Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 180729
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
329 AM EDT THU SEP 18 2014

.SYNOPSIS...
A TROUGH OF LOW PRESSURE OVER EASTERN NORTH AMERICA WILL SLOWLY
WEAKEN INTO SATURDAY BEFORE RE-INTENSIFYING LATER ON SUNDAY ONCE
AGAIN. OVERALL IT SHOULD BE A RELATIVELY COOL AND DRY PERIOD WITH
A BRIEF WARM UP OVER THE WEEKEND.

&&

.NEAR TERM /UNTIL 8 AM THIS MORNING/...
A COMPACT MID/UPPER SHORT WAVE WAS SLIDING EAST ACROSS SOUTHERN
PENN EARLY TODAY...WHILE A COLD FRONT WAS SAGGING SLOWLY SOUTH
FROM SRN ONTARIO. THESE TWO WEATHER FEATURES /AND A RESULTANT
AREA OF WEAK THETA-E ADVECTION AROUND THE 850 MB LEVEL/...WERE
LEADING TO AN AREA OF SCT-BKN HIGH-BASED STRATO CU CLOUDS THAT
WILL HANG AROUND THROUGH AT LEAST THE MID MORNING HOURS
/ESPECIALLY ACROSS THE ALLEGHENY PLATEAU OF NWRN PENN.

LIGHT AND VARIABLE WIND...AND A TIGHT 1-3F T/TD SPREAD AT 07Z WILL
LEAD TO AREAS OF FOG INCREASING IN BOTH COVERAGE AND THICKNESS
ACROSS THE REGION EARLY TODAY. VSBYS WILL LOCALLY DIP TO UNDER
1/4SM FOR A FEW HOURS AROUND SUNRISE IN SOME OF THE DEEPER
VALLEYS CONTAINING LARGER STREAMS AND RIVERS.

LOWS TEMPS WILL VARY FROM 39F IN THE COLDEST SPOTS IN THE NRN
MTNS...TO THE MID AND UPPER 40S THROUGHOUT MUCH OF CENTRAL AND
SOUTHERN PENN.

&&

.SHORT TERM /8 AM THIS MORNING THROUGH 6 AM FRIDAY/...
ANOTHER DRY AND SEASONABLY COOL DAY IS EXPECTED. A WEAK FRONTAL
BOUNDARY WILL DRIFT SOUTH ACROSS THE REGION DURING THE LATE
MORNING AND EARLY AFTERNOON HOURS...BRINGING SLIGHTLY COOLER AIR
AND JUST SCATTERED CLOUD COVER.

TONIGHT WILL BY QUITE COLD WITH FROST POSSIBLE ACROSS THE COLDEST
VALLEYS. A FROST ADVISORY MAY HAVE TO BE ISSUED /DURING THE DAY
TODAY/ FOR PORTIONS OF WESTERN PA FOR FRIDAY MORNING. CURRENT
LATEST...00Z NUMERICAL GUIDANCE IS INDICATING BORDERLINE
TEMP/DEWPONTS FOR WIDESPREAD FROST UP NORTH ATTM...SO AFTER
COORDINATION WITH SURROUNDING WFOS...DECISION WAS TO DELAY THE
ISSUANCE OF ANY FLAGS UNTIL THE DAYSHIFT CAN BOOST CONFIDENCE
IN EITHER DIRECTION WITH MORE DEFINITIVE GUIDANCE.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
WARMER AIR AND HIGHER MOISTURE WILL ADVECT INTO THE REGION THIS
WEEKEND ON INCREASING SW FLOW AROUND A HIGH PRESSURE AREA
/RETREATING TO THE EAST/. AT THE SAME TIME...TROUGH BEGINS TO
CARVE INTO ZONAL FLOW OVER THE GREAT LAKES AS A SYSTEM APPROACHES
PA FOR SUN/MON. THE RESULT WILL BE A PAIR OF ABOVE NORMAL
TEMPERATURE DAYS SAT-SUN WITH TEMPS MAINLY IN THE 70S...AND TAKING
A RUN AT 80F IN THE SE. WE/LL ALSO GET A BREAK FROM OUR RUN OF
CHILLY OVERNIGHTS AS LOWS REMAIN WELL INTO THE 40S AND 50S. SHOWER
ACTIVITY SHOULD REMAIN CONFINED TO THE UPPER MIDWEST THROUGH EARLY
SUNDAY.

