946
FXUS61 KPBZ 021714
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
114 PM EDT WED SEP 2 2026
WHAT HAS CHANGED
ADDITIONAL DEVELOPMENT OF THUNDERSTORMS EXPECTED WEDNESDAY
AFTERNOON AND EVENING WITH UNCERTAINTY BEYOND THAT FOR THURSDAY,
THOUGH EXPECT ANOTHER ROUND AT SOME POINT DURING THE DAY. TIMING
AND IMPACTS WILL BE DEPENDENT ON PREVIOUS CONVECTION EVOLUTION.
KEY MESSAGES
1) ROUNDS OF SHOWERS AND STORMS CONTINUE THROUGH FRIDAY WITH
ASSOCIATED SEVERE WEATHER THREATS.
2) UNSEASONABLY WARM CONDITIONS ALSO CONTINUE THROUGH THURSDAY. 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 WEST-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 48 HOURS.
FOR THE REST OF WEDNESDAY, EXPECT THAT WE'LL BE MOSTLY DRY INTO THE
EARLY AFTERNOON HOURS WITH LOCALIZED SUBSIDENCE IN THE WAKE OF
MORNING CONVECTION. BY LATE AFTERNOON AND EVENING, WE SHOULD SEE
REINVIGORATION OF SHOWERS AND STORMS POSSIBLY DRIVEN BY TWO
FEATURES. THE FIRST WILL BE A SUBTLE SURFACE TROUGH AND WEAK MID-
LEVEL WAVE TRACKING THROUGH SOUTHERN MICHIGAN AND EVENTUALLY OVER
LAKE ERIE. PUTTING STOCK IN CURRENT CAMS IS TOUGH, ESPECIALLY AS
THEY CONTINUE TO STRUGGLE EVEN WITH ONGOING CONVECTION, BUT THEIR
CONSENSUS TO FIRE STORMS OFF OF THAT FEATURE COMBINED WITH A LAKE
BREEZE WILL LIKELY BE ONE FOCUS. THE OTHER IS LIKELY TO BE A DENSITY
GRADIENT ALONG THE OUTFLOW/CIRRUS SHIELD FROM THE MORNING
CONVECTION. IT HAS SAGGED SOUTH TOWARD PITTSBURGH LATE THIS
MORNING, BUT EXPECTATION IS IT WILL SHIFT A BIT BACK FARTHER
NORTHEAST AS SOUTHWESTERLY FLOW ESTABLISHES. CAMS AREN'T EXCITED
ABOUT DEVELOPMENT ALONG IT, BUT STRUGGLE TO BELIEVE THAT THAT'S
REALLY GOING TO BE THE CASE. THE ENVIRONMENT WILL BE POTENT;
MODIFYING OUR MORNING SOUNDING IN UNTAPPED AIR SUGGESTS DEW
POINTS WITH A FLOOR IN THE MID 70S AND AFTERNOON HIGHS IN THE
UPPER 80S TO LOW 90S. A BELT OF 40-50 KNOT 500 MB FLOW WILL
SUPPORT EFFECTIVE SHEAR OF 30-40 KNOTS AND MLCAPE VALUES >3000
J/KG AND STEEP, NEARLY DRY ADIABATIC MID-LEVEL LAPSE RATES. ANY
STORM THAT DEVELOPS WILL HAVE A SEVERE THREAT. AGAIN, THINK
COVERAGE WILL BE HIGHEST NORTH AND EAST OF PITTSBURGH WITH MOST
LIKELY TIMING FROM 4PM-MIDNIGHT.
CONFIDENCE IN FUTURE STORM COMPLEX PROGRESSION DECREASES WITH TIME
IN THIS SETUP AS IT'S HIGHLY DEPENDENT ON POORLY MODELED PRECEDING
ROUNDS, BUT THURSDAY LOOKS MORE FAVORABLE TO SEE MORE WIDESPREAD
COVERAGE OF STORMS. THE MID-LEVEL RIDGE AXIS WILL AMPLIFY A BIT MORE
AND GRADUALLY SLIDE EAST WHICH WILL REORIENT THE MID-LEVEL FLOW MORE
NORTHWESTERLY SUCH THAT WE'RE BETTER IN THE PATH OF IMPULSES AND
RESULTANT MCSS. THE QUESTION IS WHEN WE GET THE MOST COVERAGE. SOME
SOLUTIONS SUGGEST MORNING CONVECTION AGAIN SIMILAR TO WEDNESDAY
MORNING WHILE OTHERS DON'T AND HOLD OFF UNTIL THE AFTERNOON. THE
LATTER CASE WOULD RESULT IN MORE WIDESPREAD, SEVERE STORMS IN A
FAVORABLE ENVIRONMENT WITH A 70+% PROBABILITY OF 1000 J/KG SBCAPE
AND 30 KNOTS OF SHEAR. IF STORMS DO MOVE THROUGH IN THE MORNING,
THEY WILL CARRY A SEVERE RISK WITH THEM AS WELL, THERE WILL JUST BE
MORE QUESTION ABOUT THREATS AND WHETHER OR NOT THEY'RE SURFACE-
BASED. THEN THE WATERS WILL BECOME MUDDIER FOR THE AFTERNOON, SO WE
JUST HAVE TO TAKE THIS SETUP 12-24 HOURS AT A TIME.
