242
FXUS61 KCTP 210742
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
242 AM EST SAT NOV 21 2009
SYNOPSIS
HIGH PRESSURE SHOULD PROVIDE RELATIVELY DRY WEATHER OVER THE
REGION THROUGH SUNDAY. EASTERLY FLOW AND A WAVE COMING OUT OF THE
GULF SHOULD INCREASE THE CHANCE OF RAIN LATE SUNDAY INTO MONDAY.
THE PATTERN OVER NORTH AMERICA IS CHANGING...THE ENSEMBLES SHOW A
TROUGH ATTEMPTING TO ESTABLISH ITSELF OVER EASTERN NORTH AMERICA
WITH A RIDGE OVER NORTHWESTERN CANADA. A SERIES OF WAVES WILL CARVE
OUT THE TROUGH BRINGING UNSETTLED WEATHER TO THE REGION NEXT WEEK.
NEAR TERM /UNTIL 6 AM THIS MORNING/
HIGH PRESSURE TO OUR WEST CONTINUES TO PUSH INTO THE REGION.
DESPITE THE HIGH...MOISTURE IN THE WEAK COLD ADVECTION IS KEEPING
A BROAD REGION OF LOW CLOUDS IN PLACE AS VIEWED IN THE 11-3.9
MICRON SATELLITE DATA. THE CLOUDS SHOULD SLOW THE COOLING AND BE
SLOW TO DISSIPATE. UPDATE GRIDS SHOWING MORE CLOUDS THAN PREVIOUS
FORECAST.
DEW POINTS MAINLY IN THE LOW TO MID 30S AND WITH THE CLOUDS STAYED
CLOSE TO GUIDANCE WITH LOWS MAINLY IN THE MID TO UPPER 30S.
SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/
LITTLE MORE THAN SOME SPRINKLES OVR THE MTNS WITH PASSAGE OF TROF
ON SAT. WESTERLY FLOW SHOULD ENSURE MOST SOLID CLOUD COVER OVR
THE ALLEGHENIES AND MOST BRKS ACROSS THE SUSQ VALLEY. WSW FLOW
ABOVE 700 MB WILL KEEP PA IN A RELATIVELY MILD AIRMASS FOR
NOVEMBER. NAEFS DATA CONTINUES TO POINT TWD HIGHS SATURDAY SEVERAL
DEG ABV NORMAL...WITH MAXES RANGING FROM U40S ACROSS THE
ALLEGHENIES...TO M50S THROUGHOUT SUSQ VALLEY.
THE MEAN BOUNDARY LAYER WIND WILL GRADUALLY VEER AROUND TO THE
NORTH SATURDAY NIGHT. THIS WILL KEEP 60% CLOUD COVER OR MORE
ACROSS THE NRN MTNS...WITH GENERALLY PARTLY CLOUDY SKIES ACROSS
MUCH OF THE REGION TO THE SOUTH OF INTERSTATE 80.
MIN TEMPS SHOULD BE A FEW DEG COLDER SATURDAY NIGHT ACROSS THE
FAR NORTH (COMPARED TO 24 HOURS PRIOR) WITH LESS CLOUD COVER.
CENTRAL AND SOUTHERN SECTIONS OF PENN WILL ONCE AGAIN SEE LOW
LOW TEMPS IN THE M/U 30S OR ABOUT 3-6F ABOVE NORMAL.
DUE TO GEFS AND SREF INTRODUCED A 20 PERCENT CHANCE OF LIGHT RAIN
IN THE SOUTHERN AND SOUTHEASTERN AREAS LATE SUNDAY AFTERNOON. GEFS
IS FASTER.
LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
AN ACTIVE SPLIT FLOW PATTERN IS FCST TO CONTINUE THROUGH MUCH OF THE
PD BY LONG TERM GUIDANCE. SEVERAL UPR LEVEL TROFS ARE FORECAST TO
TRAVERSE THE CONUS IN BOTH THE NRN AND SRN STREAM FLOW WITH
VARYING LEVELS OF INFLUENCE ON PA. OVERALL HOWEVER...MOST OF THE
NEXT WEEK LOOKS TO BE DRY WITH CONTINUED ABOVE NORMAL TEMPERATURES.
