Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 301953
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
353 PM EDT WED JUL 30 2014

.SYNOPSIS...
UPPER LEVEL LOW PRESSURE WILL STAY ANCHORED OVER JAMES BAY CANADA
THROUGH FRIDAY EVENING BEFORE WEAKENING AND MOVING TO THE
NORTHEAST. ANOTHER TROUGH FORMING OVER THE LOWER OHIO VALLEY AND
TRANSPORT A PLUME OF DEEP GULF AND WESTERN ATLANTIC MOISTURE
NORTHWARD THIS WEEKEND...BRINGING NUMEROUS SHOWERS AND
THUNDERSTORMS ACROSS THE SOUTHEASTERN HALF OF PENNSYLVANIA.
TEMPERATURES WILL REMAIN COOLER THAN NORMALS.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
2 PM UPDATE...

MU CAPE GRADUALLY INCREASING THROUGH THE EARLY AFTERNOON
HOURS...AND HAS REACHED BETWEEN 500-1000 J/KG ACROSS THE NW HALF
OF THE CWA AS OF 18Z.

THIS WEAK TO MODERATE INSTABILITY /NEAR THE LEADING EDGE OF
SLIGHTLY STEEPER MID LEVEL LAPSE RATES/ IS COMBINING WITH WEAK
LARGE SCALE LIFT AHEAD OF AN APPROACHING UPPER LEVEL SHORT WAVE TO
BRING A A FEW BKN LINES AND CLUSTERS OF SHOWERS AND ISOLATED LOW-
TOPPED TSRA TO THE NW THIRD OF THE CWA SO FAR.

ACROSS THE SE HALF OF THE STATE...SCATTERED/FLATTER CU AND MID
LEVEL CLOUDS WERE NOTED...AS A RESULT OF WEAK WESTERLY ISENTROPIC
UPGLIDE WITHIN THE 300-310K THETA LAYER.

THE LOWER SUSQ VALLEY SHOULD STAY DRY RIGHT THROUGH THE REST OF
THE DAYLIGHT HOURS BEFORE SOME WEAKENING SHOWERS DRIFT INTO THE
AREA BETWEEN 00-04Z THURSDAY...AS THE LEADING EDGE OF THE POOL OF
SLIGHTLY STEEPER MID LEVEL LAPSE /6-6.5C PER KM/ APPROACHES.

TEMPS WILL RISE JUST ANOTHER 1-3 DEG F FOR THE REST OF THIS
AFTERNOON...WITH HIGHS VARYING FROM THE MID AND UPPER 60S ACROSS
THE NW MTNS...TO THE LOWER AND MID 70S IN THE CENTRAL
VALLEYS...AND UPPER 70S TO AROUND 80F THROUGHOUT THE LOWER SUSQ
VALLEY.

THESE READINGS ARE STILL 6-9 DEGREES F BELOW NORMAL IN MOST
LOCATIONS /ESPECIALLY ACROSS THE NW MTNS WHERE THE EARLIER DVLPMT
OF THE CLOUD COVER HAS FLATTENED THE DIURNAL TEMP CURVE/.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
THE DIURNAL CONVECTION WILL SLIDE TO THE EAST ACROSS THE SUSQ
VALLEY THIS EVENING WHILE FIZZLING OUT. THE COLD AIR ALOFT AND
CYCLONIC FLOW WILL LIKELY KEEP A FEW /LOW TO MID/ CLOUD LAYERS
AROUND THROUGH THE NIGHT /WITH A FEW SHOWERS POSSIBLE MAINLY
ACROSS THE NW MTNS/.

MIN TEMPS WILL BE CLOSER TO NORMAL TONIGHT...BUT SOME READINGS
IN THE 40S ARE STILL POSSIBLE ACROSS THE NR MTNS REGION AND
PERHAPS A FEW OF THE COLD SPOTS ACROSS THE HIGH TERRAIN OF
SOMERSET COUNTY.

THE UPPER LOW THROWS ONE MORE UPPERCUT AT NRN PENN THURSDAY
MORNING...BEFORE REFUELING TEMPORARILY FOR A DAY OR SO ACROSS THE
LOWER OHIO VALLEY.

SCT/NMRS SHOWERS ARE EXPECTED TO AFFECT THE NRN THIRD TO HALF OF
THE CWA IN THE MORNING. THE AFTERNOON SHOULD TURN OUT TO BE MAINLY
DRY - WITHIN AN AREA OF LARGE SCALE SUBSIDENCE AND WEAK SFC HI
PRESSURE IN THE WAKE OF THE UPPER WAVE.

TEMPS ALOFT WILL STILL BE COOL AND DAYTIME INSTABILITY SHOULD BE
GOOD ENOUGH FOR ISOLD-SCT SHOWERS IN THE WEST/NORTH DURING THE MID
TO LATE AFTERNOON.

HIGHS TEMPS THURSDAY MAY TRY TO SNEAK BACK TO NORMAL IN THE
SE...BUT THE N/W ZONES WILL PROBABLY STILL BE 8-10 DEGS BELOW
SEASONAL NORMALS GIVEN MORE IN THE WAY OF CLOUDS AND SCATTERED
SHOWERS.

