437
FXUS61 KPBZ 071756
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
156 PM EDT TUE OCT 7 2025
SYNOPSIS
AREA RAIN SHOWERS, AT TIMES LOCALLY HEAVY, WILL EXIT EAST OF THE
REGION BY WEDNESDAY MORNING AHEAD OF A COLD FRONTAL PASSAGE.
DRIER, COOLER WEATHER MAY POST FROST RISKS THURSDAY AND FRIDAY
MORNINGS BEFORE GRADUAL WARMING COMMENCES INTO THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- AREA RAIN SHOWERS, AT TIMES LOCALLY HEAVY, WILL CONTINUE INTO
THIS EVENING BEFORE TAPERING OFF.
- PEAK INTENSITY IS LIKELY WITH SHOWERS ALONG THE COLD FRONT
THIS EVENING, BUT PROBABILITY OF FLOODING REMAINS LOW
---------------------------------------------------------------
BROAD ASCENT AHEAD OF AN UPPER TROUGH AXIS CONTINUES TO AID
AREAS OF LIGHT TO LOCALLY MODERATE RAIN SHOWERS ACROSS THE UPPER
OHIO RIVER VALLEY. DESPITE PWATS APPROACHING 1.7" THAT ARE NEAR
THE DAILY MAX, EXCESSIVE CLOUD COVER AND LACK OF STRONG
FRONTOGENESIS CONTINUE TO MUTE RAINFALL RATES THROUGH THE EARLY
AFTERNOON PERIOD. HI-RES MODELING SUGGESTS A SLIGHT UPTICK IN
INTENSITIES AS A SURFACE COLD FRONT APPROACHES FROM THE NW LATE
THIS AFTERNOON INTO THE LATE EVENING HOURS; THE COMBINATION OF
STRONGER FORCING AND A NARROW CORRIDOR OF HIGHER BUOYANCY
CREATES 20-30% PROBABILITIES FOR SHOWERS TO HAVE ~1"/HR RATES.
EVEN WITH THIS UPTICK, ANTECEDENT DRY CONDITIONS HAVE 1/3/6HR
FFG VALUES IN EXCESS OF 2-3", MAKING IT EXTREMELY DIFFICULT FOR
ANY ONE LOCATION TO EXPERIENCE FLOODING OTHER THAN NUISANCE OR
STORM DRAIN BLOCKAGE (FROM LEAVE/OTHER DEBRIS). IT IS ALSO WITH
THESE FRONTAL SHOWERS THAT OFFER THE BEST (BUT LIMITED) CHANCE
FOR LIGHTNING. NO SEVERE CONCERNS EXIST AS SBCAPE REMAINS
GENERALLY BELOW 500 J/KG AND SHEAR INCREASES OCCUR IN THE POST-
FRONTAL ENVIRONMENT.
THERE IS HIGH CONFIDENCE IN A WEST TO EAST ENDING OF SHOWERS
AFTER FRONTAL PASSAGE AROUND MIDNIGHT. AN UPTICK IN MIXING MAY
ALLOW FOR 20-30MPH NW WIND GUSTS WITH AND SHORTLY AFTER ITS
PASSAGE WHILE STRONG SUBSIDENCE SLOWLY ERODES CLOUD COVER A FEW
HOURS LATER. OVERNIGHT LOWS WILL BE PREDICATED ON TIMING OF
FRONTAL PASSAGE AND QUICKNESS OF STRATOCU EROSION, WITH
NORTHWEST FORECAST POINTS POTENTIALLY SEEING GREATER DROPS AS
CLOUDS CLEAR JUST PRIOR TO DAWN.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
KEY MESSAGES:
- COOLER, DRIER AIR MASS WEDNESDAY/THURSDAY.
- OVERNIGHT LOWS IN THE MID TO UPPER 30S, OFFERING THE POTENTIAL FOR
MORNING FROST.
- GUSTS UP TO 20-30 MPH ON WEDNESDAY.
----------------------------------------------------------------
SURFACE HIGH PRESSURE WILL QUICKLY FILTER IN BEHIND THE EXITING
FRONT AND OFFER A NOTABLE AIRMASS CHANGE WEDNESDAY AND THURSDAY.
THIS RESULTS IN AN INCREASED PRESSURE GRADIENT SUFFICIENT FOR 20 TO
30MPH GUSTS DURING THE AFTERNOON WITH HIGHEST POSSIBLE GUSTS NOT
LIKELY TO EXCEED 30-35MPH. THE WIND WILL EASE WEDNESDAY EVENING INTO
THE OVERNIGHT HOURS.
