632
FXUS61 KPBZ 261815
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
215 PM EDT SUN JUL 26 2026
WHAT HAS CHANGED
INCREASED CONFIDENCE IN TIMING AND PREFERRED LOCATION FOR A
POTENTIAL MCS (MESOSCALE CONVECTIVE SYSTEM) LATE MONDAY INTO
EARLY TUESDAY.
KEY MESSAGES
1) STORMS TODAY WITH A CONDITIONALLY LOW SEVERE RISK IN EAST
OHIO AND PERHAPS NORTHWEST PENNSYLVANIA.
2) THUNDERSTORMS POSSIBLE MONDAY AND MONDAY NIGHT WITH
HEIGHTENED SEVERE WEATHER POTENTIAL.
DISCUSSION
KEY MESSAGE 1...
A MID-LEVEL SHORTWAVE ON THE NORTHERN END OF A MID-LEVEL JET
MAX IS EXPECTED TO CROSS INTO THE AREA TODAY, BRINGING WITH IT
CHANCES OF SHOWERS AND THUNDERSTORMS. THE 12Z WOULD CERTAINLY
NOT ALLUDE TO SEVERE CHANCES WITH AN 800MB AND 600MB CAPPING
INVERSION, THOUGH THERE IS SOME IDEA THIS PROFILE WILL MODULATE
INTO THE AFTERNOON WITH MID-LEVEL ASCENT, BUT THE QUESTION IS
HOW MUCH.
THE MOST LIKELY SCENARIO IS THAT CAPPING DOESN'T ERODE FULLY,
LEAVING A QUASI-STABLE LAYER WITH FAIRLY DRY AIR ABOVE, WHICH
WOULD SUPPRESS VERTICAL DEVELOPMENT, AND FURTHER ANY SEVERE
CHANCES. IN THE LOW PROBABILITY EVENT THAT THE CAPS FULLY
ERODE, DCAPE VALUED FROM 800-1000 J/KG WOULD BE A DOUBLE EDGED
SWORD FOR DEVELOPMENT. THIS COULD SERVE TO ENTRAIN DRY AIR INTO
UPDRAFTS WITH FAIRLY WEAK FORCING SQUASHING DEVELOPMENT, OR IT
COULD CONTRIBUTE TO A DOWNBURST WIND THREAT SHOULD UPDRAFTS
DEVELOP VERTICALLY DESPITE ALL ODDS. ONE WAY YOU MIGHT ACTUALIZE
THIS IS MULTIPLE FAILED CI ATTEMPTS WET-BULBING PROFILES, OR
FORCING STRONGER THAN FORECAST. ALL THIS TO SAY, THE SEVERE
ENVIRONMENT IS CONDITIONALLY MARGINAL, WITH A LOW PROBABILITY
OF ANY DAMAGING WINDS THIS AFTERNOON IN STORMS OVERALL.
KEY MESSAGE 2...
AS AN EASTERN TROUGH SHIFTS EAST, AND A MIDWEST RIDGE FILLS IN
BEHIND, THE POTENTIAL FOR UPSTREAM MCS DEVELOPMENT INCREASES
INTO MONDAY AND TUESDAY, ALONG WITH THE CHANCE OF RUN-OF-THE-
MILL AFTERNOON CONVECTION.
THE CHANCES OF AN ACTUAL MCS MONDAY AFTERNOON APPEAR LOW FOR
NOW, BUT AFTERNOON STORM CHANCES ARE CERTAINLY PREVALENT.
DIURNAL HEATING AND DESTABILIZATION ALOFT PUSHED NBM 25TH-75TH
SBCAPE TO 1000-2000 J/KG, AND SFC-6KM SHEAR INCREASES TO 30KTS
TO 35KTS, WITH THE LARGEST PROPORTIONAL INCREASE TO WINDS IN
THE SFC-3KM LAYER FROM THE DAY PRIOR. 25TH TO 75TH HREF DCAPE
SHOWS 800 TO 1000, CERTAINLY CAPABLE OF DOWNBURST WIND THREATS
WITH HIGH ENOUGH VERTICAL DEVELOPMENT. THAT BEING SAID, THERE IS
STILL A SPLIT IN CAMS FOR CONVECTION PRESENCE/INTENSITY MONDAY.
MODELS LIKE THE FV3/HRRR/ARW SHOW MORE ROBUST MID-LEVEL ASCENT
AND LESS CAPPING WITH MORE WIDESPREAD CONVECTION, WHILE CAMS
LIKE THE NAM/RGEM HAVE WEAKER FORCING AND SLIGHTLY MORE CAPPING.
