831
FXUS61 KPBZ 072333 AAA
AFDPBZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PITTSBURGH PA
733 PM EDT WED OCT 7 2026
WHAT HAS CHANGED
SCATTERED SHOWERS WERE ADDED TO THE FORECAST NEAR AND NORTH OF
THE I-80 CORRIDOR THIS EVENING WITH A CROSSING COLD FRONT.
OTHERWISE, RAINFALL FROM THE EXPECTED REMNANT LOW OF ISAIAS MAY
ARRIVE A BIT EARLIER THAN PREVIOUSLY FORECAST, AND OVERALL
RAINFALL TOTALS HAVE SHOWN A BIT OF AN UPWARD TREND. WIDESPREAD
FLOODING RISKS REMAIN LOW.
KEY MESSAGES
1) SCATTERED SHOWERS ALONG/N OF I-80 THIS EVENING, OTHERWISE
DRY WEATHER CONTINUES INTO THE WEEKEND WITH A WARMING TREND BY
SATURDAY
2) THE REMNANT LOW OF ISAIAS MAY PROVIDE A SOAKING RAIN SUNDAY
INTO SUNDAY NIGHT, ALTHOUGH WIDESPREAD FLOOD RISKS REMAIN LOW
DISCUSSION
KEY MESSAGE 1...
A WEAK SHORTWAVE TROUGH AND SURFACE COLD FRONT WILL CROSS THE
REGION THIS EVENING/TONIGHT. ENOUGH CONVERGENCE, MOISTURE AND
INSTABILITY WAS OBSERVED ALONG THIS FRONT NEAR THE LAKE ERIE
SHORELINE FOR SCATTERED SHOWERS TO DEVELOP. THERE HAVE EVEN BEEN
A FEW LIGHTNING STRIKES/THUNDERSTORMS WITH THIS ACTIVITY. WHILE
THE THUNDER SHOULD BE CONFINED TO AREAS CLOSER TO THE LAKE,
SCATTERED SHOWERS COULD MAINTAIN LONG ENOUGH TO TRACK ACROSS
AREAS NEAR AND NORTH OF I-80 THIS EVENING AS THE FRONT CROSSES.
ELSEWHERE, DRY AIR (AS SEEN IN THE ONGOING 00Z PIT UPPER AIR
FLIGHT) SHOULD PRECLUDE SHOWER DEVELOPMENT.
OTHERWISE, DRY WEATHER THEN CONTINUES THROUGH FRIDAY AND
SATURDAY AS SURFACE HIGH PRESSURE REMAINS IN CONTROL.
TEMPERATURES REMAIN A A BIT ABOVE CLIMATOLOGY THROUGH FRIDAY.
SOUTHERLY FLOW AND RISING HEIGHTS BEHIND THE DEPARTING HIGH MAY
PUSH DAYTIME HIGHS SOME 10 DEGREES ABOVE CLIMATOLOGY ON
SATURDAY.
KEY MESSAGE 2...
CURRENT NHC GUIDANCE STILL HAS ISAIAS LANDFALLING ON THE GULF
COAST FRIDAY NIGHT, AND THEN ITS REMNANT LOW REACHING THE LOWER
OHIO VALLEY LATER SUNDAY NIGHT OR EARLY MONDAY MORNING. MODEL
GUIDANCE STARTS TO DIVERGE THEREAFTER ON THE EXACT TRACK, BUT
MOST HAVE THE LOW TURNING EAST AND NEARING OR CROSSING THE
ATLANTIC COAST BY MONDAY. THIS RELATIVELY SPEEDY CROSSING OVER
OR NEAR OUR REGION WILL MOST LIKELY KEEP RAINFALL AMOUNTS FROM
BECOMING EXCESSIVE. THERE DOES SEEM TO BE A LEAN TOWARDS A
FASTER ARRIVAL TIME OF THE RAIN, WITH ONSET POSSIBLE AROUND OR
AFTER MIDNIGHT SATURDAY NIGHT.
THE 13Z NBM HAS 48-HOUR MEAN RAINFALL TOTALS THROUGH 8 AM
MONDAY OF BETWEEN 0.8 AND 1.2 INCHES, WITH A NORTH-TO-SOUTH
GRADIENT. 50TH PERCENTILE LEVELS ARE RELATIVELY SIMILAR TO THE
MEAN VALUES, SUGGESTING LESS OF A BIMODAL DISTRIBUTION IN
SOLUTIONS THAN FROM THE NBM RUNS YESTERDAY. HOWEVER, THERE HAS
BEEN AN INCREASE IN THE MEAN VALUES AS COMPARED TO YESTERDAY.
