136
FXUS61 KCTP 170132
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
932 PM EDT TUE SEP 16 2025
SYNOPSIS
* INCREASING CLOUDS ACROSS THE REGION TONIGHT AND WEDNESDAY WITH
COOLER TEMPERATURES WEDNESDAY AFTERNOON.
* PERIODS OF LIGHT RAIN WILL CONTINUE ACROSS SOUTHEASTERN
PENNSYLVANIA THROUGH WEDNESDAY NIGHT; ACCUMULATIONS GENERALLY
0.1-0.25 INCHES.
* DRY CONDITIONS RETURN AREAWIDE ON THURSDAY AND WILL PERSIST THROUGH
THE WEEKEND.
NEAR TERM /THROUGH WEDNESDAY/
A COASTAL LOW PRESSURE SYSTEM IS CURRENTLY LOCATED OFF THE
COAST OF VIRGINIA AND CONTINUES TO PRODUCE A SHIELD OF CLOUDY
SKIES EXTENDING INTO NORTHERN PA THIS EVENING. PERIODS OF LIGHT
RAIN CONTINUE TO ROTATE COUNTER CLOCKWISE AROUND THE LOW,
BRINGING OCCASIONAL SHOWERS TO PORTIONS OF SOUTHEAST
PENNSYLVANIA. VERY DRY AIR AT THE SURFACE CHARACTERIZED BY
DEWPOINTS IN THE MID 50S HAS LIMITED THE AMOUNT OF RAINFALL
MAKING IT TO THE SURFACE THUS FAR.
OVERNIGHT, CLOUDS WILL CONTINUE TO EXPAND NORTHWESTWARD AS RAIN
CONTINUES. LOW CLOUDS ARE PROGGED TO REACH I-80/I-99 BY
DAYBREAK, LIMITING FOG POTENTIAL SOUTH AND EAST OF THERE.
FARTHER NORTH, SOME VALLEY FOG FORMATION IS EXPECTED ONCE AGAIN.
LOWS WILL RANGE FROM THE UPPER 40S IN NORTHWEST PA TO NEAR 60 IN
THE SOUTHEAST.
ON WEDNESDAY, THICKENING CLOUDS AND PERSISTENT EASTERLY FLOW
WILL KEEP TEMPERATURES SIGNIFICANTLY COOLER THAN RECENT DAYS
EAST OF THE MOUNTAINS. HIGHS SHOULD STAY IN THE UPPER 60S TO
NEAR 70S ALONG SOUTH/EAST OF I-99/I-80, WHILE LOCATIONS FARTHER
WEST SOAR INTO THE 80S WHERE SKIES SHOULD BE MOSTLY SUNNY OR
PARTLY CLOUDY. PERIODS OF RAIN WILL CONTINUE TO AFFECT SOUTHEAST
PA ON WEDNESDAY AS DEWPOINTS GRADUALLY INCREASE. DEWPOINTS WILL
CREST THE 60F MARK FOR THE FIRST TIME IN QUITE AWHILE AS
TROPICAL MOISTURE SWIRLS INTO THE REGION ACCOMPANIED BY PWATS
OVER 1.5". IF YOU LOOK AT RADAR ON WEDNESDAY, YOU MAY SEE
RETURNS EXTENDING INTO NORTHERN PA (NORTH OF I-80). DRY AIR AT
THE SURFACE SHOULD PREVENT MOST OF THE RAIN FROM REACHING THE
SURFACE THERE, THOUGH. RAINFALL TOTALS BY WEDNESDAY EVENING
SHOULD REMAIN BELOW 0.5" FOR MOST, AND LITTLE TO NO ACCUMULATION
IS EXPECTED ALONG SOUTH/EAST OF I-80/I-99.
SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/
THE SURFACE LOW WILL MOVE EAST OF THE AREA WEDNESDAY NIGHT AS
SURFACE HIGH PRESSURE BENEATH A BLOCKING RIDGE OF HIGH PRESSURE
WORKS ITS WAY BACK INTO THE REGION. COOL AFTERNOON HIGHS AND
RELATIVELY HIGH DEWPOINTS COMBINED WITH CLEARING SKIES IN THE
WAKE OF THE LOW WILL PROMOTE WIDESPREAD FOG FORMATION INTO
THURSDAY MORNING. SATELLITE IMAGERY OVER CENTRAL PA AT DAYBREAK
WILL BE QUITE STRIKING AS MOST VALLEYS ARE BLANKETED WITH FOG.
THURSDAY AND FRIDAY WILL BE A CONTINUATION OF WHAT WE'VE SEEN
FOR A MAJORITY OF THE PAST COUPLE WEEKS WITH PLENTY OF SUNSHINE,
SEASONABLY MILD TEMPERATURES, AND LIGHT WINDS. IT WILL TAKE A
LITTLE WHILE FOR THE MOISTURE IN SOUTHEAST PA TO BE REPLACED BY
A DRIER AIRMASS, SO EXPECT THE AIR TO FEEL A BIT HUMID STILL ON
THURSDAY. HIGHS WILL GENERALLY BE IN THE 80S WITH LOWS IN THE
UPPER 40S (NW) TO LOWER 60S (SE). A BACKDOOR, MOISTURE-DEPRIVED
COLD FRONT WILL SAG SOUTH INTO NORTHERN PENNSYLVANIA FRIDAY
AFTERNOON, WITH AN INCREASE IN CLOUD COVER NORTH OF US-6 BEING
THE ONLY NOTEWORTHY ASPECT OF ITS ARRIVAL. DRIER AIR AWAITS IN
ITS WAKE...
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
ON FRIDAY NIGHT, THE AFOREMENTIONED BACKDOOR COLD FRONT WILL
SLIDE THROUGH PENNSYLVANIA WITH A STRONG 1028MB HIGH SURGING IN
BEHIND IT. DEWPOINTS WILL PLUMMET BY SATURDAY MORNING,
SUPPORTING A RETURN TO BELOW-NORMAL OVERNIGHT TEMPERATURES WITH
CLEAR SKIES AND CALM WINDS. SURFACE HIGH PRESSURE WILL SET UP
OFF THE NEW ENGLAND COAST FOR THE WEEKEND, ENSURING MOIST
SOUTHEAST FLOW AND TRANQUIL WEATHER. HIGHS WILL TICK DOWN A FEW
DEGREES FOR THE WEEKEND, WITH HIGHS IN THE 70S AND LOWS IN THE
50S MOST LIKELY AT THIS TIME.
HEADING INTO NEXT WEEK, HIGH PRESSURE WILL BEGIN TO LOSE ITS
GRIP ON THE REGION AS AN UPPER TROUGH TRIES TO DISRUPT THE
PERSISTENT RIDGE OF HIGH PRESSURE ALOFT. STILL PLENTY OF
UNCERTAINTY ON HOW MUCH, IF ANY, PRECIPITATION WILL GET INTO
PENNSYLVANIA BUT SOUTHERLY FLOW AHEAD OF THE APPROACHING SYSTEM
WILL SUPPORT CONTINUED WARMER THAN AVERAGE TEMPERATURES FOR THE
START OF ASTRONOMICAL FALL.
AVIATION /01Z WEDNESDAY THROUGH SUNDAY/
CURRENT SATELLITE/RADAR AS OF 2320Z OUTLINES A FAIR AREA OF
HIGH-LEVEL CLOUDS GENERAL AT OR ABOVE 25,000 FT WITH RAIN ACROSS
MAINLY SOUTHEASTERN PENNSYLVANIA (MDT/LNS). DEW POINT
DEPRESSIONS REMAIN RELATIVELY HIGH WITH LOW-LEVEL DRY AIR
LIMITING THE AMOUNT OF PRECIPITATION OUTSIDE OF THE HEAVIEST
BANDS THIS EVENING, WHICH ARE GENERALLY EXPECTED TO STAY OUT OF
THE AIRFIELDS. DESPITE THIS, HAVE CONTINUE A PROB30 OVER THE
NEXT 1-2 HRS AT LNS DUE TO SOME CONTINUED DEVELOPMENT ACROSS THE
REGION WITH THE BULK OF PRECIPITATION SOUTH OF MDT.
