022
FXUS61 KPBZ 031904
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
304 PM EDT THU SEP 3 2026
WHAT HAS CHANGED
SEVERE THUNDERSTORM WATCH ISSUED FOR OUR ENTIRE AREA THROUGH
10PM. INTRODUCTION OF AN ENHANCED RISK (LEVEL 3/5) FOR SEVERE
THUNDERSTORMS ON THURSDAY.
KEY MESSAGES
1) ROUNDS OF SHOWERS AND STORMS CONTINUE THROUGH FRIDAY NIGHT WITH
ASSOCIATED SEVERE WEATHER THREATS.
2) UNSEASONABLY WARM CONDITIONS ALSO CONTINUE. HEAT ADVISORIES
REMAIN IN EFFECT FOR MOST OF OUR AREA THROUGH THURSDAY.
DISCUSSION
KEY MESSAGE 1...
STRONG 594 DAM RIDGING REMAINS CENTERED ACROSS THE SOUTHEAST
WITH THE AXIS OF THE RIDGE EXTENDED NORTH THROUGH THE PLAINS.
LOCALLY, WE'RE PARKED BENEATH NORTHWEST MID-LEVEL FLOW, AND
SUBTLE IMPULSES IN THE FLOW COMBINED WITH MESOSCALE SURFACE
FEATURES WILL CONTINUE TO BE THE DRIVER OF OUR THUNDERSTORM
COMPLEXES OVER THE NEXT 24-36 HOURS.
LINGERING SHOWERS AND DEBRIS CLOUD COVERAGE FROM THURSDAY MORNING'S
CONVECTION WILL CLEAR OUT BY EARLY AFTERNOON, AND SATELLITE IMAGERY
SHOWS CLEAR SKIES ARRIVING IN THE WAKE. THIS SHOULD ALLOW FOR QUICK,
EFFICIENT HEATING AND DIURNAL CU DEVELOPMENT WHILE THE ATMOSPHERE
RECOVERS. WHAT WE THEN TURN OUR ATTENTION TO IS A DEVELOPING
THUNDERSTORM COMPLEX OVER LOWER MICHIGAN THAT 12Z CAMS ALL DIVE
SOUTHEAST AND INTO NORTHWEST PA AFTER 3-4PM. SOME SUGGEST THAT THERE
COULD BE A FEW DISCRETE CELLS POPPING OUT AHEAD OF THE COMPLEX IN
WESTERN PA AROUND THAT SAME TIME. THESE SHOULD HAVE A RATHER POTENT
ENVIRONMENT TO WORK WITH AS EXPLORATION OF POINT SOUNDINGS
ACROSS THE AREA SHOWS 2500-3000 J/KG OF MLCAPE, 35-40 KNOTS OF
EFFECTIVE SHEAR, AND STEEP MID-LEVLE LAPSE RATES EXCEEDING 7
C/KM. ONE DIFFERENCE FROM WEDNESDAY IS THAT THERE APPEARS TO BE
A BIT LESS MID- LEVEL DRY AIR WHICH COULD SUPPORT BETTER STORM
ORGANIZATION AND INTENSITY TODAY. ALL HAZARDS WILL BE ON THE
TABLE WITH BOTH MODES; INITIAL DISCRETE CELLS COULD BECOME
SUPERCELLULAR AND POSE A WIND, HAIL, AND TORNADO THREAT,
ESPECIALLY IF DEW POINTS DON'T MIX OUT IN TIME AND WE'RE LEFT
WITH LOW TO MID 70S AS NOTED BY THE USUALLY DRIER HRRR. DAMAGING
WIND WILL BE THE PRIMARY THREAT WITH THE MORE LINEAR MODE, BUT
CAN'T IGNORE 0-3 KM SHEAR VALUES NEARING 30 KNOTS AND THE
POTENTIAL EXISTING FOR A QUICK QLCS TORNADO SPIN UP. AGAIN,
THINK MOST LIKELY TIMING IS INTO NW PA AROUND 4-5PM AND
PITTSBURGH METRO AROUND 6-7PM. A LOCALIZED ENHANCED RISK HAS
BEEN INTRODUCED FOR THE HEIGHTENED WIND THREAT FROM PITTSBURGH
NORTH. IN ADDITION, WITH REPEATED ROUNDS OF RAIN THE PAST 24-36
HOURS, FLASH FLOODING WILL ALSO POSE A THREAT AS FLASH FLOOD
GUIDANCE VALUES ALONG I-80 SIT AROUND 1-1.25" IN ONE HOUR. THAT
MAY BE ACHIEVED RATHER EASILY THIS AFTERNOON WITH A STORM OR TWO
IN THE SAME AREA. FOR THAT REASON, HAVE ISSUED A FLOOD WATCH
THROUGH TONIGHT NORTH OF PITTSBURGH.