SO, THERE IS AGAIN A CONDITIONAL PROBABILITY FOR SEVERE MONDAY,
PERHAPS MORE LIKELY THAN SUNDAY. DOWNBURST WINDS AND TORRENTIAL
DOWNPOURS ARE MOST LIKELY, THOUGH HAIL AND ISOLATED TORNADOES
COULD NOT BE RULED OUT.
OVERNIGHT, UNCERTAINTIES COMPOUND. THE FIRST WILL BE THE AFFECT
OF WHAT HAPPENS MONDAY. IF WIDESPREAD SEVERE OCCURS MONDAY,
THAT WOULD PERHAPS MUDDLE THE ENVIRONMENT FOR OVERNIGHT
CONVECTION MONDAY NIGHT WHETHER AN MCS OCCURS OR NOT. SECOND
WILL BE THE EXACT POSITION AND TIMING OF AN MCS. WHILE CERTAINTY
HAS INCREASED IN THE LAST 24 HOURS, THE WINDOWS ARE STILL FAIRLY
WIDE FOR POSITION AND TIMING. AT THE MOMENT, A BEST-GUESS
ENVELOPE FOR AN MCS PASSAGE IS BETWEEN 8PM MONDAY AND 8AM
TUESDAY, WITH A "BEST GUESS" LOCATION BEING ANYWHERE BETWEEN
INDIANA AND EASTERN OHIO. IN ANY EVENT, A BLOW TO EASTERN OHIO
WOULD HAVE THE HIGHEST CHANCE OF IMPACTING OUR AREA. SHOULD
CONVECTION NOT OCCUR MONDAY, THE HIGHEST CONDITIONAL THREAT
SEVERE WINDOW WOULD BE EARLIER IN THE NIGHT. THIS WOULD BRING
THE HIGHEST CHANCE OF DAMAGING WINDS, WITH ISOLATED TORNADOES
AND A FLASH FLOODING THREAT. SHOULD CONVECTION OCCUR DURING THE
DAY MONDAY, THE HIGHEST CONDITIONAL THREAT OF SEVERE WEATHER
WOULD BE A LATER ARRIVAL PERHAPS, WITH SLIGHTLY LOWER THREATS OF
WIND AND TORNADOES WITH DIURNAL COOLING. BE SURE TO MONITOR THE
FORECAST FOR UPDATES AS WE DRAW CLOSER.
TUESDAY WILL AGAIN DEPEND ON WHAT HAPPENS OVERNIGHT MONDAY. IF
AN MCS OCCURS, SEVERE THREAT WOULD BE CONDITIONALLY LOWER AND
VISE VERSA. ENSEMBLES SHOW SOME STEEPENING LAPSE RATES BEHIND A
COLD FRONT, BUT BY THEN THE MID-LEVEL JET HAS PUSHED EAST.
NONETHELESS, SCATTERED STORMS REMAIN POSSIBLE WITH A MARGINAL
DOWNBURST THREAT, FAVORING SOUTH OF I-70. NCAR ML, CSU ML, AND
CIPS AGREE WITH A MORE "MID-ATLANTIC" THREAT TUESDAY.
AVIATION /18Z SUNDAY THROUGH FRIDAY/
SCATTERED TO BROKEN CU WITH VFR CEILINGS AND ISOLATED SHOWERS
PREVAIL THROUGH THE REST OF TODAY. SHOWER ACTIVITY DISSIPATED
AFTER SUNSET WITH THE LOSS OF DAYTIME HEATING. WINDS REMAIN
LIGHT AND GENERALLY OUT OF THE WEST.
SHOWERS AND THUNDERSTORMS ARE POSSIBLE AGAIN DURING THE DAY
MONDAY ALONG WITH THEIR ASSOCIATED RESTRICTIONS. SOME OF THE
STRONGER STORMS COULD BE CAPABLE OF PRODUCING DAMAGING WIND
GUSTS.
OUTLOOK...
THUNDERSTORM CHANCES INCREASE MONDAY INTO TUESDAY WITH THE
APPROACH AND PASSAGE OF A COLD FRONT. A FEW STORMS COULD BE
SEVERE. LOW SHOWER/STORM CHANCES CONTINUE WEDNESDAY WITH ANOTHER
PASSING WAVE, BEFORE VFR RETURNS THURSDAY UNDER BUILDING HIGH
PRESSURE.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...MILCAREK
AVIATION...CERMAK/WM
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