COME FRIDAY, A COLD FRONT THAT'S BEEN MEANDERING WELL OFF TO OUR
NORTH FINALLY GETS A PUSH TO MOVE THROUGH AND WILL PUT AN END TO THE
UNSETTLED PATTERN FOR THE WEEKEND. MORE STORMS ARE POSSIBLE IN THE
MORNING HOURS AHEAD OF THE FRONT, BUT WE SHOULD SEE A CESSATION FROM
NORTH TO SOUTH IN THE SECOND HALF OF THE DAY AS THE FRONT PASSES
THROUGH. IT'LL BE VERY TIMING DEPENDENT, BUT THERE IS A SCENARIO IN
WHICH MOST OF OUR ACTIVITY IS DONE BY MID-AFTERNOON. OTHERS SUGGEST
IT LINGERS A BIT, ESPECIALLY SOUTH OF PITTSBURGH, INTO THE EVENING
HOURS. THE SEVERE OUTLOOK FOR FRIDAY HAS APPROPRIATELY BEEN PULLED
SOUTH AND ONLY LEFT OUR AREA SOUTH OF PITTSBURGH IN A MARGINAL RISK.
KEY MESSAGE 2...
ASIDE FROM THE STORMS, UNSEASONABLY WARM CONDITIONS CONTINUE
THROUGH THE END OF THE WEEK WITH THE HOTTEST DAYS BEING
WEDNESDAY AND 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. OVERNIGHT LOWS
WEDNESDAY NIGHT WILL ONLY DIP INTO THE LOW 70S. THUS, THE HEAT
ADVISORY REMAINS IN EFFECT THROUGH THURSDAY.
HAVE SOME LOWER CONFIDENCE THAT ADVISORY CRITERIA WILL BE
REACHED WIDESPREAD ON THURSDAY IF CONVECTION IS MORE WIDESPREAD
IN COVERAGE, BUT WITH HOW MUCH UNCERTAINTY THERE IS, WILL LET
THE HEADLINES RIDE AS IS AS AREAS WITHOUT CONVECTIVE
CONTAMINATION WILL HEAT UP EFFICIENTLY.
AVIATION /18Z WEDNESDAY THROUGH MONDAY/
SUBSIDENCE BEHIND AN EXITING LINE OF THUNDERSTORMS WILL MAINTAIN
VFR THROUGH MID TO LATE AFTERNOON. THE LATEST VISIBLE SATELLITE
SHOWS A BOUNDARY ACROSS SE MI/LAKE ERIE, WITH A LEFTOVER
BOUNDARY FROM EARLIER CONVECTION ACROSS WRN PA. THE LATEST
MESOANALYSIS ALSO SHOWS A SUBTLE TROUGH AT 700MB ACROSS NRN IN
MOVING EASTWARD. THESE BOUNDARIES AND WAVES SHOULD BE THE FOCUS
FOR ADDITIONAL CONVECTION LATER THIS AFTERNOON AND EVENING. ML
CAPE HAS RECOVERED TO BETWEEN 2500 AND 3500 J/KG ACROSS MUCH OF
THE AREA. INCLUDED A PROB30 MENTION FOR THUNDERSTORMS GENERALLY
SOUTH OF A PHD-BVI-IDI LINE, WITH A TEMPO MENTION AT FKL AND
DUJ WHERE STORMS ARE MORE LIKELY CLOSER TO THE BOUNDARY.
EXPECT MOST OF THE CONVECTION TO WANE BY LATE EVENING. THERE IS
A MINIMAL POTENTIAL FOR SHOWERS OR A STORM OVERNIGHT, THOUGH THE
PROBABILITY FOR THIS IS TOO LOW FOR A TAF INCLUSION. ADDITIONAL
THUNDERSTORMS AND RESTRICTIONS ARE LIKELY FROM LATE MORNING INTO
THE AFTERNOON ON THURSDAY AS A COLD FRONT BEGINS TO DRIFT
SOUTHWARD ACROSS THE REGION.
OUTLOOK...
PATCHY MORNING FOG IS POSSIBLE THURSDAY. OTHERWISE, ADDITIONAL
SHOWERS AND THUNDERSTORMS, AND ASSOCIATED RESTRICTIONS, ARE
EXPECTED AT TIMES THURSDAY NIGHT AND FRIDAY AS A COLD FRONT
DROPS SLOWLY SOUTH ACROSS THE REGION. VFR IS EXPECTED FOR THE
WEEKEND INTO EARLY NEXT WEEK UNDER HIGH PRESSURE.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...HEAT ADVISORY UNTIL 8 PM EDT THURSDAY FOR PAZ020-021-029-031-
073-075.
HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR PAZ013-014-022.
OH...HEAT ADVISORY UNTIL 8 PM EDT THURSDAY FOR OHZ039-040-048>050-
057>059-068-069.
HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR OHZ041.
WV...HEAT ADVISORY UNTIL 8 PM EDT THURSDAY FOR WVZ001>004-012-021-
509.
DISCUSSION...MLB
AVIATION...WM
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