Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 311953
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
353 PM EDT FRI OCT 31 2014

.SYNOPSIS...
A STRONG UPPER LEVEL TROUGH DROPPING FROM THE UPPER MIDWEST FRIDAY
AFTERNOON TO THE CAROLINAS BY SATURDAY AFTERNOON WILL DEEPEN A
COASTAL LOW PRESSURE SYSTEM ALONG THE MID ATLANTIC COAST...WHICH
EVENTUALLY TRACKS SOUTHEAST OF CAPE COD SATURDAY NIGHT AND SUNDAY.
FOR THE LOCAL AREA...THIS WILL LEAD TO MUCH COOLER AIR ARRIVING
ON A BRISK NORTHERLY WIND LATER SATURDAY AND SUNDAY. HIGH
PRESSURE WILL RETURN TO THE AREA BEHIND THE DEPARTING STORM SYSTEM
ON MONDAY WITH MODERATING TEMPERATURES INTO THE MIDDLE OF NEXT
WEEK.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
EXTENSIVE CLOUDCOVER ACROSS 90% OF MY FORECAST AREA. DRY SLOT
WITHIN CAD EXTENDING SWD FROM CENTRAL NEW ENGLAND TO THE DEL MARVA
REGION IS PERSISTING BETWEEN THE WIDESPREAD MULTI LAYERED CLOUDS
ACROSS THE WESTERN 3/4 OF PA AND BACK EDGE OF BAROCLINIC LEAF
ASSOCIATED WITH OFFSHORE DEEPENING SFC LOW. AS LLVL WINDS INCREASE
AND ADVECT LONG FETCH WESTERN ATLANTIC AIR WEST OF LONG ISLAND AND
NEW JERSEY...THIS BREAK SHOULD CLOSE MID TO LATE AFTERNOON.

MEANWHILE SHOWERS WILL INCREASE ACROSS THE NORTHWEST AND WEST
CENTRAL MOUNTAINS THROUGH LATE AFTERNOON AS UPPER CUTOFF SWINGS
SOUTHWARD THROUGH OHIO AND WEAK SURFACE LOW DROPS ALONG THE OH/PA
BORDER...FOCUSING SHOWERS IN THESE AREAS. FATHER EAST...LLVL RIDGE
AXIS SHOULD KEEP CENTRAL AND EASTERN AREAS PROTECTED FROM SHOWER
ACTIVITY UNTIL THE LLVL EASTERLY FLOW PENETRATES INTO THE CENTRAL
MOUNTAINS LATE TONIGHT INTO SATURDAY MORNING...BRINGING THE BEST
CHANCE OF SHOWERS THERE AT THAT TIME.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
DEEP EASTERLY FLOW AROUND OFFSHORE SFC LOW SHOULD DELIVER A SOGGY
MORNING TO MUCH OF EASTERN AND SOUTH CENTRAL PA EARLY SATURDAY.
DESPITE RELATIVELY LOW DEEP LAYER MOISTURE...ANOMALOUS
EASTERLY FLOW OF THIS SORT TYPICALLY PRODUCES FAIRLY WIDESPREAD
ALBEIT LIGHT MEASURABE...SO IN CONCERT WITH PHL HAVE BUMPED UP
POPS AND QPF IN THESE AREAS. STILL NOT ANTICIPATING MUCH MORE THAN
A TENTH OR TWO IN ANY ONE LOCATION...BUT COMBO OF INCREASING EAST
FLOW...LOW CLOUDS AND LIGHT BUT STEADY RAIN SHOWERS WILL MAKE FOR
A LESS THAN PLEASANT START TO THE WEEKEND.

