679
FXUS61 KPBZ 032353
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
753 PM EDT WED SEP 3 2025
SYNOPSIS
SHOWERS AND THUNDERSTORMS RETURN THURSDAY WITH THE APPROACH AND
PASSAGE OF A COLD FRONT. GUSTY WIND AND ISOLATED SEVERE STORMS
MAY BE POSSIBLE. COOLER CONDITIONS ARE EXPECTED OVER THE
WEEKEND.
NEAR TERM /THROUGH THURSDAY/
KEY MESSAGES:
- PRE-FRONTAL SHOWERS POSSIBLE THIS EVENING MAINLY SOUTH OF
PITTSBURGH
- TEMPERATURES TREND WARMER THAN RECENT DAYS/NIGHTS
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AS A POTENT TROUGH STRENGTHENS INTO A CLOSED LOW IN SOUTH-
CENTRAL CANADA AND ADVANCES INTO THE NRN GREAT LAKES, WARM
ADVECTION STRENGTHENS IN TURN, SUPPORTING TEMPS BROADLY
APPROACHING 80F TODAY AMID GENERALLY SUNNY CONDITIONS.
HEATING ALONG RIDGE LINES ALSO IS SUPPORTING DEEPER UPDRAFT
GROWTH WITHIN THE DEEPLY MIXED ENVIRONMENT. IN THIS AREA OF NRN
WV, THE POSSIBILITY OF ISOLATED SHOWERS/STORMS EXISTS FOR A
BRIEF WINDOW THIS AFTERNOON, THOUGH LIMITED MOISTURE AND A MID-
LEVEL THERMAL INVERSION WILL LIMIT INTENSITY OF ANY DEEP, MOIST
CONVECTION AS THE CAPE PROFILE WILL BE HEAVILY CENTERED IN THE
LOWER LEVELS OF THE ATMOSPHERE.
AHEAD OF THE CLOSED UPPER LOW, AND AS AN EMBEDDED SHORTWAVE
TROUGH APPROACHES THE REGION, INCREASING WARM, MOIST ADVECTION
WILL SUPPORT RAPID INCREASE IN CLOUD COVER AND POTENTIAL ONSET
OF SHOWERS BY SUNRISE.
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/
KEY MESSAGES:
- SHOWERS AND LOCALIZED THUNDERSTORMS FAVORED THURSDAY, LIKELY
IN A MORNING AND AFTERNOON WAVE
- MARGINAL RISK FOR DAMAGING WIND DEPENDENT ON HEATING AHEAD OF
AFTERNOON WAVE
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WITHIN THE INCREASED FLOW AHEAD OF A CLOSED LOW/EMBEDDED
SHORTWAVE TROUGH, MODEST ELEVATED CAPE MAY YIELD WEAK, BROAD
CONVECTIVE DEVELOPMENT WITHIN A PRE-FRONTAL SFC TROUGH THU
MORNING. WITH A LACK OF MID-LEVEL DRY AIR AND ELEVATED UPDRAFTS,
ANY MORNING SHOWERS/STORMS DO NOT SUGGEST POTENTIAL FOR A
SEVERE-WEATHER RISK.
THE PRE-FRONTAL TROUGH ADVANCES EWD TO THE RIDGES BY EARLY
AFTERNOON, FOCUSING A PRIMARY SEVERE WEATHER RISK NEAR AND EAST
OF THE RIDGES. ADDITIONAL STORM POTENTIAL EXISTS THU AFTERNOON
ALONG THE SYSTEM'S COLD FRONT BEGINNING EARLY AFTERNOON THRU
EARLY EVENING.
SEVERE-WEATHER POTENTIAL IN THE AFTERNOON REMAINS UNCLEAR,
HOWEVER, AND WILL BE HIGHLY DEPENDENT ON RECOVERY IN THE WAKE OF
MORNING SHOWERS/STORMS. THE CHANCE OF THIS RECOVERY APPEARS LOW,
GIVEN THAT CLOUD COVER WILL BE ABUNDANT AND FRONTAL TIMING MAY
BE QUICK BEHIND THE MORNING RAIN. HOWEVER, THERE REMAINS
UNUSUALLY LARGE UNCERTAINTY WITH RESPECT TO THE TIMING OF
FRONTAL ARRIVAL, AND A DELAYED FRONTAL TIMING WOULD BETTER FAVOR
AFTERNOON RECOVERY AND POTENTIAL FOR GREATER STORM INTENSITY.