COME FRIDAY, SOME CAMS SUGGEST ANOTHER EARLY MORNING PUSH OF SHOWERS
AND STORMS ALBEIT WITH LESS INTENSITY. FINER DETAILS ON THAT SHOULD
ARISE LATER TODAY WHEN WE SEE THE INITIATION OF IT OFF TO OUR
NORTHWEST. LATER FRIDAY, WE'LL YET AGAIN FACE ANOTHER MCS THREAT
WITH A CLUSTER DEVELOPING WAY OFF TO OUR NORTH IN MINNESOTA AND
DIVING ITS WAY THROUGH THE GREAT LAKES INTO OUR NECK OF THE WOODS.
EXACT TRACK AND TIMING OF IT IS EVEN MORE UNCERTAIN AS ITS SEVERAL
DOMINO PIECES AWAY FROM WHERE WERE AT CURRENTLY, AND MORNING
CONVECTION WILL HAVE A SAY IN AFTERNOON INTENSITY AS WELL. THE FRONT
ITSELF SHOULD THEN PASS THROUGH DURING THE LATE AFTERNOON ON FRIDAY
USHERING IN A DRIER AIRMASS AS SURFACE HIGH PRESSURE ARRIVES FROM
THE NORTH, THOUGH MANY OF THE 12Z CAMS NOW THINK WE HAVE YET ANOTHER
CAR IN THE MCS TRAIN RIDING THE SOUTHEASTERN PERIPHERY OF THE
SURFACE HIGH AND PERHAPS IMPACTING US AGAIN OVERNIGHT FRIDAY NIGHT.
NOT PUTTING A TON OF STOCK IN THIS POSSIBILITY YET, BUT IT'S
INTRIGUING THAT A COUPLE MODELS ARE COMING TO A SIMILAR SOLUTION.
KEY MESSAGE 2...
ASIDE FROM THE STORMS, UNSEASONABLY WARM CONDITIONS CONTINUE
THROUGH THURSDAY. HEAT RISK WILL REMAIN IN THE MAJOR CATEGORY
WITH POCKETS OF EXTREME IN THE VALLEYS AND URBAN AREAS WHERE
TEMPERATURES REACH THE LOW TO MID 90S AND DEW POINTS IN THE 70S
RESULTING IN HEAT INDICES EXCEEDING 100F. SOME LOCALIZED COOLER
AREAS ARE POSSIBLE UNDERNEATH INCREASED CLOUD COVER FORM EARLY
MORNING STORMS, BUT STILL EXPECT THAT WE'LL BE ABLE TO RECOVER
AND HEAT WELL.
AVIATION /19Z THURSDAY THROUGH TUESDAY/
VFR AREAWIDE AT PRESENT, BUT WE ARE MONITORING CONVECTION TO THE
NORTHWEST OVER LOWER MICHIGAN THAT MOST MODELS DIVE SOUTHEAST
INTO OUR REGION DURING THE LATE AFTERNOON AND EVENING HOURS.
INITIAL DISCRETE CELLS WILL LIKELY ORGANIZE INTO A FAIRLY POTENT
SQUALL LINE, WITH WIND GUSTS IN THE 40-50 KNOT RANGE (AND
PERHAPS A BIT HIGHER) POSSIBLE FROM PIT ON NORTH. DOWNPOURS WITH
IFR/LIFR VISIBILITY ARE ALSO LIKELY, AS IS FREQUENT LIGHTNING.
TIMING LOOKS TO BE GENERALLY BETWEEN 20Z AND 02Z FROM NORTH TO
SOUTH. HAVE USED 3 HOUR TEMPO GROUPS AT EACH TERMINAL TO
ILLUSTRATE THE MOST LIKELY TIMING, WHILE ALLOWING FOR SOME
MODEST UNCERTAINTY.
A PERIOD OF VFR IS EXPECTED IN THE WAKE OF THE MCS, AND SOME
MVFR TO IFR CEILINGS/VISIBILITIES ARE EXPECTED DURING THE
PREDAWN HOURS WITH LINGERING LOW-LEVEL MOISTURE. A COUPLE OF
MODELS SUGGEST SOME SCATTERED MORNING SHOWERS/STORMS. CONFIDENCE
IS NOT HIGH AT PRESENT, AND ONLY INCLUDED PRECIP AT FKL/DUJ FOR
NOW. PAST 14Z, VFR SHOULD REESTABLISH, BUT ANOTHER MCS WITH
EVEN MORE UNCERTAIN TIMING IS POSSIBLE DURING THE
AFTERNOON/EVENING HOURS OF FRIDAY.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR PAZ007>009-015-016.
OH...NONE.
WV...NONE.
DISCUSSION...MLB
AVIATION...CL
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