676
FXUS61 KCTP 061921
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
321 PM EDT SUN JUL 6 2025
SYNOPSIS
* DRY WEATHER PREVAILS TODAY AND TONIGHT AS HUMIDITY BEGINS TO
INCREASE.
* THE REMNANTS OF TROPICAL DEPRESSION CHANTAL WILL MOVE ACROSS
SOUTHEAST PA AS A COLD FRONT MOVES INTO NORTHWEST PA, BRINGING
A CHANCE FOR SCATTERED SHOWERS AND THUNDERSTORMS MONDAY &
TUESDAY AFTERNOON.
* A STALLED FRONT DRAPED ALONG THE MASON-DIXON LINE WILL KEEP
SHOWERS AND THUNDERSTORMS IN THE FORECAST EACH DAY THROUGH THE
END OF THE WEEK.
NEAR TERM /UNTIL 6 AM MONDAY MORNING/
ABUNDANT SUNSHINE AND CLOUD-FREE SKIES EXTEND ALONG THE
ALLEGHENIES INTO THE ENDLESS MOUNTAINS REGION OF NORTHEAST PA
THIS AFTERNOON AS CENTRAL PA SITS IN THE SUBSIDENCE ZONE
BETWEEN AN APPROACHING COLD FRONT TO THE WEST AND TROPICAL
DEPRESSION CHANTAL MOVING NORTHWARD THROUGH NORTH CAROLINE.
BENEATH THE AXIS OF THE UPPER LEVEL RIDGE SHIFTING EAST ACROSS
THE COMMONWEALTH TODAY, MID LEVEL TEMPS WILL WARM TO AROUND
+10C, LIKELY PREVENTING ANY CONVECTION, EXCEPT FOR PERHAPS ONE
OR 2 ISOLATED CELLS OVER THE RIDGETOPS AND NEAR THE SE BOUNDARY
OF THE LAKE ERIE BREEZE. HIGHS WILL TOP OUT IN THE 85 TO 90
DEGREE RANGE AREAWIDE TODAY.
OVERNIGHT, MOIST SOUTHEAST FLOW AHEAD OF THE CIRCULATION
ASSOCIATED WITH CHANTAL WILL BRING LOW CLOUDS AND RIDGETOP FOG
TO THE REGION AS TEMPERATURES REMAIN FAIRLY MILD - RANGING FROM
THE MID 60S IN THE NORTHWEST TO MID 70S IN THE SOUTHEAST. DRY
CONDITIONS SHOULD PREVAIL MOST OF THE NIGHT, ALTHOUGH A FEW
LIGHT SHOWERS COULD MAKE IT INTO SOUTHEAST PA BY DAYBREAK AS
CHANTAL'S REMNANTS EDGE EVER CLOSER.
SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/
POPS INCREASE INTO MONDAY AS A RELATIVELY WEAK NORTHERN STREAM
UPPER LEVEL TROUGH ARRIVES AND TAPS INTO SOME TROPICAL MOISTURE
OFF THE EAST COAST. WITH MORE MOISTURE IN PLACE, HEAT INDEX
VALUES MONDAY AFTERNOON WILL CLIMB INTO THE 90S FOR MOST VALLEY
LOCATIONS SOUTH OF THE NORTHERN TIER.
SPC HAS THE NW 20-25 PERCENT OF THE CWA IN A MRGL RISK FOR SVR
MONDAY, ALONG WITH A MRGL RISK FOR EXCESSIVE RAIN. THESE
CATEGORIES LOOK REASONABLE AT THIS POINT BASED ON INSTABILITY
(MU CAPE NEARING 2000 J/KG ACROSS THE NW MTNS), DEEP LAYER SHEAR
AND PWAT VALUES OF 1.75+ INCHES ACROSS THE NW MTNS (AND
SLIGHTLY OVER 2 INCHES ACROSS THE FAR SE THANKS TO MOISTURE FROM
THE REMNANTS OF TS CHANTAL BRUSHING THAT PART OF THE STATE).
THE LATEST CAMS PAINT THE HEAVIEST RAINFALL STAYING EAST OF
CENTRAL PA, THOUGH A VERY MOIST AIRMASS MOVING OVER SOME
PARTICULARLY VULNERABLE AREAS (LANCASTER, DAUPHIN, AND LEBANON
COUNTIES) REQUIRES AT LEAST SOME SPECIAL ATTENTION. IN THE BEST
CASE SCENARIO, CHANTAL TRACKS EAST OF THE AREA AND MOST OF
CENTRAL PA IS IN A SUBSIDENCE ZONE, WHICH WOULD MEAN
INSIGNIFICANT RAINFALL. IF CHANTAL TRACKS A BIT MORE WEST, A
CORRIDOR OF HEAVY RAINFALL THROUGH THE LOWER SUSQUEHANNA VALLEY
COULD REQUIRE AN UPGRADE TO A SLIGHT RISK FOR EXCESSIVE RAINFALL
AND POTENTIAL FOR FLASH FLOODING.
TEMPS WILL FALL A FEW DEGREES INTO TUE AS SHOWERS AND STORMS
STICK AROUND. THE AFOREMENTIONED COLD FRONT WILL LIKELY PUSH
THROUGH THE CENTRAL AND SOUTHEAST COUNTIES OF THE CWA DURING
THE DAY TUESDAY. SPC HAS THE SE 40 PERCENT OF THE CWA IN A MRGL
RISK FOR SVR TUESDAY, ALONG WITH A MRGL RISK FOR EXCESSIVE RAIN.