COLD AIR ADVECTION IS EXPECTED FROM THE GENERAL NORTHERLY FLOW
ACROSS THE VERTICAL PROFILE THROUGH THURSDAY. THIS WILL RESULT IN
MORE SEASONABLE TEMPERATURES WEDNESDAY (UPPER 60S) AND SLIGHTLY
BELOW AVERAGE TEMPERATURES THURSDAY (LOW TO MID 60S) DESPITE MOSTLY
SUNNY SKIES.
THIS CHANGE ALSO CREATES POTENTIAL FROST CONCERNS AS COOLER AIR PLUS
RADIATIONAL COOLING AFTER LOW LEVEL WINDS DECOUPLE LIKELY CREATES
LOWS IN THE 30S AND 40S. THE KEY LIMITING FACTOR TO ANY FREEZING
TEMPERATURE OR FROST WILL BE POTENTIAL FOR ELEVATED NORTHERLY WINDS
OVERNIGHT FROM THE RESIDUAL PRESSURE GRADIENT THURSDAY MORNING. EVEN
THOUGH THERE WILL BE A LIGHT AND WARMER DOWNSLOPE EASTERLY WIND
FRIDAY MORNING, LOW TEMPERATURES ARE FORECAST TO REMAIN BELOW 40F
ACROSS WESTERN PENNSYLVANIA AND EASTERN OHIO WHILE PARTS OF NORTHERN
WEST VIRGINIA HAVE A SMALL CHANCE OF EXCEEDING 40F.
LONG TERM /FRIDAY THROUGH MONDAY/
KEY MESSAGES:
- DRY WEATHER FAVORED THROUGH THE WEEKEND.
- PATTERN VARIABILITY EXISTS AT THE START OF NEXT WEEK.
-------------------------------------------------------------------
THERE IS HIGH CONFIDENCE IN STRONG SURFACE HIGH PRESSURE POSITIONING
OVER THE NEW ENGLAND FRIDAY INTO THE WEEKEND AS THE UPPER OHIO RIVER
VALLEY SITS UNDERNEATH A WEAK, SAGGY TROUGH. THIS RIDGE WILL PROMOTE
DRY WEATHER AND GRADUAL WARMING TO ABOUT 5 DEGREES ABOVE THE DAILY
AVERAGE THROUGH THE PERIOD.
AT THE START OF NEXT WEEK, AN UPPER LEVEL TROUGH IS FORECAST TO
APPROACH THE REGION. PRESENTLY, THERE IS A HIGH LEVEL OF UNCERTAINTY
WITH THE STRENGTH OF THE TROUGH. THIS HAS A CHANCE OF BRINGING A
CHANCE OF RAIN LATER IN THE WEEK FOR AREAS NORTH OF PITTSBURGH.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
AREA SHOWERS AND MOISTURE CONVERGENCE AHEAD OF AN INCOMING
SURFACE COLD FRONT PLUS UPPER TROUGH AXIS WILL SUPPORT CONTINUED
CIG DETERIORATION WITH VISIBILITY DROPS TIED TO LOCALLY HIGHER
RAINFALL RATES.
THE FRONT IS EXPECTED TO APPROACH/CROSS THE REGION BETWEEN
02Z-08Z WITH A LINE OF SHOWERS COULD HAVE HIGHER RAINFALL RATES
(CAUSING MORE DRASTIC VISIBILITY RESTRICTIONS) AND LOW
PROBABILITY THUNDER (TOO LOW FOR TAF MENTION). FRONTAL PASSAGE
WILL YIELD AN END TO PRECIPITATION CHANCES, RAPID CHANGE TO NW/N
WIND WITH 15-25KT GUSTS, AND LINGERING MVFR STRATOCU.
DRY ADVECTION AND INCREASING SURFACE HIGH PRESSURE WILL QUICKLY
ERODE STRATOCU WEDNESDAY, FAVORING VFR FOR MOST TERMINALS BY 16Z
(THOUGH LINGERING LONGER WITH LAKE INFLUENCE AT FKL/DUJ).
DIURNAL MIXING AND RESIDUAL PRESSURE GRADIENTS MAY ALLOW FOR AN
OCCASIONAL NNW WIND GUST UP TO 30KTS.
OUTLOOK
HIGH PRESSURE WILL SUPPORT VFR FOR THE MAJORITY OF THE TIME
THROUGH THE WEEKEND AS SURFACE WIND VEERS E THEN S AS THE HIGH
POSITIONS OVER NEW ENGLAND.
THE COOLER AIR MASS MAY ALLOW FOR LOCALIZED MORNING RIVER
VALLEY STEAM FOG GIVEN WARMER WATER TEMPERATURE, BUT ANY
TERMINAL IMPACTS ARE LIKELY TO BE SHORT LIVED.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...FRAZIER
NEAR TERM...FRAZIER
SHORT TERM...LUPO
LONG TERM...LUPO
AVIATION...FRAZIER
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