925
FXUS61 KPBZ 020112
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
912 PM EDT SAT AUG 1 2026
WHAT HAS CHANGED
CONFIDENCE OF RAINFALL AMOUNTS EXCEEDING MORE THAN TWO OR THREE
INCHES IS RISING AND FAVORS ISOLATED LOCATIONS IN NW PA AND
ALONG OUR EASTERN RIDGES. A FLASH FLOOD WATCH MAY BE NEEDED FOR
THESE AREAS BEFORE TOMORROW AFTERNOON. SEVERE THREAT LOOKS TO
FAVOR EASTERN OHIO INTO NW PA.
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...
NEW MODEL DATA CONTINUES TO REINFORCE FLASH FLOODING AS THE
PRIMARY THREAT FOR TOMORROW WITH QPF ESTIMATES NEAR 3-4 INCHES
IN SPOTS. SEVERE THREAT WILL BE DEPENDENT ON HEATING BUT REMAINS
AND LOOKS TO FAVOR AREAS WEST OF OUR HEAVY RAIN TOMORROW
AFTERNOON.
FLASH FLOODING:
A PLUME OF HIGH PWATS (IN EXCESS OF 2.00" AND NEAR THE DAILY
MAX) WILL OVERSPREAD MOST OF THE REGION OVERNIGHT INTO SUNDAY
WITH HIGH CONFIDENCE. MEANWHILE, THE VERTICALLY STACKED CYCLONE
ALLOWS FOR SOUTHERLY WIND FLOW PARALLEL TO THE BAROCLINIC ZONE,
SETTING THE STAGE FOR TRAINING.
RAINFALL SURGES NORTHEASTWARD INTO WESTERN PA OVERNIGHT RIDING
ALONG WARM ADVECTION. THIS RAIN LOOKS TO BE LOW TO MODERATE IN
INTENSITY AND LACKS A HIGH LIKELIHOOD OF FLOOD RISKS ITSELF BUT
COULD PRIME LOCATIONS FOR HIGH WATER ISSUES LATER IN THE DAY.
THERE IS LIKELY A SMALL BREAK BETWEEN MORNING SHOWER ACTIVITY
DECAYING AND THE PICKUP OF MORE SUSTAINED STORMS TOMORROW
AFTERNOON.
WARM RAINFALL PROCESSES WILL BE EFFICIENT WITH FREEZING LEVELS
NORTH OF 12-13 KFT. THREE HOUR FLASH FLOOD GUIDANCE (FFG) ACROSS
THE REGION IS NEAR 2 INCHES OWING TO OUR RECENT DRY STRETCH.
ONE HOUR FFG VALUES ACROSS MUCH OF THE REGION ARE NEAR 1.50
INCHES BUT THOSE IN URBAN CENTERS STILL REMAIN CLOSE TO AN INCH.
PROBABILITIES OF RAINFALL RATES GREATER THAN 1.5"/HR PEAK NEAR
30% ACROSS PORTIONS OF THE REGION AND SUGGEST 1-HR FFG MAY NOT
BE REACHED BY ANY SINGLE STORM (EXCEPT IN URBAN CENTERS). THIS
WOULD POINT OUR FLASH FLOOD THREAT TOWARDS REQUIRING MULTIPLE
ROUNDS OF STORMS CROSSING THE SAME AREA TARGETING OUR 3-HR FFG
VALUES INSTEAD.
HREF AND REFS 95TH PERCENTILES FAVOR ISOLATED POCKETS OF 3-4
INCHES OF RAINFALL IN 6 HOURS TOMORROW AFTERNOON. WHILE EXACT
LOCATION REMAINS A LITTLE FUZZY AND LIKELY COULD UNTIL THE FIRST
ROUND OF STORMS BEGIN TO FIRE, THE MOST FAVORED LOCATIONS APPEAR
TO BE NW PA AND AREAS ALONG THE RIDGES THAT COULD BE PRIMED FROM
MORNING RAIN. AVERAGE RETURN INTERVALS HIGHLIGHT THE POTENTIAL
TO SEE A 10-20 YEAR RAIN EVENT AT SOME LOCATIONS ACROSS THE
REGION TOMORROW. PROBABILITIES OF 3" OR MORE OF RAIN IN 24H
FROM THE HREF FEATURES SEVERAL RELATIVE MAXIMA, INCLUDING AN
AXIS FROM YNG-FKL (PROBABILITIES OF 60-70%) AND FROM MGW-AOO
(PROBABILITIES OF 60-80%). A SHORT FUSE FLASH FLOOD WATCH MAY BE
NEEDED ACROSS THE REGION TO HIGHLIGHT THESE RISK AREAS.
SEVERE THUNDERSTORMS:
MODEL TRENDS CONTINUE TO SUGGEST LESS-FAVORABLE SHEAR PROFILES
FOR POTENTIAL WEAK TORNADOES GIVEN LARGELY STRAIGHT-LINE
HODOGRAPHS AND LOW SRH AND 0-1KM SHEAR VALUES ACROSS MUCH OF THE
AREA. HOWEVER, PROBABILITIES OF STP VALUES >1 AND LOCALIZED
AREAS OF ENHANCED LOW LEVEL CURVATURE IN MODEL HODOGRAPHS DO
SEEM TO EXIST IN NE OH ALONG THE SURGING WARM FRONT AND TUCKED
UP AGAINST THE EASTERN RIDGES. TORNADIC ACTIVITY TONIGHT IN A
SIMILAR AIRMASS AND SETUP ACROSS FAR WESTERN OH SHOWED
DISTINCTLY DIFFERENT AND FAR BETTER HODOGRAPHS FOR TOR
DEVELOPMENT. SAMPLED 12Z AND ACARS SOUNDINGS ACROSS THE REGION
TOMORROW WILL GO A LONG WAY TO FLESH OUT OUR TOR RISK SUNDAY.
