074
FXUS61 KPBZ 082314
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
714 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 /UNTIL 6 AM WEDNESDAY MORNING/
KEY MESSAGES:
- DRY WEATHER FAVORED OVERNIGHT
- FOG DEVELOPMENT EXPECTED AGAIN TONIGHT
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AS THE SURFACE BOUNDARY SETTLES NEAR TO JUST SOUTH OF INTERSTATE
68 AND THE UPPER SHORTWAVES REMAINS EAST, THE REGION IS FAVORED
TO EXPERIENCE DRY WEATHER OVERNIGHT AS SUBSIDENCE ALOFT TAKES
HOLD.
THE APPROACH OF A WESTERN GREAT LAKES TROUGH WILL ATTEMPT
TO INCREASE HIGH TO MID LEVEL CLOUDS STARTING AROUND MIDNIGHT
THROUGH WEDNESDAY MORNING; TIMING AND THICKNESS OF THESE CLOUDS
LAYERS WILL PLAY A CRITICAL ROLE IN THE DEVELOPMENT AND AREAL
COVERAGE OF FOG. LATEST MODEL GUIDANCE FAVORS RIVER VALLEY
LOCATIONS AND LOCATIONS SOUTH OF PITTSBURGH WHERE LIMITED DRY
INTRUSION OCCURRED BEHIND THE FRONT. GIVEN UNCERTAINTY IN THE
SPACIAL COVERAGE AND IMPACTS OF INCOMING HIGHER CLOUD DECKS WILL
PRECLUDE ANY FOG HAZARD PRODUCTS AT THIS TIME.
SHORT TERM /6 AM WEDNESDAY MORNING 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 /00Z WEDNESDAY THROUGH SUNDAY/
THE SURFACE FRONT HAS DIPPED SOUTH OF ALL AREA TERMINALS, WHICH
WILL ALLOW UPPER SUBSIDENCE TO ERODE RESIDUAL STRATOCU THROUGH
MIDNIGHT AND MAINTAIN VFR CONDITIONS.
UNCERTAINTY SIGNIFICANTLY RAISES FOR THE 06Z-12Z PERIOD
REGARDING THE AREAL COVERAGE AND DEGREE OF INTENSITY FOR FOG
FORMATION. FACTORS FAVORING FOG INCLUDE ENOUGH BOUNDARY LAYER
MOISTURE, VERY LIGHT WIND, AND A PERIOD OF CLEARER SKIES
FOSTERING STRONG RADIATIONAL COOLING. FACTORS THAT COULD LIMIT
FOG INCLUDE THE INFLUX OF MID-HIGH LEVEL CLOUDS OVERNIGHT AHEAD
OF THE NEXT SHORTWAVE AND ITS TIMING TO DISRUPT COOLING
PROCESSES. TAFS ARE TRENDED TOWARD A LESS FOGGY SOLUTION, BUT
PROBABILITIES REMAIN HIGH ENOUGH FOR IFR/LIFR VIS MENTION AT
RIVER VALLEY SITES OR TERMINALS THAT SAW MINIMAL DRY ADVECTION.
DIURNAL HEATING/MIXING WILL ERODE ANY FOG/LOW STRATUS BY 15Z,
WITH VFR EXPECTED THE REST OF THE DAY. SHORTWAVE MOVEMENT IS
LIKELY TO BE DISPLACED TOO FAR NORTH/SOUTH TO GENERATE BUT A LOW
PROBABILITY (20%) SHOWER BETWEEN 18Z-00Z THAT ISN'T WORTH TAF
MENTION AT THIS TIME.
OUTLOOK...
A WEAKLY FORCED BUT WARM/HUMID ENVIRONMENT IS FAVORED THROUGH
THE END OF THE WEEK THAT WILL ALLOW FOR PERIODS OF
SHOWERS/THUNDERSTORMS ALONG WITH DRY PERIODS; CONFIDENCE IS
LIKELY TO BE LOWER ON TIMING VARIOUS ROUNDS OF PRECIPITATION AS
WELL AS THE RESULTANT CIG/VIS IMPACT THEY COULD HAVE DURING THE
MORNING HOURS.
MORE SIGNIFICANT UPPER LEVEL AND SURFACE BOUNDARY MOVEMENT
APPEARS TO ARRIVE OVER THE WEEKEND THAT WILL CREATE A MORE
FOCUSED AND BETTER TIMED PERIOD FOR CONVECTION AND RESTRICTION
DEVELOPMENT.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...MLB/CL
NEAR TERM...FRAZIER
SHORT TERM...CL
LONG TERM...CL
AVIATION...FRAZIER
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