Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 080204
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1004 PM EDT TUE JUL 7 2015

.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH OVERNIGHT...THEN STALL OUT ALONG
OR JUST SOUTH OF THE MASON DIXON LINE FOR MUCH OR THE REST OF THE
WEEK KEEPING UNSETTLED CONDITIONS IN THE FORECAST FOR THE NEXT
COUPLE OF DAYS. HIGH PRESSURE SHOULD RETURN FOR FRIDAY AND BRING
SLIGHTLY COOLER AND NOTABLY LESS HUMID WEATHER WITH LITTLE CHANCE
FOR RAIN.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
NUMEROUS BOWING LINE SEGMENTS ASSOCIATED WITH AN APPROACHING 850
MB JET MAX AND WEAK MCV TRACKING THROUGH WEST CENTRAL PA PRODUCED
ISOLATED TO SCATTERED WIND DAMAGE ACROSS THE ALLEGHENY PLATEAU
REGION THIS EVENING. IT APPEARS THAT STRONG SPEED SHEAR IS NOW
OVERWHELMING THE FINAL REMNANT CAPE...DECREASING THE DAMAGING WIND
THREAT FROM THE EARLIER MATURE BOWS WHICH PRODUCED A MEASURED WIND
GUSTS OF 64 MPH AT CHICKAREE SUMMIT...AND SEVERAL DAMAGE REPORTS
ACROSS THE NORTHWEST MOUNTAINS.

SPORADIC REPORTS OF POOR DRAINAGE AND AN ISOLATED FLOODED BASEMENT
HAVE BEEN RECEIVED OVER THE NORTHWEST MOUNTAINS...BUT THE HEAVIEST
RAIN IS SHIFTING EASTWARD AS OF LATE EVENING...SO DO NOT SEE THESE
IMPACTS BECOMING MORE WIDESPREAD OR PERSISTING LONG THAN THE NEXT
HOUR OR TWO.

SFC COLD FRONT AT 00Z WAS JUST PUSHING INTO THE NORTHWEST
MOUNTAINS AND APPEARS TO BE BETWEEN KHZY AND KERI AT THIS HOUR.
THE FRONT WILL SLOWLY DROP SSEWARD ACROSS THE COMMONWEALTH
OVERNIGHT...WITH SHOWER COVERAGE CONTINUING TO DIMINISH AS THE
FRONT MOVES SOUTH.

TEMPERATURES WILL BE GENERALLY MILD OVERNIGHT AS MOST OF THE AREA
WILL BE CLOUDY AND HUMID WITH SCATTERED SHOWERS.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
THE SURFACE COLD FRONT WILL STALL OUT CLOSE TO THE MASON DIXON
LINE ON WEDNESDAY. THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL
SHIFT TOWARDS THE SOUTHERN HALF OF PENNSYLVANIA TOMORROW. QPF
VALUES WILL BE LESS THAN A THIRD OF AN INCH IN OUR COUNTIES.

MAX TEMPS WEDNESDAY WILL BE AROUND 10 DEGREES COOLER THAN TODAY AS
CLOUDS WILL DOMINATE THE SKY.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
THE LINGERING QUASI-STATIONARY FRONTAL ZONE EXTENDING FROM THE
MID ATLANTIC COAST WWD INTO THE OHIO VALLEY IS EXPECTED TO REMAIN
A FOCUS FOR PCPN ON DAY 3/THURS. THERE IS REASONABLY GOOD MODEL
AGREEMENT IN A CONVECTIVELY ENHANCED PERTURBATION/SFC WAVE
EMERGING FROM THE SRN PLAINS AND PROGRESSING EWD AROUND THE
PERIPHERY OF A SUBTROPICAL RIDGE OVER THE SOUTHEAST STATES. THE
GLOBAL MODELS TEND TO HAVE A NORTHERN BIAS WITH QPF AXES ASSOCD
WITH THESE MESO FEATURES...AND THEREFORE FOLLOWED WPC LEAD WITH
CLUE FROM THE HI-RES MODELS IN SHIFTING MAX POPS SWD OF CONSENSUS.
THERE IS THE POTENTIAL FOR THIS FEATURE TO MAINTAIN INTENSITY OR
RE-INTENSIFY AS IT REACHES CENTRAL PA THURSDAY AFTERNOON..IN WHICH
CASE IT WOULD BE ACCOMPANIED BY SEVERE WX AND HEAVY RAINFALL
RISK. LATER FORECASTS SHOULD BE ABLE TO PROVIDE GREATER VISIBILITY
AND INCREASED CONFIDENCE IN THE EVOLUTION AND POTENTIAL IMPACTS
ASSOCD WITH THIS SYSTEM.

