FXUS61 KCTP 251257
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
757 AM EST WED NOV 25 2009
.SYNOPSIS...
A MOIST SOUTHEAST FLOW OF AIR WILL CONTINUE TO PRODUCE WIDESPREAD
CLOUDS AND SOME AREAS OF LIGHT RAIN OR DRIZZLE THROUGH MUCH OF
TODAY. A WEAK COLD FRONT WILL SLIDE ACROSS THE REGION LATE THIS
AFTERNOON AND THIS EVENING. A STRONGER COLD FRONT WILL CROSS THE
REGION THANKSGIVING EVENING. FOLLOWING THIS SECOND FRONT...A POTENT
UPPER AIR DISTURBANCE WILL BRING FREQUENT SNOW SHOWERS...OR EVEN A
FEW PERIODS OF STEADY SNOW TO THE WESTERN AND NORTHERN MOUNTAINS OF
THE STATE LATE THURSDAY NIGHT INTO FRIDAY. LIGHT ACCUMULATIONS OF
SNOW WILL OCCUR ACROSS THE HIGHER ELEVATIONS. BELOW NORMAL DAYTIME
TEMPERATURES WILL OCCUR FOR THE END OF THE WEEK...AND CONTINUE RIGHT
THROUGH THE HOLIDAY WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
A LOW OVC (CLOUD BASES AOB 1000 KFT AGL ACROSS THE CENTRAL ZONES AND
SUSQ VALLEY) WITH OCCASIONAL LGT RAIN/DZ WILL CONTINUE TO AFFECT
MUCH OF CENTRAL AND EASTERN PENN THROUGH THIS MORNING...AS WEAK TO
MDT ISENTROPIC ASCENT OCCURS FROM THE SE ALONG THE I290-295K THETA
SFCS.
WEAK OCCLUDED FRONT OVER CENTRAL OHIO ATTM WILL MOVE EAST AND BRING
ADDITIONAL SHOWERS AND LIGHT QPF...GENERALLY 0.10" OR LESS THIS
AFTERNOON AND EVENING.
MAX TEMPS THIS AFTERNOON WILL BE ABOUT 6 OR 7F ABOVE NORMAL...
RANGING FROM THE UPPER 40S ACROSS THE MTNS...TO THE MID 50S IN THE
SE VALLEYS.
FOLLOWING THIS FRONT...A FEW BREAKS IN THE OVC SHOULD OCCUR TONIGHT
THROUGH THANKSGIVING MORNING...AS THE FLOW ALONG THE AFOREMENTIONED
ISENTROPIC SFCS STRENGTHENS AND VEERS TO A "DOWNSLOPE" SWRLY
DIRECTION. NOTHING MORE THAN A STRAY SHOWER (OR PATCHY DRIZZLE ON
THE WEST FACING RIDGES) IS EXPECTED OVERNIGHT. WORTH NOTING IS THAT
WITH THE VERY LIGHT WIND AND MOIST LLVL AIR OVERNIGHT...ANY CLEARING
WILL LIKELY LEAD TO AREAS OF FOG ACROSS THE CENTRAL AND EAST.
MIN TONIGHT WILL DIP INTO THE MID/UPR 30S ACROSS THE CENTRAL AND
NORTH...WITH DAYBREAK TEMPS IN THE LOWER 40S FOUND ACROSS THE SUSQ
VALLEY.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
AFTER A DECENT START TO THANKSGIVING DAY (WITH RELATIVELY LIGHT
WIND...MILD TEMPS IN THE 40S/50S...AND A FEW BREAKS OF SUN ACROSS
THE CENTRAL AND ERN VALLEYS)...A SHARP TRANSITION WILL BEGIN WITH
THE DEVELOPMENT OF THICKENING CLOUDS/SHOWERS LATER IN THE DAY AHEAD
OF A STRONG COLD FRONT.
00Z OPERATIONAL MODELS...AND SHORT RANGE ENSEMBLE GUIDANCE STILL
SHOW SOME UNCERTAINTY WITH RESPECT TO THE TRACK OF THE DEEPENING
UPPER LOW AND TIMING OF THE SFC LOW BOMBING LATER THURSDAY NIGHT AND
FRIDAY AS IT MOVES NORTH NORTHEAST (FROM JUST EAST OF THE MID
ATLANTIC COAST TO THE COAST OF MAINE BY 00Z SAT).
A BRIEF...FEW HOUR PERIOD OF "ELEVATED" INSTABILITY IS POSSIBLE
LATE HUR/THUR EVENING ACROSS THE LOWER SUSQ VALLEY WITH NEAR ZERO
925-850 MB LIFTED INDICES BEING ADVECTED NWD TWD KTHV/KLNS. HAVE
INCLUDED THE MENTION OF ISOLATED TSRA ACROSS OUR SE ZONES FROM
00Z-06Z FRIDAY.
