078
FXUS61 KPBZ 250638
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
238 AM EDT THU JUN 25 2026
WHAT HAS CHANGED
NOT MUCH CHANGE TO THINKING REGARDING SEVERE WEATHER CHANCES FOR
TODAY, BUT TRENDS NEED TO BE MONITORED FOR A POTENTIAL RISE IN
RISK LEVELS. CONFIDENCE IN HEAT AND HUMIDITY NEXT WEEK CONTINUES
TO CLIMB.
KEY MESSAGES
1) ISOLATED STRONG TO SEVERE STORMS POSSIBLE THIS AFTERNOON AND
EVENING.
2) A STALLED BOUNDARY KEEPS RAIN CHANCES IN THE FORECAST FRIDAY
AND SATURDAY, WITH SOME POTENTIAL FOR ISOLATED HEAVY RAINFALL
TOTALS AND INSTANCES OF FLOODING.
2) HIGH CONFIDENCE IN THE DEVELOPMENT OF HOT AND HUMID
CONDITIONS NEXT WEEK.
DISCUSSION
KEY MESSAGE 1...
MID-LEVEL TROUGHING SWINGS ACROSS THE GREAT LAKES INTO THE
NORTHEAST CONUS THROUGH TONIGHT. COINCIDENT WITH THIS, SURFACE
LOW PRESSURE TRACKS ACROSS MICHIGAN TOWARDS THE SAINT LAWRENCE
RIVER BY 12Z FRIDAY. THIS WILL PUSH A SURFACE BOUNDARY TOWARDS
THE UPPER OHIO VALLEY BY THIS EVENING. LIFT WILL ALSO BE
SUPPORTED BY THE LEFT EXIT REGION OF A 300MB JET STREAK. WITH
THESE FACTORS, THERE IS BROAD MODEL AGREEMENT ON THE DEVELOPMENT
OF SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ACROSS OHIO
AND FAR NORTHWEST PENNSYLVANIA BY MID-AFTERNOON, WITH ACTIVITY
SPREADING EAST AND SOUTHEAST THROUGH THE LATE AFTERNOON AND
EVENING.
SHEAR IN THE 0-6KM LAYER IS CERTAINLY SUPPORTIVE OF ORGANIZED
CONVECTION, WITH HREF/REFS MEANS OF 40-50 KNOTS DURING PEAK
HEATING. HOWEVER, THERE ARE LIMITING FACTORS THAT SHOULD TEMPER
THE SEVERE WEATHER THREAT SOMEWHAT. SURFACE DEWPOINTS MAINLY IN
THE LOWER 60S ARE FORECAST, WHICH WILL INHIBIT CAPE LEVELS
SOMEWHAT. HREF PROBABILITIES OF 1000 J/KG OR GREATER ARE 30
PERCENT OR LESS ACROSS A GOOD PORTION OF THE CWA, SAVE FOR
POTENTIALLY PORTIONS OF FAR NW PA/EASTERN OH WHERE BUOYANCY
COULD BE A BIT GREATER. PLUS, WHILE THE LOWER DEWPOINTS MAY
FOSTER LOW-LEVEL DRYING AND STEEPENING LOW-LEVEL LAPSE RATES,
MID-LEVEL LAPSE RATES ARE MOST LIKELY TO REMAIN NEAR OR BELOW
6C/KM, WHICH WILL LIMIT DEEP UPDRAFT STRENGTH. ALSO, SURFACE
DELTA THETA-E VALUES ARE MOSTLY BELOW 20C, SUGGESTING VERY LOW
DOWNBURST WIND POTENTIAL. STILL, THE LEVEL OF SHEAR SHOULD
SUPPORT SOME STORM ORGANIZATION AND PERHAPS EVEN TRANSIENT
SUPERCELL STRUCTURES THAT JUSTIFY ISOLATED DAMAGING WIND AND
HAIL THREATS. ANY VERY LOW TORNADO THREAT APPEARS LIMITED TO
AREAS NORTH OF I-80, WHERE LOW-LEVEL SRH MAY BE A TOUCH HIGHER
AND WHERE LCLS MAY BE A BIT LOWER. THE MAIN THING TO WATCH IN
THE CAMS THROUGH THE DAY: IF DEWPOINTS MANAGE TO CLIMB A BIT
HIGHER, TOWARDS THE MID TO UPPER 60S, BUOYANCY POTENTIAL WOULD
INCREASE, AS WOULD THE CHANCES OF ALL SEVERE THREATS. WHAT SEEMS
MORE CERTAIN IS THAT HEAVY RAIN/FLOODING THREATS WILL REMAIN
LARGELY SQUASHED BY SUFFICIENT STORM MOTION AND NON-REMARKABLE
PRECIPITABLE WATER VALUES.