IN THE INTEREST OF CONDITIONAL-THREAT AWARENESS, IF STORMS CAN
FORM ALONG THE FRONTAL ZONE, MID-LEVEL DRY AIR, COUPLED WITH A
DEEP-SHEAR VECTOR LARGELY PARALLEL TO THE BOUNDARY, SUGGESTS A
QUICK GROWTH TO LINEAR MODE WITH THREATS FOR WIND GUSTS AND A
MESOVORTEX TORNADO.
FARTHER SOUTH, IN THE VICINITY OF MGW AND ADJACENT NRN WV/SW
PA, SHEAR WILL BE MORE OBLIQUE TO THE BOUNDARY, SUGGESTING
POTENTIAL FOR DISCRETE UPDRAFTS SHOULD RECOVERY OCCUR.
OVERALL, A LOW UNCONDITIONAL SEVERE THREAT (WIND GUSTS AND
POSSIBLY A MESOVORTEX TORNADO) SEEMS REASONABLE, AND MESSAGING
WILL HIGHLIGHT THE GREATEST PROBABILITY FOCUSED IN NRN WV/FAR
SWRN PA AS NOTED BY PRIOR SHIFTS.
FRONTAL PASSAGE OUT OF THE REGION IS ANTICIPATED BY EARLY
EVENING. CLEARING BEHIND THE FRONT WILL BE QUICK, AS A STRONGER
TROUGH DEVELOPS TO THE WEST, FAVORING RAPID WEAKENING OF HIGH
PRESSURE AND RETURN TO LIGHT SLY FLOW BY FRI MORNING.
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
KEY MESSAGES:
- ARRIVAL OF A STRONG COLD FRONT WILL INCREASE PRECIPITATION
CHANCES LATE FRIDAY INTO SATURDAY
- DRY, BUT SEASONABLY COOL WEATHER, IS LIKELY SUNDAY AND MONDAY
BEFORE A RETURN TO NEAR-NORMAL TEMPERATURE MID-WEEK
-------------------------------------------------------------------
STRONG SWLY FLOW ALOFT WILL PERSIST FRI TO THE SOUTH OF A DEEP
CLOSED LOW OVER CENTRAL CANADA. A SERIES OF SHORTWAVE TROUGHS
EMBEDDED IN THE FLOW WILL INFLUENCE THE UPPER OHIO VALLEY
FRI/FRI NIGHT, WITH A PARTICULARLY STRONG TROUGH ADVANCING A
STRONG COLD FRONT ACROSS THE REGION ON SAT.
AFTER A QUICK POST-FRONTAL RECOVERY FROM THU'S FRONT, FRI MAXIMA
ARE LIKELY TO RETURN TO NEAR- OR SLIGHTLY ABOVE-SEASONAL LEVELS
IN THE 80S ALONG WITH GUSTY SYNOPTIC WIND. HOWEVER, ATTENDANT
CLOUDS/PRECIPITATION AND POST-FRONTAL COLD ADVECTION WILL
CONTINUE THE THERMAL ROLLER COASTER, WITH SAT MAXIMA BACK IN THE
60S ONCE FRI NIGHT/SAT RAIN CLEARS OUT BY MID-AFTERNOON.
PRIMARY UNCERTAINTY DRIVING THE FRI/SAT TIME PERIOD REVOLVES
AROUND TIMING OF SHORTWAVE TROUGHS EMBEDDED IN THAT STRONGER
FLOW ALOFT, AND MODULATED BY VARIANCES IN SPATIAL POSITIONING OF
THE CLOSED UPPER LOW.
GIVEN THESE RELATED UNCERTAINTIES, BEST TIMING FOR RAIN ONSET
ASSOCIATED WITH THE FRONTAL APPROACH APPEARS TO BE AFTER 8PM
FRI, BUT IT COULD BEGIN AS EARLY AS LATE FRI AFTERNOON IN ERN
OH.
EVENTUAL POST-FRONTAL CLEARING AND SLACKENING OF THE NWLY FLOW
AS HIGH PRESSURE BUILDS WILL SUPPORT RADIATIONAL COOLING WITHIN
A COOLER AIRMASS, SUGGESTING OVERNIGHT LOWS COULD FALL INTO THE
40S SAT NIGHT THRU MON NIGHT, WITH SEASONABLY COOL MAXIMA
PERSISTING IN THE 60S DURING THIS TIME.
AMID CONTINUED WRN-CONUS RIDGING AND A DEPARTING NERN-CONUS
TROUGH, CONSIDERABLE MODEL VARIANCE DEVELOPS EARLY NEXT WEEK.
