325
FXUS61 KPBZ 081735
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
135 PM EDT TUE JUL 8 2025
SYNOPSIS
A MEANDERING BOUNDARY REMAINS IN OUR REGION INTO THE WEEKEND,
WITH OCCASIONAL SHOWER AND THUNDERSTORMS CHANCES. LOCALLY HEAVY
RAINFALL REMAINS POSSIBLE AT TIMES, WITH SEVERE THUNDERSTORM
CHANCES REMAINING FAIRLY LIMITED.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- SHOWERS AND STORMS ALONG A SAGGING BOUNDARY
- DRY NORTH OF PITTSBURGH AND IN EASTERN OHIO
- FOG DEVELOPMENT EXPECTED AGAIN TONIGHT
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SHOWERS HAVE DEVELOPED AND ARE TRACKING ALONG A NORTHEAST TO
SOUTHWEST ORIENTED BOUNDARY DRAPED ACROSS THE AREA. IT WILL SAG
SOUTH AND EAST THROUGH THE DAY TODAY FOCUSING CONVECTIVE
DEVELOPMENT ALONG IT. BEHIND IT, FROM PITTSBURGH NORTH AND
EAST, MOST OF THE REST OF TODAY WILL BE DRY WITH CLOUD COVER
GRADUALLY SCATTERING THROUGH THE AFTERNOON HOURS AS SOME DRIER
AIR WORKS IN IN NORTHWEST FLOW.
ALONG AND AHEAD OF THE BOUNDARY, ANOTHER DAY OF SHOWERS AND STORMS
IS EXPECTED, AND SOME MAY AGAIN PRODUCE HEAVY RAINFALL. PWAT VALUES
STILL REMAIN IN THE 1.5-1.8" RANGE WHICH IS ABOVE THE 90TH
PERCENTILE OF CLIMATOLOGY. MBE VECTORS AGAIN ARE SLOW (<10 KNOTS)
WITH CLOUD-BEARING LAYER FLOW PARALLELING THE BOUNDARY SUPPORTING
UPSCALE GROWTH. FORECAST MUCAPE VALUES ARE UP TO AROUND 1500 J/KG
AND A WARM CLOUD LAYER UP TO 12-13KFT. THAT SAID, THE BOUNDARY IS
MOVING, AND DEVELOPMENT SO FAR HAS LEFT SOMETHING TO BE
DESIRED, LIKELY OWING TO WEAK SURFACE CONVERGENCE AND LITTLE
UPPER LEVEL SUPPORT. HREF PROBS FOR 1"/HOUR AMOUNTS ARE ONLY UP
TO ~30% WHICH IS LESS BULLISH THAN THOSE ON MONDAY. SO,
LOCALIZED FLASH FLOODING CONCERNS STILL REMAIN, BUT IT WILL
LIKELY TAKE PROLONGED TRAINING TO RESULT IN CONCERNING AMOUNTS
UNLESS RATES PICK UP. THE HIGHEST LIKELIHOOD FOR THAT IS ALONG
AND SOUTHEAST OF A LINE ROUGHLY FROM IDI TO MGW.
PRECIP SHOULD EXIT THE AREA NOT LONG AFTER SUNSET AND GIVE WAY TO A
DRIER BUT MUGGY NIGHT. DEW POINTS ARE FORECAST TO COME DOWN A BIT
BEHIND THE FRONT, AND WITH LIGHT TO CALM WIND AND PLENTY OF
LINGERING NEAR-SURFACE MOISTURE, FOG DEVELOPMENT IS PROBABLE
AGAIN. PROBABILITY FOR DENSE FOG IS ELEVATED AT 50-60% ACROSS
NORTHWEST PA AND NORTHERN WV.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
KEY MESSAGES:
- STALLED BOUNDARY KEEPS MOST OF THE ISOLATED CONVECTION SOUTH
OF PITTSBURGH ON WEDNESDAY.
- BETTER COVERAGE OF SCATTERED STORMS THURSDAY AS BOUNDARY LIFTS
BACK NORTH.
- TEMPERATURES JUST ABOVE NORMAL.