CONVECTION MAY SURVIVE FOR AN HOUR OR TWO AFTER SUNSET GIVEN
ONGOING MOMENTUM AND THE SUPPORT OF THE STRONG SHEAR, BUT
COVERAGE AND INTENSITY SHOULD RAPIDLY TAPER AFTER 02Z WITH
DIURNAL STABILIZATION AND DECREASING UPPER SUPPORT. ONLY A FEW
SHOWERS SHOULD REMAIN THROUGH THE OVERNIGHT HOURS, WITH
STRATUS/FOG POTENTIALLY LINGERING IN MOST AREAS.
KEY MESSAGE 2...
AS THE FRONT LOSES MUCH OF ITS UPPER SUPPORT AND BECOMES
PARALLEL TO QUASI-ZONAL MID-LEVEL FLOW, MUCH OF ITS FORWARD
SPEED WILL BE LOST, AND IT SHOULD EVENTUALLY OOZE TO A NEARLY
STATIONARY POSITION EITHER IN OR JUST SOUTH OF THE FORECAST
AREA, WHERE IT WOULD LIKELY REMAIN THROUGH AT LEAST SATURDAY.
ADDITIONAL SHORTWAVE ENERGY SHOULD PROVIDE SUPPORT FOR ROUNDS OF
SHOWERS AND THUNDERSTORMS, ESPECIALLY FRIDAY NIGHT AND
SATURDAY, WITH BEST COVERAGE GENERALLY SOUTH OF US-422. SEVERE
WEATHER RISK FROM THIS ACTIVITY APPEARS RELATIVELY LOW GIVEN THE
DAYTIME HEATING ISSUES THIS PATTERN COULD PROVIDE. HOWEVER,
BUILDING PRECIPITABLE WATER SOUTH OF THE BOUNDARY (1.7-1.8 INCH
VALUES EVENTUALLY) AND THE POTENTIAL FOR TRAINING THUNDERSTORMS
SUPPORTS THE NOTION OF A RISK FOR AT LEAST ISOLATED FLOODING
ISSUES ACROSS THE SOUTHERN CWA INTO SATURDAY. BY SUNDAY, THE
FRONT MAY MORE DECISIVELY NUDGE TO OUR SOUTH, BRINGING AN END TO
THE HEAVY RAIN THREAT.
KEY MESSAGE 3...
THE BOUNDARY IS SET TO LIFT BACK NORTH OF THE REGION MONDAY.
THERE IS BROAD MODEL AGREEMENT ON A STRONG 500MB UPPER HIGH OVER
THE LOWER MISSISSIPPI VALLEY BUILDING NORTH AND EAST WITH TIME
TO ENCOMPASS MOST OF THE OHIO VALLEY AND DEEP SOUTH. THE MAIN
IMPACT OF THIS PATTERN IS LIKELY TO BE THE SEASON'S FIRST
SUSTAINED RUN OF HEAT AND HUMIDITY, WITH THE NBM INDICATING 70
PERCENT OR GREATER CHANCE OF 90+ HIGH TEMPERATURES OVER MOST OF
THE NON-RIDGE AREAS TUESDAY THROUGH THURSDAY. ACCORDINGLY,
PROBABILISTIC HEAT RISK GUIDANCE SHOWS 70% OR GREATER CHANCE OF
MAJOR (LEVEL 3 OF 4) OR HIGHER IMPACTS OVER MOST OF THE CWA.