AT THIS TIME, IT STILL REMAINS POSSIBLE TO SEE A BRIEF WEAK
TORNADO OR TWO BUT THIS THREAT COULD WAX OR WANE DEPENDING ON
DATA WE RECEIVE OVERNIGHT AND EARLY TOMORROW MORNING.
NONETHELESS, A DAMAGING WIND THREAT DOES EXIST GIVEN 30-35
KNOTS OF DEEP- LAYER SHEAR, MLCAPE AROUND 1300 J/KG AND MODEL
SOUNDINGS SUGGESTING DCAPE VALUES NEAR 1000 J/KG. ALL OF THESE
AND OUR HIGH PWATS SUGGEST WATER LOADED DOWNBURSTS COULD OCCUR.
THE COVERAGE/INTENSITY OF STORMS DEPENDS ON HOW MUCH HEATING WE
OBSERVE TOMORROW. LOOKING UPSTREAM OVER PARTS OF IND AD KY
WHERE THE DRY SLOT ALLOWED FOR BREAKS IN THE CLOUDS,
EXTRAPOLATION BRINGS THAT ACROSS EASTERN OHIO AND POSSIBLY INTO
NORTHERN WV AND WESTERN PA SUNDAY AFTERNOON. MODEL DEPICTIONS OF
THE EVENT SHOW THIS AS WELL WITH HEAVY RAIN FOCUSED FURTHER
EAST AND STORMS FIRING IN EASTERN OHIO AND MOVING NORTH ALONG
WITH THE SURGING WARM FRONT. EITHER WAY, BREAKS IN CLOUDS AND
RAIN WILL LIKELY PLAY A LARGE ROLE IN STORM INTENSITY TOMORROW
AFTERNOON.
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 AND EVENING HINTING AT LOW END TORNADO
PROBABILITIES IN NE OH. MANY PIECES STILL NEED TO FALL IN LINE
FOR SEVERE WEATHER TO OCCUR, BUT SEVERAL KEY INGREDIENTS LOOK
LIKE THEY COULD LOCALLY COME TOGETHER.
KEY MESSAGE 2...
THE SLOW-MOVING UPPER-LEVEL LOW FINALLY KICKS OUT OF HERE MID
WEEK, QUICKLY FOLLOWED BY BROAD TROUGHING ACROSS THE GREAT LAKES.
THIS SPELLS CONTINUED CHANCES OF SHOWERS AND THUNDERSTORMS
THROUGH NEXT WEEK. SHOWER AND STORM PROBABILITIES WILL COINCIDE
WITH THE AFTERNOON PEAK HEATING HOURS. DESPITE NEAR DAILY
CHANCES, SOME LOCATIONS MAY NOT SEE A DROP OF RAIN AND EVEN IN
LOCATIONS WHERE IT DOES RAIN, LONG STRETCHES OF DRY WEATHER ARE
EXPECTED. 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 /00Z SUNDAY THROUGH THURSDAY/
THE FORECAST FOR THE NEXT 24 HOURS HAS GAINED A SLIGHT BIT OF
CLARITY LATELY.
ONGOING LIGHT RAIN SHOWERS FROM HIGH-BASED CLOUDS ARE CONTINUING
TO WEAKEN AND ERODE, WHICH WILL PRESERVE VFR CONDITIONS AT ALL
SITES THRU THE NEXT SEVERAL HOURS.
DEEPER CONVECTIVE ELEMENTS ARE LIKELY TO DEVELOP LATE TONIGHT AS
WARM ADVECTION OVERSPREADS THE UPPER OH VALLEY. THIS CONVECTION
WILL BLOSSOM AFTER 04Z NEAR ZZV, AND IN THE 06-12Z PERIOD AT
MOST OTHER TERMINALS. TSRA REMAINS LESS CERTAIN, BUT WARM-RAIN
PROCESSES WILL SUPPORT LIGHT-OCCASIONALLY MODERATE RAIN RATES
FROM EPISODIC SHOWERS DURING THIS TIME.
SEVERAL WAVES OF RAIN MAY AFFECT TERMINALS ALONG AN AXIS FROM
MGW-AGC/LBE-DUJ DURING SUN MORNING, BUT AN EVENTUAL BREAK IN
SHOWERS IS APPEARING INCREASINGLY LIKELY FOR AT LEAST A FEW
HOURS MID-/LATE-MORNING TO VERY EARLY AFTERNOON.
INCREASINGLY VIGOROUS STORMS ARE POSSIBLE AT MOST TERMINALS
DURING SUN AFTERNOON, ALTHOUGH PRECISE TIMING AT THE MOMENT IS
STILL UNCLEAR, AND DEPENDENT ON DEGREE OF HEATING IN THE WAKE OF
MORNING SHOWERS. THE TAFS REFLECT THE BEST GUESS AT TIMING THE
AFTERNOON STORM POTENTIAL, BUT LIKELY WILL BE BETTER REFINED AS
THE TIME NEARS.
ALTHOUGH IT IS BEYOND THE TAF PERIOD, OVERNIGHT FOG WITH VSBY
RESTRICTIONS SEEMS LIKELY IN THE WAKE OF SUN AFTERNOON STORMS,
AS IS TYPICAL FOLLOWING HEAVY RAIN.
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/AK
AVIATION...KRAMAR/MLB
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