Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 200019
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
819 PM EDT FRI SEP 19 2014

.SYNOPSIS...
GENERALLY FAIR WEATHER WILL BE INTERRUPTED FRIDAY NIGHT AND
SATURDAY MORNING AS ATLANTIC MOISTURE POOLS OVER THE CENTRAL PA
MOUNTAINS. A FRONTAL SYSTEM WILL BRING A CHANCE OF SHOWERS TO THE
REGION ON SUNDAY...BEFORE ANOTHER LARGE AREA OF HIGH PRESSURE AND
A BLOCKING UPPER-LEVEL RIDGE OVER CENTRAL CANADA BRINGS MORE FAIR
AND COOL WEATHER FOR MOST OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
LAST OF THE VISUAL SHOTS SHOWED LOW CLOUDS INVADING NORTH UNDER
THE SSE MARITIME FLOW. EXPECT THESE CLOUDS TO LOWER AND BECOME
MORE WIDESPREAD OVERNIGHT AS THE LONG FETCH OFF THE ATLANTIC
ASCENDS THE MOUNTAINS OF CENTRAL PA. THIS SHOULD CREATE A
WIDESPREAD OVERCAST WITH AREAS OF DRIZZLE/FOG WHICH WILL LAST
THROUGH THE SUNRISE HOURS.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
THE WINDS SHOULD CONTINUE TO VEER ON SATURDAY ALLOWING THE LOW
CLOUDS TO BREAK UP BY LATE MORNING AND EARLY AFTERNOON. AFTER A
CLOUDY START...TEMPS WILL REBOUND NICELY IN THE AFTERNOON WITH
MAXES RISING INTO THE 70S FOR MOST PLACES - ESP IN THE VALLEYS OF
THE SE WHERE THERE SHOULD BE LESS CLOUD COVER. WILL HOLD THE TEMPS
AROUND 70F ALONG THE SPINE OF THE MOUNTAINS WHERE THE CLOUDS WILL
TAKE LONGEST TO BREAK.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
ALL OF THE GUIDANCE SHOWS A FRONTAL SYSTEM MOVING NORTHWEST TO
SOUTHEAST ACROSS THE STATE OVERNIGHT SATURDAY INTO SUNDAY EVENING.
THIS IS MOST LIKELY THE ONLY RAIN EVENT THAT SHOULD AFFECT THE
REGION OF THE NEXT 7-12 DAYS AS A BLOCKING 500 HPA RIDGE WITH OVER
2 SIGMA HEIGHT ANOMALIES SHOULD PROVIDE A PROLONGED PERIOD OF DRY
WEATHER.

AT THIS TIME THE MODELS AND ENSEMBLES ALL IMPLY AN INCREASE IN
SHOWER ACTIVITY AFTER MIDNIGHT NORTHWESTERN PENNSYLVANIA AND
TOWARD SUNRISE IN CENTRAL AREAS EARLY MORNING. THE GEFS AND SREF
BOTH IMPLY THE 12 HOUR PERIOD FOR THE BEST RAINFALL WILL BE
BETWEEN ABOUT 8 AM AND 8 PM SUNDAY. THE RAINFALL LINGERS IN THE
ENSEMBLE PDF UNTIL BETWEEN 8 AND 2 AM SUNDAY NIGHT INTO MONDAY IN
THE EAST. THE RAPIDLY LOWERING PW FIELD IMPLIES ALL RAIN GONE IN
EAST AFTER MIDNIGHT SUNDAY.

AT THIS TIME THE HIGHER POPS AND HIGHER QPFS SHOULD BE IN THE
NORTHERN AREAS. FEW MEMBERS OF ANY EFS SHOW MUCH MORE THAN 0.25
INCHES WITH PERHAPS 40 PERCENT SHOWING 0.50 INCHES IN THE NORTHERN
AREAS. MOST QPFS IMPLY A 0.10 TO 0.20 INCH RAINFALL EVENT. KIND OF
ANEMIC. DID MENTION THUNDERSTORMS AS THERE IS A WARM SURGE AND
SOME HINTS OF MODEST CAPE IN THE HIGHER RESOLUTION MODELS AND EFS
PERHAPS 600 TO 800JKG-1. LOWER IN THE GEFS. A FEW THUNDERSTORMS
COULD BOOST QPFS UP A BIT IF THEY APPEAR.