THE CENTER OF THE APPROACHING LOW PRESSURE SYSTEM WILL REMAIN WELL
TO OUR NORTH...BUT A WEAK COLD FRONT WILL PUSH THROUGH PA SUNDAY
INTO SUN NIGHT. THIS WILL BE THE BEST CHANCE OF RAIN/SHOWERS
THROUGH DURATION OF THE EXTENDED FORECAST. THE LATEST ECMWF IS THE
WETTEST WITH QPF POTENTIALLY UP TO 0.25...WHILE THE GFS BRINGS
LIGHTER AMOUNTS.

THE 500 HPA TROUGH BEHIND THE FRONT DEEPENS OVER THE REGION MONDAY
INTO TUESDAY. THIS WILL KEEP MENTION FOR SCT INSTABILITY SHOWERS
MONDAY INTO TUESDAY...MAINLY IN HIGHER TERRAIN OF N/W CWA. COOLER
AIR ON NW FLOW WILL GRADUALLY FILTER BACK INTO THE REGION...WITH
MONDAY/S HIGHS ABOUT 8-10F COOLER AND TUESDAY FALLING ANOTHER 5F
OR SO. OVERNIGHT LOWS WILL SLIP BACK INTO THE 40S MON NIGHT...WITH
SOME MID/UPPER 30S POSS IN THE NORTHERN MTNS TUE NIGHT.

TROUGH LIFTS TO THE NE BY MIDWEEK AS HIGH PRESSURE SETTLES BACK
IN. AS FLOW AGAIN TURNS AROUND TO THE SW...REGION SHOULD SEE
ANOTHER GRADUAL WARMUP FOR LATE WEEK.

&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
IR SATELLITE SHOWS BROKEN LAYER OF SC OVER CENTRAL AND SOUTHWEST
PENNSYLVANIA TONIGHT. IF THESE CLOUDS PERSIST...IT WILL LIMIT FOG
FORMATION OVERNIGHT. HOWEVER...AS PREVIOUS DISCUSSION
NOTED...CONFIDENCE NOT THAT HIGH TO TOTALLY RULE OUT A PERIOD OF
MVFR TO IFR VSBYS BY EARLY MORNING. HAVE CONTINUED TREND OF
INCLUDING MVFR FOG CONDITIONS FOR SEVERAL HOURS AT ALL TAF
LOCATIONS...EXCEPTION IS AT KIPT...WHERE HAVE FOLLOWED GUIDANCE
SUGGESTING THE TYPICAL LOW STRATUS AT JUST A FEW HUNDRED FEET
EARLY IN THE MORNING.

ANY FOG THAT DOES FORM SHOULD BURN OFF BTWN 13Z-14Z. A MOISTURE-
STARVED COLD FRONT WILL BE PUSHING SOUTHEAST THRU THE REGION THIS
AFTERNOON. EXPECT VFR CONDITIONS ACROSS ALL OF CENTRAL
PENNSYLVANIA TODAY INTO TONIGHT...THEN AGAIN WILL SEE SOME FOG
FORMATION THURSDAY NIGHT.


OUTLOOK... FRI...PATCHY AM FOG POSSIBLE...MAINLY NORTH.
SAT...AM LOW CIGS/FOG POSSIBLE.
SUN...SLIGHT CHC OF PM TSRA IMPACTS W MTNS.
MON...NO SIG WX EXPECTED.

&&

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

&&

$$
SYNOPSIS...ROSS/LAMBERT
NEAR TERM...DEVOIR/LAMBERT
SHORT TERM...ROSS
LONG TERM...RXR
AVIATION...JUNG/FITZGERALD



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