542
FXUS61 KPBZ 011821
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
221 PM EDT TUE JUL 1 2025
SYNOPSIS
SHOWERS AND THUNDERSTORMS WILL CONTINUE TODAY WITH A CROSSING
COLD FRONT. HIGH PRESSURE WILL RETURN DRY WEATHER TO THE REGION
WEDNESDAY. A WEAK COLD FRONT WILL BRING A SLIGHT CHANCE OF
SHOWERS AND THUNDERSTORMS THURSDAY, BEFORE HIGH PRESSURE
RETURNS DRY AND WARM WEATHER THROUGH SATURDAY.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:
- SHOWER AND THUNDERSTORM CHANCES CONTINUE TODAY
- MARGINAL RISK FOR EXCESSIVE RAIN ACROSS EASTERN OH AND PORTIONS OF
WESTERN PA & SLIGHT RISK FOR EXCESSIVE RAIN OVER SOUTHWESTERN PA
AND NORTHERN WV
- PATCHY FOG TONIGHT
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WIDESPREAD SHOWERS AND THUNDERSTORMS ARE EXPECTED TODAY AHEAD OF AN
APPROACHING FRONT AND AN ASSOCIATED SHORTWAVE TROUGH. THE LATEST
CAMS INDICATE THE HEAVIEST CONVECTION IS EAST OF PITTSBURGH AND IN
NORTHERN WEST VIRGINIA THROUGH MID-AFTERNOON. BEHIND THE HEAVIEST
RAINFALL, LIGHT AND STEADY SHOWERS ARE EXPECTED.
PWATS WILL GENERALLY BE LOWER TODAY FOR MUCH OF THE AREA, WITH A NW-
SE GRADIENT. NW PA SHOULD SEE VALUES AROUND 1.5, WITH AREAS ACROSS
NORTHERN WV RANGING FROM 1.8 TO 2.0. THE INCREASING FLOW ALOFT
SHOULD RESULT IN FASTER STORM MOTION TODAY, THOUGH IF ANY TRAINING
OR BACKBUILDING OCCURS A LOCALIZED FLASH FLOOD POTENTIAL IS
POSSIBLE.
THE SURFACE COLD FRONT IS FORECAST TO APPROACH THE REGION TOWARD
EVENING, DECREASING AVAILABLE MOISTURE AND INSTABILITY. THIS WILL
CREATE AN UNFAVORABLE ENVIRONMENT, WEAKENING ANY POTENTIAL
CONVECTION ALONG THE FRONT. ONCE THE FRONT HAS PASSED, THE CLEARING
SKY ALONG WITH NEARLY CALM WIND AND MOIST GROUND COULD LEAD TO SOME
PATCHY FOG TONIGHT.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
KEY MESSAGES:
- DRY WEDNESDAY
- SLIGHT CHANCES FOR SHOWERS AND THUNDERSTORMS THURSDAY
- TEMPERATURES A FEW DEGREES ABOVE AVERAGE.
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THE FOG SHOULD QUICKLY MIX OUT AND DISSIPATE WEDNESDAY MORNING. DRY
WEATHER IS EXPECTED THROUGH WEDNESDAY NIGHT AS A RIDGE OF SURFACE
HIGH PRESSURE BUILDS ACROSS THE UPPER OHIO VALLEY REGION.
A TROUGH AND ITS ASSOCIATED SURFACE COLD FRONT, IS EXPECTED TO TRACK
SOUTHEASTWARD ACROSS THE UPPER OHIO VALLEY REGION ON THURSDAY. VERY
DRY AIR ALOFT WILL LIKELY INHIBIT UPDRAFT GROWTH, INHIBITING THE
CHANCE FOR SEVERE WEATHER WHILE LIMITING THE CHANCE FOR SHOWERS AND
THUNDERSTORMS.
TEMPERATURES SHOULD CONTINUE TO AVERAGE A FEW DEGREES ABOVE
SEASONABLE LEVELS THROUGH THE PERIOD.
