FXUS61 KCTP 011203
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
703 AM EST TUE DEC 1 2009
.SYNOPSIS...
HIGH PRESSURE BUILDS INTO THE MIDDLE ATLANTIC REGION AND PROVIDES
DRY WEATHER FOR MUCH OF PENNSYLVANIA THROUGH EARLY WEDNESDAY. AN
AREA OF LOW PRESSURE WILL SLIDE NORTH FROM THE GULF OF MEXICO TO
THE OHIO RIVER VALLEY WEDNESDAY INTO THURSDAY. RAIN SHOWERS
OVERSPREAD PENNSYLVANIA MIDDAY WEDNESDAY AND CONTINUES THROUGH
THURSDAY. AS THE LOW PRESSURE SYSTEM DEPARTS THE REGION
TEMPERATURES COOL FOR FRIDAY INTO THE UPCOMING WEEKEND.
TEMPERATURES MAY BE COOL ENOUGH FRIDAY TO SUPPORT RAIN TO SNOW FOR
THE NORTHWEST MOUNTAINS.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
FORECAST CHALLENGES FOR TODAY SURROUND LINGERING MOISTURE AS TROUGH
AXIS SWINGS NE INTO NEW ENGLAND...WITH INCREASING HEIGHTS ACROSS OUR
CWFA. FLOW QUICKLY TRANSITIONS TO A W/SWSTRLY SETUP...PUSHING ANY
LINGERING LES NORTH ALONG A WARREN TO POTTER COUNTY LINE AND NORTH.
BY MIDDAY EXPECT ENUF DRY AIR IN PLACE WITH NOSE OF ANTI-CYCLONIC
FLOW ERODING BNDRY LYR MOISTURE. MIXED LYR REMAINS SHALLOW
TDY...HOWEVER BREEZY WSTRLY CONDS ARE PSBL THRU 18Z AS A CORE OF
20-30KTS SITS AT 1500KFT AGL THEN DIMINISHES FOR THE AFTN. AS DRY
AIR CONTINUES TO PUSH INTO CENTRAL PA...CLOUD SHIELD WILL EVENTUALLY
THIN FROM THE S TO N BY THIS AFTN. 925MB THERMAL RIDGE SLOWLY
ADVECTS NORTH INTO OUR CWFA...SO MAX TEMPS WILL BE DRIVEN ON WHEN WE
CAN LOSE THE THICK CLOUD SHIELD. ATTM EXPECT U30S/L40S FOR THE
NW...L40S/M40S CENTRAL...AND U40S/ARND 50 LOWER SUSQ-VALLEY.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
SFC RIDGE BEGINS TO WEAKEN AND SLIDE NE ALONG THE NJ COAST EARLY
WED. LLVL FLOW QUICKLY TURNS SWSTRLY AND INCREASES AS A LLVL 30KT
JET RIDES ALONG SPINE OF APPALACHIANS AND ARRIVES ACROSS CENTRAL PA
AFT 06Z WED. DRY WX SHUD HOLD THRU THE OVERNIGHT AS MOISTURE POOLS
N...INCREASING CLOUD SHIELD FROM SW TO NE. UNDER OPTIMAL CONDS MIN
TEMPS COULD RADIATE INTO THE 20S TO LOW 30S...HOWEVER FEEL GIVEN
INCREASING STHRLY FLOW AND WAA IN THE BNDRY LYR TEMPS WILL SLOW
THEIR RATES. THUS HAVE ADJUSTED TEMPS WARMER THAN GUIDANCE BY A
COUPLE DEGREES...OR MAINLY IN THE 30S. COULD SEE SOUTHERN TIER OF
CWFA HOLDING IN THE UPPER 30S TO ARND 40 OVERNIGHT.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
STRONG UPPER LVL LOW AND ASSOC SHRTWV TROUGH IS PROGGED TO LIFT
RAPIDLY NEWD FM ERN TX INTO THE NORTHEAST EARLY THIS PERIOD...ON
THE ERN FRINGES OF A MUCH LARGER LW TROUGH WHICH WILL EVENTUALLY
ENCOMPASS MOST OF THE CONUS AND ERN CANADA INTO THE UPCOMING
WKEND. 120KT JETMAX ROUNDING THE BASE OF THE UPPER LOW /CURRENTLY
SPINNING OVR NRN MEXICO SW OF EL PASO TX/ WILL FUEL INTENSE
CYCLOGENESIS OVR THE CENTRAL GULF COAST AND INTO THE SERN
U.S...SPAWNING A HIGHLY ANOMALOUS /-3SD/ SFC CYCLONE WHICH WILL
QUICKLY MOVE NNEWD ALONG THE APPALACHIANS THRU WRN PENN AND INTO
NRN NEW ENG/MARITIMES BY 04/00Z.
