373
FXUS61 KPBZ 251727
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
127 PM EDT SAT JUL 25 2026
WHAT HAS CHANGED
LOWER CHANCES OF ANY MCSS SUNDAY NIGHT INTO MONDAY MORNING.
SLIGHTLY MORE PRECISION IN THE SEVERE THREAT MONDAY INTO
TUESDAY. UPDATED AVIATION DISCUSSION FOR 18Z ISSUANCE.
KEY MESSAGES
1) ISOLATED SHOWERS SATURDAY; STORM CHANCES INCREASE SUNDAY.
2) SEVERE THUNDERSTORM CHANCES INCREASE MONDAY INTO TUESDAY AS
CHANCES OF A MESOSCALE CONVECTIVE SYSTEM (MCS) INCREASE.
DISCUSSION
KEY MESSAGE 1...
ISOLATED SHOWERS CONTINUE TO BE POSSIBLE THROUGH SATURDAY
AFTERNOON/EVENING. THE 12Z SOUNDING DESCRIBES AN ENVIRONMENT
WITH SATURATED LOW LEVELS UP TO 750MB, WITH A CAPPING INVERSION
SEPARATING DRY AIR ABOVE. THIS GENERALLY ALLUDES TO LOW
POTENTIAL FOR STORMS, WITH MOST OF THE SATURATED LAYER ABOVE
FREEZING AND CAPPING AS A LIMITER FOR VERTICAL DEVELOPMENT.
FORCING ALONG A WEAK SHORTWAVE WILL EXIT TO THE EAST TONIGHT,
CUTTING OFF RAIN POTENTIAL. THE HIGHEST CHANCES OF RAIN ARE EAST
OF I-79, AND LOW AT THAT.
THE SUBSIDENCE CAP IS EXPECTED TO ERODE SOME INTO THE DAY
TOMORROW, WHICH MAY MAKE THUNDERSTORM CHANCES COMPARATIVELY
HIGHER WITH SOME CHANCE AT VERTICAL DEVELOPMENT. IN GENERAL,
CAMS ARE MORE FOCUSED ON DEVELOPMENT OFF OF LAKE ERIE INTO
TOMORROW ON A WEAK MID-LEVEL WAVE. THE MAIN QUESTION IS WILL
THESE STORMS BE CAPABLE OF BECOMING VERTICALLY DEVELOPED. FLOW
OVER WESTERN PA AND NORTHERN WEST VIRGINIA WILL BE WEAK (~25KT
SFC-6KM SHEAR AT KPIT), WHILE EASTERN OHIO MAY BE A BIT STRONGER
(~40KT SFC-6KM SHEAR AT KZZV) WITH MOST SHEAR IN THE 3KM TO 6KM
LAYER. DRY AIR ABOVE 700MB, MAY ACT AS A DOUBLE EDGED SWORD FOR
ANY SEVERE CHANCES. FOR NOW, THE MOST LIKELY SCENARIO IS THAT
DRY AIR LIMITS VERTICAL DEVELOPMENT, DOES NOT ALLOW CELLS TO TAP
INTO SHEAR ALOFT, AND MINIMIZED DCAPE ACTUALIZATION. IN THE
LESS LIKELY, BUT NOTABLE SCENARIO WHERE STORMS ARE ABLE TO PUSH
PAST THE DRY AIR ALOFT, THEY MAY BE ABLE TO ACTUALIZE ~600-900
DCAPE, MAKING FOR DOWNBURST CHANCES. THE NARROW WINDOW FOR THIS
CONDITIONAL THREAT FAVORS 4P-8P. ML CONVECTIVE OUTLOOKS SUPPORT
THIS CONDITIONAL, LOW-END THREAT.
KEY MESSAGE 2...
THE HIGHEST SEVERE THUNDERSTORM CHANCES PERSIST FOR MONDAY AND
TUESDAY, AS AN MIDWEST RIDGE AXIS PUSHES CLOSER AND SHUNTS A
NORTHEAST TROUGH EAST. THIS WILL INCREASE THE CHANCES OF
UPSTREAM DEVELOPMENT OF AN MCS THAT MAY CROSS THE AREA. THE
FIRST OF SUCH CHANCES WILL COME SUNDAY NIGHT INTO MONDAY
MORNING, BUT GUIDANCE CONTINUES TO KEEP THIS FIRST CHANCE WELL
WEST OF THE FORECAST AREA INTO MICHIGAN/INDIANA/WEST OHIO.
