337
FXUS61 KPBZ 021717
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
117 PM EDT TUE SEP 2 2025
SYNOPSIS
WIDESPREAD RAIN CHANCES RETURN THURSDAY WITH THE APPROACH AND
PASSAGE OF A COLD FRONT. GUSTY WINDS AND ISOLATED STORMS ARE
ALSO POSSIBLE WITH THE PASSAGE OF THE FRONT. COOLER CONDITIONS
ARE EXPECTED OVER THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- ISOLATED SHOWERS ALONG THE RIDGES THIS AFTERNOON
---------------------------------------------------------------
A SHALLOW LAYER OF INCREASED MOISTURE HAS STREAMED WEST ACROSS THE
AREA IN MID-LEVEL EASTERLY FLOW AND SUPPORTED A BROKEN LAYER OF
CLOUDS EARLY THIS MORNING. THIS HAS PREVENTED MUCH IN THE WAY OF
RIVER VALLEY FOG DEVELOPMENT AND WILL CONTINUE TO DO SO AS IT
BLANKETS THE AREA.
THAT MOISTURE IS LIKELY TO ERODE SOME HEADED INTO THE AFTERNOON AND
GIVE WAY TO A DIURNALLY DRIVEN CUMULUS DECK SIMILAR TO MONDAY. THE
ONLY DIFFERENCE TODAY WILL BE POSSIBLE ISOLATED, TERRAIN-DRIVEN
SHOWERS ALONG THE LAUREL HIGHLANDS THIS AFTERNOON (BETWEEN 1PM AND
5PM) WITH SHALLOW INSTABILITY. WITH A CAPPING LAYER AROUND 700 MB,
ANY SHOWERS WILL BE SHALLOW AND LIKELY SHORT LIVED GIVEN LACKING
COLUMN MOISTURE AND WEAK LIFT. OTHERWISE, MOSTLY DRY CONDITIONS
ACROSS THE REGION.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
KEY MESSAGES:
- PRE-FRONTAL RAIN SHOWERS POSSIBLE WEDNESDAY EVENING
----------------------------------------------------------------
BY EARLY WEDNESDAY MORNING, A LOW PRESSURE SYSTEM WILL
STRENGTHEN NORTH OF MINNESOTA AND MOVE TOWARDS THE GREAT LAKES.
AS SOUTHWEST FLOW INCREASES AHEAD OF THIS DISTURBANCE AND BRINGS
MOISTURE INTO THE REGION WEDNESDAY AFTERNOON, EXPECT CLOUDS AND
ISOLATED SHOWERS TO DEVELOP IN SOME AREAS. LOCATIONS SOUTH OF
PITTSBURGH HAVE THE HIGHEST CHANCE, THOUGH STILL LOW (20-30%),
OF SEEING SHOWERS.
WITH INCREASING WARM ADVECTION AHEAD OF THE APPROACHING
DISTURBANCE, EXPECT AFTERNOON HIGH TEMPERATURE TO BE NEAR
AVERAGE.
LONG TERM /FRIDAY THROUGH TUESDAY/
KEY MESSAGES:
- SHOWERS, THUNDERSTORMS, AND GUSTY WINDS ARE EXPECTED WITH A
COLD FRONT THURSDAY
- SECONDARY FRONT MAY CREATE ADDITIONAL SHOWERS ON FRIDAY
- COOLER WEATHER RETURNS OVER THE WEEKEND
-------------------------------------------------------------------
BY LATE WEDNESDAY NIGHT INTO EARLY THURSDAY MORNING, THE
PREVIOUSLY MENTIONED LOW PRESSURE SYSTEM IN THE SHORT TERM
DISCUSSION IS EXPECTED TO MOVE ACROSS LAKE SUPERIOR, WITH ITS
TRAILING COLD FRONT EXTENDED SOUTH INTO CENTRAL MICHIGAN AND
INDIANA. STRENGTHENING SOUTHWEST FLOW ALOFT WILL KEEP THURSDAY
MORNING TEMPERATURES NEAR AVERAGE, WHILE CLOUDS INCREASE FROM
THE WEST.
RAIN CHANCES INCREASE AFTER 6AM THURSDAY AS THE APPROACHING
COLD FRONT MOVES INTO EASTERN OHIO AND PROGRESSES INTO WESTERN
PENNSYLVANIA BY LATE MORNING OR EARLY AFTERNOON. THUNDERSTORMS
ARE EXPECTED TO DEVELOP ALONG THE FRONT, SUPPORTED BY STRONG
WIND SHEAR BUT LIMITED INSTABILITY (GENERALLY LESS THAN
500J/KG) DUE TO INCREASING MOISTURE AT THE SURFACE. MACHINE
LEARNING GUIDANCE SUGGESTS A 5-15% CHANCE OF STRONGER STORMS IN
SOME SCENARIOS, WHICH WILL NEED TO BE MONITORED OVER THE NEXT 48
HOURS. THE EXACT TIMING OF THE FRONT WILL BE CRITICAL IN
DETERMINING HOW MUCH INSTABILITY CAN BUILD ON THURSDAY.
