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FOUS30 KWBC 140824
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
424 AM EDT SUN SEP 14 2025
DAY 1
VALID 12Z SUN SEP 14 2025 - 12Z MON SEP 15 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN THE WESTERN DAKOTAS...
..NORTHERN PLAINS
UPPER TROUGH EXITING THE ROCKIES HAS SPLIT OFF ITS SOUTHERN
PORTION INTO AN UPPER LOW THAT WILL MOVE ONTO THE HIGH PLAINS LATER
THIS MORNING. SOUTHERLY FLOW WILL CONTINUE ACROSS THE NORTHERN
PLAINS ALONG WITH AMPLE MOISTURE -- PW ANOMALIES +2 TO +3 SIGMA --
AS A SURFACE LOW OVER SD MOVES NORTHWARD LATER THIS AFTERNOON.
CONVERGENT FLOW TOWARD THE NOSE OF THE SFC-BASED INSTABILITY
GRADIENT JUST TO THE EAST IS EXPECTED TO PROMOTE SOME SOUTH-TO-
NORTH CONVECTION THAT MAY OVERLAP AREAS THAT SAW A FEW INCHES OF
RAIN ON SATURDAY. MAINTAINED THE SLIGHT RISK OUTLINE HERE WITH A
MARGINAL RISK BUFFER EXTENDING TO THE SOUTH TO THE EDGE OF THE SAND
HILLS.
..CENTRAL AND SOUTHERN PLAINS
SPLIT THE LONGER MARGINAL RISK AREA FROM THE PREVIOUS FORECAST
INTO ITS OWN ENTITY AND EXTENDED IT EVEN FARTHER SOUTHWARD TO THE
MEXICAN BORDER TO ACCOUNT FOR ANOTHER TICK UP IN EXPECTED
CONVECTION FROM KS SOUTHWARD TO TX. STORMS SHOULD FIRE ALONG AND
AHEAD OF A LOW-LEVEL CONFLUENCE AXIS AND WITHIN A STRIPE OF DEEPER
MOISTURE. SOME OF THESE AREAS IN W TX SAW A COUPLE/FEW INCHES OF
RAIN ON SATURDAY AND FFG VALUES ARE LOWER. SOME MODELS DO INDICATE
THE POTENTIAL FOR SLOW-MOVING OR BACKBUILDING CELLS, RESULTING IN
LOCALLY HEAVY AMOUNTS AND PERHAPS ISOLATED FLASH FLOODING CONCERNS.
FRACASSO
DAY 2
VALID 12Z MON SEP 15 2025 - 12Z TUE SEP 16 2025
THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS LESS
THAN 5 PERCENT.
FRACASSO
DAY 3
VALID 12Z TUE SEP 16 2025 - 12Z WED SEP 17 2025
...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL IN SOUTHERN NEW
MEXICO, THE CENTRAL PLAINS, AND COASTAL VIRGINIA...
..SOUTHERN NEW MEXICO
MOISTURE WILL START TO NUDGE UPWARD OVER SOUTHERN NM (THOUGH MUCH
MORE WELL WEST OF THERE) WITH SOME AFTERNOON INSTABILITY AND
EXPECTED ISOLATED CONVECTION, MAINLY OVER THE MOUNTAINS CLOSE TO
THE MEXICAN BORDER. LOW-END MARGINAL RISK IS OUTLINED HERE THOUGH
ACTIVITY SHOULD BE RATHER ISOLATED.
..CENTRAL PLAINS
POSITIVELY-TILTED TROUGH OVER THE NORTHERN ROCKIES WILL MOVE
EASTWARD TO THE HIGH PLAINS TUESDAY AFTERNOON. BROAD WESTERLY MID-
LEVEL FLOW AMID INCREASING MOISTURE WILL HELP FIRE OFF SOME STORMS
OVER AT LEAST NE NEAR THE BETTER FORCING BUT ALSO SOUTHWARD INTO
KS. A MARGINAL RISK IS OUTLINED HERE FOR AN ISOLATED FLASH FLOOD
THREAT.
..COASTAL VIRGINIA
OVER THE PAST COUPLE OF DAYS, THE MODELS HAVE TRENDED TOWARD
BRINGING IN AN AREA OF LOW PRESSURE NEAR THE OUTER BANKS TUESDAY
MORNING OR SO. RAIN SHOULD SPREAD INLAND ON MONDAY WITH ADDITIONAL
AND PERHAPS HEAVIER RAIN ON WEDNESDAY. THIS AREA HAS BEEN RATHER
DRY RECENTLY AND RAIN RATES MAY NOT BE ALL THAT HIGH, BUT SOME
CONVECTION-DRIVEN RAIN IS POSSIBLE DEPENDING ON THE FLAVOR OF THIS
AREA OF LOW PRESSURE. A MARGINAL RISK IS DEPICTED FOR
SOUTHEASTERN/COASTAL VIRGINIA AND FAR NORTHEASTERN NORTH CAROLINA
BUT WITH A LOT OF UNCERTAINTY IN THE RAINFALL
PATTERN/RATES/DURATION.
FRACASSO
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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