550
FXUS61 KPBZ 021807
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
207 PM EDT TUE SEP 2 2025
SYNOPSIS
SHOWERS AND THUNDERSTORMS RETURN THURSDAY WITH THE APPROACH AND
PASSAGE OF A COLD FRONT. GUSTY WINDS AND ISOLATED SEVERE STORMS
MAY BE POSSIBLE. COOLER CONDITIONS ARE EXPECTED OVER THE
WEEKEND.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- ISOLATED SHOWERS ALONG THE RIDGES THIS AFTERNOON
- MAINLY DRY WEATHER CONTINUES WITH HIGH PRESSURE
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SIMILAR CONDITIONS TO MONDAY ARE EXPECTED TODAY WITH A HEALTHY
FAIR WEATHER CUMULUS DECK ALREADY DEVELOPED. ONE DIFFERENCE,
HOWEVER, IS THE CHANCE FOR LOW-PROBABILITY DIURNAL SHOWERS
MAINLY COMING OFF THE HIGHER TERRAIN IN EASTERLY FLOW.
INSTABILITY WILL REMAIN SHALLOW THROUGH THE AFTERNOON, WITH A
CAPPING INVERSION JUST ABOVE 700 MB. ANY SHOWERS THAT DO DEVELOP
WILL ALSO BE SHALLOW, LIGHT, AND SHORT-LIVED. MOST OF THE AREA
WILL REMAIN DRY.
MOSTLY CLEAR SKIES WITH LIGHT WINDS ARE EXPECTED OVERNIGHT,
LEADING TO FAIRLY EFFICIENT COOLING ONCE AGAIN. OVERNIGHT LOWS
WILL END UP IN THE 40S AND 50S.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
KEY MESSAGES:
- PRE-FRONTAL RAIN SHOWERS POSSIBLE WEDNESDAY EVENING
- SHOWERS, THUNDERSTORMS, AND GUSTY WINDS EXPECTED WITH THURSDAY
COLD FRONT
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BY EARLY WEDNESDAY, SURFACE LOW PRESSURE WILL DEVELOP ACROSS THE
NORTHERN GREAT LAKES UNDER A DEEPENING AND INCREASINGLY CUT OFF
UPPER LOW OVER WESTERN ONTARIO. FARTHER EAST, A SHORTWAVE TROUGH
WILL SWING THROUGH OUR AREA BY WEDNESDAY AFTERNOON AS
SOUTHWESTERLY FLOW WITH MOISTURE RETURN INCREASES. AT THIS TIME,
IT STILL APPEARS MOISTURE RETURN WILL NOT BE SUFFICIENTLY TIMED
WITH SHORTWAVE LIFT TO SEE MORE THAN A FEW ISOLATED SHOWER SOUTH
OF I-70, BUT SHOULD SEE AN INCREASE IN CLOUD COVER. MOST OF THE
AREA WILL LIKELY REMAIN DRY. INCREASING WARM ADVECTION WILL
BOOST AFTERNOON HIGHS BACK INTO THE 80S FOR MUCH OF THE AREA.
LOW PRESSURE WILL SHIFT EAST BY THURSDAY, BRINGING A COLD FRONT
THROUGH THE REGION BY THURSDAY AFTERNOON/EVENING. SHOWERS AND
THUNDERSTORMS ARE EXPECTED TO DEVELOP AHEAD OF AND ALONG THE
FRONT, THOUGH SOME UNCERTAINTY IN TIMING AND SEVERE POTENTIAL
REMAINS. INITIAL CAM RUNS FAVOR A PREFRONTAL LINE OF SHOWERS
CROSSING THE REGION THROUGH THE LESS-FAVORABLE MID-MORNING HOURS
BEFORE CONVECTION DEVELOPS WITH THE FRONT DURING THE AFTERNOON.
THIS WOULD POSE A CHALLENGE FOR SUFFICIENT RECOVERY BEFORE THE
AFTERNOON CONVECTION. HOWEVER, OUTSIDE OF THIS, ENVIRONMENTAL
PARAMETERS DO SUPPORT ISOLATED SEVERE STORMS. MODELED MLCAPE
VALUES RANGE FROM 500-1000 J/KG, WITH A HEALTHY 60-70 KTS OF
BULK SHEAR INTO THE AFTERNOON HOURS. SO, WITH A BIT LATER ONSET
OR LONGER RECOVERY TIME, IT IS POSSIBLE WE SEE A BROKEN QLCS
CAPABLE OF PRODUCING ISOLATED SPIN-UPS LATE THURSDAY MORNING OR
AFTERNOON. SPC HAS INTRODUCED A LEVEL 1 MARGINAL RISK FOR
SEVERE, AND THIS IS MIRRORED BY THE GEFS ML FORECAST. WILL
CONTINUE TO MONITOR THIS THREAT...
RAINFALL TOTALS FOR THURSDAY HAVE TRENDED UPWARD IN THE LAST FEW
CYCLES. NBM INTERQUARTILE RANGES FROM ABOUT 0.3 ON THE LOW END
TO OVER AN INCH IN PLACES ON THE HIGH END, ESPECIALLY WITH
LOCALIZED HEAVY RAIN IN THUNDERSTORM. GIVEN THE RECENT STRETCH
OF DRY WEATHER, FLOODING RISK WILL REMAIN LOW, BUT LOCALIZED
FLOODING REMAINS A POSSIBILITY. RAIN CHANCE WILL DECREASE
THROUGH THE EVENING WITH FRONTAL PASSAGE.
OUTSIDE OF CONVECTIVE RISK, TIGHTENING PRESSURE GRADIENT AND A
STRENGTHENING LLJ WILL LEAD TO GUSTY CONDITIONS IN AND AROUND
SHOWERS. 30 TO MAYBE 40 MPH GUSTS MAY BE POSSIBLE AT TIMES
THURSDAY MORNING.
LONG TERM /FRIDAY THROUGH MONDAY/
KEY MESSAGES:
- SECONDARY FRONT MAY CREATE ADDITIONAL SHOWERS ON FRIDAY
- COOLER WEATHER RETURNS OVER THE WEEKEND
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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 LATER
FRIDAY INTO SATURDAY MAY TRIGGER ADDITIONAL CONVECTION. RAIN
CHANCES SHOULD DROP OFF THROUGH THE DAY ON SATURDAY BEHIND THE
FRONT.
ADVANCEMENT OF THE TROUGH AND INCREASING NORTHERLY FLOW OVER THE
WEEKEND IS LIKELY TO KEEP COOLER CONDITIONS IN THE FORECAST WITH
GENERALLY DRY CONDITIONS AS SURFACE HIGH PRESSURE BUILDS. ZONAL
FLOW LOOKS TO ARRIVE BY EARLY NEXT WEEK AS THE TROUGH EXITS
EAST, LEADING TO A GRADUAL WARMING TREND.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
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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