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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 301916
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
316 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 /THROUGH TONIGHT/...
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 /THURSDAY 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/...
A DEEP UPPER LEVEL TROUGH WILL BE PRESENT ACROSS SOUTHEASTERN
CANADA EARLY IN THE LONG TERM PERIOD...BUT WILL RELOAD WITH A
SIGNIFICANT CHUNK ENERGY DIGGING INTO IT/S SW FLANK ACROSS THE
MID MISS AND OHIO RIVER VALLEYS LATE THIS WEEK AND OVER THE
UPCOMING WEEKEND /AS THE CANADIAN PORTION SHEARS OUT TO THE NE/.

THIS POTENT SHORTWAVE TROUGH /AND AN ASSOCIATED WELL-DEFINED RIGHT
ENTRANCE REGION OF A 90-95 KT 300 MB JET/ WILL LIFT NORTHEAST
ACROSS THE MID ATLANTIC REGION FRIDAY THROUGH SUNDAY BEFORE
SHIFTING TO THE SOUTHERN NEW ENGLAND COAST BY THE START OF NEXT
WEEK. A SLOW MOVING /AND LIKELY STRENGTHENING/ BAROCLINIC ZONE...
AND ONE OR MORE WAVES OF WEAK LOW PRESSURE MVG NE ALONG IT WILL
BE LOCATED ACROSS CENTRAL OR ERN PENN DURING THIS 2-3 DAY PERIOD.

PERIODS OF UNSETTLED WEATHER /SHOWERS AND TSTMS/ WILL OCCUR LATER
FRIDAY...SATURDAY AND SUNDAY. THE STRENGTH OF THE LARGE SCALE
FORCING AND INCREASINGLY ANOMALOUS HIGH PWAT AIR BENEATH THE
NORTHWARD MIGRATING JET AND ITS THERMALLY DIRECT BRANCH WILL BRING
THE POTENTIAL FOR SOME LOCALLY HEAVY/TRAINING SHOWERS AND TSRA...
ESP ACROSS THE EASTERN HALF OF THE STATE/.

MODEL DETAILS DIFFER SLIGHTLY WITH RESPECT TO THE TIMING AND
LOCATION OF THE STRONGEST MESO/LARGER SCALE FORCING. BUT ALL
GUIDANCE AGREES ON THE BASIC EVOLUTION AND NE MOVEMENT OF THIS
TROUGH AND AXIS OF HIGH 40-50MM PWAT AIR RIDING NWD UP ALONG THE
MID ATLANTIC PIEDMONT AND SPREADING ACROSS THE EASTERN HALF OF OUR
CWA.

AS A RESULT OF THESE TIMING/LOCATION DIFFERENCES...POPS WERE
CAPPED OFF IN THE HIGH CHC CATEGORY. BUT AS THE FINER DETAILS
UNFOLD WITH HIGHER RES MODEL GUIDANCE OVER THE NEXT FEW
DAYS...POPS WILL UNDOUBTEDLY TREND HIGHER FOR SEVERAL PERIODS
BETWEEN LATE FRIDAY AND SUNDAY.

GRADUAL IMPROVEMENT WITH NEAR NORMAL TEMPS IS EXPECTED FOR EARLY
NEXT WEEK.

&&

.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...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...LAMBERT/STEINBUGL
AVIATION...LAMBERT