013
FXUS61 KCTP 202130
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
530 PM EDT SUN SEP 20 2026
WHAT HAS CHANGED
* TWEAKS TO NEAR TERM BASED ON RADAR/SAT TRENDS
* FLOOD WATCH CONSIDERED, REJECTED FOR NOW
KEY MESSAGES
1) RAIN MOVES TO THE SOUTH EARLY TONIGHT, BUT RETURNS FOR
MONDAY. FLOOD WATCH CONSIDERED.
2) RAIN POTENTIAL CONTINUES FOR MUCH OF THIS WEEK, ALTHOUGH
UNCERTAINTY REMAINS IN THE DETAILS DUE TO OFFSHORE LOW
DEVELOPMENT POSSIBILITIES. ON THE COOL SIDE AS WELL.
DISCUSSION
KEY MESSAGE 1: RAIN MOVES TO THE SOUTH EARLY TONIGHT, BUT
RETURNS FOR MONDAY. FLOOD WATCH CONSIDERED.
NEBULOUS/BROAD SFC LOW PRESSURE OVER THE CWA AT 18Z, SEEMINGLY
CENTERED SOMEWHERE WITHIN 40 MILES OF UNV. SEVERAL SHORT WAVE
TROUGHS CONTINUE TO ROLL INTO AND OVER THE MID-ATLANTIC, BUT
NONE HAVE INSTABILITY TO WORK WITH NORTH OF THE MASON-DIXON LINE.
PWATS REMAIN HIGH, TOUCHING THE 2" MARK IN YORK/LANC COS. FLOW
IS WESTERLY AND CONSTANT, BUT SLIGHTLY CONFLUENT ALOFT. THE
CLOSEST THUNDER AT 18Z IS IN ERN OH AND DROPPING STEADILY SOUTH
ENOUGH THAT IT WILL LIKELY MISS OUR CWA. BUT, OCCASIONAL
SHOWERS/RAIN CONTINUE TO MOVE IN FROM UPSTREAM. QPF STILL LOOKS
LOW ENOUGH (<0.75") THROUGH MIDNIGHT IN THE LAURELS WHERE THE
FFG IS LOWEST (JUST UNDER AN INCH IN SOME PLACES). THAT SHOULD
BE LOW ENOUGH IN INTENSITY/DURATION TO KEEP ANY HYDO PROBLEMS
MINOR AND ISOLATED. AFTER COLLABORATION WITH NEIGHBORING
OFFICES, WE HAD LOW ENOUGH CONFIDENCE IN FLOODING-INTENSITY
RAINFALL TO STAY AWAY FROM A FLOOD WATCH AT THIS POINT IN TIME.
BUT, THE LAURELS (PARTICIULARLY SOMERSET CO) WOULD BE THE PLACE
MOST-SUSCEPTIBLE TO ANY FLOODING INTO LATE THIS EVENING.
CONDITIONS ARE TOO DRY FARTHER EAST, AND THE BULK OF THE RAIN
SHOULD STAY SOUTH OF I-80 FOR THE REST OF THE DAY.
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KEY MESSAGE 2: RAIN POTENTIAL CONTINUES FOR MUCH OF THIS WEEK,
ALTHOUGH UNCERTAINTY REMAINS IN THE DETAILS DUE TO OFFSHORE LOW
DEVELOPMENT POSSIBILITIES. ON THE COOL SIDE AS WELL.
A FAIRLY STRONG SHORT WAVE TROUGH CURRENTLY OVER ROLLS IN FROM
LOWER LM LATE TONIGHT. THAT SHOULD YIELD A RENEWAL OF RAINFALL
IN THE LAURELS. THE SYSTEM WILL STILL BE WORKING WITH 1.5-2.0"
PWATS. BUT, IT WILL ARRIVING AT AN EVEN MORE-STABLE TIME OF DAY.
THE STEADY EAST AND SLIGHTLY NORTHWARD SPREAD OF PRECIP WILL
ONLY REINFORCE THE STABILITY (AND KEEP TEMPS CHILLY) MONDAY.
AGAIN, THUNDER CANNOT BE RULED OUT, BUT WOULD LIKELY BE
ELEVATED. IT MAY REMAIN DRY (OR JUST PATCHY DRIZZLE) ACROSS THE
NORTHERN TIER FOR MUCH OF THE DAY. MODELS FUNNEL THE BEST
MOISTURE INTO THE EASTERN HALF OF PA MONDAY NIGHT, EASING THE
FLOODING POTENTIAL SOMEWHAT FOR THE LAURELS.
EXTREMELY BLOCKY PATTERN ALOFT YEILDS VERY LOW CONFIDENCE IN SFC
FEATURES AND PRECIP POTENTIAL/PLACEMENT BEYOND TUESDAY. LOW
PRESSURE TRIES TO DEVELOP OFF SHORE (ALONG THE GULF STREAM) WED,
BUT MAY BE SHUNTED EASTWARD THROUGH THE SECOND HALF OF THE
WEEK. THE SURE BET THIS WEEK IS FOR BELOW NORMAL MAX TEMPS.
AVIATION /21Z SUNDAY THROUGH FRIDAY/
SCATTERED RAIN CONTINUES TO PLAGUE THE AIRSPACE THIS AFTERNOON
ALONG WITH OVERCAST SKIES AND LOW CLOUDS. MANY AREAS WILL
CONTINUE TO SEE MVFR OR LOWER CEILINGS THROUGH THE REMAINDER OF
THIS AFTERNOON AND INTO TONIGHT. RAIN WILL BE LIKELY ACROSS ALL
AIRFIELDS OVER THE NEXT 12 HOURS, AND ANY SITE IMPACTED BY
PRECIPITATION WILL SEE A REDUCTION IN VISIBILITY. STRENGTH OF
THESE RAIN SHOWERS REMAINS UNCERTAIN, BUT RADAR RETURNS AS OF
18Z SUGGEST RAIN IS LIGHT OVERALL. TIMING OUT THE MAIN LINE OF
PRECIPITATION, IT IS EXPECTED TO RESUME RAINING OVER THE WESTERN
TERMINALS OF BFD AND JST NEAR 20Z.
TONIGHT LINGERING RAIN AND LOW CEILINGS WILL KEEP FLIGHT
CONDITIONS POOR. THERE IS SOME SUGGESTION FROM THE LAMP AND
NAM-MOS THAT A BRIEF PERIOD OF VFR IS POSSIBLE AT IPT NEAR 09Z,
BUT CONFIDENCE REMAINS LOW WITH THE MORE LIKELY SOLUTION WILL BE
CONTINUED MVFR TO IFR CEILINGS. IMPROVEMENT MONDAY MORNING WILL
BE VERY SLOW, WITH CLOUDS NOT EXPECTED TO FULLY SCATTER TO VFR
CONDITIONS UNTIL THE LATE MORNING/EARLY AFTERNOON.
OUTLOOK...
TUE-THU...RESTRICTIONS POSSIBLE FROM -SHRA/BR AND LOW CEILINGS,
MAINLY S.
CLIMATE
AS OF 5 PM, 1.05 INCHES OF RAIN FELL AT AOO (ALTOON) PA TODAY.
THIS BROKE THE OLD RECORD OF 0.73 INCHES SET IN 1957.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
WHAT HAS CHANGED...DANGELO
KEY MESSAGES...DANGELO
DISCUSSION...DANGELO/COLBERT
AVIATION...BOWEN
CLIMATE...MARTIN
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