IT'S WORTH NOTING THAT THERE ARE STILL A NUMBER OF POTENTIAL
OUTCOMES FOR SEVERE WEATHER INTO MONDAY AND TUESDAY. WE WILL
WALK THROUGH THE TWO MOST LIKELY SCENARIOS:
1) A MCS DEVELOPS UPSTREAM DURING THE DAY ON MONDAY AND PASSES
NEAR THE AREA SOMETIME MONDAY / TUESDAY MORNING. A LATER
ARRIVAL TIME LOWERS THE CHANCES OF SEVERE, BUT NOCTURNAL SEVERE
REMAINS POSSIBLE. A DIRECT HIT WOULD LIMIT ADDITIONAL SEVERE
CHANCES TUESDAY WITH A COLD FRONT PASSAGE, WHILE A GLANCING BLOW
WOULD ALLOW SEVERE CHANCES AGAIN TUESDAY.
2) A MCS DEVELOPS UPSTREAM MONDAY, BUT MISSES THE AREA TO THE
WEST. THIS WOULD HEIGHTEN THE CHANCES OF SEVERE ON A COLD FRONT
AND/OR TIED TO AN MCS PASSAGE INTO THE DAY TUESDAY.
ANY SEVERE CHANCES WOULD PRIMARILY BRING THE THREAT OF DAMAGING
WIND, THOUGH ALL HAZARDS ARE POSSIBLE INCLUDING HAIL AND
ISOLATED TORNADOES. THOUGH STORMS WOULD LIKELY BE MOVING FAST,
TRAINING CONVECTION WOULD HEIGHTEN THE FLASH FLOOD THREAT FOR
ANY LOCATIONS THAT GET HIT MULTIPLE TIMES. SEVERE THREATS WILL
NEED TO CONTINUE TO BE MONITORED FOR MORE TIMING, INTENSITY, AND
HAZARD UPDATES. AS OFTEN IS THE CASE WITH MCSS, THIS MORE
CERTAIN DETAILS MAY NOT BE AVAILABLE UNTIL 12-24 HOURS BEFORE
THE EVENT, SO STAY TUNED TO THE FORECAST.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
A SCATTERED (LOCALLY BROKEN ALONG THE RIDGES) CU FIELD HAS
DEVELOPED THIS AFTERNOON WITH CEILINGS GENERALLY IN THE 3-5KFT
RANGE. EXPECT THESE CONDITIONS AS WELL AS ISOLATED SHOWERS TO
CONTINUE THROUGH THE REST OF THE DAY BEFORE DISSIPATING THIS
EVENING WITH THE LOSS OF DAYTIME HEATING. MOSTLY VFR PREVAILS
OVERNIGHT, BUT ENSEMBLES DO SUGGEST SOME POTENTIAL FOR PATCHY
FOG DEVELOPMENT DURING PRE-DAWN HOURS ON SUNDAY. LOCATIONS VARY
BETWEEN THE NBM AND HREF/REFS, HOWEVER, WITH THE FORMER
SUGGESTING THE GREATEST POTENTIAL SOUTHEAST OF PIT AND THE
LATTER SUGGESTING NORTHEAST OF PIT. INTRODUCED TEMPOS TO
REFLECT THIS, BUT KEPT VISIBILITIES AT MVFR FOR MOST TERMINALS
EXCEPT THE TYPICAL TROUBLE SPOTS WHERE IFR WAS FAVORED INSTEAD.
OUTLOOK...
ISOLATED TO SCATTERED SHOWERS/STORMS ARE POSSIBLE AGAIN SUNDAY
AFTERNOON DURING PEAK HEATING HOURS, BUT WITH A COVERAGE TOO
LIMITED TO WARRANT MENTION IN THE TAFS. THUNDERSTORM CHANCES
INCREASE MONDAY INTO TUESDAY WITH THE APPROACH AND PASSAGE OF A
COLD FRONT. A FEW STORMS COULD BECOME STRONG TO SEVERE. LOW
SHOWER/STORM CHANCES CONTINUE WEDNESDAY WITH ANOTHER PASSING
WAVE, BUT THE POTENTIAL FOR SEVERE STORMS DECREASES.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...MILCAREK
AVIATION...CERMAK
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