925
FXUS61 KCTP 141728
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
128 PM EDT SUN SEP 14 2025
SYNOPSIS
* CLEARING SKIES TONIGHT WITH VALLEY FOG PROBABLE FOR THE
MORNING COMMUTE ACROSS NORTHERN PENNSYLVANIA.
* HIGH CONFIDENCE IN DRY WEATHER CONTINUING THROUGH TUESDAY.
* LIGHT RAIN POSSIBLE MID-TO-LATE WEEK, ESPECIALLY ACROSS
SOUTHERN AND EASTERN PENNSYLVANIA.
NEAR TERM /THROUGH TONIGHT/
RECENT SATELLITE LOOP OUTLINES SCATTERED CUMULUS CLOUDS
BEGINNING TO FIRE ACROSS THE NORTHERN HALF OF PENNSYLVANIA AND
ALONG THE LAUREL HIGHLANDS. COVERAGE WILL CONTINUE TO GRADUALLY
INCREASE OVER THE NEXT 2-3 HOURS BEFORE DECREASING NEAR SUNSET
AND ALLOWING FOR CLEAR SKIES OVERNIGHT. VALLEY FOG POTENTIAL
LOOKS MORE FAVORABLE TONIGHT COMPARED TO THIS MORNING GIVEN THE
OVERALL LACK OF MID-TO-HIGH LEVEL CLOUDS. RECENT HREF
PROBABILITIES ARE PUSHING CLOSER TO 40-50% FOR VALLEY FOG
FORMATION ACROSS THE NORTHERN VALLEYS OF PENNSYLVANIA, WITH A
SECONDARY AREA OF FOG FORMATION POSSIBLE ACROSS LANCASTER,
LEBANON, AND FAVORED AREAS IN SCHUYLKILL COUNTY. AT THIS TIME,
THE NORTHERN TIER LOOKS LIKE THE BETTER BET, THUS HAVE
HIGHLIGHTED THIS POTENTIAL SLIGHTLY HEAVIER IN THIS FORECAST
PACKAGE. LOW TEMPERATURES OVERNIGHT BASED ON MAV GUIDANCE UNDER
RADIATIONAL COOLING OUTLINES MINTS IN THE UPPER 40S ACROSS NW PA
TO THE UPPER 50S ACROSS THE SOUTHERN TIER.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
ALL MODEL GUIDANCE POINTS TO FAIR WEATHER UNDER HIGH PRESSURE
STATIONED OVER ONTARIO/QUEBEC AND INTO THE NORTHEAST CONUS,
ALLOWING FOR CONTINUED DRY CONDITIONS THROUGH TUESDAY WITH HIGH
CONFIDENCE. MOSTLY SUNNY SKIES ARE EXPECTED ON MONDAY WITH
SCATTERED CUMULUS CLOUD DEVELOPMENT DURING THE AFTERNOON BEFORE
EASTERLY FLOW ON TUESDAY PUSHES MORE WIDESPREAD CLOUD COVERAGE
TO THE AREA. INCREASING CLOUD COVER WITH EASTERLY FLOW WILL
ALLOW FOR A SLIGHT DECREASE IN TEMPERATURES ON TUESDAY, PUSHING
CLOSER TO SEASONAL AVERAGES WITH PORTIONS OF THE SOUTHEASTERN
PENNSYLVANIA TIPPING JUST BELOW AVERAGE FOR MID-SEPTEMBER. UNDER
CLEAR SKIES, DEW POINTS WILL BE THE TRICKIEST PART OF THE
FORECAST ON MONDAY. SOME SIGNALS FOR RELATIVELY DRY AIR ALOFT
MIXING DOWN ARE PRESENT WITH THE MINRH "FLOOR" REACHING DOWN
TOWARDS THE 20-25% RANGE ACROSS PORTIONS OF WEST-CENTRAL
PENNSYLVANIA TO 30-35% ACROSS THE NORTHERN TIER.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
A CLOSED LOW STATIONED ACROSS THE SOUTHERN MID- ATLANTIC WILL
BRING INCREASED CHANCES FOR PRECIPITATION CHANCES ON WEDNESDAY
AND INTO THE SECOND HALF OF THE WEEK. RECENT DETERMINISTIC MODEL
GUIDANCE HAS BEGAN TO CONVERGE TOWARDS THE LOW PRESSURE SYSTEM
SETTING UP ALONG THE VA-NC BORDER ON WEDNESDAY WHICH WILL BRING
ABOUT SOME CHANCES OF PRECIPITATION ACROSS SOUTHERN AND EASTERN
PENNSYLVANIA; HOWEVER, MODEL GUIDANCE STILL SHOWS A FAIR AMOUNT
OF SPREAD WITH RESPECT TO TRACK OF THE LOW, THUS THERE REMAINS
UNCERTAINTY LATER IN THE WEEK. THUS, THE CURRENT FORECAST
OUTLINES THE BEST CHANCES FOR SHOWERS AND (AFTERNOON/EVENING)
THUNDERSTORMS ACROSS SOUTHERN AND EASTERN PENNSYLVANIA ON
WEDNESDAY.
A BRIEF SPELL OF DRY CONDITIONS IS ONCE AGAIN EXPECTED IN THE
WAKE OF THE COASTAL LOW, WITH MODERATE-TO-HIGH CONFIDENCE IN DRY
CONDITIONS ON FRIDAY. RECENT MODEL GUIDANCE HAS SLIGHTLY SLOWED
DOWN WITH RESPECT TO THE LOW PRESSURE SYSTEM IN THE MIDWEST
WITH A FAIR AMOUNT OF UNCERTAINTY BETWEEN DETERMINISTIC MODEL
GUIDANCE. GIVEN THESE CHANGES, HAVE DECIDED TO ROLL WITH NBM
THROUGH SUNDAY, WITH THE BEST CHANCES OF PRECIPITATION COMING
AFTER SUNRISE ON SUNDAY.
AVIATION /17Z SUNDAY THROUGH THURSDAY/
FOG WILL GRADUALLY DISSIPATE THROUGH 14Z, GIVING WAY TO MAINLY
CLEAR SKIES AND LIGHT WINDS FOR THE REST OF THE DAY. HIGH
PRESSURE BUILDING IN FROM THE NORTH WILL KEEP SKIES CLEAR
OVERNIGHT AND INTO MONDAY MORNING. THERE IS A FAIRLY STRONG
SIGNAL IN MOST OF THE GUIDANCE FOR VALLEY FOG FORMATION, BUT
CONFIDENCE ON IMPACTS AT TAF SITES IS LOW. MODEL RH PROFILES
WOULD SUGGEST THAT BFD AND IPT WILL HAVE THE BEST CHANCE OF
SEEING IFR VISIBILITIES AND THE 00Z HREF HAS A 40-60% CHANCE OF
VISIBILITY DROPPING BELOW 1/2SM AT BFD.
OUTLOOK...
MON-TUE... VFR WITH AM VALLEY FOG.
WED-THU...GENERALLY VFR, SOME SHRA POSSIBLE (20-40%) SE PA.
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...NPB
NEAR TERM...NPB
SHORT TERM...NPB
LONG TERM...NPB
AVIATION...BAUCO
CLIMATE...STEINBUGL
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