SECONDARY TO THE HEAT WILL BE THE EVENTUAL REINTRODUCTION OF
SOME LEVEL OF SEVERE WEATHER RISK. MOST LIKELY, GIVEN THE
ABUNDANT BUOYANCY POTENTIAL AND WEAK FLOW, THIS WOULD COME IN
THE FORM OF TYPICAL MID-SUMMER WET DOWNBURST WIND THREATS.
THERE IS A LOWER-END POTENTIAL FOR A SUPPRESSED RIDGE BY THE END
OF THE WEEK, WHICH COULD CREATE A UPPER LEVEL NORTHWEST FLOW
SETUP, A PATTERN WHICH HAS BEEN RESPONSIBLE FOR NOTABLE SEVERE
WEATHER EVENTS IN THE PAST. OF COURSE, THERE IS PLENTY OF TIME
TO MONITOR FOR THAT POTENTIAL.
AVIATION /03Z THURSDAY THROUGH MONDAY/
VFR CONDITIONS REMAIN IN PLACE THROUGH MID-MORNING, AS MID AND
UPPER CLOUDS CONTINUE TO THICKEN AHEAD OF AN APPROACHING UPPER
TROUGH. THERE IS A LOW RISK FOR A NON-RESTRICTIVE RAIN SHOWER
LATER THIS MORNING AT FKL/DUJ FROM ACTIVITY CURRENTLY ACROSS
SOUTHEAST MICHIGAN/NORTHWEST OHIO, BUT THAT WAS NOT INCLUDED IN
THE TAFS AT THIS TIME.
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
DEVELOP WITH THE SUPPORT OF THE TROUGH AND AN APPROACHING COLD
FRONT. HREF/CAMS TIMING CONTINUE TO FAVOR THE 19Z TO 00Z WINDOW
FOR THE HIGHEST LIKELIHOOD OF THUNDERSTORM IMPACTS, AND THE
TAFS CONTINUE TO SHOW THIS THINKING VIA TEMPO GROUPS. AS NOTED
EARLIER, THIS TIMING COULD STILL SHIFT AN HOUR OR TWO IN EITHER
DIRECTION DEPENDING ON MESOSCALE TRENDS. BRIEF IFR VISIBILITY
RESTRICTION AND GUSTY, ERRATIC WIND WILL BE POSSIBLE IN ANY
THUNDERSTORM.
THE MOST LIKELY OUTCOME BY THE END OF THE TAF PERIOD WILL BE
LIGHT, LINGERING SHOWERS FROM VFR CEILINGS. THERE IS A LOW
PROBABILITY FOR A WEAKER SECOND ROUND OF CONVECTION AFTER 00Z
WITH THE PASSAGE OF THE SHORTWAVE AXIS, BUT CHANCES OF THAT
REMAIN TOO LOW FOR MENTION AT THIS TIME. ALSO, THE DEVELOPMENT
OF STRATUS AND FOG AT ANY ONE TERMINAL WILL BE HIGHLY DEPENDENT
ON RAINFALL TOTALS IN THOSE AREAS, AND IN ANY CASE ARE MOST
LIKELY AFTER THE CURRENT TAF PERIOD.
OUTLOOK...
AS NOTED, ANY OVERNIGHT RESTRICTIONS ARE LIKELY DEPENDENT ON
DEGREE OF LOCALIZED WETTING AND OVERNIGHT CLEARING THAT COULD
FAVOR STRATUS AND/OR FOG DEVELOPMENT.
STARTING FRIDAY, AN ACTIVE PATTERN IS FAVORED THROUGH THE
WEEKEND FEATURING MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS
WITHIN QUASI-ZONAL FLOW.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...CL
AVIATION...CL
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