Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 312116
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
516 PM EDT FRI JUL 31 2015

.SYNOPSIS...
HIGH PRESSURE OVER THE CENTRAL U.S. WILL NOSE INTO THE REGION THIS
WEEKEND. A PERSISTENT UPPER LEVEL TROUGH WILL SIT OVER THE GREAT
LAKES AND NORTHEAST STATES THIS WEEKEND...AND SEND A FEW WEAK
FRONTS SOUTHEAST ACROSS PENNSYLVANIA. EACH OF THESE FRONTS WILL
CONTAIN LIMITED MOISTURE...WITH THE ABILITY TO PRODUCE JUST
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
HIGH PRESSURE RIDGE EXTENDING NE INTO THE REGION FROM THE OHIO
RIVER VALLEY WILL PROVIDE MOSTLY SUNNY SKIES ACROSS THE SOUTHEAST
HALF OF PENN...WITH NEARLY ZERO CHC FOR SHOWERS.

INCREASING MOISTURE...REFLECTED BY A FEW SW/NE ORIENTED RIBBONS
OF HIGHER THETA-E AT 850 MB /AND 1.25-1.5 INCH PWATS/ WILL PUSH
ACROSS NWRN PENN LATE THIS AFTERNOON INTO TONIGHT AHEAD OF AN
UPPER TROUGH AND CFRONT DROPPING ESE FROM THE UPPER GLAKES.
CU FIELD HAS EXPANDED AND GROWN ENOUGH VERTICALLY TO PRODUCE
ISOLATED LIGHT SHOWERS ACRS THE NW MTNS INVOF KBFD...AND THIS
COVERAGE IS EXPECTED TO GROW JUST SLIGHTLY THROUGH DUSK.

SFC BASED CAPE /VIA THE MORE AGGRESSIVE NAM/ WILL REMAIN UNDER
500 J/KG ACROSS THE SE HALF OF THE STATE...WHILE RAMPING UP TO
OVER 1000 J/KG ACRS FAR NWRN PENN BY 00Z SAT. 14Z RUN OF THE 13KM
RAP...AND A SIMILAR SOLUTION GIVEN BY THE 09Z SREF INDICATE THAT
ENOUGH INSTABILITY TO PRODUCE SCTD SHRA/TSRA WONT ARRIVE ACROSS
OUR FAR NW ZONES UNTIL AT LEAST 02Z SAT /ENHANCED BY COOLING MID
LEVELS AND INCREASING UPPER LVL DIFFLUENCE/.

TEMPS ARE NEARING LATE AFTERNOON HIGHS THAT WILL BE SEVERAL DEG F
ABOVE NORMAL.

APPROACHING SFC TROUGH /CURRENTLY NEAR THE OHIO-PENN BORDER/ AND
QUICKLY TRAILING CFRONT PUSHING THROUGH LOWER MICHIGAN
ATTM....WILL BRING A FEW SHOWERS AND ISOLATED TSRA TO MAINLY THE
NRN MTNS OF PENN LATE TODAY AND TONIGHT. CHC FOR ANY CONVECTION
WILL QUICKLY DIMINISH TO THE SOUTH OF INTERSTATE 80.

LOWS TONIGHT WILL VARY FROM THE MID 50S ACROSS THE NW MTNS...TO
THE LOWER AND MID 60S THROUGHOUT THE SOUTHERN VALLEYS.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
THE WEAK COLD FRONT WILL EXIT OUR EASTERN ZONES DURING THE MID TO
LATE MORNING HOURS WITH ISOLATED-SCATTERED SHOWERS.
AFTERWARD /AND VERY SIMILAR TO FRIDAY/...SFC HIGH PRESSURE RIDGE
WILL BUILD BACK INTO THE REGION FROM THE OHIO RIVER VALLEY.

SFC DEWPOINTS SHOULD EDGE DOWN BY 3-5 DEG F COMPARED TO FRIDAY/S
VALUES. THIS WILL LEAD TO MAINLY SCATTERED FAIR WEATHER CU...WITH
LITTLE IF ANY CHC FOR AFTERNOON SHOWERS TO THE SOUTH OF I-80.
SLIGHTLY STEEPER MID-LEVEL LAPSE RATES /AROUND 6C PER KM/ ACROSS
THE NRN MTNS WILL LEAD TO AREAS OF MDT TO TCU WITH A FEW SHOWERS
DOTTING THE RADAR SCOPE AFTER 17Z.

MAX TEMPS WILL BE NEAR NORMAL OVER THE CENTRAL AND SE
VALLEYS...BUT A FEW DEG COOLER THAN NORMAL ACROSS THE NRN AND WRN
MTNS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
LITTLE CHANGE IS ANTICIPATED IN LARGE SCALE FLOW PATTERN ACROSS
THE CONUS THROUGH THE EXTENDED PERIOD. A BROAD UPPER TROUGH
EXTENDS SOUTHWARD FROM EASTERN CANADA ACROSS THE ERN U.S.

TEMPERATURES SHOULD AVG NEAR NORMAL INTO EARLY NEXT WEEK BEFORE
TRENDING COOLER LATER IN THE WEEK. SEVERAL SHORT WAVES WILL ROTATE
AROUND THE UPPER LOW IN A FASHION REMINISCENT OF WINTER. AS IS THE
CASE WITH MOST UPPER LOW VS. SHORT WAVE SPOKES...CONFIDENCE IS
LOW ON TIMING OF PCPN CHANCES.

&&

.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
NICE MID SUMMER AFTERNOON OUTSIDE. VFR CONDITIONS PREVAIL ACROSS
THE AREA. SOME SHOWERS AND STORMS NEAR THE LOWER LAKES...BUT
THESE SHOULD STAY NORTH OF OUR AREA.

ONLY MINOR CHANGES NEEDED FOR 21Z TAF PACKAGE.

EARLIER DISCUSSION BELOW.

SFC HIGH PRESSURE RIDGING NE INTO THE REGION FROM THE OHIO RIVER
VALLEY...WILL SAG SE LATE TODAY AND TONIGHT...ALLOWING A WEAK SFC
TROUGH...THEN MOISTURE CHALLENGED CFRONT TO SLIDE SE OVERNIGHT.

ISOLATED TO SCTD SHOWERS AND TSRA ARE POSSIBLE LATE THIS AFTERNOON
AND TONIGHT...MAINLY AT TAF SITES TO THE NORTH OF INTERSTATE 80.

OTHERWISE...WIDESPREAD VFR WILL CONTINUE THROUGH THIS WEEKEND.

OUTLOOK...

SAT...MAINLY VFR...SCATTERED SHOWERS/THUNDERSTORMS.

SUN...MAINLY VFR.

MON-WED...VFR...EXCEPT FOR BRIEF MVFR IN ISOLATED-SCATTERED
MAINLY AFTERNOON AND EVENING SHOWERS/THUNDERSTORMS.

&&

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

&&

$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...MARTIN/TYBURSKI
AVIATION...LAMBERT/MARTIN


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