910
FXUS61 KPBZ 122326
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
726 PM EDT WED AUG 12 2026
WHAT HAS CHANGED
UPDATED AVIATION DISCUSSION.
HIGHER CONFIDENCE HAS DEVELOPED IN STORM OCCURRENCE FOR
NORTHWEST PA THIS LATE AFTERNOON/EVENING WITH INCREASED
LOCALIZED FLOODING RISKS, BUT LOWER SEVERE THREAT.
THE TIMING OF THE NEXT WAVE FEATURING FLOODING RISKS APPEAR
MORE VARIABLE THAN PREVIOUSLY ALLUDED TO, AS WELL.
KEY MESSAGES
1) A GENERALLY NARROW CORRIDOR OF STORMS FAVORED TO DEVELOP THIS
EVENING OVER NW PA THAT COULD POSE A FLASH FLOOD RISK ALONG WITH
A MORE LIMITED DAMAGING WIND/HAIL THREAT.
2) LARGE UNCERTAINTY AT PLAY, WITH VARIABLE TIMING AND PATHS,
BUT ANOTHER WAVE OF STORMS COULD RESULT IN FLASH FLOODING
SOMETIME BETWEEN LATE THURSDAY INTO FRIDAY.
3) ADDITIONAL ROUNDS OF SHOWERS AND THUNDERSTORMS ARE POSSIBLE
INTO EARLY NEXT WEEK, BUT BREAKS BETWEEN ACTIVITY IS LIKELY
WHILE INITIAL THREAT ANALYSIS SUGGESTS LIMITED RISKS.
DISCUSSION
KEY MESSAGE 1...
HI-RESOLUTION CONVECTIVE MODELS HAVE GROWN INCREASINGLY
CONFIDENT THAT THE CONVERGENCE OF STRONG 850MB WARM ADVECTION
(ASSOCIATED WITH MCS ACTIVITY TO THE WEST) AND WEAK SHORTWAVE
ADVECTION WITHIN NORTHWEST FLOW THROUGH THE NEW ENGLAND REGION
RESULTS IN SCATTERED THUNDERSTORM DEVELOPMENT THIS EVENING
MAINLY IN NORTHWEST PA.
THE ENVIRONMENT WILL FEATURE ENOUGH CAPE (GENERALLY BETWEEN
800-1000 J/KG) AND SHEAR (25-35KTS) TO OFFER LOW PROBABILITY
DAMAGING WIND AND HAIL THREATS. THOSE RISKS ARE MAINLY BEFORE
8PM AS NOCTURNAL COOLING REDUCES BUOYANCY ENOUGH TO SAP AT THAT
POTENTIAL. OF MORE INTERESTING IS A GROWING POTENTIAL FOR SOME
STORM CONVERGENCE ALONG A STALLED WARM AXIS ORIENTED NW-SE
SOMEWHERE EAST OF I-79 ALONG THE I-80 THAT COULD PROLONG STORM
DURATION, RESULTING IN FLASH FLOODING. THOUGH IT COULD SHIFT
SLIGHTLY WEST/EAST, THIS AXIS FAVORS NORTH CENTRAL MERCER COUNTY
THROUGH THE CLARION/ARMSTRONG BORDER AND HAS HI-REF PEAK TOTALS
THAT COULD EXCEED 2", ENOUGH TO CAUSE FLOODING ON SATURATED
GROUNDS. THIS RISK LINGERS TOWARDS THE MIDNIGHT HOUR BEFORE
ENOUGH PUSH FROM THE MID-LEVEL NW SHORTWAVE DRAGS THE STORMS OUT
OF THE REGION SOUTHEAST.
KEY MESSAGE 2...
PREVIOUS DISCUSSION OF THE NEXT FLOOD RISK ARRIVING THURSDAY
HAS BEEN SEVERELY UNDERCUT BY THE 12Z OF MODEL DATA THAT
SUGGESTS ENOUGH HIGH PRESSURE AND SHORTWAVE RIDGING BUILDS
THURSDAY MORNING TO SLOW THE PROGRESSION OF THE NEXT NW WAVE
ROUNDING THE SOUTHERN RIDGE. SUBDUED POPS HELP HIGHLIGHT THIS AS
THAT RISK APPEARS TO HAVE SHIFTED EITHER OVERNIGHT THURSDAY
INTO FRIDAY OR AT SOME POINT IN THE DAY FRIDAY. FOR NOW, NOTE
THAT A SHORTWAVE COMBINED WITH OVERRUNNING WARM ADVECTION AGAIN
FAVORS THE DEVELOPMENT OF THUNDERSTORMS ALONG A FAIRLY
STATIONARY AXIS THAT RESULTS IN HEIGHTENED FLASH FLOOD RISKS.