BY TUESDAY, CHANTAL WILL BE ALL BUT DISSIPATED, BUT THE MOISTURE
ASSOCIATED WITH THE SYSTEM WILL REMAIN DRAPED ACROSS THE I-95
CORRIDOR. ANY SHOWERS AND STORMS THAT FIRE ALONG THE STATIONARY
BOUNDARY WILL BE CAPABLE OF PRODUCING TORRENTIAL RAINFALL AND
ISOLATED INSTANCES OF FLOODING.
THERE REMAINS A LOW, BUT NON ZERO CHANCE OF HEAT INDEX VALUES
APPROACHING THE CENTURY MARK ON TUESDAY IN SOUTHEAST PA. THE
REALIZATION OF THESE HOT/HUMID CONDITIONS WILL BE CONTINGENT ON
THE COLD FRONT HANGING UP NORTHWEST OF THE I-81 CORRIDOR AND
CONVECTION HOLDING OFF IN THE AFTERNOON. IF THE COLD FRONT MOVES
FARTHER SOUTHEAST AND/OR STORMS DEVELOP DURING THE AFTERNOON,
TEMPERATURES WILL REMAIN LOW ENOUGH TO PRECLUDE ANY HEAT
ADVISORY CONSIDERATION. AS IT STANDS RIGHT NOW, THE RISK OF HEAT
INDEX VALUES OF 100F OR GREATER IS LESS THAN 15%.
IT WILL BE ANOTHER MILD NIGHT TUESDAY ACROSS THE SOUTHEAST WHERE
MUGGY DEWPOINTS AND CLOUD CLOVER WILL KEEP LOWS IN THE 70S.
FARTHER NORTHWEST, HIGH PRESSURE MOVING IN WILL SUPPORT DRIER
AIR AND SUBSIDENCE TUESDAY NIGHT WITH CLEARING SKIES AND LOWS IN
THE 50S TO LOW 60S.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
POPS DROP INTO THE 20-40 PCT RANGE ON WED AS HEIGHTS BRIEFLY
RISE OVER THE AREA, BUT MOST MODEL GUIDANCE STILL SHOWS ENOUGH
INSTABILITY FOR AT LEAST A FEW ISOLATED SHOWERS AND STORMS,
ESPECIALLY ACROSS THE SOUTHERN PART OF THE CWA WHERE SFC BASED
CAPE STILL PEAKS BETWEEN 1500-2500 J/KG WED AND THU AFTERNOON.
THE SPARSER COVERAGE OF STORMS SHOULD PRECLUDE ANY FLOOD THREAT
ON WEDNESDAY, BUT THE RICHEST MOISTURE WILL NOT BE TOO FAR SOUTH
OF THE REGION.
POPS RISE AGAIN THURSDAY WITH THE APPROACH OF ANOTHER SHORTWAVE
TROUGH. THE FORECAST FOR FRIDAY AND THE WEEKEND IS MORE
UNCERTAIN, WITH SOME GUIDANCE SUGGESTING A BREAK IN THE
UNSETTLED PATTERN, AND OTHERS SUGGESTING ACTIVE WEATHER
CONTINUES. AN ACTIVE PATTERN WOULD FAVOR CONTINUE HEAT/HUMIDITY
WHILE A QUIETER PATTERN COULD SUPPORT THE INTRUSION OF LOWER
DEWPOINTS AND MORE REFRESHING CONDITIONS.
AVIATION /19Z SUNDAY THROUGH FRIDAY/
VFR PREVAILS TODAY WITH NOTHING THAN SCATTERED FAIR WEATHER
CUMULUS CLOUDS. WINDS OUT OF THE SOUTH OR SOUTHWEST WILL
OCCASIONALLY GUST TO 15KTS THIS AFTERNOON WITH TRANQUIL WEATHER
CONTINUING.
LOW LEVEL MOISTURE CREEPING UP THE EAST COAST WILL LIKELY BRING
A DECK OF MVFR/IFR CLOUDS INTO THE SUSQ VALLEY TERMINALS OF
IPT/LNS/MDT AFTER 08-10Z TONIGHT. RESTRICTIONS MAY MAKE IT AS
FAR WEST AS UNV AND AOO, BUT CONFIDENCE REMAINS LOW ENOUGH TO
MAINTAIN VFR CONDITIONS THERE. IFR IS MOST LIKELY AT MDT AND LNS
IN THE 10-12Z WINDOW WITH IMPROVEMENT AFTER DAYBREAK.
A FEW SHOWERS AND THUNDERSTORMS MAY AFFECT MDT/LNS IN THE
MORNING AS TROPICAL MOISTURE MOVES OVERHEAD. THEN, SCATTERED
SHOWERS AND STORMS WILL MOVE ACROSS CENTRAL PA ALONG A COLD
FRONT DURING THE AFTERNOON AND EVENING.
OUTLOOK...
TUE...RESTRICTIONS IN MVFR CLOUD (NORTHWEST) AND SCATTERED
SHOWERS/STORMS (SOUTHEAST).
WED...BEST CHANCE FOR STORMS AND RESTRICTIONS IN SOUTHERN PA.
THU-FRI...POTENTIAL FOR SHOWERS AND THUNDERSTORMS, MAINLY
AFTN/EVE.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...BANGHOFF
NEAR TERM...BANGHOFF
SHORT TERM...LAMBERT/BANGHOFF
LONG TERM...LAMBERT/BANGHOFF
AVIATION...BANGHOFF/RXR
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