THE MEDIUM RANGE MODEL AND ENSEMBLE GUIDANCE REMAINS CONSISTENT
IN ITS PROJECTION THAT THE FLOW ALOFT WILL STEADILY EVOLVE TOWARD
AN AMPLIFIED TROUGH/RIDGE/TROUGH PATTERN FROM WEST TO EAST ACROSS
THE LOWER 48. THIS SHOULD OCCUR BY WAY OF NRN PAC ENERGY FEEDING
INTO A TROUGH ALONG THE WEST COAST...A STRENGTHENING UPPER RIDGE
THAT RETROGRADES WWD FROM THE SOUTHEAST INTO THE PLAINS EVENTUALLY
EXPANDING NWD OVER THE ROCKIES INTO WRN CANADA...AND DOWNSTREAM
TROUGHING FROM THE BUILDING RIDGE OVER THE EAST EXTENDING SWD FROM
HUDSON BY VORTEX.

A 24-48HR PERIOD OF DRY WEATHER...WHICH HAS BEEN QUITE ELUSIVE AS
OF LATE...COULD BE IN STORE FOR THE AREA BY THE END OF THE WEEK
AS WEAK RIDGING FOLLOWS IN THE WAKE OF THE D3 CONVECTIVE LOW. THE
PLACEMENT OF PIVOTING FRONTAL BOUNDARY AND ASSOCIATED MSTR/PW AXIS
WILL BE CRUCIAL FOR DETERMINING PCPN RISK INTO THE WEEKEND...WITH
THE LATEST MODEL CONSENSUS KEEPING MOST OF THE ACTIVITY TO THE NW
OR SW OF CENTRAL PA. THE OTHER FACTOR WILL BE WHAT HAPPENS TO
ENERGY EJECTING FROM UPPER LOW MOVING ONSHORE CA IN THE SHORT
RANGE. THERE IS REASONABLE AGREEMENT IN PRINCIPLE THAT THIS
ENERGY SHOULD ROUND THE BUILDING ROCKIES/HIGH PLAINS RIDGE AND
THEN HELP TO CARVE OUT THE DEVELOPING ERN TROUGH DOWNSTREAM.
HOWEVER SOLUTIONS HAVE NOT LOCKED ONTO HOW SHEARED THE ENERGY WILL
BECOME...WHICH ALONG WITH A FEW ADDITIONAL FACTORS LEADS TO
DIFFERENCES IN THE DEPTH OF THE TROUGH AND TIMING OF NEXT PCPN
OPPORTUNITY.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
MOST OF CWA REMAINS VFR THIS EVENING...AS REGION REMAINS IN THE
WARM SECTOR AHEAD OF AN APPROACHING COLD FRONT OVER THE OHIO
VALLEY. BUT THUNDERSTORMS ARE ALREADY IMPACTING THE NW MTNS AND
KBFD AT 22Z...BRINGING SHORT-LIVED REDUCTIONS TO BOTH CIG AND VSBY
ALONG WITH SOME GUSTY WINDS.

AS THE FRONT ENTERS NW PA THIS EVENING...SHOWERS AND THUNDERSTORMS
WILL CONTINUE TO IMPACT THE NW MTNS AND KBFD THROUGH THE EVENING
HOURS. EXPECT ANOTHER WAVE OF TSTMS TO SLIDE ACROSS THROUGH
03Z...FOLLOWED BY A COUPLE HOUR PERIOD OF STRATIFORM RAIN
WITH FROPA AS CIG RESTRICTIONS BEGIN.

AS THE COLD FRONT PUSHES SLOWLY SOUTH ACROSS THE AIRSPACE
OVERNIGHT...SCATTERED TO NUMEROUS SHOWERS/TSTMS WILL IMPACT
CENTRAL MTNS STARTING MID EVEING...WITH JUST SCT TSTMS POSS IN
THE SE OVERNIGHT. BY MORNING...CONDITIONS WILL BE MVFR/IFR IN ALL
BUT FAR SE. THE FRONT WILL SETTLE SOUTH WEDNESDAY BEFORE STALLING
OUT ALONG THE MASON DIXON LINE.

WAVES OF LOW PRESSURE WILL MOVE ALONG THE FRONT AND BRING PERIODS
OF SHOWERS/THUNDERSTORMS ALONG WITH REDUCED CONDITIONS INTO
THURSDAY.

OUTLOOK...

WED...SHOWERS/TSTMS LIKELY SOUTH...SCATTERED NORTH.

THU...SHOWERS/TSTMS LIKELY. CIG RESTRICTIONS LIKELY NORTH...LOCAL
RESTRICTIONS SOUTH.

FRI-SUN...MAINLY VFR. CHC OF SHOWERS/TSTMS SW 1/3 OF AIRSPACE.

&&

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

&&

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


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