252
FXUS61 KCTP 031802
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
202 PM EDT SAT MAY 3 2025
SYNOPSIS
* SEVERAL ROUNDS OF SHOWERS AND SCATTERED AFTERNOON AND EVENING
THUNDERSTORMS FOR TODAY WITH THE STRONGEST STORMS LIKELY NEAR
AND TO THE SOUTH OF INTERSTATE 81.
* LARGELY BENEFICIAL MULTI-DAY RAINFALL EVENT SHAPING UP FOR
SUNDAY THROUGH TUESDAY AS AN UPPER LOW SWIRLS NEARBY; SOME
MINOR FLOODING WILL BE POSSIBLE WITH ANY REPEATED ROUNDS OF
HEAVY RAIN.
* TRENDING DRIER LATE WEEK WITH A TREND TOWARD BELOW NORMAL
TEMPERATURES.
NEAR TERM /THROUGH TONIGHT/
A QUASI-STATIONARY OR PERHAPS VERY SLOW MOVING COLD FRONT IS
DRAPED ACROSS NORTHWEST PA INTO UPSTATE NEW YORK EARLY THIS
AFTERNOON AND CONTINUES TO BE THE FOCUS FOR WIDESPREAD SHOWERS
DUE TO OVERRUNNING. AN UPPER LEVEL JET MAX IS COINCIDENT WITH
THE ORIENTATION OF THE BOUNDARY AND ITS RIGHT ENTRANCE REGION
WILL MOVE ACROSS CENTRAL AND EASTERN PA THIS AFTERNOON. PLENTY
OF CLOUD COVER IN MULTIPLE LAYERS WILL BE FOUND ACROSS THE
ENTIRE REGION TODAY, WHICH WILL PUT IN QUESTION THE INSTABILITY
INGREDIENT OF A GOOD CONVECTIVE RECIPE FOR TODAY.
LATEST HREF DOES CREATE POCKETS OF MU CAPE EXCEEDING 1000 J/KG
IN A MODERATELY SHEARED LOW-MID LEVEL ENVIRONMENT OVER THE LOWER
AND SUSQ VALLEY LATER THIS AFTERNOON INTO THIS EVENING, WITH
NUMEROUS CELLS DEVELOPING MAX 1 HOUR 2-5 KM HELICITY VALUES OVER
75 M2/S2 NEAR AND TO THE SE OF THE I-81 CORRIDOR. SPC HAS
ADDRESSED THESE ASPECTS OF TODAY'S CONVECTIVE EVENT WITH THE
SLGT FOR SVR TSRA ACROSS ROUGHLY THE SE THIRD OF THE CWA.
24 HOUR MAX 2-5 KM UPDRAFT HELICITY IS FORECAST TO BE CENTERED
OVER THE KMDT/KMUI AND KLNS AREA.
LCL HEIGHTS PER NBM GUIDANCE WILL RISE TO 3500-4000 FT AT THE
TIME OF PEAK HEATING TODAY, BUT WILL GRADUALLY LOWER TO
1500-2000 FT AFTER 22Z, WHICH WILL POSE THE BEST CHANCE FOR
SEEING AN ISOLATED WEAK TORNADO FROM ANY OF THE STRONGER TSRAS,
ESPECIALLY THOSE THAT DRIFT OVER THE QUASI-STNRY BOUNDARY
FORECAST TO LINGER NEAR THE I-81 CORRIDOR FROM THE GREATER
HARRISBURG AREA, NORTHEAST. BEST WINDOW OF SEVERE WEATHER
POTENTIAL IN SOUTHEAST PA AT THIS POINT LOOKS LIKE 5-9PM WITH
CONVECTION INITIATION STARTING AS EARLY AS 3PM.
FOR THE REST OF THE FORECAST AREA, LOOK FOR SEVERAL ROUNDS OF
LIGHT TO MODERATE, BENEFICIAL RAIN SHOWERS TODAY AND TONIGHT,
AND A FEW BRIEF PERIODS OF HEAVY RAIN FROM EMBEDDED, FAIRLY LOW
TOPPED TSRA. BASIN AVERAGE MEAN QPF TODAY WILL BE ON THE ORDER
OF 0.5 TO 1.0 INCH THROUGH DAYBREAK SUNDAY, THOUGH ANY LOCATION
RECEIVING 2-3 TSRA COULD EASILY SEE UPWARDS OF AROUND 2 INCHES.
WPC HAS ALL BUT THE NORTHERN TIER COUNTIES IN THEIR MRGL RISK
FOR EXCESSIVE RAIN TODAY AND TONIGHT. ANTECEDENT PRECIPITATION
DEFICITS PRECLUDE ANY MAJOR FLOODING CONCERNS.
