514
FXUS61 KPBZ 252317
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
717 PM EDT THU JUN 25 2026
WHAT HAS CHANGED
CONFIDENCE IN LOCALIZED SEVERE THUNDERSTORMS WITH LARGE HAIL AND
DAMAGING WIND GUSTS HAS INCREASED FOR THE NORTHERN 2/3RDS OF THE
FORECAST AREA, AND SPC HAS ISSUED A SLGT RISK OF SEVERE
THUNDERSTORMS ACCORDINGLY FOR THIS AFTERNOON AND EVENING.
KEY MESSAGES
1) ISOLATED STRONG TO SEVERE STORMS POSSIBLE THIS AFTERNOON AND
EVENING.
2) A STALLED BOUNDARY KEEPS RAIN CHANCES IN THE FORECAST FRIDAY
AND SATURDAY, WITH SOME POTENTIAL FOR ISOLATED HEAVY RAINFALL
TOTALS AND INSTANCES OF FLOODING.
3) HIGH CONFIDENCE IN THE DEVELOPMENT OF HOT AND HUMID
CONDITIONS NEXT WEEK.
DISCUSSION
KEY MESSAGE 1...
MID-LEVEL TROUGHING SWINGS ACROSS THE GREAT LAKES INTO THE
NORTHEAST CONUS THROUGH TONIGHT. COINCIDENT WITH THIS, SURFACE
LOW PRESSURE TRACKS ACROSS MICHIGAN TOWARDS THE SAINT LAWRENCE
RIVER BY 12Z FRIDAY. THIS WILL PUSH A SURFACE BOUNDARY TOWARDS
THE UPPER OHIO VALLEY BY THIS EVENING. LIFT WILL ALSO BE
SUPPORTED BY THE LEFT EXIT REGION OF A 65 KNOT 500MB JET STREAK.
0-8KM SHEAR IS IN THE 60-70 KNOT RANGE CREATING LONG STRAIGHT
HODOGRAPHS THAT ARE FAVORABLE FOR SPLITTING SUPERCELLS WITH
LARGE HAIL. THERE IS BROAD MODEL AGREEMENT ON THE DEVELOPMENT
OF SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ACROSS OHIO
AND FAR NORTHWEST PENNSYLVANIA BY MID- AFTERNOON, WITH ACTIVITY
SPREADING EAST AND SOUTHEAST THROUGH THE LATE AFTERNOON AND
EVENING.
SHEAR IN THE 0-6KM LAYER IS CERTAINLY SUPPORTIVE OF ORGANIZED
CONVECTION, WITH HREF/REFS MEANS OF 40-50 KNOTS DURING PEAK
HEATING. HOWEVER, THERE ARE LIMITING FACTORS THAT SHOULD TEMPER
THE SEVERE WEATHER THREAT SOMEWHAT. SURFACE DEWPOINTS MAINLY IN
THE LOWER 60S ARE FORECAST, WHICH WILL INHIBIT CAPE LEVELS
SOMEWHAT. HREF PROBABILITIES OF 1000 J/KG OR GREATER ARE 30
PERCENT OR LESS ACROSS A GOOD PORTION OF THE CWA, SAVE FOR
POTENTIALLY PORTIONS OF FAR NW PA/EASTERN OH WHERE BUOYANCY
COULD BE A BIT GREATER. MLCAPE OF 500-1,000 J/KG ALONG WITH THE
SHEAR SUPPORT MARGINALLY SEVERE HAIL UP TO 1.25 TO 1.50". LOW
LEVEL SHEAR WILL BE MARGINAL FOR STRONG TORNADOES, MAINLY IN THE
10-15 KNOT RANGE DURING THE DAYLIGHT HOURS AND INCREASING A BIT
TO 15-20 KNOTS IN THE EVENING. STEEP 0-3KM LAPSE RATES AND
RELATIVELY HIGH LCLS SHOULD LIMIT TORNADO POTENTIAL TO 1 OR 2
WEAK BRIEF EVENTS AT MOST.
