136
FOUS30 KWBC 221550
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1150 AM EDT SUN MAR 22 2026
DAY 1
VALID 16Z SUN MAR 22 2026 - 12Z MON MAR 23 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE UPPER
OHIO VALLEY TO THE NEW YORK CITY METRO...
..16Z UPDATE
FORECAST REMAINS ON TRACK FOR ISOLATED FLASH FLOODING POTENTIAL
FROM THE OHIO VALLEY TO THE NORTHERN MID-ATLANTIC/NORTHEAST AS
THUNDERSTORMS FORM AND TRACK ALONG AN APPROACHING COLD FRONT
BEGINNING THIS AFTERNOON. 12Z CAMS CONTINUE TO HIGHLIGHT THE BEST
ENVIRONMENT FOR TRAINING THUNDERSTORMS AND LOCALIZED RAINFALL
TOTALS UP TO 2 INCHES (20-40% CHANCES PER THE 12Z HREF) ACROSS
CENTRAL/SOUTHWEST PA THROUGH TONIGHT, BUT WITH MOST LOCATIONS
WITHIN THE MRGL RISK RECEIVING LESS THAN AN INCH OF RAIN. STEEP
MID-LEVEL LAPSE RATES AND LIMITED LOW-LEVEL MOISTURE WILL LEAD TO
THE PRESENCE OF HAIL IN MANY OF THE STRONGER UPDRAFTS, WHICH COULD
ACTUALLY FURTHER LIMIT IMPACTS ASSOCIATED FROM HEAVY RAIN.
SNELL
PREVIOUS DISCUSSION...
A STRONG COLD FRONT, SUPPORTED BY A PASSING UPPER LEVEL SHORTWAVE,
WILL PRESS SOUTHWARD FROM THE GREAT LAKES TOWARDS THE UPPER OHIO
VALLEY AND THE MID-ATLANTIC. THE WARM AIR MASS AHEAD OF THE FRONT
IS CHARACTERIZED BY DEW POINTS IN THE LOWER 60S ACROSS THE OHIO
VALLEY AND UPPER 50S ACROSS THE MID-ATLANTIC. THESE ARE HARDLY
GREAT AMOUNTS OF MOISTURE. NONETHELESS, ESPECIALLY OVER THE OHIO
VALLEY, INSTABILITY WILL INCREASE SUNDAY AFTERNOON TO BETWEEN 1,000
AND 2,000 J/KG. THIS WILL BE ENOUGH TO SUPPORT WIDESPREAD
THUNDERSTORM DEVELOPMENT AHEAD OF THE FRONT. THE FLOW OF WARM AIR
WILL BE OUT OF THE WSW, ESSENTIALLY PARALLEL TO THE FRONT. THIS
WILL SUPPORT CELLS WITHIN THE SSE-WARD MOVING LINE MOVING EAST,
ALLOWING FOR SOME OPPORTUNITY FOR SOME TRAINING. THE COMBINATION OF
BETTER UPPER LEVEL SUPPORT FROM THE AFOREMENTIONED SHORTWAVE,
GREATER INSTABILITY, AND AVAILABLE MOISTURE WILL BEGIN TO COUNTER
THE MUCH DRIER-THAN-NORMAL SOILS AND RATHER FAST MOVEMENT OF THE
COLD FRONT. ORGANIZED CONVECTION WILL BREAK OUT ACROSS PENNSYLVANIA
IN THE LATE AFTERNOON, THEN "ZIP" SOUTHWESTWARD ACROSS THE UPPER
OHIO VALLEY DURING THE EVENING, WITH STORMS PERSISTING WELL INTO
THE OVERNIGHT HOURS. THE INHERITED MARGINAL RISK AREA WAS EXPANDED
SOUTH AND WEST TO INCLUDE MORE OF SOUTHEAST OHIO AND NORTHERN WEST
VIRGINIA, WHERE THE THREAT FOR TRAINING STORMS COULD RESULT IN
ISOLATED INSTANCES OF FLASH FLOODING.
FURTHER EAST, ACROSS MUCH OF PENNSYLVANIA, WETTER-THAN-NORMAL
SOILS FROM RECENT RAINS COULD SUPPORT ENOUGH RAINFALL FROM STORMS
TO RESULT IN ISOLATED INSTANCES OF FLASH FLOODING. EAST OF THE
APPALACHIANS, HOWEVER, INSTABILITY RAPIDLY DECREASES THE CLOSER TO
THE OCEAN YOU GO. THIS WILL RESULT IN DECREASING RAINFALL RATES FOR
ANY STORMS THAT MOVE EAST OFF THE MOUNTAINS. THE FRONT WILL ALSO
BE SLOWER TO MOVE SOUTH THAN THE SAME FRONT FURTHER EAST. THUS,
WHILE ANY RAIN RATES FROM MOSTLY STRATIFORM PRECIPITATION WILL BE
LOW, A LONGER PERIOD OF TIME OF RAIN ALONG WITH WETTER SOILS COULD
ALSO PROVE ENOUGH TO RESULT IN ISOLATED FLASH FLOODING. THE
INHERITED MARGINAL RISK FROM CENTRAL PENNSYLVANIA EAST TO THE NEW
YORK CITY METRO IS UNCHANGED FROM INHERITED.
WEGMAN
DAY 2
VALID 12Z MON MAR 23 2026 - 12Z TUE MAR 24 2026
THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS LESS
THAN 5 PERCENT.
WEGMAN
DAY 3
VALID 12Z TUE MAR 24 2026 - 12Z WED MAR 25 2026
THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS LESS
THAN 5 PERCENT.
PORTIONS OF WESTERN WASHINGTON STATE, SPECIFICALLY THE OLYMPIC AND
CASCADES MOUNTAINS, WILL BE MONITORED FOR A POTENTIAL MARGINAL
RISK INTRODUCTION WITH FUTURE UPDATES. A FRONT MOVING INTO THE AREA
WILL MAKE FOR A BRIEF TIME (12-HOUR) OF HEAVY RAIN TUESDAY MORNING.
WHILE THIS WOULD NORMALLY NOT BE NEARLY LONG ENOUGH TO RESULT IN
FLASH FLOODING, GIVEN THERE IS ONGOING RIVER FLOODING FROM THE LAST
EVENT, AND BOTH SOILS AND STREAMS/CREEKS ARE FULL, THIS ROUND OF
HEAVY RAIN MAY BE ENOUGH TO CAUSE RENEWED ISOLATED FLASH FLOODING.
WEGMAN
DAY 1 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/94EPOINTS.TXT
DAY 2 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/98EPOINTS.TXT
DAY 3 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/99EPOINTS.TXT
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