MOST RECENT HREF/RAP/GLAMP GUIDANCE INDICATES A BRIEF PERIOD OF
DRY CONDITIONS AT THE AIRFIELDS OVERNIGHT; HOWEVER, SCATTERED
SHOWERS ARE PROGGED BY MODEL GUIDANCE IN THIS TIMEFRAME. THUS,
CONFIDENCE REMAINS LOW WITH RESPECT TO THE PRECIPITATION
FORECAST OVERNIGHT AT MDT/LNS AS SHOWERS WILL HAVE SOME
POTENTIAL TO GO OVER THE AIRFIELD BETWEEN 00Z-12Z WED. BETTER
SIGNALS FOR PRECIPITATION COME THROUGHOUT THE MORNING HOURS ON
WEDNESDAY AND CONTINUING INTO EXPAND SLOWLY NORTH/WESTWARD WITH
THE CLOSEST APPROACH OF THE COASTAL LOW. MODEL GUIDANCE
INDICATED MDT/LNS SHARE RESPECTABLE (40-50%) CHANCES FOR
RAINFALL WITH SCATTERED COVERAGE LIMITING CHANCES AT IPT/UNV/AOO
CLOSER TO THE 10-30% RANGE, THUS HAVE LIMITED MENTIONS FOR THE
00Z TAF PACKAGE. SOME INSTABILITY WILL BE PRESENT; HOWEVER,
LOWER CONFIDENCE GIVEN EASTERLY FLOW AND COVERAGE OF TSRA AT
MDT/LNS, THUS NO MENTIONS THIS CYCLE.
GIVEN THE AFOREMENTIONED EASTERLY FLOW, LOWER CEILINGS ARE ALSO
EXPECTED ACROSS THE SOUTHERN TIER OF PENNSYLVANIA. RECENT MODEL
GUIDANCE HAS TANKED MDT/LNS FURTHER DOWN, WHICH IS PLAUSIBLE
GIVEN INCREASING LOW-LEVEL MOISTURE FROM THE ATLANTIC. RECENT
HREF GUIDANCE INDICATED ANYWHERE BETWEEN 40-60% OF IFR
RESTRICTIONS OR BELOW THROUGHOUT THE AFTERNOON/EVENING HOURS AT
MDT/LNS, THUS HAVE BEGAN MENTIONS OF IFR THRESHOLDS IN THE 00Z
TAF. ELSEWHERE, MVFR WILL BE POSSIBLE (30-40%) FOR BRIEF
PERIODS AT AOO/IPT; HOWEVER, LESS CONVINCING SIGNALS FOR IFR
MENTIONS BASED ON MODEL GUIDANCE AT THIS TIME.
OUTLOOK...
THU...GENERALLY VFR.
FRI-SUN...VFR WITH AM VALLEY FOG.
CLIMATE
ASTRONOMICAL FALL OFFICIALLY BEGINS WITH THE AUTUMNAL EQUINOX
ON MONDAY, SEPTEMBER 22, 2025 @ 2:19 P.M. EDT. THE AUTUMN 2025
SEASON WILL LAST 89 DAYS, 20 HOURS, AND 43 MINUTES. DAYLIGHT
SAVING TIME WILL END JUST AFTER HALLOWEEN WITH CLOCKS FALLING
BACK AT 2 A.M. SUNDAY, NOVEMBER 2, 2025.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...BANGHOFF
NEAR TERM...BANGHOFF
SHORT TERM...BANGHOFF
LONG TERM...BANGHOFF
AVIATION...NPB
CLIMATE...STEINBUGL
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