Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 191842
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
242 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 MIDNIGHT TONIGHT/...
VIS SATL IMAGERY AND SFC OBS SHOW THAT LOW CLOUDS AND HAVE FOG
DISSIPATED...WITH ABUNDANT SUNSHINE EXPECTED ACROSS CENTRAL PA
INTO THE AFTERNOON HOURS. TEMPS SHOULD RESPOND NICELY...REACHING
INTO 60S AND L70S. THESE VALUES ARE JUST A FEW DEGS BELOW NORMAL
FOR THE BEGINNING OF FALL.

&&

.SHORT TERM /MIDNIGHT THROUGH 6 PM SATURDAY/...
HIGH PRESSURE MOVING OFF THE NEW ENGLAND COAST TONIGHT WILL FORCE
A LONG-FETCH OFF THE ATLANTIC TO ASCEND THE MOUNTAINS OF CENTRAL
PA. THIS SHOULD CREATE A BLANKET OF CLOUDS AND DRIZZLE/FOG AS IT
SETTLES IN THROUGH THE NIGHT. BUT...THE WINDS CONTINUE TO VEER
ON SATURDAY AND SHOULD ALLEVIATE THE LOW-CLOUD PROBLEM LATE IN
THE MORNING AND EARLY AFTERNOON ON SATURDAY. OVERNIGHT MINS WILL
LIKELY BE A TOUCH ABOVE NORMAL...BUT WITH THE EXPECTED INCREASE
IN SUNSHINE THROUGH THE DAY...MAXES WILL TRY TO RUN UP 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 THURSDAY/...

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 /19Z FRIDAY THROUGH WEDNESDAY/...
A LARGE AND RATHER STRONG AREA OF SURFACE HIGH PRESSURE CENTERED
OVER SRN QUEBEC THIS AFTERNOON WILL CREATE A LIGHT EAST TO
SOUTHEAST WIND AT ALL TAF SITES THROUGH THIS EVENING. VFR
EXPECTED IN ALL AREAS THROUGH 04-06ZZ SATURDAY.

WIDESPREAD LOWS CIGS IN THE LOW MVFR TO IFR RANGE /WITH SOME
DRIZZLE/ LOOK LIKELY AT MANY AIRFIELDS LATE TONIGHT THROUGH THE
MORNING HOURS SATURDAY AS THE SERLY-SOUTHERLY LLVL FLOW
TRANSPORTS ATLANTIC MOISTURE /FROM NEAR THE VA/NC COAST/ OVER THE
APPALACHIANS. LLWS IS ALSO PROBABLE AT ALL TAF SITES LATE TONIGHT
AND SATURDAY MORNING THANKS TO A MODERATELY STRONG SOUTHERLY WIND
OF 30-35 KTS AT 1.5-2KFT AGL TOPPING THE 5-10KT SSERLY SFC WIND.

OUTLOOK...
SAT...AM LOW CIGS/FOG POSSIBLE.
SUN...SLIGHT CHC OF PM TSRA IMPACTS W MTNS.
MON-TUE...NO SIG WX EXPECTED.

&&

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

&&

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



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