280
FXUS61 KPBZ 210546
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
146 AM EDT TUE JUL 21 2026
WHAT HAS CHANGED
A MESOSCALE CONVECTIVE SYSTEM (MCS) TO OUR WEST AND NORTHWEST
WILL DRIVE THE POTENTIAL FOR SEVERE WEATHER THIS AFTERNOON. AN
ENHANCED RISK REMAINS IN EFFECT FOR TODAY FOR SEVERE STORMS.
KEY MESSAGES
1) ENHANCED RISK FOR SEVERE WEATHER ON TUESDAY; SLIGHT RISK FOR
EXCESSIVE RAINFALL.
DISCUSSION
KEY MESSAGE 1...
A STRONG LOW-PRESSURE SYSTEM TRACKING ACROSS SOUTHERN ONTARIO
UNZIPS A WARM SECTOR ACROSS THE REGION ON TUESDAY. UPPER LEVEL
SUPPORT IS PROVIDED BY AN UNCHARACTERISTICALLY STRONG (FOR THIS
TIME OF YEAR) JET LEFT EXIT REGION. WARM AND HUMID AIR (LOW 70S
DEW POINTS) FUEL INSTABILITY ESTIMATES THAT RANGE FROM 1500 J/KG
ON THE LOW END TO REASONABLY HIGH END EXPECTATIONS NEAR 2500
J/KG. THIS IN COMBINATION WITH STRONG WIND SHEAR (35-45 KTS OF
0-6KM SHEAR) WILL CREATE A FAVORABLE ENVIRONMENT FOR ORGANIZED
THUNDERSTORMS.
MODELING FAVORS EARLY MORNING CONVECTION WELL TO OUR WEST
ALTHOUGH A FEW PRE-DAWN STORMS CAN'T BE RULED OUT IN CENTRAL AND
EASTERN OHIO. SOME UNCERTAINTY REMAINS IN THE INITIAL
CONVECTION DUE TO HOW THE MOST RECENT RUN OF MODELS HANDLE A
DECAYING MCS NEAR CINCINNATI TOMORROW MORNING. DESPITE THIS, THE
MOST LIKELY TIMING OF SEVERE WEATHER REMAINS BETWEEN 12-8PM.
MODELS SUGGEST ACTIVITY BEGINS LATE MORNING OR MIDDAY ALONG A
LAKE BOUNDARY CLOSER TO CLE AND ADVANCES ESE INTO OUR AREA.
STORMS ARE THEN INCREASINGLY FAVORED FURTHER SOUTH AND EAST
ACROSS PITTSBURGH AND THE I-70 CORRIDOR INTO THE AFTERNOON
BEFORE CONVECTIVE COVERAGE BEGINS TO WANE AFTER SUNSET.
THE PRIMARY THREAT FROM STORMS TOMORROW REMAINS DAMAGING WIND
GUSTS ALONG SOME KIND OF DEVELOPING SQUALL LINE ALTHOUGH
TORNADOES AND LARGE HAIL REMAIN POSSIBLE IN ISOLATED SUPERCELLS
THAT COULD DEVELOP OUT IN FRONT OF THE MAIN LINE. THE STORM
PREDICTION CENTER HAS MAINTAINED THEIR ENHANCED RISK (LEVEL 3
OUT OF 5) ACROSS THE REGION FOR TOMORROW.
ANOTHER THREAT FROM THIS ACTIVITY REMAINS HEAVY RAIN. PWATS ARE
EXPECTED TO BE ABOVE THE 95TH PERCENTILE AND COULD REACH UP
TOWARDS THE DAILY MAXIMUM VALUES (1.96 INCHES). THIS ACCOMPANIED
WITH A RELATIVELY HIGH FREEZING LEVEL WILL ALLOW FOR EFFICIENT
WARM RAIN PROCESSES IN A VERY MOIST ENVIRONMENT. STORMS ARE
EXPECTED TO BE RATHER PROGRESSIVE, WHICH WOULD FAVOR FLASH FLOOD
CONCERNS REQUIRING TRAINING OR MULTIPLE ROUNDS OF RAIN IN THE
SAME AREA. MODELING SEEMS TO SUPPLY THIS IN AGGRESSIVE ESTIMATES
HAVING 3.00-4.00 INCHES OF RAIN IN PLACES MAINLY ALONG THE I-70
CORRIDOR. THIS SOUTHERN FOCUS COULD POTENTIALLY KEEP THE
HEAVIEST RAIN OUT OF AREAS THAT HAVE RECENTLY SEEN IT BUT BRINGS
IT MUCH CLOSER TO OUR URBAN CENTERS WHERE FLOOD RISK IS
INHERENTLY HIGHER. ADDITIONAL CONFIDENCE IN THE AREAL LOCATION
OF THESE HIGHER RAINFALL TOTALS IS NEEDED BEFORE THE ISSUANCE OF
ANY FLOOD WATCH. HOURLY RATES IN THE HEAVIEST THUNDERSTORMS
LOOK LIKE THEY COULD TOP OUT NEAR 2.00 INCHES/HR. THE WEATHER
PREDICTION CENTER HAS HELD THEIR SLIGHT RISK OF EXCESSIVE
RAINFALL (LEVEL 2 OUT OF 5).
EXPECT LINGERING SHOWERS AND NON-SEVERE THUNDERSTORMS INTO
EARLY WEDNESDAY BEFORE A COLD FRONT TRACKS THROUGH THE REGION
AFTER SUNRISE.
THE POTENTIAL FOR PRECIPITATION REMAIN LOWS THROUGH THE
REMAINDER OF THE WORK WEEK AND INTO THE WEEKEND BEFORE SHOWERS
AND STORMS AGAIN LOOK POSSIBLE ON SUNDAY.
AVIATION /06Z TUESDAY THROUGH SATURDAY/
VFR CONDITIONS WILL PREVAIL THROUGH AT LEAST 12Z. A NUMBER OF
HIGH-RESOLUTION MODELS INDICATE THE POTENTIAL OF SHOWER AND
STORM DEVELOP TO OUR WEST THAT COULD ADVANCE INTO OUR REGION
BETWEEN 13Z AND 16Z; PROB30S COVERS THAT IMPACT.
THE BEST POTENTIAL FOR STRONG TO SEVERE STORMS REMAINS IN
EFFECT FROM 18Z TO 23Z TODAY WITH THE PASSAGE A LARGE LOW
PRESSURE SYSTEM. TEMPOS HAVE BEEN ADDED TO HIGHLIGHT VIS AND CIG
RESTRICTIONS WITH PASSING -TSRA IN THE REGION.
BETWEEN 00Z AND 06Z WEDNESDAY SHOWER AND STORM INTENSITY AND
COVERAGE WILL DECREASE WITH INCREASING SUBSIDENCE IN THE MID-
LEVELS. WINDS WILL SHIFT FROM THE NORTHWEST BETWEEN 06Z TO 10Z
WEDNESDAY AND CREATE MVFR CIGS.
OUTLOOK...
THERE MAY BE SOME MVFR CIGS IN THE VICINITY OF DUJ/FKL EARLY
THURSDAY MORNING WITH COOL NORTHERLY FLOW. OTHERWISE, VFR
CONDITIONS WILL PREVAIL UNDER HIGH PRESSURE INTO FRIDAY.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...LUPO/AK
AVIATION...HEFFERAN
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