THE FIRST TROF...IN THE SRN STREAM...IS FCST TO MOVE ACROSS THE GULF
COAST SATURDAY THEN LIFT NE ALONG THE MID ATLC COAST LATE SUNDAY.
THE WAVE WILL BE LIFTING INTO THE NRN STREAM MEAN UPR RIDGE WITH
HIGH PRESSURE IN PLACE AT THE SFC. MODEL TRENDS ARE FOR A
SMALLER...FARTHER EAST SOLUTION OF THE SFC LOW ASSCD WITH THE SRN
TROF AND FORECASTS DRIER THAN PVS RUNS. GFS APPEARS AN OUTLIER WITH
A SIG WET FORECAST FOR SUN NIGHT INTO MONDAY ACROSS MUCH OF
PA...AND SUCH HAVE LOWERED POPS FOR THIS TIME PD FOLLOWING THE
MULTITUDE OF OTHER LONG TERM GUIDANCE.
THE NEW 18Z GEFS IS MORE IN LINE BUT STILL FASTER THAN THE 15Z SREF
SHOWING A CHANCE OF LIGHT RAIN SUNDAY NIGHT INTO MONDAY MORNING.
HIGHEST ENSEMBLE POPS ARE MONDAY DURING THE DAY INTO MONDAY NIGHT.
SOME TIMING ISSUES. LOWERED THE POPS INTO THE 50 PERCENT RANGE
MONDAY DURING THE DAY AND UPPED THEM MONDAY NIGHT INTO TUESDAY DUE
TO THE UNCERTAINTY IN THE TIMING. PRETTY WEAK SYSTEM AND THE RAIN
SHOULD BE VERY LIGHT.
AMPLIFICATION IN THE NRN STREAM IS FCST TO OCCUR OVER THE GREAT
LAKES BY TUE...WITH A WEAKENING SFC FRONT REACHING WRN ON WED AS
SUPPORTING CLOSED UPPER TROF LIFTS INTO SERN CANADA. A STRONGER UPR
TROF/COLD FRONT IS FCST TO MOVE THROUGH PA THANKSGIVING NIGHT...IF
CURRENT TIMING HOLDS...WITH A NOTICEABLE COOL DOWN IN STORE FOR
SHOPPERS NEXT FRIDAY. ANY SHOWER ACTIVITY OVER NW PA COULD BE IN
THE FORM OF SNOW THUR-FRI AS 850 TEMPERATURES FALL BELOW 0C.
AVIATION /06Z SATURDAY THROUGH WEDNESDAY/
WEAK FRONTAL BNDRY ARRIVING AT BFD ARND 06Z WILL SLOWLY DIMINISH
CIGS TO ARND 1000-1500FT AGL. IFR CIGS ARRIVE AT JST/AOO/UNV/IPT
BTWN 08-12Z...BOUNCING BACK TO VFR CONDS BY 16-18Z WITH BETTER
MIXING. MDT SHUD HOLD AT VFR CONDS FROM WEAK DOWNSLOPING. BY 00Z
SUN LGT NORTHERLY FLOW TURNING NE SHUD KEEP VFR CONDS THRU EARLY
SUN WITH PATCHY MVFR CIGS ACROSS SUSQ-VALLEY AIRFIELDS.
OUTLOOK...
SUN...MVFR/VFR.
MON...MVFR LCL IFR. PSBL SHRA IN THE AFTN.
TUE...MVFR/IFR CIGS. SHRA IN THE AM.
WED...MVFR TO VFR EARLY.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...GRUMM
NEAR TERM...GRUMM
SHORT TERM...LAMBERT
LONG TERM...GRUMM/GARTNER
AVIATION...BEACHLER/RXR
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