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THE BOUNDARY LIKELY CONTINUES TO MEANDER SOUTH OF OUR REGION
WEDNESDAY, KEEPING THE DEEPER MOISTURE/INSTABILITY TO THE SOUTH AND
EAST. SOME ISOLATED DIURNAL CONVECTION REMAINS POSSIBLE, ALTHOUGH
MODEL SOUNDINGS SHOW SOME LIMITED CAPPING POTENTIAL IN THE MIDDLE
LEVELS, KEEPING A LID ON COVERAGE. ANY LIMITED SEVERE POTENTIAL
WOULD EXIST IN PORTIONS OF NORTHERN WEST VIRGINIA, WHERE BETTER
INSTABILITY/STRONGER UPDRAFT POTENTIAL WOULD LIE, ALONG WITH
ANY POTENTIAL FOR LOCALIZED HEAVY RAINFALL, BUT THE OVERALL
THREAT APPEARS QUITE LOW. TEMPERATURES SHOULD RISE A DEGREE OR
TWO AS COMPARED TO TODAY, GIVEN INCIPIENT WEAK SOUTHWEST FLOW.
CONVECTION FADES WEDNESDAY NIGHT, WITH THURSDAY LIKELY DAWNING
DRY. A CROSSING SHORTWAVE TROUGH SHOULD BEGIN TO PUSH THE
BOUNDARY NORTH AGAIN AS A WARM FRONT, WITH A BIT MORE WIDESPREAD
DIURNAL CONVECTIVE COVERAGE POSSIBLE. SKINNY CAPE PROFILES AND
LOW SHEAR SUGGEST THAT THE SEVERE THREAT REMAINS LOW, BUT THAT
LOCALIZED HIGH RAINFALL RATES REMAIN POSSIBLE, ESPECIALLY AS
PWAT LEVELS BEGIN TO RECOVER.
LONG TERM /FRIDAY THROUGH TUESDAY/
KEY MESSAGES:
- STALLED BOUNDARY LINGERS INTO THE WEEKEND AT LEAST WITH
CONTINUED DAILY RAIN CHANCES, CURRENTLY HIGHEST SUNDAY.
- LOW RAIN CHANCES NEXT WEEK AS PATTERN UNCERTAINTY INCREASES.
- CONTINUED NEAR TO ABOVE-NORMAL TEMPERATURE.
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ON FRIDAY, A WAVE OF LOW PRESSURE ALONG THE BOUNDARY MAY PUSH IT
BACK SOUTH OF PITTSBURGH, PERHAPS TOWARDS THE MASON-DIXON LINE. THIS
WOULD KEEP HIGHER DIURNAL SHOWER/STORM CHANCES ACROSS OUR SOUTHERN
ZONES. PRECIPITABLE WATER REMAINS ELEVATED NEAR AND SOUTH OF THE
BOUNDARY, WITH A REASONABLE RANGE OF 1.3 TO 1.6 INCHES, SO LOCALLY
HEAVY RAINFALL WILL REMAIN POSSIBLE.
MORE ORGANIZED SURFACE LOW PRESSURE LIKELY LIFTS ACROSS THE WESTERN
GREAT LAKES ON SATURDAY, WHICH WOULD PUSH THE BOUNDARY BACK NORTH,
BEFORE A POTENTIAL COLD FRONTAL PASSAGE SATURDAY NIGHT OR SUNDAY.
THERE REMAINS ENSEMBLE DISAGREEMENT ON HOW THIS COULD PLAY OUT,
PARTICULARLY WITH THE TIMING. FOR NOW, SUNDAY APPEARS TO HAVE BETTER
RAIN CHANCES THAN SATURDAY, AND GIVEN THE FROPA UNCERTAINTY, THE
SECOND HALF OF THE WEEKEND ALSO HAS GREATER HIGH TEMPERATURE
UNCERTAINTY. NBM 10TH TO 90TH PERCENTILE SPREADS EXCEED 10 DEGREES
FOR MOST OF THE REGION, WITH POSSIBLE MAX VALUES RANGING FROM AROUND
80 TO THE LOWER 90S. SEVERE POTENTIAL WILL DEPEND ON TIMING AS WELL,
WITH ENSEMBLE SOUNDINGS AND MACHINE LEARNING ADVERTISING AT LEAST
LOW-END POTENTIAL - FORECAST DEEP SHEAR REMAINS ON THE LOW SIDE,
LIMITING ORGANIZED CONVECTION POTENTIAL. LOCALIZED HEAVY RAIN
REMAINS POSSIBLE AS WELL.
