523
FXUS61 KPBZ 011729
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
129 PM EDT SAT AUG 1 2026
WHAT HAS CHANGED
CONFIDENCE OF RAINFALL AMOUNTS EXCEEDING MORE THAN TWO OR THREE
HAS INCREASED, THUS INCREASING THE POTENTIAL FOR HIGH WATER
SOMEWHERE SUNDAY AFTERNOON. NO OTHER SIGNIFICANT CHANGES THIS
FORECAST CYCLE.
KEY MESSAGES
1) POTENTIAL FOR HIGH WATER AND ISOLATED SEVERE STORMS SUNDAY
2) UNSETTLED WEATHER FOR MOST OF NEXT WEEK, BUT NO WASHOUTS
DISCUSSION
KEY MESSAGE 1...
NOT A LOT OF CHANGE IN THE FORECAST EVOLUTION FOR SUNDAY WITH
THE LATEST MODEL SUITE. IT APPEARS THAT FLASH FLOODING WOULD GET
THE NOD OVER SEVERE WEATHER IF YOU HAD TO PUT THE THREATS IN
ORDER.
FLASH FLOODING:
A PLUME OF HIGH PWATS (> GREATER TWO INCHES) IS FORECAST TO
OVERSPREAD MOST OF THE REGION SUNDAY. MEANWHILE, THE VERTICALLY
STACKED CYCLONE ALLOWS SOUTHERLY WIND FLOW TO BECOME PARALLEL TO
THE BAROCLINIC SETTING THE STAGE FOR TRAINING. HREF 95TH PRECIP
PUTS POCKETS OF OVER 4" ACROSS PARTS OF NORTHWEST PA, WHILE LPMM
HAS SEVERAL POCKETS OF 3". WE CAN'T TAKE THE LOCATIONS LOCK
STEP, BUT THIS DOES HIGHLIGHT THE POTENTIAL TO SEE BETWEEN A 10
TO 20 YEAR RAINFALL RETURN INTERVAL. PROBABILITY OF 3" OR MORE
OF RAIN FROM THE HREF WITH A 25 MILES NEIGHBORHOOD RADIUS
RESIDES BETWEEN 10% TO 15%. ALL THIS SAID, WE MAY NEED TO HOIST
A SHORT FUSE FLOOD WATCH AS THIS EVENT UNFOLDS. THE AREA OF MOST
CONCERN WOULD BE NORTHWESTERN PA GIVEN PAINTBALL PLOTS OF
HIGHEST QPF.
THERE WILL BE UPPER LEVEL SUPPORT THROUGH AGEOSTROPHIC WIND
DIVERGENCE AT H2 THANKS TO FAVORABLE JET LOCATION. IT WILL BE
AN EFFICIENT RAIN PROCESS WITH WARM CLOUD DEPTHS OVER 11-12KFT.
INTERESTING ENOUGH, THE PROBABILITY OF 1" PER HOUR RAIN RATES
ARE LOW, SO IT SHOWS MORE OF REPEATED ROUNDS OF STORMS WILL GET
PLACES INTO POTENTIAL TROUBLE FOR STREAMS COMING OUT OF THEIR
BANKS AND / OR ROAD CLOSURES. WITH THE DRY RUN RECENTLY, FLASH
FLOOD GUIDANCE FOR THREE HOURS IS RUNNING AROUND 2.00" WHILE THE
URBAN GUIDANCE OF 0.75" IN ONE HOUR REMAINS THE SAME.
SEVERE THUNDERSTORMS:
THE TRENDS CONTINUES TO BE A LESS FAVORABLE SHEAR PROFILE FOR
POTENTIAL WEAK TORNADOES GIVEN HODOGRAPHS AND SRH VALUES. FRIDAY
IT WAS BECAUSE OF A BACK VEER BACK SETUP AND TODAY MORE SPEED
SHEAR CHALLENGES. NONETHELESS, A DAMAGING WIND THREAT DOES EXIST
GIVEN 30-35 KNOTS OF DEEP-LAYER SHEAR AND MLCAPES AROUND 1.0
KJKG-1. THE AMOUNT OF STORMS DEPENDS ON HOW MUCH DIURNAL HEATING
WE OBSERVE TOMORROW. LOOKING UPSTREAM OVER PARTS OF IND AD KY
WERE THE DRY SLOT IS ALLOWING FOR BREAKS IN THE CLOUDS,
EXTRAPOLATION BRINGS THAT ACROSS EASTERN OHIO AND POSSIBLY INTO
NORTHERN WV AND WESTERN PA SUNDAY AFTERNOON. THIS WOULD CREATE
SUFFICIENT HEATING TO FIRE OFF STORMS THAT COULD KNOCK DOWN
TREES AND WIRES. THE WAY THE CAMS ARE PLAYING THINGS, I COULD
SEE A SCENARIO WHERE THE SEVERE THUNDERSTORM POTENTIAL RESIDES
OVER OUR OHIO COUNTIES AND THE EXCESSIVE RAIN THREAT STAYS IN
NORTHWEST PA. EITHER WAY, THERE WILL BE A BREAK BETWEEN SHOWERS
OVERNIGHT AND THE STORMS SUNDAY AFTERNOON. THE LONGER THE BREAK
AND MORE SUNSHINE WE SEE, THE HIGHER CHANCE OF STORMS SOME OF
WHICH COULD BE SEVERE.