AGREE WITH HPC DAY 2-3 SNOW GRAPHICS AND WILL CONTINUE TO PAINT A
FEW INCHES OF SNOW ACROSS THE HIGHER TERRAIN OF NORTHERN AND WESTERN
PENN THURS NIGHT AND FRIDAY (WITH LOCALLY AROUND 4 INCHES POSSIBLE
OVER AN 18 HOUR PERIOD ACROSS THE UPSLOPE AREAS OF THE LAUREL
HIGHLANDS - AND SEVERAL HOURS LATER ACROSS THE MTNS NORTH AND EAST
OF KIPT AS COLD CONVEYOR BELT/DEFORMATION SNOW DEVELOPS NORTH OF THE
UPPER LOW TRACK).
03Z SREF AND THE 06Z NAM TRACKS THE UPPER LOW FURTHEST SOUTH (ACROSS
CENTRAL OR SRN PENN LATE THUR NIGHT)...WHILE THE GFS/EC SOLUTIONS
ARE ABOUT 150 KM OR SO FURTHER NORTH (ALSO A LITTLE FASTER...WEAKER
AND MORE EAST WITH THE ULTIMATE SFC LOW DEVELOPMENT). 03Z SREF IS
SURPRISINGLY THE FURTHEST WEST AND STRONGER WITH THE SFC LOW (1004
MB) TRACKING FROM EAST OF KORF AT 00Z FRIDAY...AND DEEPENING TO 993
MB NEAR CAPE COD BY 12Z FRIDAY.
A LIGHT COATING OF SNOW IS POSSIBLE EARLY FRIDAY EVEN THROUGHOUT THE
CENTRAL VALLEYS. BOUNDARY LAYER TEMPS MAY WARM ENOUGH FRIDAY TO MIX
THE SNOW WITH RAIN SHOWERS ON FRIDAY.
A GUSTY NORTHWEST WIND WILL DEVELOP FRIDAY AS THE LOW INTENSIFIES
OFF THE SRN NEW ENGLAND COAST...QUICKLY TIGHTENING THE LLVL PRESS
GRADIENT. 3 HOURLY PRESSURE CHANGES WILL RAMP UP TO 3-4 MB DURING
THE DAY - PRODUCING WIND GUSTS OF AROUND 30 MPH.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
SFC RIDGING WILL BUILD NEWD SAT/SUN...PROVIDING IMPROVING CONDS AND
MODERATING TEMPS AS LLVL FLOW VEERS AROUND TO THE SW. GFS/GEFS/GEM
ARE FASTER WITH THE NEXT FNTL SYS MOVG INTO THE GRT LKS LATER SUN
INTO MON. IN THE LONGER RANGE THE GFS IS LKLY TOO AMPLIFIED WITH A
980MB LOW OVR THE AREA ON TUE. CONFIDENCE IS LOW BEYOND SUNDAY AND
HAVE SIMPLY BLENDED THE HPC/GMOS GUID FOR MAIN WEATHER ELEMENTS EARLY
NEXT WEEK.
&&
.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
MOIST SE/S FLOW OF AIR WILL CONTINUE TO PRODUCE WIDESPREAD
IFR/MVFR CLOUDS AND REDUCED VSBYS IN AREAS OF DRIZZLE OR LIGHT
RAIN THROUGH THE DAY...ESPECIALLY IN THE EAST. A BAND OF SHOWERS
WILL SLIDE FROM W-E ACROSS THE REGION AROUND NOONTIME...WHICH WILL
BRING A RETURN OF MVFR/IFR CIGS FOR SEVERAL HOURS IN THE WEST AS
WELL. CONDITIONS WILL GRADUALLY IMPROVE TONIGHT INTO THU ACROSS THE
WEST...BUT MVFR CIGS WILL LIKELY LINGER INTO THU IN THE EAST /KIPT-
KMDT/.
A SIG COLD FRONT FOLLOWED BY A POTENT UPPER LOW WILL MOVE THROUGH
LATE WEEK BRINGING COLD/BLUSTERY AND DETERIORATING CONDITIONS
AGAIN THU NIGHT THRU SAT.
OUTLOOK...
THU...MVFR/SOME VFR WITH CHC -SHRASN.
THU NIGHT-FRI...IFR W WITH LKLY -SHRASN / MVFR E WITH CHC -SHRASN.
FRI NIGHT-SAT...IFR/MVFR IN THE WEST/NORTH WITH FREQUENT HIGH TERRAIN
SNOW SHOWERS. VFR OVER CENT/EAST WITH BRIEF MVFR IN PASSING
RAIN/SNOW SHOWERS.
SUN...GENERALLY VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...LA CORTE/LAMBERT
NEAR TERM...FITZGERALD
SHORT TERM...LA CORTE/LAMBERT
LONG TERM...LAMBERT/STEINBUGL
AVIATION...RXR