THREE AREAS OF CONCERN ASSOC WITH THIS DYNAMIC SYS: 1) HVY RNFL
POTENTIAL 2) PSBL CONVECTIVE ACTIVITY AND 3) STRONG WINDS.
FAVORABLE DEEP LYR FORCING/UPPER LEVEL JET DYNAMICS AND ROBUST
SSELY LLJ SURGING NWD OUT OF THE GOMEX WILL EFFECTIVELY TRANSPORT
VERY HI PW AIRMASS INTO THE REGION BY WED NGT...AS THE DEEP SFC
LOW TRACKS WELL-INLAND FROM THE UPR OH VLY TWD THE LWR GRT LKS.
THIS SHUD INITIALLY SUPPORT A PERIOD OF MOD TO HVY WAA RAINS
OVERSPREADING THE AREA FROM SW-NE WED AFTN THRU THE OVERNIGHT
HOURS. MDLS EVENTUALLY SUGGEST THAT SCENTRAL/SERN PENN WILL BREAK
INTO THE INCREASINGLY UNSTABLE WARM SECTOR AS THE SFC LOW MOVES
INTO NYS AND TRAILING CLD FNT SWEEPS EWD. WL CONT TO MNTN T GIVEN
ELEVATED INSTABILITY AND NEAR-ZERO SFC LI/S PROGGED IMMEDIATELY
ALONG/AHEAD OF THE SFC CLD FNT. FINALLY...STRONG TO POTENTIALLY
DAMAGING NON-CONVECTIVE WINDS MAY DEVELOP IN THE WAKE OF THIS
SYS...WITH 6HR ISALLOBARIC PRES RISES ON THE ORDER OF 10-15MB.
LATER SHIFTS MAY NEED TO CONSIDER A WIND ADVY ON THUR AS THE
PASSAGE OF THE PRES RISE COUPLET COINCIDES WITH AFTN PEAK DIURNAL
MIXING.
NOT SURPRISINGLY GIVEN THE FAVORABLE HVY RAIN PATTERN AND
AVAILABLE MSTR...ENSEMBLE DATA AND PLUME DIAGRAMS SUGGEST A
FAIRLY HIGH LIKELIHOOD OF 24HR QPF AROUND 1 INCH IN MOST LOCATIONS
/ENDING 12Z THUR/. HIGHEST POPS ARE CONFINED TO THE 00-12Z THUR
TIMEFRAME.
MUCH COOLER AIR WILL ARRIVE BY THUR NGT WITH TEMPS LKLY FALLING
THUR AFTN GIVEN INC CAA. COLD/BRIEF OVER-LAKE FETCH SHOULD BRING
SNOW SHWRS INTO THE WRN ALLEGHENIES FRI AM BEFORE THE LLVL FLOW
BECOMES MORE SWLY. A LGT ACCUM IS PSBL ACROSS THE NW SNOWBELT AS
WELL AS THE FAVORABLE UPSLOPE AREAS.
MDLS SHOW A SECOND STORM SYS LIFTING NEWD OFF THE ECOAST THIS
WEEKEND...BUT IT DOES NOT APPEAR TO DIRECTLY AFFECT THE LOCAL
AREA. GEFS DATA SUGGESTS WE STAY IN A COOL CYC FLOW INTO EARLY
NEXT WEEK AS H5 FLOW GRADUALLY BECOMES MORE ZONAL AND H85 TEMPS
MODERATE BACK TWD NORMAL.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
IR IMAGERY INDICATES CONSID MID-LVL CLOUDS SLIDING E/NE ACROSS THE
NORTHERN PA AIRFIELDS...WITH SCT SHSN. VSBYS/CIGS IN AND ARND SHSN
WILL FLUCTUATE RAPIDLY TO IFR...THEN BACK TO VFR. ELSEWHERE EXPECT
VFR CONDS TO PERSIST. WINDS COULD BECOME BREEZY AFT 15Z THRU 21Z
FROM THE W/SW ARND 15-20KTS. CIGS WILL STEADILY LIFT AS DRY AIR
AND HIGH PRESSURE BUILD IN FROM THE WEST. AFT 06Z WED CLOUDS
THICKEN...HOWEVER EXPECT VFR CONDS TO CONTINUE UNTIL AFT 12Z WED.
OUTLOOK...
WED...VFR.
WED PM-THU...MVFR TO IFR CIGS. RA/BR.
FRI AND SAT...MVFR/IFR W SHSN - VFR E.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...BEACHLER
NEAR TERM...BEACHLER
SHORT TERM...BEACHLER
LONG TERM...STEINBUGL
AVIATION...BEACHLER