MACHINE LEARNING IS MOSTLY IN LINE WITH SPC WITH NADOCAST
PUTTING A 15% CHANCE OF SEVERE WIND OVER WESTERN PA AND THE
NORTHERN WV PANHANDLE. DEPENDING ON THE HOW MUCH WE CLEAR OUT AND
HOW LONG GOES A LONG WAY TO PUTTING THE PIECES OF THIS ATMOSPHERIC
PUZZLE TOGETHER.
KEY MESSAGE 2...
THE SLOW MOVING UPPER LEVEL LOW FINALLY KICKS OUT OF HERE MID
WEEK, HOWEVER BROAD TROUGHING OVER THE GREAT LAKES QUICKLY
ESTABLISHES. THIS SPELLS A FORECAST WITH A CONTINUED CHANCE OF
SHOWERS AND THUNDERSTORMS EVERY DAY NEXT WEEK. THE TIME WINDOW
WHEN THEY ARE MOST LIKELY TO HAPPEN IS DURING PEAK HEATING
HOURS. AS STATED IN THE KEY MESSAGES ABOVE, NO ALL DAY RAINS ARE
FORECAST AND SOME LOCATIONS MAY NOT SEEN A DROP ALL WEEK. THERE
WILL BE PERIODS OF SUNSHINE AS WELL, SO DON'T PUT AWAY THE
SUNGLASSES JUST BECAUSE YOU SEE A CHANCE OF RAIN IN THE
FORECAST.
TEMPERATURES WILL BE ABOVE AVERAGE ALL WEEK AS HUMIDITY RETURNS.
DAYTIME HIGHS WILL BE WIDESPREAD IN THE 80S WITH SOME
COMMUNITIES HITTING 90F IN WEST VIRGINIA AND EASTERN OHIO.
OVERNIGHT LOWS WON'T GET BELOW 65 UNLESS YOU RESIDE NORTH OF I80
OR IN THE MOUNTAINS OF SOUTHWESTERN PA AND NORTHERN WV. AS OF
NOW, NO ORGANIZED SEVERE WEATHER IS EXPECTED.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
VFR IS EXPECTED THROUGH MUCH OF THE DAY AS SURFACE HIGH PRESSURE
DEPARTS TO THE EAST. AN OVERCAST DECK OF MID AND HIGH LEVEL
CLOUDS, AHEAD OF AN APPROACHING MID-LEVEL TROUGH, WILL CONTINUE
TO STREAM ACROSS THE REGION THROUGH THE DAY. A WEAK IMPULSE AND
CONVERGENCE ALONG THE NOSE OF A LOW-LEVEL JET WILL OVERSPREAD SHOWERS
AND A FEW THUNDERSTORMS ACROSS THE AREA TONIGHT INTO SUNDAY
MORNING. INCLUDED PREDOMINANT MENTION OF SHOWERS FOR ALL
TERMINALS WITH PROB30S FOR THUNDER COVERING THIS TIME PERIOD
WITH COVERAGE RAMPING UP A BIT MORE IN THE LATTER HALF OF THE
OVERNIGHT HOURS ON THE NOSE OF THE IMPINGING JET.
LATEST ENSEMBLE RUNS HAVE TRENDED TO DECREASE POPS A BIT
QUICKER FROM WEST TO EAST SUNDAY MORNING, SO FOLLOWED SUIT WITH
THAT, BUT REMNANT LOW-LEVEL MOISTURE WITHOUT ANY NOTABLE DRY
ADVECTION LIKELY RESULTS IN MVFR CIGS ACROSS THE AREA WITH
40-70% PROBS FOR IFR HIGHEST AT FKL/DUJ. THOSE PROBS HAVE
INCREASED SOME FARTHER SOUTH FOR PIT AND SURROUNDING TERMINALS,
BUT HAVE LEFT OUT IFR CIGS FOR NOW UNTIL CONFIDENCE IN PLACEMENT
OF MOST PERSISTENT RAIN, WHICH IS THE LIKELY DRIVER OF THE
LOWER CIG PROBABILITIES, BECOMES CLEARER.
FOLLOWING THE MORNING RAIN, ADDITIONAL DEVELOPMENT OF SHOWERS
AND STORMS IS LIKELY AFTER 17Z OR SO AREAWIDE. COVERAGE AND
INTENSITY WILL BE DEPENDENT ON THE EXTENT OF MORNING SCATTERING
OF CLOUDS, BUT THE STRONGEST STORMS COULD BRING HEAVY RAINFALL
RESULTING IN PERIODIC RESTRICTIONS TO IFR OR LOWER AND GUSTY
WIND. OUTSIDE OF RAIN, MVFR PROBS REMAIN ELEVATED AT >50%
THROUGH THE LATE AFTERNOON.
OUTLOOK...
PERIODIC SHOWER AND THUNDERSTORM CHANCES WILL CONTINUE,
ESPECIALLY DURING THE AFTERNOON AND EVENING, THROUGH MID-WEEK
AS AN UPPER TROUGH LINGERS ACROSS THE UPPER OHIO VALLEY REGION.
IN ADDITION, EARLY MORNING FOG AND STRATUS WILL BE POSSIBLE
WITH LOW-LEVEL MOISTURE IN PLACE.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...MCMULLEN
AVIATION...MLB
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page