UNCERTAINTY THEM PROPAGATES INTO NEXT WEEK. ELEVATED 500MB HEIGHTS
AND ZONAL FLOW ALOFT ARE MOST LIKELY, KEEPING TEMPERATURES NEAR TO
ABOVE NORMAL, BUT DIFFERENCES IN DISTURBANCES IN THAT FLOW
REQUIRE LOW-END POPS FOR BOTH MONDAY AND TUESDAY.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
SHOWERS AND THUNDERSTORMS CONTINUE ALONG A SAGGING BOUNDARY NOW
LOCATED SOUTH OF PIT. THE ONLY TERMINALS LEFT TO SEE IMPACTS
THIS AFTERNOON ARE LBE AND MGW, THOUGH THE LIKELIHOOD OF
RESTRICTIONS IS DECREASING AS THE BOUNDARY PASSES THROUGH AND
ANY NOTABLE RAINFALL RATES ARE STRUGGLING TO SET UP. STILL,
BRIEF PERIODS OF LOW END MVFR TO HIGH END IFR IN HEAVY RAIN ARE
POSSIBLE, SO INCLUDED THIS IN A TEMPO GROUP FOR LBE AND MGW. THUNDER
IS POSSIBLE WITH ANY SHOWERS, BUT GIVEN RECENT RADAR TRENDS AND
OVERALL LACK OF LIGHTNING, OPTED TO HOLD MENTION OUT; REDUCTION
TO VISIBILITY WITH HEAVY RAIN IS MORE LIKELY TO BE THE GREATER
IMPACT, SO WILL FURTHER AMEND IF THE THUNDER THREAT IS MORE
APPARENT. WIND WILL BE LIGHT FROM THE WEST-SOUTHWEST THE
DURATION OF THE FORECAST OUTSIDE OF ANY SHOWERS/THUNDERSTORMS.
OVERNIGHT, WIND IS LIKELY TO GO VARIABLE TO CALM, AND FOG IS
AGAIN LIKELY WITH HIGHEST PROBABILITY (50-60%) FOR DENSE FOG
IMPACTING FKL/DUJ/LBE/MGW. ELSEWHERE, DO STILL EXPECT SOME
IMPACTS WITH CROSSOVER TEMPERATURE ACHIEVEMENT, BUT
PROBABILITIES ARE LESS AGGRESSIVE FOR <1/4SM. AS SUCH, HAVE
INCLUDED PREVAILING LOW END MVFR WITH TEMPOS TO IFR GENERALLY
AFTER 07Z. FOG WILL DISSIPATE SIMILAR TO TUESDAY MORNING WITH
MIXING ON WEDNESDAY AND ANY LOW CEILINGS ACCOMPANYING THE FOG
WILL SCATTER OUT GIVING WAY TO MID-LEVEL CLOUD COVERAGE
TOMORROW. THERE IS A LOW PROBABILITY (~20%) OF SHOWERS IN THE
AFTERNOON WITH WIDELY SCATTERED NATURE.
OUTLOOK...
AN UNSETTLED PATTERN WILL CONTINUE FOR MUCH OF THE REST
OF THE WEEK AS THE FRONT STALLS TO THE SOUTHERN HALF OF OUR AREA.
DIURNALLY DRIVEN STORM CHANCES WILL GOVERN CONDITIONS THE REST
OF THE WEEK WITH PERIODIC AFTERNOON AND EVENING IMPACTS POSSIBLE
EACH DAY.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...MLB/CL
NEAR TERM...MLB
SHORT TERM...CL
LONG TERM...CL
AVIATION...MLB
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