RAINFALL TOTALS ARE EXPECTED TO RANGE FROM 0.35" TO 0.65", WITH
LOCALIZED SWATHS OF HIGHER AMOUNTS WHERE THUNDERSTORMS OCCUR.
GIVEN THE RECENT STRETCH OF DRY WEATHER, THE RISK FOR FLOODING
REMAINS LOW.
INCREASING DRY AIR ALOFT LATE THURSDAY WILL DIMINISH THE CHANCE
OF HEAVY RAINFALL. HOWEVER, STRAY SHOWERS MAY LINGER EAST OF
PITTSBURGH.
BEHIND THE FRONT, THE BROAD DISTURBANCE STRETCHING FROM THE
NORTHERN PLAINS TO NEW ENGLAND IS EXPECTED TO STALL. A PASSING
SHORTWAVE AND SECONDARY FRONT MOVING THROUGH THE REGION FRIDAY
INTO SATURDAY MAY TRIGGER ADDITIONAL CONVECTION.
ADVANCEMENT OF THE TROUGH AND INCREASING NORTHERLY FLOW OVER THE
WEEKEND WILL LIKELY INCREASE THE CHANCES OF COOLER THAN AVERAGE
TEMPERATURES.
AVIATION /17Z TUESDAY THROUGH SATURDAY/
HIGH PRESSURE CENTERED OVER NEW ENGLAND WILL RESULT IN MOSTLY DRY
WEATHER AND LIGHT EASTERLY WIND THROUGH THE TAF PERIOD. LINGERING
MOISTURE BETWEEN 6-10KFT THEN GIVING WAY TO DIURNAL CU DEVELOPMENT
FAVORS PERIODS OF SCATTERED TO BROKEN VFR CIGS IN THAT HEIGHT
RANGE.
HI-RESOLUTION MODELING SUGGESTS THAT THE COMBINATION OF HEATING AND
EASTERLY UPSLOPE FLOW MAY BE ENOUGH TO FOSTER A TUESDAY AFTERNOON
SHOWER ALONG THE LAUREL HIGHLANDS. ANY CONVECTION IS LIKELY TO BE
VERY ISOLATED WITH LOW PROBABILITY TO IMPACT LBE/DUJ, BUT IF IT
DOES, EXPECT ANY RESTRICTIONS WOULD BE MINIMAL AND SHORT-LIVED;
THUNDER PROBABILITY IS LOW WITH UPDRAFT HEIGHTS LIKELY STUNTED AT OR
JUST ABOVE THE FREEZING LEVEL.
DIURNAL CU DISSIPATES AFTER SUNSET AND WIND GOES LIGHT TO
VARIABLE OVERNIGHT WITH A FEW MID-LEVEL CLOUDS. MORNING RIVER
VALLEY FOG IS AGAIN POSSIBLE BUT WITH LOW PROBABILITY IMPACTS TO
ANY TERMINAL.
OUTLOOK.
HIGH CONFIDENCE IN VFR CONDITIONS THROUGH WEDNESDAY, THOUGH AN
APPROACHING UPPER TROUGH MAY AID ENOUGH MOISTURE ADVECTION TO
GENERATE AN ISOLATED AFTERNOON SHOWER SOUTH OF KPIT.
AN UPPER LEVEL TROUGH AND SURFACE COLD FRONT ARE HIGHLY LIKELY TO
PRODUCE WIDESPREAD RAIN WITH LOW-PROBABILITY THUNDERSTORMS STARTING
EARLY THURSDAY MORNING BEFORE TAPERING OFF EARLY FRIDAY MORNING.
EARLY MODEL ANALYSIS SUGGESTS A 50-70% PROBABILITY FOR MVFR
CONDITIONS ASSOCIATED WITH THE RAIN THURSDAY, WITH CONDITIONS
POTENTIALLY IMPROVING WEST TO EAST SHORTLY AFTER FRONTAL
PASSAGE. NON-CONVECTIVE WIND IS LIKELY TO INCREASE AS WELL WITH
GUSTS AS HIGH AS 20-25 KNOTS THURSDAY AND FRIDAY AFTERNOONS.
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...HEFFERAN
NEAR TERM...RACKLEY
SHORT TERM...RACKLEY
LONG TERM...HEFFERAN/RACKLEY
AVIATION...MLB
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