HIGHS TODAY WILL HIGHLIGHT THE QUASI STNRY BOUNDARY WITH
LOCATIONS ACROSS THE LOWER SUSQ VALLEY TOPPING OUT IN THE 80-83F
RANGE, WHILE THE NORTHERN TIER COUNTIES WILL STRUGGLE TO MAKE IT
ABOVE 60F. LOWS TONIGHT REMAIN QUITE MILD, RANGING FROM NEAR 50F
NORTH OF US-6 TO THE LOWER 60S IN SOUTHEAST PA.
SHORT TERM /SUNDAY THROUGH TUESDAY/
A BLOCKING PATTERN WILL REMAIN OVER THE FCST AREA SUNDAY INTO
NEXT WEEK WITH A DEEP/VERTICALLY STACKED LOW IN THE OH VALLEY.
SOUTHERLY FLOW ON THE EAST SIDE OF THE LOW WILL CHANNEL MOISTURE
INTO THE AREA WITH PERIODS OF RAIN AND AFTERNOON STORMS EXPECTED
SUNDAY THROUGH TUESDAY. A FEW STRONGER STORMS ARE POSSIBLE IN
SOUTHWEST PA SUNDAY AFTERNOON THANKS TO THE COMBINATION OF
MARGINAL INSTABILITY, SUFFICIENT SHEAR, AND STEEP MID-LEVEL
LAPSE RATES. THE THREAT FOR SEVERE WEATHER APPEARS TO DECREASE
INTO NEXT WEEK.
WHILE RAINFALL WILL BE CERTAINLY BENEFICIAL AND BRING
SOME RELIEF TO DROUGHT CONDITIONS PARTICULARLY IN THE SOUTHEAST
PART OF THE FORECAST AREA, WE WILL NEED TO MONITOR CONDITIONS
FOR REPEATED ROUNDS OF HEAVY RAINFALL WHICH COULD PRODUCE
LOCALLY HEAVY TOTALS AND MAY RESULT IN LOCALIZED FLOODING IN
URBAN AND POOR DRAINAGE AREAS. WPC HAS MAINTAINED MARGINAL
EXCESSIVE RAIN RISKS FOR SATURDAY-TUESDAY WITH A GRADUAL
EASTWARD SHIFT OF THOSE AREAS COINCIDENT WITH A SLOWLY ADVANCING
UPPER LOW. SHOWER ACTIVITY SHOULD TREND MORE STRATIFORM IN
NATURE (AS OPPOSED TO CONVECTIVE) AS WE GET INTO NEXT WEEK,
WHICH WILL LIMIT THE RISK OF HEAVY RAINFALL SOMEWHAT, BUT A
SLIGHT RISK UPGRADE AT SOME POINT WOULD NOT BE TOO SURPRISING.
ENSEMBLE MEANS PAINT A WIDESPREAD 2-3" ACROSS THE REGION THROUGH
TUESDAY, WITH LOCALLY HIGHER AMOUNTS IN THUNDERSTORMS.
THIS PERIOD WILL REMAIN MILD RELATIVE VS. CLIMO WITH THE
LARGEST DEPARTURES FROM NORMAL IN THE OVERNIGHT MIN TEMPS
ON THE ORDER OF +10-20F ABOVE THE HISTORICAL AVERAGE. NOT MUCH
IN THE WAY OF SUNSHINE.
LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/
BLOCKY PATTERN WITH CLOSED LOW LIFTING VERY SLOWLY TO THE
NORTHEAST FROM THE OHIO VALLEY WILL MAINTAIN A STRONG WET
PATTERN SIGNAL OVER THE AREA THROUGH MIDWEEK. INITIALLY,
RAINFALL SHOULD BE BENEFICIAL PARTICULARLY OVER THE SOUTHEAST
ZONES/LOWER SUSQ WHERE D1/D2 DROUGHT CONDITIONS HAVE PERSISTED
FOR SOME TIME. WPC HAS INDICATED A MARGINAL RISK OF EXCESSIVE
RAIN WITH SOME POTENTIAL FOR REPEATED ROUNDS OF RAIN CAPABLE OF
PRODUCING LOCALIZED FLOODING RISK IN URBAN AND POOR DRAINAGE
AREAS. THE MAIN UNCERTAINTY IN THE FORECAST PERIOD IS IN REGARD
TO HOW QUICKLY THE UPPER LOW BEGINS TO MOVE OFF TO THE EAST.