THE THURSDAY NIGHT PERIOD CONTINUES TO LOOK LIKE THE LEAST LIKELY
TIME FOR ANY SHOWERS TO DEVELOP WITH 500 MB HEIGHT RISE OF A FEW
DAM...AND WEAK RIDGING OVER THE AREA AT THE SFC. LOWS EARLY FRIDAY
MORNING WILL BE SIMILAR TO THE PREV FEW NIGHTS WITH SKIES TRYING
TO CLEAR AND WINDS GENERALLY LIGHT/VARIABLE.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
THE GLOBAL MODELS AND ENSEMBLE MEMBERS SHOW THE HIGHLY AMPLIFIED
NOAM WESTERN RIDGE/EASTERN TROUGH CONFIGURATION RELAXING INTO
EARLY NEXT WEEK...BUT OTHERWISE MAINTAINING ITS ORIENTATION. THE
RISING 500MB HGTS SHOULD ALLOW TEMPERATURES TO EDGE BACK TOWARD
EARLY AUGUST CLIMATE NORMALS. THE GENERAL PATTERN REMAINS UNSETTLED
THROUGH THE WEEKEND.

THE MEAN UPPER TROUGH AXIS SHIFTS WWD TO NEAR 90W WHICH SHOULD
ALLOW THE QSTNRY FRONTAL ZONE DRAPED ALONG THE EASTERN SEABOARD
TO DRIFT WWD ALONG THE I-95 CORRIDOR. THE 12Z GEFS SHOWS PLUME OF
HI PWATS POOLING NEAR THE SFC BOUNDARY ALONG/E OF THE APPLCHN
SPINE. THIS SUGGESTS THE POTENTIAL FOR HVY RAFL SETTING UP FROM
THE SRN MID ATLC STATES UP INTO SERN PA/DELMARVA/NJ AREAS. THERE
ARE STILL SOME QPF DIFFERENCES BUT THE LATEST RUNS SEEM TO BE
CONVERGING TOWARD THE IDEA THE THE MAIN QPF AXIS WILL BE EAST OF
THE APPLCHNS...ALTHOUGH THE DIURNAL CYCLE AND INDIVIDUAL SHORTWAVES
MOVING THROUGH THE LW TROUGH WILL PLAY A ROLE IN THE DURATION AND
PLACEMENT.

CONDITIONS SHOULD IMPROVE INTO EARLY NEXT WEEK AS THE HI PWAT
PLUME SHIFTS S/E AND DRIER AIR ARRIVES ACCOMPANIED BY SFC HIGH
PRES ON MON. NRN STREAM ENERGY IS SLATED TO PUSH A COLD FRONT SWD
INTO THE AREA BY NEXT TUE/WED WHICH MAY STALL OUT FROM THE OH VLY
INTO THE MID ATLC STATES.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
INCREASING /BUT MAINLY VFR CLOUDS/ WILL OCCUR EAST OF THE
I-99/ROUTE 22 CORRIDOR IN CENTRAL PENN AND THE SUSQ VALLEY
THROUGH LATE THIS AFTERNOON. THE NW MTNS AND LAUREL HIGHLAND
AIRFIELDS WILL SEE A DUAL LAYER OF STRATO CU AND ALTO CU CLOUDS
WITH CONVECTIVE BASES AROUND 3-4 KFT AGL WITH THE MID LEVEL BASES
AROUND 7 KFT AGL.

THE APPROACH OF A WEAK COLD FRONT AND UPPER TROUGH WILL LEAD TO
INCREASINGLY NUMEROUS SHOWERS /AND ISOLATED TSRA WITH BRIEF MVFR
RESTRICTIONS POSSIBLE/ LATE THIS AFTERNOON AND EARLY THIS
EVENING...MAINLY TO THE NW OF A LINE FROM KAOO TO KIPT.

MAINLY VFR FOR TONIGHT WITH LINGERING BKN ALTO CU CLOUDS...AND
PERHAPS A FEW STRAY LIGHT SHOWERS.

A STRONGER 500 MB TROUGH WILL ROTATE ACROSS THE AREA
ON THU...ACCOMPANIED BY ANOTHER ROUND OF SCTD SHOWERS AND STORMS
/MAINLY ACROSS NRN PENN/.

A BRIEF DRY PERIOD WITH WEAK RIDGING AT THE SFC AND ALOFT OVER THE
REGIONAL AIRFIELDS THU NIGHT AND FRI.

AFTERWARD...A POTENT UPPER TROUGH WILL FORM OVER THE LOWER OHIO
VALLEY AND LIFT SLOWLY NE TWD THE MID ATL REGION OVER THE WEEKEND.
DEEP MOISTURE SURGING NWD FROM THE GULF AND WRN ATLANTIC WILL
BRING PERIODS OF SHOWERS AND TSRA OVER THE WEEKEND /FOCUSED ACROSS
THE SE HALF OF THE STATE/.

OUTLOOK...
THU...SCT TSRA IMPACTS POSSIBLE.
FRI-SUN...SCT PM TSRA IMPACTS POSSIBLE.
MON-TUE...SLOW IMPROVEMENT EXPECTED WITH AREAS OF MVFR POSSIBLE
MAINLY IN THE MORNING.

&&

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

&&

$$
SYNOPSIS...DANGELO/LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...DANGELO/LAMBERT
LONG TERM...STEINBUGL
AVIATION...LAMBERT



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