LIKE MANY PREVIOUS DISCUSSIONS NOTE, THIS PATTERN HAS FEATURED A
LOT OF UNCERTAINTY THAT MAY BE HIGHLY INFLUENCED BY THE PREVIOUS
6-24 HOURS OF CONVECTIVE ACTIVITY. THIS LATE THURSDAY/FRIDAY
PERIOD WILL BE NO DIFFERENT, MEANING TIMING OF THESE STORMS
ALONG WITH POSITIONING OF THE AXIS COULD SEE LARGE VARIATIONS
LEADING UP THE EVENT. MORE SIMPLY, THERE ARE SCENARIOS WHERE
STORMS OCCUR AT SOME POINT THAT DROP MULTIPLE INCHES OF RAIN
OVER SOME PORTION OF THE REGION (RESULTING IN FLASH FLOODING)
WITH OTHER PORTIONS ARE WET A LOT OF THE DAY, OR THERE ARE
SCENARIOS WHERE THE REGION REMAINS COMPLETELY DRY. AS ALWAYS,
STAY TUNED FOR THE LATEST UPDATES FOR THIS PERIOD.
KEY MESSAGE 3...
THE OVERALL SYNOPTIC PATTERN ONLY SEES MINOR VARIATIONS THIS
WEEKEND INTO NEXT WEEK AS THE PREDOMINANT FLOW SETUP (RIDGE
SOUTH TO SOUTHWEST OF REGION; ZONAL TO NORTHWEST FLOW OVERHEAD)
STAYS IN TACK. PERIODIC SHOWERS AND THUNDERSTORMS, GENERALLY
SHORTER IN DURATION COMPARED TO THIS PAST WEEK, REMAIN POSSIBLE
IN SUCH FLOW WHILE TEMPERATURE LARGELY STAYS NEAR SEASONAL
AVERAGES. SATURDAY IS THE MORE LIKELY DAY OF BREAK FROM
ACTIVITY, BUT EVEN THAT SCENARIO COULD ADJUST AS MODELS ATTEMPT
TO BETTER TIME SHORTWAVE MOVEMENT/TIMING.
INITIAL GLANCE FROM ENSEMBLE MEANS AS WELL AS PUBLICLY AVAILABLE
MACHINE-LEARNING MODELS SUGGESTS MORE LIMITED SEVERE/HYDRO RISK
THAN THE PREVIOUS WEEK. BUT IT REMAINS PRUDENT TO FOLLOW THE
LATEST TRENDS AS THERE ARE (LOW PROBABILITY) SCENARIOS STILL IN
PLAY THAT BRING ONE OR BOTH MORE PROMINENTLY INTO PLAY.
AVIATION /00Z THURSDAY THROUGH MONDAY/
SHOWERS AND ISOLATED THUNDERSTORMS, MAINLY NORTH OF PIT, WILL
CONTINUE THIS EVENING WITH A CROSSING SHORTWAVE. THIS ACTIVITY
SHOULD DIMINISH OVERNIGHT AS THE SHORTWAVE EXITS, AND
INSTABILITY WANES. MVFR STRATUS IS EXPECTED TO DEVELOP THROUGH
THE EVENING, LOWERING TO IFR CIGS OVERNIGHT INTO THURSDAY
MORNING. CEILING LEVELS SHOULD INCREASE TO MVFR AS MIXING BEGINS
ON THURSDAY, AND EVENTUALLY SCATTER OUT THROUGH THE AFTERNOON,
WITH INCREASING MID/HIGH LEVEL CLOUDS ABOVE. VFR IS THEN
EXPECTED TO CONTINUE INTO EARLY THURSDAY EVENING AHEAD OF AN
APPROACHING SHORTWAVE TROUGH.
OUTLOOK...
RESTRICTIONS IN SHOWERS AND A FEW THUNDERSTORMS ARE EXPECTED
THURSDAY NIGHT INTO FRIDAY MAINLY SOUTH OF A ZZV-LBE LINE. VFR
IS EXPECTED, OUTSIDE OF EARLY MORNING FOG, FRIDAY NIGHT THROUGH
SATURDAY AS HIGH PRESSURE MOVES ACROSS THE REGION. RESTRICTION
AND SHOWER/THUNDERSTORM POTENTIAL RETURN SUNDAY INTO MONDAY
WITH THE APPROACH AND PASSAGE OF A COLD FRONT.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...FRAZIER
AVIATION...WM
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