798
FXUS61 KPBZ 181709
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
109 PM EDT MON MAY 18 2026
WHAT HAS CHANGED
ON THE WHOLE, THE FORECAST REMAINS UNCHANGED, EXCEPT FOR HIGHER
CONFIDENCE IN AN 8P TO 2A ARRIVAL OF STORMS IN NORTHWEST PA AND
EASTERN OHIO TUESDAY NIGHT.
KEY MESSAGES
1) HEAT IMPACTS FOR SENSITIVE POPULATIONS CONTINUE EARLY THIS
WEEK, WITH TEMPERATURES UP TO THE UPPER-80S TO LOW-90S.
2) CONDITIONAL TERRAIN/LAKE DRIVEN SEVERE CHANCES TODAY,
HIGHEST SEVERE CHANCES TOMORROW EVENING FOR NW PA AND EAST OH,
AND CONDITIONAL SEVERE THREATS WEDNESDAY SE OF PITTSBURGH WITH
DEPARTING FRONT.
DISCUSSION
KEY MESSAGE 1...
THE 12Z SURFACE ANALYSIS HAS THE 587DM HEIGHT LINE DRAPED
ACROSS THE AREA, WHICH GENERALLY SUGGESTS THAT UPPER 80S ARE
MOST LIKELY FOR HIGHS TODAY. A NON-BC MODEL LIKE THE LREF AND
HREF, GENERALLY AGREE, WITH THE 25TH-75TH PERCENTILE SPREADS
NARROW AND GENERALLY BETWEEN 86F AND 90F. WITH HIGH CONFIDENCE
IN MOSTLY CLEAR SKIES FOR MOST TODAY, ITS POSSIBLE THESE
DETERMINISTIC HIGH TEND TOWARD THE HIGHER END OF THE NON-BC
DISTRIBUTION. SO THIS WOULD GENERALLY MEAN TEMPERATURES NEAR-90,
WITH SOME 90S POSSIBLE WITH URBAN AND RIVER-VALLEY TERRAIN
INFLUENCE. SOME "COOLER SPOTS" INTO THE LOW-TO-MID 80S ARE
FAVORED FOR HIGH TERRAIN AND NORTH OF I-80. HIGHS TODAY WILL BE
WITHIN A FEW DEGREES OF RECORD HIGHS FOR ALL CLIMATE SITES.
THE HREF ONLY ALLUDES TO TEMPERATURES DROPPING INTO THE MID-TO-
UPPER 60S, WHICH WILL PROVIDE LITTLE CHANCE FOR TEMPERATURE
RECOVERY OVERNIGHT. THIS WILL CHALLENGE A FEW "MAX-LOW
TEMPERATURE" RECORDS. MEAN HEIGHTS MAY DROP SLIGHTLY TUESDAY
WITH THE BEGINNING OF A RIDGE BREAKDOWN. ADDITIONALLY, MORE MID-
MOISTURE WILL ALSO ALLOW FOR MORE CLOUD COVER. ALL IN ALL,
TEMPERATURES MAY BE A DEGREE OR TWO COOLER IN AREAS THAT DO NOT
SEE RAIN, BUT CUMULATIVE HEAT STRESS CONTINUES. SO UPPER-80S,
ARE AGAIN FAVORED FOR MOST.
THE NWS HEAT RISK SHOWS MOSTLY A MODERATE RISK MONDAY INTO
TUESDAY, WHEREBY HEAT MAY GENERALLY IMPACT THE MOST SENSITIVE
POPULATIONS. MAKE SURE TO STAY HYDRATED OR MONITOR FOR SIGNS OF
HEAT ILLNESS IF SPENDING EXCESSIVE TIME OUTDOORS.
KEY MESSAGE 2...
ALL OF THE AREA WILL BE UNDER THE NORTHERN PERIPHERY OF THE
RIDGE AXIS TODAY, WITH CORRESPONDING SUBSIDENCE ENFORCING MID-
LEVEL CAPPING. WHILE DIURNAL CUMULUS ARE DEVELOPING, AS WE
CONTINUE TO MIX INTO A DRY LAYER (EVIDENCED ON 12Z SOUNDING
FROM 750MB TO 600MB), WE EXPECT MOST VERTICAL DEVELOPMENT TO BE
LIMITED. THERE'S A COUPLE EXCEPTIONS THAT WILL NEED TO BE
ADDRESSED. FIRST WILL BE THE HIGH TERRAIN. WITH RIDGE-TOP
CONVERGENCE IN MOSTLY NE FLOW ALOFT, WE COUDN'T RULE OUT A STORM
FIRING IN AN ENVIRONMENT OF 1000-1200 DCAPE, WHICH COULD
CERTAINTY CARRY A CONDITIONAL DOWNBURST WIND THREAT IN THE LOW
PROBABILITY THIS HAPPENS. CONSISTENTLY, THE HIGHEST CHANCE OF
DEVELOPMENT HAS BEEN EASTERN TUCKER COUNTY, BUT WITH NW FLOW
ALOFT, THE THOUGHT WOULD BE THAT THE HIGHEST RISK WOULD BE TO
THE EAST FOR THE FORECAST AREA. THE SECOND AREA WOULD BE A
CONDITIONAL THREAT OF STORM DEVELOPMENT ON A LAKE BREEZE THIS
AFTERNOON. THIS IS LOWER CONFIDENCE, BUT SHOULD IT OCCUR, THE
SAME DOWNBURST THREAT IS POSSIBLE, WITH OUTFLOW POTENTIALLY
CARRYING DEVELOPMENT INTO NW PENNSYLVANIA. BOTH THREATS ARE
CONDITIONAL ON DEVELOPMENT (<30% CHANCE), BUT SHOULD DEVELOPMENT
OCCUR, DAMAGING WIND RISKS WOULD INCREASE SUBSTANTIALLY.