DCAPE VALUES OF 500-800 J/KG ARE MARGINALLY SUPPORTIVE OF
DAMAGING WINDS, WHICH WOULD BE MORE LIKELY LATER IN THE EVENT AS
MERGING COLD POOLS PROVIDE MORE CONCENTRATED WIND THREAT.
WHAT SEEMS MORE CERTAIN IS THAT HEAVY RAIN/FLOODING THREATS
WILL REMAIN LARGELY SQUASHED BY SUFFICIENT STORM MOTION AND NON-
REMARKABLE PRECIPITABLE WATER VALUES.
UPDATED DISCUSSION...
A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED MAINLY FOR HAIL AND
DAMAGING WIND THREAT. HOWEVER, GIVEN WEAK LOW LEVEL SHEAR AND
LONG HODOGRAPHS THERE IS STILL A THREAT OF A TORNADO OR 2. ABOUT
4 TORNADO WARNINGS HAVE BEEN ISSUED WITH NO CONFIRMED REPORT
YET. THERE IS ALSO A MINOR FLOOD THREAT GOING ON THROUGH THE
EVENING. THE STORMS WILL BEGIN TO MOVE INTO SW PA IMPACTING
MAINLY ALL THE COUNTIES HERE. THE WATCH IS IN EFFECT THROUGH 5AM
BUT THE THREAT ACCORDING TO THE CAMS WILL LIKELY WIND DOWN BY
02Z. STAY TUNED FOR UPDATES.
KEY MESSAGE 2...
AS THE FRONT LOSES MUCH OF ITS UPPER SUPPORT AND BECOMES
PARALLEL TO QUASI-ZONAL MID-LEVEL FLOW, MUCH OF ITS FORWARD
SPEED WILL BE LOST, AND IT SHOULD EVENTUALLY OOZE TO A NEARLY
STATIONARY POSITION EITHER IN OR JUST SOUTH OF THE FORECAST
AREA, WHERE IT WOULD LIKELY REMAIN THROUGH AT LEAST SATURDAY.
ADDITIONAL SHORTWAVE ENERGY SHOULD PROVIDE SUPPORT FOR ROUNDS OF
SHOWERS AND THUNDERSTORMS, ESPECIALLY FRIDAY NIGHT AND
SATURDAY, WITH BEST COVERAGE GENERALLY SOUTH OF US-422. SEVERE
WEATHER RISK FROM THIS ACTIVITY APPEARS RELATIVELY LOW GIVEN THE
DAYTIME HEATING ISSUES THIS PATTERN COULD PROVIDE. HOWEVER,
BUILDING PRECIPITABLE WATER SOUTH OF THE BOUNDARY (1.7-1.8 INCH
VALUES EVENTUALLY) AND THE POTENTIAL FOR TRAINING THUNDERSTORMS
SUPPORTS THE NOTION OF A RISK FOR AT LEAST ISOLATED FLOODING
ISSUES ACROSS THE SOUTHERN CWA INTO SATURDAY. A MARGINAL RISK OF
EXCESSIVE RAINFALL COVERS MUCH OF THE FORECAST AREA SOUTH OF
I-80 FOR FRIDAY AND FRIDAY NIGHT. BY SUNDAY, THE FRONT MAY MORE
DECISIVELY NUDGE TO OUR SOUTH, BRINGING AN END TO THE HEAVY
RAIN THREAT.
KEY MESSAGE 3...
THE BOUNDARY IS SET TO LIFT BACK NORTH OF THE REGION MONDAY.