HIGH PRESSURE BUILDS IN MONDAY BEHIND THE FRONT AND SORT OF PARKS
ITSELF OVER NEW YORK AND NEW ENGLAND WITH +2 TO +3 SIGMA ABOVE
NORMAL MSLP ANOMALIES BY WEDNESDAY-THURSDAY. HIGH CONFIDENCE IN
THIS FORECAST AS THE MODELS ALL SHOW A BLOCKING 500 HPA
ANTICYCLONE TO THE NORTHWEST AS A MASSIVE 500 HPA POSITIVE HEIGHT
ANOMALY OF +2 TO +3 SIGMA DEVELOPS OVER CENTRAL CANADA BY THURSDAY
AND INTO FRIDAY.

OUR MODELS AND EFS DO WELL FORECASTING ANTICYCLONES. SO I AM
HIGH ON THE FAIR WEATHER FORECAST NEXT WEEK.

ONLY FUN ISSUES ARE HOW MUCH RAIN SUNDAY AND HOW SUNNY WILL IT GET
BEHIND THE FRONT MONDAY. DID NOT ATTEMPT TO DRAW THE DIURNAL FOG
AND LOW CLOUDS LIKELY TO AFFECT THE REGION ONCE THE BIG HIGH TAKES
HOLD. THIS WILL BE A NEARLY IDEAL DIURNAL FOG PATTERN WED-SUNDAY.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
MOIST SERLY FLOW OFF OF THE ATLANTIC...COMBINED WITH OROGRAPHIC
LIFT AND COOLING BLYR...IS CAUSING STRATO-CU TO EXPAND ACROSS
CENTRAL PA THIS EVENING. AT 00Z...CIGS ARE GENERALLY IN THE 5-7KFT
RANGE. HOWEVER...MODEST RADIATIONAL COOLING OF BLYR WILL CAUSE
CIGS TO LOWER OVERNIGHT. LATEST MDL SOUNDINGS SUGGEST ALL SITES
WILL REMAIN VFR THROUGH ABOUT 04-06Z BEFORE CONDS DETERIORATE TO
MVFR/IFR. A GRADUAL WIND SHIFT FROM SE TO SOUTH OVERNIGHT WILL FAVOR
THE N MTNS FOR THE BEST OROGRAPHIC LIFT AND HIGHEST CHANCE OF IFR
CIGS. FURTHER SOUTH...CONFIDENCE IN IFR CONDS LATE TONIGHT IS NOT
VERY HIGH. CONDITIONAL CLIMATOLOGY AND LATEST SREF OUTPUT SUGGEST
MVFR CIGS MORE LIKELY LATE TONIGHT ACROSS CENTRAL AND SOUTHERN
PA...DESPITE THE MORE PESSIMISTIC MOS GUIDANCE.

EARLY LOW CLOUDS SHOULD MIX OUT BY LATE AM. MDL DATA THEN
SUPPORTS A HIGH CONFIDENCE OF VFR CONDS DURING THE AFTN AND
EVENING...AS HIGH PRES RIDGE REMAINS OVR THE AREA.

OUTLOOK...
SUN...AM FOG POSSIBLE EASTERN PA. SLIGHT CHC OF PM TSRA IMPACTS W MTNS.
MON...AM LOW CIGS POSS W MTNS.
TUE-WED...NO SIG WX EXPECTED.

&&

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

&&

$$
SYNOPSIS...GRUMM/LA CORTE/GARTNER
NEAR TERM...LA CORTE/GARTNER
SHORT TERM...DANGELO/GARTNER
LONG TERM...GRUMM
AVIATION...FITZGERALD


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