A RIDGE BREAKDOWN BEGINS TUESDAY, WITH AFTERNOON STORM
DEVELOPMENT IN WESTERN OHIO LIKELY. THE MOST LIKELY TIMING OF
THIS APPEARS LATE- DAY. THERE'S A BIT OF A CONDITIONAL RISK
FROM 20Z TO 00Z, BUT THE CURRENT THOUGHT IS THAT CAPPING WILL
BE TOO STRONG TO LET THE ENVIRONMENT UTILIZE THE ~1500 TO 2500
MUCAPE FOR "BUBBLE-UP" CONVECTION IN NW PA IN THE AFTERNOON.
LATER, SOME COMBINATION OF OUTFLOW FROM THE OHIO CONVECTION ON A
PRE-FRONTAL TROUGH AND/OR A LAKE BREEZE WILL MAKE CONVECTION
MORE LIKELY IN THE 00Z TO 06Z WINDOW. SINCE THIS TIMING IS
MOSTLY AFTER SUNSET, STORMS ARE EXPECTED TO HAVE A DECAYING
TREND AS THEY ENTER THE AREA, BUT THEY CERTAINTY COULD BE STRONG
ENOUGH TO PRODUCE WIND GUSTS UP TO 60MPH, MOST LIKELY FOR THE
I-80 CORRIDOR WITH DCAPE OF 900 TO 1000, WITH THREATS ALSO
POSSIBLE INTO EASTERN OHIO. CONVECTIVE INTENSITY IS EXPECTED TO
WAIN OVERNIGHT AS THE PARENT COLD FRONT MOVES IN, BUT SOME
ISOLATED SHOWERS/STORMS REMAIN POSSIBLE.
WEDNESDAY WILL BRING MORE OF A CONDITIONAL SEVERE THREAT
SOUTHEAST OF PITTSBURGH, WITH THE MAIN UNCERTAINTY BEING 1)
FRONTAL TIMING AND 2) CLOUD COVER. IN A SCENARIO WITH A SLOWER
FRONT AND LIMITED CLOUD COVER, RECOVERY OF INSTABILITY AND A
LIMITED SEVERE THREAT IS POSSIBLE FOR NORTHERN WV AND FAR SW PA.
BUT SHOULD THE FRONT BE FASTER OR CLOUDS COMPLICATE INSTABILITY
GENERATION, SEVERE THREATS ARE LOWER. SEVERE CHANCES TAPER OVER
THE NEXT WEEK.
AVIATION /18Z MONDAY THROUGH SATURDAY/
HIGH CONFIDENCE VFR THROUGH THE TAF PERIOD UNDER THE INFLUENCE
OF HIGH PRESSURE EAST OF THE REGION. A FEW CU DEVELOPS THIS
AFTERNOON WITH PEAK HEATING/MIXING WHILE SOUTHWEST WINDS
OCCASIONALLY GUST BETWEEN 15-25KTS. ANY CONVECTIVE CHANCES ARE
TIED TO WEAK CONVERGENCE ALONG THE WV RIDGE-LINE, WITH STORMS
DRIFT NORTHEAST. RECENT DETERMINISTIC MODELS ARE SHOWING A LOWER
LIKELIHOOD FOR THIS OCCURRING. THERE IS A NON-ZERO CHANCE FOR ISOLATED
SHOWERS AND THUNDERSTORMS DEVELOP OFF ITS OUTFLOW NEAR TO AFTER
00Z TONIGHT AROUND NORTHWEST PA BUT PROBABILITY IS TOO LOW FOR
TAF MENTION.
NOCTURNAL INCREASES IN THE LOW-LEVEL JET MAY CREATE BRIEF PERIODS
OF LLWS, HOWEVER, THE LACK OF DURATION OR MEETING CRITERIA
(EITHER BY SPEED/DIRECTION OR BY HEIGHT) LED TO AN OMISSION FROM
TAFS. AREA MID TO HIGH LEVEL CLOUD COVER INCREASES OVERNIGHT
INTO TUESDAY MORNING IN ASSOCIATION WITH AN EASTWARD MOVING BUT
DECAYING MCS. THESE CLOUDS ARE EXPECTED TO DISSIPATE WITH
DAYTIME HEATING ALLOWING VFR CEILINGS TO PERSIST THROUGH THE
DAY. SOME ISOLATED THUNDERSTORMS POSSIBLE IN NORTHWESTERN PA,
HOWEVER, THEY WERE OMITTED FROM THE TAFS DUE TO <25% PROBABILITY
OF OCCURRENCE.
OUTLOOK...
AN UPPER SHORTWAVE AND SURFACE FRONT WILL PUSH A
SHOWER/THUNDERSTORM AXIS EAST TUESDAY EVENING THROUGH WEDNESDAY
AFTERNOON. INITIAL RESTRICTIONS WILL BE TIED TO RAINFALL
INTENSITIES WITH HEIGHT FALLS NOT OCCURRING UNTIL AFTER FRONTAL
PASSAGE.
HIGH PRESSURE AND VFR RETURNS BY THURSDAY AREAWIDE BEFORE AN
ACTIVE PATTERN FEATURE MULTIPLE RAIN CHANCES DEVELOPS FRIDAY
INTO THE WEEKEND.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...MILCAREK
AVIATION...FRAZIER/LUPO
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