THERE IS BROAD MODEL AGREEMENT ON A STRONG 500MB UPPER HIGH ON
THE ORDER OF 597 DM FORMING OVER THE OHIO VALLEY IN THE VICINITY
OF SOUTHERN INDIANA. THE MAIN IMPACT OF THIS PATTERN IS LIKELY
TO BE THE SEASON'S FIRST SUSTAINED RUN OF HEAT AND HUMIDITY,
WITH THE NBM INDICATING 70 PERCENT OR GREATER CHANCE OF 90+ HIGH
TEMPERATURES OVER MOST OF THE NON- RIDGE AREAS TUESDAY THROUGH
THURSDAY. ACCORDINGLY, PROBABILISTIC HEAT RISK GUIDANCE SHOWS
70% OR GREATER CHANCE OF MAJOR (LEVEL 3 OF 4) OR HIGHER IMPACTS
OVER MOST OF THE CWA. WE HAVE DETERMINISTIC HEAT INDICES IN THE
LOWLANDS OF 100 TO 105 BOTH TUESDAY AND WEDNESDAY WHICH ARE
REPRESENTATIVE. LOOKING AT THE NBM WEDNESDAY JULY 1ST 21Z
APPARENT TEMPERATURE PERCENTILES, THE 10TH AND 90TH RANGE FROM
93F-104F AT KPIT, BUT FOR DOWNTOWN PITTSBURGH THE VALUES ARE
100-115F. THOSE LARGE SPREADS ARE TYPICAL AND DURING HEAT WAVES
THE DAILY CLOUD COVER AND THUNDERSTORMS CHANCES ALSO CAUSE
UNCERTAINTY BUT THE MAIN MESSAGE IS HOT AND HUMID NEXT WEEK.
SECONDARY TO THE HEAT WILL BE THE EVENTUAL REINTRODUCTION OF
SOME LEVEL OF SEVERE WEATHER RISK. MOST LIKELY, GIVEN THE
ABUNDANT BUOYANCY POTENTIAL AND WEAK FLOW, THIS WOULD COME IN
THE FORM OF TYPICAL MID-SUMMER WET DOWNBURST WIND THREATS.
THERE IS A LOWER-END POTENTIAL FOR A SUPPRESSED RIDGE BY THE END
OF THE WEEK, WHICH COULD CREATE A UPPER LEVEL NORTHWEST FLOW
SETUP, A PATTERN WHICH HAS BEEN RESPONSIBLE FOR NOTABLE SEVERE
WEATHER EVENTS IN THE PAST. OF COURSE, THERE IS PLENTY OF TIME
TO MONITOR FOR THAT POTENTIAL.
AVIATION /00Z FRIDAY THROUGH TUESDAY/
AREA COVERAGE OF SHOWERS AND THUNDERSTORMS (CURRENTLY FOCUSED
NORTH OF KPIT) WILL GENERALLY DISSIPATE THROUGH 06Z TONIGHT WITH
LOSS OF DIURNAL HEATING. THE EXCEPTION IS PASSAGE OF A MID-LEVEL
SHORTWAVE TROUGH AXIS THAT COULD SPUR MOSTLY ISOLATED RAIN
SHOWERS UP UNTIL 09Z, BUT IS TOO LOW FOR TAF MENTION.
VFR CLOUDS ARE LIKELY TO HOLD THROUGH 12Z WHERE MID TO HIGH
LEVEL CLOUDS REMAIN THICK, BUT AREAS THAT CLEAR AND/OR AREAS
THAT SAW HIGHER RAINFALL ACCUMULATIONS MAY SEE IFR/LIFR
STRATUS/FOG DEVELOP NEAR 08Z-12Z. THEREAFTER, VFR RESUMES SAVE
FOR A PERIOD OF CU DEVELOPMENT PLUS MOIST ADVECTION AGAINST THE
STALLED SURFACE BOUNDARY THAT LENDS TO MVFR CIGS BETWEEN
14Z-18Z.
HI-RES MODELING IS FAIRLY BULLISH ON DELAYS IN THE NEXT
SHORTWAVE'S ARRIVAL, SO TAFS REFLECT A LATER START TIME FOR THE
ENSUING ROUND'S SHOWER/THUNDERSTORM POTENTIAL.
OUTLOOK...
THE ACTIVE WEATHER PATTERN CONTINUES THROUGH THE WEEKEND WITH
MULTIPLE PERIODS OF SHOWERS/THUNDERSTORMS AS WELL AS
RESTRICTIONS (MAINLY ASSOCIATED WITH STORMS).
CHANCES WANE THROUGH THE DAY SUNDAY WITH DRIER NW FLOW AND
HEIGHT RISES THAT RESULT IN HIGH PRESSURE DOMINATING THE REGION
BY MONDAY.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...CRAVEN
AVIATION...FRAZIER
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