TO ABOUT 240 DEG SUNDAY
AFTERNOON.
OPERATIONAL GFS/EC...AND GEFS HAVE TRENDED A BIT WETTER WITH THE
NEXT CFRONTAL PASSAGE MONDAY AFTERNOON AND NIGHT. ALL MODEL
SOLUTIONS SHOW AN INITIALLY WEAK (1000+ MB) SFC LOW SLIDING NE ALONG
THE SLOWING FRONT BEFORE SLOWLY DEEPENING OVER THE NEW ENGLAND
STATES MONDAY NIGHT/TUES. CONSENSUS 12-18 HOUR QPF OF 0.10"-0.30"
MAY WARRANT HIGHER POPS THAN OUR CURRENT 30-40 PERCENT VALUES FOR
THAT TIMEFRAME. SEVERAL GEFS PLUMES HINT AT THE POTENTIAL FOR A
SLIGHTLY MORE EASTWARD TRACK TO THE SFC LOW (MOVING NE FROM THE
OHIO/TENN RIVER VALLEYS MONDAY)...LEADING TO A LOW PROBABILITY FOR
OVER 0.50" OF STORM TOTAL RAIN...WITH SOME WET SNOW POSSIBLE
ACROSS THE NW HALF OF THE CWA.
HIGH PRESSURE BUILDS NE FOR TUES/WED BRING GENERALLY FAIR WEATHER
WITH NEAR TO SLIGHTLY ABOVE NORMAL TEMPS.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
IR IMAGERY INDICATES CLOUDS DEV OVERHEAD THIS MORNING...WHICH WILL
HELP LIFT VSBYS TOWARDS MVFR. CIGS HOWEVER WILL HOVER DOWN AT IFR
CONDS FOR JST/AOO/UNV/IPT. BFD WILL SEE BETTER MIXING AND CLOUDS
WITH MVFR/VFR CONDS. MDT VSBYS WILL IMRPOV ARND 14Z AS MIXING AND
CLOUDS INCREASE TO MVFR/VFR. FRONT PUSHES THRU AND INCREASES
UPSLOPE ACROSS THE ALLEGHENIES AFT 00Z...THUS EXPECT CIGS/VSBYS TO
DETERIORATE TO MVFR/IFR AND PATCHY RASN. AT MDT CIGS SHUD PUSH TO
VFR FROM WEAK DOWNSLOPING...HOWEVER SOME MOISTURE COULD SLIDE INTO
SUSQ-VALLEY AIRFIELDS FROM COASTAL STORM EFFECTS THIS EVE.
OUTLOOK...
EARLY FRI...IFR WEST W/SHRASN. ELSEWHERE MVFR W/SCT SHRASN.
FRI-SAT...IFR/MVFR W/N W/FREQUENT HIGH TERRAIN SHSN. VFR EAST OF
THE ALLEGHENIES BRIEF MVFR IN SHRASN.
SUN...VFR.
MON...IFR/MFR SHRASN.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR PAZ006-011-
012-017>019-024>028-033>037-041-042-045-046-049>053-056>059-
063>066.
&&
$$
SYNOPSIS...LA CORTE
NEAR TERM...BEACHLER
SHORT TERM...LAMBERT
LONG TERM...LAMBERT/MARTIN
AVIATION...BEACHLER
