424
FXUS61 KPBZ 201845
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
245 PM EDT MON JUL 20 2026
WHAT HAS CHANGED
A CODE ORANGE AIR QUALITY ALERT HAS BEEN ISSUED TODAY FOR MOST
OF NORTHERN WEST VIRGINIA. UNCERTAINTY IN OUR CONVECTIVE
ENVIRONMENT FOR TOMORROW LARGELY HINGES ON HOW MODELING IS
DEALING WITH AN MCS DIVING THROUGH THE GREAT LAKES AND CENTRAL
OH VALLEY TONIGHT. A FAILURE POINT FOR TOMORROW'S SEVERE
POTENTIAL HINGES ON WHERE THIS SYSTEM IS TOMORROW MORNING AND
HOW STRONG IT REMAINS. HOWEVER, AT THIS TIME, CONFIDENCE IN
LOCATION AND STRENGTH ARE BOTH VERY LOW.
KEY MESSAGES
1) CODE ORANGE AIR QUALITY ALERTS REMAIN FOR PARTS OF
SOUTHWESTERN PA TODAY DUE TO LINGERING CANADIAN WILDFIRE SMOKE
2) ENHANCED RISK FOR SEVERE WEATHER ON TUESDAY; SLIGHT RISK FOR
EXCESSIVE RAINFALL.
DISCUSSION
KEY MESSAGE 1...
LINGERING WILDFIRE SMOKE ACROSS THE REGION PROMPTED
A CODE ORANGE AIR QUALITY ALERT (ISSUED BY THE PENNSYLVANIA
DEPT. OF ENVIRONMENTAL PROTECTION). MUCH OF THE EFFECTS ACROSS
THE REGION WERE FROM LINGERING SMOKE TRAPPED UNDERNEATH THE
MORNINGS SFC INVERSION BUT AS THAT HAS BROKEN AND MIXED OUT,
AIR QUALITY HAS BEEN ON THE RISE AND IS BACK INTO MODERATE
ACROSS THE PITTSBURGH METRO. SMOKE SHIFTS NORTH AND EAST
THROUGH THE DAY IMPROVING AIR QUALITY AS IT DOES.
KEY MESSAGE 2...
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 /18Z MONDAY THROUGH SATURDAY/
BRIEF HIGH PRESSURE WILL REMAIN IN PLACE FOR TODAY KEEPING
MAINLY CLEAR SKIES AND LIGHT WINDS. SOME ADDITIONAL FOG IS
POSSIBLE AGAIN TONIGHT BUT MAINLY IN THE RIVER VALLEYS. THIS
COULD DROP A FEW TERMINALS TO MVFR AT TIMES.
VFR CONDITIONS WILL PERSIST AT LEAST THROUGH 12Z TOMORROW FOR
MOST TERMINALS. EXPECT SOME IMPACTS TO FLIGHT CATEGORIES IN THE
12Z TO 18Z TIMEFRAME. HAVE ALSO USED SOME PROB30S FOR TERMINALS
FOR THE LAST 6 HOURS OF THE TAF. EXPECT SOME MVFR AND IFR
CONDITIONS IN THIS PERIOD. PIT IS EXPECTED TO SEE SOME PROLONGED
REDUCTION IN THE CONDITIONS FROM 18Z TO 00Z. CIGS WILL BEGIN TO
DROP INTO BELOW IFR CATEGORIES BY 21Z.
WINDS FOR THIS EVENT ARE EXPECTED TO BE LIGHT THROUGH THE
OVERNIGHT AND INTO TUESDAY MORNING. THROUGH THE DAY, EXPECTED
WINDS OUTSIDE OF THUNDERSTORMS GUSTING UP TO 25 KNOTS FROM THE
SOUTHWEST.
OUTLOOK... REMNANT SHOWERS AND NON-SEVERE STORMS MAY TRACK
THROUGH THE REGION EARLY WEDNESDAY MORNING BEFORE A COLD TRACK
ADVANCES.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...AIR QUALITY ALERT UNTIL MIDNIGHT EDT TONIGHT FOR PAZ013-014-
020>022-029-031-073>078.
OH...NONE.
WV...AIR QUALITY ALERT UNTIL MIDNIGHT EDT TONIGHT FOR WVZ001>004-
012-021-509>512.
DISCUSSION...LUPO/AK
AVIATION...SHALLENBERGER
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