933
FXUS61 KPBZ 182354
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
754 PM EDT FRI SEP 18 2026
WHAT HAS CHANGED
NO SIGNIFICANT CHANGES TO THE FORECAST. UPDATED FOR THE 00Z TAF
ISSUANCE.
KEY MESSAGES
1) RAIN CHANCES RETURN SUNDAY INTO EARLY NEXT WEEK. RAIN MAY BE
HEAVY AT TIMES, AND COULD LEAD TO LOCALIZED FLOODING AND/OR RIVER
RISES.
DISCUSSION
KEY MESSAGE 1...
ANOTHER PERIOD OF EXTENDED WET WEATHER IS FORECAST TO ENTER THE
AREA SATURDAY NIGHT AND INTO SUNDAY MORNING. ASCENT WILL MOSTLY
BE DUE TO A SHORTWAVE TROUGH AND RIDGE BREAKDOWN IN A TRANSITION
TO MORE QUASI-ZONAL FLOW FOR THE BEGINNING OF NEXT WEEK.
THE HIGHEST CHANCE OF CONVECTIVE RAIN WILL LIKELY COME EARLY
SUNDAY MORNING OR PERHAPS SUNDAY AFTERNOON/EVENING WITH A SPLIT
IN MODELING BETWEEN WHEN EXACTLY THE HEAVIEST RAIN OCCURS. THE
MORNING SCENARIO IS TIED MORE TO OVERRUNNING WARM FRONTAL
CONVECTION, WHILE THE LATER CHANCES ARE CONVERGENCE ALONG THE
DEPARTING COLD FRONT. IN THIS PERIOD, THE HIGHEST RISK OF
RAINFALL IS GENERALLY EASTERN OHIO AND NORTHWEST PENNSYLVANIA.
EXACT TIMING IS A BIT UNCERTAIN, BUT MODELING SEEMS TO FAVOR
THAT EITHER ONE OF THESE SCENARIOS WILL BE THE ONE DOMINANT ONE
FOR QPF, WITH HREF/NBM 95TH- MAX QPF SHOWING UP TO 2"-3" WHERE
TRAINING CONVECTION IS MOST LIKELY.
THE MAIN RISK WITH THESE CONVECTIVE WAVES WOULD BE FLASH
FLOODING, BUT ENSEMBLE AGREE THAT THERE GENERALLY WOULDN'T BE IN
IMMEDIATE REFLECTION IN SIGNIFICANT RIVER RISES REGARDLESS OF
SCENARIO. FLOOD WATCHES MAY BE NEEDED, SHOULD CONFIDENCE
INCREASE. SEVERE RISK REMAINS QUITE LOW WITH MOIST ADIABATIC
PROFILES AND LOW DCAPE (>400). UP TO 40KTS OF SFC-6KM SHEAR ARE
POSSIBLE, BUT MOST OF THIS IS ALOFT FOR NOW. IF IT BECOMES MORE
PACKED IN THE LOW LEVELS A QUICK SPIN UP COULDN'T NOT BE RULED
OUT.
CONTINUED RAIN CHANCES ARE FORECAST INTO MONDAY, TUESDAY, AND
WEDNESDAY, THOUGH TEMPERATURES WILL BE COOLER AND RAIN IS
EXPECTED TO BE MOSTLY STRATIFORM. THAT BEING SAID, LONG DURATION
ACCUMULATIONS HAVE THE POTENTIAL TO BE SIZABLE, WITH 90TH
PERCENTILE 48HR TOTALS OF UP TO 2" TO 4". WHILE THIS WOULDN'T
POSE AS MUCH A THREAT FOR FLASH FLOODING, AREAL FLOODING AND
RIVER FLOODING CHANCES MAY INCREASE SHOULD THIS HIGH-END
POTENTIAL BE REALIZED. THE PRIMARY WAY TO REALIZE HIGH END
POTENTIAL WOULD BE TO BE POSITIONED IMMEDIATELY NORTH OF THE
STATIONARY BOUNDARY WITH OVERRUNNING AND/OR ON THE NORTHWEST
SIDE OF A DEVELOPING COASTAL LOW. SHOULD THE STATIONARY BOUNDARY
BE TOO FAR SOUTH OR THE COASTAL LOW TO FAR EAST, THESE THREATS
WOULD NOT BE REALIZED. THESE SCENARIOS WILL NEED TO BE
MONITORED THROUGH THE WEEKEND AND INTO NEXT WEEK.
AVIATION /00Z SATURDAY THROUGH WEDNESDAY/
VFR PREVAILS THROUGH THE TAF WINDOW AS THE RULE. THE EXCEPTION
COULD BE FOG DEVELOPMENT FAVORED AT MGW EARLY TOMORROW MORNING.
DIURNAL CLOUDS HAVE DISSIPATED WITH THE LOSS OF HEATING. LARGELY
CLEAR SKIES CONTINUE UNTIL BROKEN MID-LEVEL DECKS BEGIN TO MOVE
IN AHEAD OF SATURDAY'S SHORTWAVE. LIGHT WINDS GRADUALLY VEER
FROM NORTHERLY TO EASTERLY OVERNIGHT INTO SATURDAY MORNING.
OUTLOOK... RESTRICTIONS ARE LIKELY TO RETURN SATURDAY NIGHT INTO
SUNDAY MORNING WITH AN INCREASED CHANCE FOR SHOWERS AND
THUNDERSTORMS ASSOCIATED WITH AN APPROACHING DISTURBANCE.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...MILCAREK
AVIATION...CERMAK/AK
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