LONG TERM /FRIDAY THROUGH TUESDAY/
KEY MESSAGES:
- DRY THROUGH THE FIRST HALF OF THE HOLIDAY WEEKEND
- INCREASINGLY HOT AND HUMID WITH SHOWER AND THUNDERSTORM
CHANCES RETURNING SUNDAY AND MONDAY
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FRIDAY AND SATURDAY, A RIDGE IS FORECAST TO SHIFT EASTWARD RESULTING
IN DRY AND WARM WEATHER ACROSS THE UPPER OHIO VALLEY REGION.
THE RIDGE IS THEN PROGGED TO FLATTEN SUNDAY INTO EARLY NEXT WEEK,
WITH WESTERLY FLOW ALOFT ACROSS THE UPPER OHIO VALLEY REGION.
DISTURBANCES EMBEDDED IN THIS FLOW ALOFT ARE EXPECTED TO
PERIODICALLY CROSS THE REGION, WITH DAILY SHOWER AND THUNDERSTORM
CHANCES RETURNING.
EVEN AS THE RIDGE FLATTENS, 500 MB HEIGHTS ARE STILL EXPECTED TO BE
APPROACH 590 DAM, BRINGING HOT AND HUMID CONDITIONS ACROSS THE
REGION. HIGH PROBABILITY (70%-90%) OF MAXIMUM TEMPERATURES AT OR
ABOVE 90 DEGREES ON SUNDAY AND MONDAY.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
EXITING SHOWERS AND THUNDERSTORMS ALONG A PRE-FRONTAL TROUGH
WILL LEAVE AREAS OF LIGHTER RAIN OVER THE REGION THROUGH 23Z;
ADDITIONAL SHORTWAVE MOVEMENT MAY CREATE LOCALIZED ENHANCEMENT
OF RAINFALL RATES THAT COULD BRIEFLY DROP VISIBILITIES TO
MVFR/IFR. OTHERWISE, LOWERING PRECIPITATION TRENDS WILL FAVOR
VFR IMPROVEMENTS THROUGH 00Z.
THE DEGREE OF CLOUD CLEARING OVERNIGHT WILL DICTATE THE
EXTENT/SPREAD OF LOW IFR/LIFR FOG STRATUS AS THE SURFACE COLD
FRONT REMAINS NW OF THE REGION. LATEST HIGH RESOLUTION MODELING
CONTINUES TO SUGGEST A 50-70 PERCENT PROBABILITY FOR
VISIBILITIES BELOW 3SM, WITH ONLY ABOUT A 10 PERCENT REDUCTION
FOR SEEING VISIBILITIES BELOW 1SM. THOUGH RIVER VALLEY LOCATIONS
AND LOCALES SE OF PITTSBURGH ARE LIKELY TO SEE THESE
RESTRICTIONS, THERE IS LESS CERTAINTY IN WHETHER FOG/LOW STRATUS
BECOMES WIDESPREAD TO IMPACT HARDER-TO-FOG TERMINALS LIKE
KPIT/KZZV/KBVI.
DIURNAL HEATING/MIXING WITH THE NW WIND SHIFT AFTER THE COLD
FRONTAL PASSAGE SHOULD RETURN VFR AREAWIDE BY WEDNESDAY
AFTERNOON, SAVE FOR INITIAL CU DEVELOPMENT THAT MAY BE SCT/BKN
BELOW 3KFT.
OUTLOOK...
SUBTLE SHORTWAVE MOVEMENT COULD GENERATE AN ISOLATED SHOWER
WITH THE RESIDUAL MOISTURE EAST OF KPIT, OTHERWISE VFR IS
FAVORED. VERY LOCALIZED RIVER VALLEY FOG SOUTHEAST OF KPIT CAN'T
BE RULED OUT EARLY THURSDAY MORNING.
ADDITIONAL SHORTWAVE MOVEMENT WITHIN NORTHWEST FLOW MAY CREATE
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THURSDAY INTO
FRIDAY. BRIEF RIDGING ALOFT AND SURFACE HIGH PRESSURE FAVORS
DRY WEATHER SATURDAY BEFORE STORM CHANCES RETURN EARLY NEXT
WEEK.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...WM
NEAR TERM...WM/LUPO
SHORT TERM...WM/LUPO
LONG TERM...WM/LUPO
AVIATION...FRAZIER
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