90TH PERCENTILE LEVELS NOW FALL IN THE RANGE OF 1.75 TO 2.25
INCHES, ALSO HIGHER THAN YESTERDAY. THIS IS STILL BELOW CURRENT
6-HOUR FLASH FLOOD GUIDANCE VALUES, WHICH ARE ABOVE 2.5 INCHES
AREAWIDE SAVE FOR VERY SMALL POCKETS. OVERALL, THE THREAT OF
WIDESPREAD FLOODING CONCERNS REMAINS LOW, ALTHOUGH ISOLATED
URBAN AND POOR DRAINAGE ISSUES COULD IN THEORY ARISE. IN
PARTICULAR, LOCALIZED STREET FLOODING FROM DEBRIS-BLOCKED STORM
DRAINS COULD BE A PROBLEM IN THE HIGHER-END RAINFALL SCENARIOS.
TRENDS WILL BE MONITORED. IF SLOWER MOTION OF THE REMNANT LOW
BECOMES MORE LIKELY, THEN HIGHER RAINFALL TOTALS COULD BE MORE
OF A CONCERN. SEVERE THUNDERSTORMS RISKS ARE ALSO VERY LOW. THE
PROBABILITY OF 250 J/KG OF SBCAPE REMAINS UNDER 30%, AND LONGER-
RANGE MACHINE LEARNING GUIDANCE KEEPS SEVERE PROBABILITIES LESS
THAN 5%.
WITH THE FASTER OVERALL MOTION, ANY HEAVY RAINFALL THREAT
CURRENTLY DECREASES AFTER 12Z MONDAY AS THE REMNANTS HEAD TO OUR
EAST. STILL, RELATIVELY LIGHT SHOWERS MAY LINGER INTO TUESDAY AS
SOME LONG-RANGE SCENARIOS BRING ANOTHER SHORTWAVE ACROSS THE
GREAT LAKES.
AVIATION /00Z THURSDAY THROUGH MONDAY/
MOSTLY CLEAR SKIES EARLY THIS EVENING WILL BE REPLACED BY SCT
TO BKN MID-LEVEL CLOUDS (THICKER TO THE NORTH) ALONG A PASSING
COLD FRONT. AN EXTREMELY DRY COLUMN DEPICTED ON RECENT PIT ACARS
SOUNDINGS AND OUR 00Z BALLOON LEND HIGH CONFIDENCE TO DRY
CONDITIONS SOUTH OF I-80. FOR FKL, HAVE INCLUDED A PROB30 GROUP
FOR TSRA MENTION JUST AFTER 00Z AS THE FRONT HAS PICKED UP
ENOUGH MOISTURE ACROSS LAKE ERIE TO SUPPORT DEVELOPMENT OF
SCATTERED SHOWERS AND EVEN SOME THUNDER WITH FUMES OF ELEVATED
INSTABILITY ALONG THE LAKESHORE. NOT VERY CONFIDENT HOW FAR
EAST THEY'LL BE ABLE TO HOLD TOGETHER WITH ARRIVAL INTO A DRIER
AIRMASS, BUT HAVE SEEN ENOUGH DEVELOPMENT AND MAINTENANCE TO
WARRANT A PROB30 MENTION.
OTHERWISE, WILL SEE A WIND SHIFT FROM SOUTHWEST TO WEST IN THE
WAKE OF THE FRONT OVERNIGHT. STILL THINK THAT SURFACE WIND WILL
REMAIN ELEVATED ENOUGH TO PRECLUDE LOW LEVEL WIND SHEAR BENEATH
35-40 KNOT FLOW AROUND 2 KFT, BUT IF WIND RELAXES MORE THAN
ANTICIPATED, A PERIOD OF LLWS IS POSSIBLE COINCIDENT WITH FROPA.
MIXING ON THURSDAY WILL PROMOTE AROUND A 10 KNOT WESTERLY WIND
GUSTING TO 15-20 KNOTS AT TIMES. SCANT BOUNDARY LAYER MOISTURE
SHOULD SUPPORT NO MORE THAN A FEW AFTERNOON CU AND HIGH
CONFIDENCE VFR.
OUTLOOK...
OTHER THAN VARYING CHANCES FOR MORNING RIVER VALLEY STEAM FOG,
VFR IS FAVORED THROUGH THE WEEKEND UNTIL THE REMNANTS OF ISAIAS
ARRIVE IN THE LATTER HALF OF THE WEEKEND.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...WM/CL
AVIATION...MLB
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