812
FXUS61 KCTP 191104
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
704 AM EDT SAT SEP 19 2026
WHAT HAS CHANGED
* NO SIG CHANGES
KEY MESSAGES
1) RAIN MOVES IN TONIGHT, HEAVY AT TIMES INTO SUNDAY.
2) RAINY PATTERN CONTINUES INTO MUCH OF NEXT WEEK, ALTHOUGH
UNCERTAINTY REMAINS IN THE DETAILS.
DISCUSSION
KEY MESSAGE 1: RAIN MOVES IN TONIGHT, HEAVY AT TIMES INTO
SUNDAY.
THE DAYLIGHT HOURS TODAY WILL REMAIN DRY DESPITE PLENTY OF
CLOUDS AROUND. RAINFALL WILL MOVE IN FROM WEST TO EAST AFTER
DARK, WITH THE STEADIEST RAIN AFTER MIDNIGHT. PWAT VALUES ARE
PROGGED TO SURGE INTO THE 1.60-2.00 INCH RANGE BY SUNDAY. A
SURFACE LOW AND PRECEDING 45 KT LLJ ARE PROGGED TO TRACK ACROSS
NORTHERN PA, PROVIDING THE FORCING FOR THE PRECIP. A FEW TO
SEVERAL HUNDRED J/KG OF MUCAPE SHOULD SUPPORT SOME HEAVIER
DOWNPOURS, BUT LITTLE CAPE ABOVE THE -10C LEVEL SUGGESTS THE
LIGHTNING THREAT WILL BE LIMITED TO A FEW RUMBLES. INSTEAD,
EXPECT A BLOSSOMING AREA OF STRATIFORM RAINFALL DURING THE
PREDAWN HOURS. WARM CLOUD DEPTH NEAR 14000 FT ALIGNED WITH THE
LLJ SUGGEST EFFICIENT RAINFALL WITH AMOUNTS TOTALING CLOSE TO
1.50" IN THE NORTHEAST QUADRANT OF PENNSYLVANIA. LESSER AMOUNTS
BETWEEN 0.25 AND 0.50" EXPECTED ACROSS THE SOUTHERN TIER. THE
SOUTHERN TIER COULD SEE A FEW ISOLATED THUNDERSTORMS ALONG A
TRAILING BOUNDARY IN THE LATER AFTERNOON AND EVENING AFTER THE
EARLIER BATCH OF STRATIFORM RAINFALL PUSHES EAST OF OUR REGION.
-------------------------------------------------------------
KEY MESSAGE 2: RAINY PATTERN CONTINUES INTO MUCH OF NEXT WEEK,
ALTHOUGH UNCERTAINTY REMAINS IN THE DETAILS.
POPS ARE PROGGED TO DROP BELOW 40 PCT ON MONDAY (NEAR 0 PCT IN
THE NORTHERN TIER) AS HIGH PRESSURE WEDGES IN FROM THE NORTH.
HOWEVER, THE JET STREAM WILL REMAIN ACTIVE AND AMPLIFIED WITH
PACIFIC DISTURBANCES MOVING ACROSS THE NATION. BY TUESDAY, MOST
GUIDANCE HAS A SLOW MOVING TROUGH IN THE OHIO VALLEY ADVECTING
WARM AIR ABOVE A WEDGE OF COOL SFC AIR IN PLACE FROM THE
AFOREMENTIONED HIGH PRESSURE SYSTEM. THIS SETUP MAY LINGER FOR A
FEW DAYS, WITH UP TO SEVERAL INCHES OF RAINFALL POSSIBLE
THROUGH THE WEEK. COLD AIR DAMMING WILL ALSO RESULT IN HIGH
TEMPS ONLY IN THE 50S TO LOW 60S TUESDAY THROUGH AT LEAST
THURSDAY.
ONE THING WE'LL NEED TO MONITOR CLOSELY IS THE LARGE QPF
GRADIENT / SHARP PRECIP CUTOFF IN THIS TYPE OF SETUP. THE SAME
HIGH PRESSURE SYSTEM PROVIDING STEEPLY SLOPED ISENTROPES WILL
HAVE VERY DRY AIR AT LOW LEVELS NOT FAR NORTH OF THE AREA OF
MAXIMUM ISENTROPIC ASCENT. MODEL GUIDANCE STILL DISAGREES ON
EXACTLY WHERE TO PLACE THE HEAVIEST RAIN ON TUE-WED, AND THE
ECMWF IN PARTICULAR HAS NO RAIN AT ALL ACROSS THE NORTHERN TIER.
LATER IN THE WEEK, A COASTAL STORM WILL LIKELY DEVELOP SOUTH
AND EAST OF LONG ISLAND, FOCUSING THE HEAVIEST RAINFALL TO OUR
EAST (MAYBE CLIPPING OUR EASTERN ZONES) AND WRAPPING A WEDGE OF
DRY AIR AROUND THE WEST SIDE OF THE LOW.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
WINDS WILL SHIFT TO THE EAST THIS MORNING ON THE BACKSIDE OF A
DEPARTING HIGH PRESSURE. LOW-LEVEL CLOUDS WILL BEGIN TO BUILD
OVER THE AREA DURING THE AFTERNOON THOUGH WE SHOULD REMAIN UNDER
VFR CONDITIONS AS ANY CLOUDS LOOK TO BE SCATTERED BETWEEN 4000
AND 5000 FEET.
THIS EVENING, WARM AIR ADVECTION (WAA) INCREASES AHEAD OF AN
APPROACHING LOW PRESSURE SYSTEM, WITH CHANCES OF RAIN/SHOWERS
INCREASING THROUGH THE EVENING AND OVERNIGHT HOURS. MVFR-IFR
CEILINGS ARE FAVORED WITH THE ONSET OF THESE SHOWERS AS LOW-
LEVEL MOISTURE INCREASES. BORDERLINE LLWS CONDITIONS ARE
POSSIBLE AS 925 MB WINDS BUILD TO AROUND 170DEG/35KTS LATER
SATURDAY EVENING INTO EARLY SUNDAY MORNING, WITH LLWS MENTIONS
POSSIBLE AREAWIDE IF PROJECTED WIND SHEAR VALUES INCREASE FROM
CURRENT GUIDANCE (25-30 KTS).
OUTLOOK...
SUN...PERIODS OF RAIN WITH LOCALIZED THUNDERSTORMS EXPECTED.
MVFR RESTRICTIONS ARE LIKELY TO PREVAIL (80%), WITH IFR POSSIBLE
(30-50%), PARTICULARLY IN HEAVIER SHOWERS/STORMS.
MON...RESTRICTIONS POSSIBLE WITH LINGERING MIST AND LOW CLOUDS,
PARTICULARLY ACROSS SOUTH-CENTRAL PA, WITH IMPROVEMENTS UP TO
VFR POSSIBLE TOWARDS NORTH-CENTRAL PA.
TUE-WED...RESTRICTIONS POSSIBLE FROM -SHRA/BR AND LOW CEILINGS.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
WHAT HAS CHANGED...COLBERT
KEY MESSAGES...COLBERT/BOWEN
DISCUSSION...COLBERT/BOWEN
AVIATION...KRANTZ/BAUCO/TEARE
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