CLUSTER ANALYSIS SUGGESTS STRONG MID-LEVEL FLOW OVER THE REGION
WITH TWO PRIMARY SOURCES OF UNCERTAINTY DRIVING POTENTIAL
OUTCOMES: THE FIRST BEING THE AMPLITUDE OF THE DEPARTING ERN-
CONUS TROUGH, AND THE SECOND BEING POTENTIAL FOR AN EMBEDDED
SHORTWAVE TROUGH ADVANCING THRU THE STRONGER FLOW. IN EITHER
CASE, COOLER AIR IS LIKELY TO PERSIST ON MON, WITH SOME VARIANCE
IN RECOVERY ON TUE.
THEREAFTER CONSIDERABLE UNCERTAINTY EXISTS IN THE FORECASTED
WEATHER PATTERN FOR THE UPPER OHIO VALLEY, AS A RESULT OF
VARIANCE IN THE AMPLITUDE OF THE LINGERING WRN-CONUS RIDGE. AT
THIS TIME, THE BLENDED MEAN (SUGGESTING A MODEST THERMAL
RECOVERY THRU LATE WEEK) WILL YIELD MINIMIZED FORECAST ERROR,
AND WILL BE ACCEPTED.
AVIATION /00Z THURSDAY THROUGH MONDAY/
A WEAK SHORTWAVE PLUS A PLUME OF MOISTURE/INSTABILITY MANAGED TO
FIRE OFF ISOLATED SHOWERS AND A COUPLE OF THUNDER STORMS OVER
THE REGION THIS AFTERNOON INTO EARLY EVENING. FKL AND MGW MAY
STILL SEE A SHOWER THROUGH 01Z BEFORE THIS ACTIVITY DISSIPATES
WITH THE LOSS OF HEATING.
LIGHT SOUTH/SOUTHWEST WIND AND VFR CONDITIONS ARE FORECAST FOR
THE NIGHTTIME HOURS. CLOUDS WILL BEGIN TO THICKEN OVERNIGHT
AHEAD OF AN APPROACHING FRONT, WITH SLOWLY LOWERING CEILINGS
THAT WILL REMAIN WELL ABOVE MVFR THRESHOLDS.
STILL LOOKING AT THE POTENTIAL FOR TWO ROUNDS OF PRECIPITATION
ON THURSDAY: ONE ASSOCIATED WITH A PREFRONTAL TROUGH, THE SECOND
WITH THE MAIN BOUNDARY. THE FIRST MAINLY OCCURS DURING THE
MORNING HOURS FROM 10Z TO 16Z FROM WEST TO EAST. THUNDER REMAINS
POSSIBLE WITH THIS FIRST ROUND, WITH LITTLE CONVECTIVE WIND GUST
POTENTIAL. HAVE USED PROB30 FOR THIS POTENTIAL.
FOR THE FRONTAL CONVECTION, POTENTIAL FOR STRONGER WIND GUSTS
(PERHAPS IN THE 30 TO 40 KNOT RANGE) WILL DEPEND ON THE AMOUNT
OF DESTABILIZATION THAT CAN OCCUR AFTER THE MORNING ROUND.
CONFIDENCE IN THIS IS LOW, AS MODELS LARGELY HINT AT PLENTY OF
CLOUDS DURING THE LATE MORNING/EARLY AFTERNOON. IN ANY CASE,
WITH INCREASING SHEAR BRINGING A BETTER POTENTIAL FOR STORM
ORGANIZATION, HAVE USED TEMPO FOR THUNDER POTENTIAL WITH FROPA,
USING 3-HOUR WINDOWS AT EACH TAF SITE. IFR WAS NOT USED AT THIS
TIME, BUT A BRIEF PERIOD OF HEAVY RAIN COULD PRODUCE 1-2 MILE
VISIBILITY. NON-CONVECTIVE WIND IS LIKELY TO INCREASE AS
WELL WITH GUSTS AS HIGH AS 20-25 KNOTS.
PRECIPITATION SHOULD LARGELY CUT OFF BEHIND THE BOUNDARY, BUT A
PERIOD OF MVFR STRATOCUMULUS MAY OCCUR BEFORE CLOUDS PARTIALLY
CLEAR DURING THE NIGHT. A WIND SHIFT TO NORTHWEST OCCURS AS
WELL, WITH GUSTS DECREASING WITH THE LOSS OF MIXING.
OUTLOOK.
ADDITIONAL SHORTWAVE MOVEMENT MAY OFFER ADDITIONAL
RAIN AND RESTRICTIONS CHANCES LATE FRIDAY INTO SATURDAY BEFORE
DRY WEATHER DEVELOPS TO START THE NEXT WEEK.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...KRAMAR/HEFFERAN
NEAR TERM...CERMAK/KRAMAR/RACKLEY
SHORT TERM...KRAMAR/FRAZIER
LONG TERM...KRAMAR/FRAZIER
AVIATION...CL
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