MARGINALLY COLD AIR MOVING INTO THE REGION LATER IN THE DAY
SHOULD PROMOTE A MIXTURE OF RAIN AND SNOW SHOWERS OVER THE LAURELS
AND WEST CENTRAL MOUNTAINS WITH LITTLE IF ANY ACCUMULATION DURING
THE DAYLIGHT HOURS. BACKING LOW LEVEL FLOW WILL ADVECT MUCH COLDER
AIR INTO THE REGION LATE SATURDAY AFTERNOON AND NIGHT. EARLY
AFTERNOON TEMPERATURES IN THE 40S WILL DROP SLOWLY ACROSS WESTERN
AND CENTRAL AREAS BY EVENING TO THE UPPER 30S TO LOWER 40S.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
LARGE UPPER TROUGH WILL BECOME MORE NARROW AS IT DIGS SOUTHWARD
SAT NIGHT INTO SUN...WITH COASTAL LOW TO THE EAST LIFTING
NORTHEASTWARD. THIS WILL CAUSE A TIGHTENING PRESSURE GRADIENT AND
BRING STRONG NW FLOW DRAWING MUCH COLDER/DRIER AIR INTO PA.
OPERATIONAL RUNS AND NEARLY ALL ENSEMBLE MEMBERS KEEP COASTAL LOW
FAR ENOUGH OUT TO SEA TO NOT DIRECTLY IMPACT CENTRAL PA.
HOWEVER...COLD NW FLOW WILL LIKELY PRODUCE SCT LAKE EFFECT SNOW
SHOWERS ACROSS THE ALLEGHENY PLATEAU AND PARTS OF THE CENTRAL
MOUNTAINS SATURDAY NIGHT. GIVEN DRYNESS OF AIR MASS MOVING
IN...DON/T EXPECT ANY SIG ACCUMS...BUT A COATING OF SNOW DOES
APPEAR POSSIBLE OVR THE W MTNS.

ENSEMBLE MEAN 8H TEMPS THIS WEEKEND POINT TOWARD DAYTIME HIGHS
FROM THE U30S-L40S OVR THE ALLEGHENIES TO 45-50F ACROSS THE LOWER
SUSQ VALLEY. THE COLDEST NIGHT WILL BE SUNDAY NIGHT...WHEN SFC
HIGH BUILDS OVR THE REGION AND SKIES CLEAR OUT. THOSE LOCATIONS
THAT HAVE YET TO SEE A FREEZE WILL LIKELY GET IT BY MONDAY AM.

HIGH CONFIDENCE IN A PERIOD OF DRY WEATHER SUNDAY INTO TUE...WHEN
ALL GUIDANCE BUILDS SFC HIGH AND ASSOC DRY AIR MASS ACROSS
PA...ALONG WITH MODERATING TEMPS. AN APPROACHING COLD FRONT WILL
BRING THE NEXT CHC OF SHRA LATE TUE INTO WED. FOLLOWED BY A
CLIPPER SYSTEM FOR LATE WEEK /MODELS DIVERGE ON TIMING/. BUT LATE
WEEK TREND WILL BE A RETURN BACK TO COOLER TEMPERATURES.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
WIDESPREAD MID AND UPPER CLOUD CENTRAL PA GIVING WAY TO
RAINSHOWERS AND MVFR CIGS WESTERN AREAS. SOUTHEAST IS LCLY VFR
WITH MOSTLY MVFR CIGS ON THE PERIPHERY OF THE DEEPER MOISTURE TO
THE WEST AND THE BAROCLINIC LEAF ASSOCIATED WITH COASTAL LOW
OFFSHORE. INCREASING LLVL FLOW WILL BRING A MARITIME AIR MASS INTO
SOUTHEAST PA LATER THIS EVENING...INCREASING LOW CIGS TO MVFR AND
LCL IFR LATE TONIGHT...ALONG WITH INCREASING SHOWERS.

GUIDANCE SUPPORTS REDUCED CONDS THROUGH MID TO LATE SATURDAY
MORNING. WINDS WILL GRAUDALLY BACK N-NW AND INCREASE THROUGH
SATURDAY...ADVECTING COLDER AND DRIER AIR SOUTHWARD WITH SLOW
IMPROVEMENT IN FLYING CONDITIONS BY SATURDAY EVENING. HOWEVER
WIDESPREAD MVFR AND LCL IFR CIGS ARE EXPECTED FOR MUCH OF
SATURDAY.

OUTLOOK...

SAT...MVFR/IFR WITH SCATTERED RAIN/SNOW SHOWERS WEST. VARYING
CONDS FROM VFR-MVFR CENTRAL/EAST WITH OCNL -SHRA. N-NW WINDS
INCREASING SATURDAY NIGHT.

SUN...GUSTY NW WINDS. RAIN/SNOW SHOWERS ENDING WEST. LOW CIGS
WEST BECOMING VFR.

MON-TUE...NO SIG WX.

WED...MVFR WITH CHC SHRA.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$
SYNOPSIS...DEVOIR
NEAR TERM...DEVOIR
SHORT TERM...
LONG TERM...RXR
AVIATION...DEVOIR/STEINBUGL



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