438
FXUS61 KPBZ 081721
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
121 PM EDT FRI MAY 8 2026
WHAT HAS CHANGED
PROBABILITY IS INCREASING FOR HAZARDOUS WEATHER SATURDAY
AFTERNOON AND EVENING FOR NORTHWEST PENNSYLVANIA DUE TO CROSSING
THUNDERSTORMS. MONDAY NIGHT MAY FEATURE ANOTHER ROUND OF FROST
AND FREEZE CONCERNS.
KEY MESSAGES
1) THERE IS A MARGINAL RISK FOR HAZARDOUS WEATHER, FAVORING
DAMAGING WIND AND LARGE HAIL, WITH A DECAYING LINE OF
THUNDERSTORMS ENTERING NORTHWEST PA SATURDAY AFTERNOON/EVENING.
2) RESUMPTION OF GREAT LAKES TROUGHING WILL MAINTAIN BELOW
AVERAGE TEMPERATURE AND PERIODIC RAIN CHANCES, WITH POTENTIAL
FOR FROST/FREEZE CONCERNS MONDAY NIGHT.
DISCUSSION
KEY MESSAGE 1...
AN EMBEDDED JET STREAK CREATING BROAD ASCENT WILL CREATE SHOWERS
AND LOW PROBABILITY THUNDERSTORMS THIS EVENING ACROSS NORTHWEST
PA BEFORE EXPANDED AREAWIDE AS THE WEAK SHORTWAVE MOVES EAST.
HAZARDOUS WEATHER IS LOW AND TIED MAINLY TO LOCALIZED FLOOD DUE
TO HEAVIER RAIN WITHIN A NARROW ENHANCED BAND STRETCHING FROM
CENTRAL OH INTO NORTHWEST PA. MEAN TOTALS RANGE BETWEEN
0.50-0.75" BUT COULD SEE AMOUNTS APPROACH 2" THROUGH SATURDAY
MORNING NEAR LAWRENCE COUNTY TO FAR NORTHERN TUSCARAWAS IF
LIFT/DURATION OF HEAVY RAIN IS MAXIMIZED.
GREATER HAZARD RISKS HAVE DEVELOPED FOCUSING ON LATE SATURDAY
AFTERNOON AND EVENING WHEN ADDITIONAL NW SHORTWAVE MOVEMENT
CREATES A BROKEN SHOWER/THUNDERSTORM LINE THAT TRACKS TOWARDS
NORTHWEST PA. LATEST HI-RES MODELING HAS BECOME MORE BULLISH ON
ENOUGH CLEARING/RECOVERY TO CREATE A 500-1000 J/KG PLUS 35-40KT
SHEAR WHICH LENDS TO A DAMAGING WIND AND LARGE HAIL THREAT
(TORNADO THREAT ONLY POSSIBLE IF LINEAR MODE DEVELOPS REAR-
INFLOW SURGES), THOUGH WIND IS THE MORE LIKELY OUTCOME/IMPACT.
TIMING, AS USUAL, ADDS TO THE UNCERTAINTY:
DELAYS IN THE EXIT OF MORNING RAIN/CLOUDS COULD LIMIT
DESTABILIZATION; DELAYS IN THE SHORTWAVE/CONVECTIVE LINE AFTER
7PM WHEN ENVIRONMENT STABILIZES LOWERS THREAT; LOWER SURFACE
MOISTURE RETURNS DAMPEN THE DEGREE OF DESTABILIZATION; ETC. FOR
NOW, THERE IS A MARGINAL RISK WITHIN SPC'S OUTLOOK HIGHLIGHTING
THIS POTENTIAL, WITH TIMING FAVORING 5PM-9PM.
KEY MESSAGE 2...
ENSEMBLE MODELS REMAIN RESOLUTE IN MAINTAINING GREAT LAKES
TROUGHING THROUGH THE LATTER PORTION OF NEXT WEEK, THOUGH SOME
VARIANCE EXISTS IN THE EXACT SHAPE/DEPTH PLUS TRAVERSAL TIMES OF
EMBEDDED SHORTWAVE TROUGHS. THIS WILL MAINTAIN RECENT WEATHER
REGIMES FEATURING BELOW AVERAGE TEMPERATURE AND SOME PERIOD OF
RAIN POSSIBLE WITHIN A 24-HOUR WINDOW WHILE KEEPING HAZARDOUS
WEATHER THREATS LOW.
ONE ITEM OF NOTE IS A POTENTIAL OF A STRONG COLD ADVECTION PUSH
BEHIND A WAVE MONDAY THAT, COMBINED WITH CALMING WIND AND
CLEARING SKIES, COULD RESULT IN MORE FROST AND FREEZE CONCERNS
MONDAY NIGHT INTO TUESDAY MORNING.
AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
WITH MARGINAL INSTABILITY IN PLACE AND DRIVEN BY MID-LEVEL JET
ASCENT, A SHIELD OF LIGHT SHOWERS WILL MOVE ACROSS THE AREA THIS
AFTERNOON, BUT ENSEMBLES SHOW EMBEDDED 20-40% PROBABILITY OF
BRIEF MVFR VIS RESTRICTIONS WITH A MORE MODERATE EMBEDDED
SHOWER. CONFIDENCE IS HIGHEST THAT THIS WOULD BE FOR ALL PORTS
SAVE MGW/ZZV, BUT TEMPOS WERE NOTED AT ALL SITES GIVEN NORTH-
SOUTH SPATIAL UNCERTAINTY AMONG ENSEMBLES. AS THE NEXT MID-LEVEL
WAVE ARRIVES LATER TONIGHT WITH BETTER ASCENT, A MORE BROAD AREA
OF STEADY LIGHT TO MODERATE RAIN WILL DEVELOP WITH HIGHEST
CONFIDENCE AGAIN FOR ALL PORTS SAVE MGW.
WITH THIS WILL BRING AN 80% PROBABILITY OF AT LEAST MVFR AFTER
03Z, EARLIEST AT FKL/DUJ, WHICH IS ALSO WHERE IFR PROBS ARE
HIGHEST AND HAVE THUS INCLUDED PREVAILING IFR CIGS INTO THE
MORNING HOURS. HOW FAR SOUTH IFR CIGS MAY REACH IS QUESTIONABLE WITH
CONTINUED SPATIAL UNCERTAINTY. EXPANDED NEIGHBORHOOD
PROBABILITY TO CAPTURE THIS UNCERTAINTY DOES EXTENT ELEVATED
PROBABILITIES AS FAR SOUTH AS PIT, SO CAN'T RULE OUT LOWER CIGS
WITH A WIDER FOOTPRINT.
RAIN SHOULD EXIT BY MID TO LATE MORNING SATURDAY BUT IT MAY BE A
COUPLE HOUR BUFFER UNTIL ENOUGH MIXING CAN ERODE CIGS AND RETURN
VFR, THOUGH PROBABILITY FOR THAT IS HIGH AREAWIDE BY AT LEAST
EARLY AFTERNOON.
OUTLOOK...
RAIN AND RESTRICTIONS ARE EXPECTED AGAIN SUNDAY INTO MONDAY
UNDER THE CONTINUED SERIES OF CROSSING SHORTWAVE TROUGHS. VFR
SHOULD RETURN TUESDAY UNDER HIGH PRESSURE.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...FRAZIER
AVIATION...MLB/MILCAREK
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