SOME GUIDANCE SUGGESTS A MAINLY DRY SECOND HALF OF THE WEEK AS
HIGH PRESSURE BUILDS IN BEHIND THE DEPARTING UPPER LOW, WHILE
SOME MODELS KEEP THE LOW AROUND A LITTLE LONGER. BECAUSE OF
THIS UNCERTAINTY, WE HAVE NOT DEVIATED FROM THE NBM THROUGH THE
END OF THE EXTENDED PERIOD.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
SCATTERED SHRA ACROSS WESTERN PENNSYLVANIA WILL GRADUALLY
OVERSPREAD THE AREA; HOWEVER, GENERALLY VFR CONDITIONS ARE
EXPECTED TO PREVAIL. TEMPORARY MVFR CEILINGS WILL REMAIN
POSSIBLE (< 30%) AT BFD/JST IN HEAVIER SHOWERS IN THE NEAR-TERM
BEFORE MORE WIDESPREAD SUB-VFR CONDITIONS OCCUR AFTER 00Z. THE
BIGGEST CHANGE IN THE 18Z TAF PACKAGE COMES WITH THUNDERSTORMS
BETWEEN 20Z SAT THROUGH 03Z SUN ACROSS THE EASTERN AIRSPACE
(MDT/LNS/IPT). HIGHEST CONFIDENCE IN THUNDERSTORMS AT MDT/LNS IN
THE 22Z SAT TO 02Z SUN TIMEFRAME, WITH HREF PROBS LIGHTING UP
BETWEEN 30-40%; HOWEVER, THE SCATTERED NATURE OF CONVECTION IS
GOING TO BE THE TRICKIEST PART OF THE FORECAST. RECENT
OBSERVATIONS OUTLINE LNS APPROACHING 60F DEW POINTS RELATIVELY
HIGHER CONFIDENCE IN THUNDERSTORM POTENTIAL COMPARED TO MDT AND
HAVE OUTLINED THIS IN THE NEWEST FORECAST PACKAGE. FURTHER
NORTH, TABLE AIR AND CLOUD COVER IS EXPECTED TO LIMIT POTENTIAL
AT IPT; HOWEVER, CANNOT RULE OUT A ROUGE THUNDERSTORM BETWEEN
00-03Z SUN WITH LIMITED CHANCES FURTHER WEST. THUNDERSTORMS
IMPACTING THE EASTERN AIRFIELDS HAVE THE POTENTIAL TO CAUSE
GUSTY-TO-DAMAGING WINDS, SO MESOSCALE TRENDS WILL NEED TO BE
OBSERVED CLOSELY BETWEEN 18Z SAT THROUGH 03Z SUN FOR
THUNDERSTORM DEVELOPMENT AT THE AIRFIELDS.
AFTER 03Z SUN, THUNDERSTORM CHANCES DECREASE DRAMATICALLY WITH
LESS INSTABILITY PRESENT ACROSS THE AREA. INCREASED LOW-LEVEL
MOISTURE IN THE LOWER LEVELS DO WARRANT WIDESPREAD MVFR-TO-IFR
CONDITIONS AS MOISTURE INCREASES ACROSS EASTERN PENNSYLVANIA
UNDER SOUTHEASTERLY FLOW. HREF MODEL GUIDANCE IS HESITANT TO
INTRODUCE IFR CONDITIONS AT MDT/LNS UNTIL AFTER 06Z; HOWEVER,
GIVEN THE AFOREMENTIONED SE'LY FLOW HAVE BROUGHT CEILINGS DOWN
OVERNIGHT WITH MODERATE (~50%) CONFIDENCE. LINGERING SHOWERS MAY
DO WELL TO QUELL THE LOWER CEILINGS; HOWEVER, AND CANNOT RULE
OUT LOW-END MVFR AT MDT/LNS/IPT OVERNIGHT BEFORE FLOW TURNS MORE
SOUTHERLY. FURTHER WEST, HIGH CONFIDENCE IN BFD/JST PREVAILING
IFR AFTER 02Z SUN WITH MODEL GUIDANCE ALL POINTING TOWARDS AN
EXTENDED PERIOD OF LIFR OVERNIGHT INTO EARLY SUNDAY MORNING. AT
AOO/UNV/IPT, MODEL GUIDANCE FAIRLY WELL-RESOLVED WITH IFR
CEILINGS AND THESE SEEM PLAUSIBLE BASED ON RECENT RAP MODEL
SOUNDINGS, THUS HAVE TRENDED CLOSE TO A COMBINATION OF
HREF/GLAMP GUIDANCE.
OUTLOOK...
MON-TUE...FREQUENT RAIN SHOWERS; SOME LOCALLY HEAVY WITH
PROLONGED SUB-VFR CONDITIONS.
WED-THU...SHOWERS BECOME MORE SCATTERED WITH HIGHER CHANCES IN
THE AFTERNOON/EVENING HOURS. RESTRICTIONS POSSIBLE.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...BANGHOFF
NEAR TERM...LAMBERT/BANGHOFF
SHORT TERM...LAMBERT/BANGHOFF
LONG TERM...STEINBUGL/BAUCO
AVIATION...NPB
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