818
FOUS30 KWBC 150027
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
827 PM EDT SUN SEP 14 2025
DAY 1
VALID 01Z MON SEP 15 2025 - 12Z MON SEP 15 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN THE CENTRAL
DAKOTAS...
..NORTHERN PLAINS
A NORTHWARD-MOVING UPPER LEVEL LOW BRINGS A SOUTHERLY FLOW REGIME
ACROSS THE NORTHERN PLAINS, WHICH COMES ALONG WITH AMPLE MOISTURE
-- PW ANOMALIES +2 TO +3 SIGMA. 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. FEW CHANGES WERE MADE TO THE
01Z UPDATE FROM THE 16Z UPDATE, WHICH RESEMBLES THE EARLIER 09Z
ISSUANCE.
..CENTRAL AND SOUTHERN PLAINS
THUNDERSTORMS IN THIS REGION SHOULD HANG ON FOR A FEW MORE HOURS.
AS THEIR COVERAGE IS ISOLATED TO WIDELY SCATTERED, KEPT THE
ASSOCIATED RISK AS MARGINAL. LITTLE CHANGE WAS MADE TO CONTINUITY
HERE.
ROTH
DAY 2
VALID 12Z MON SEP 15 2025 - 12Z TUE SEP 16 2025
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
EASTERN NORTH CAROLINA AND SOUTHEASTERN VIRGINIA...
AS A MID-TO-UPPER LEVEL LOW TAKES SHAPE OVER THE SOUTHEAST, THE
SURFACE LOW OFF OF THE SOUTHEAST COAST IS EXPECTED TO DEEPEN AND TRACK
NORTH AND THEN NORTHWEST TOWARD THE OUTER BANKS BY TUESDAY
MORNING. MODELS CONTINUE TO MOVE INTO BETTER AGREEMENT WITH THE
OVERALL TRACK OF THE SYSTEM, BUT SHOW SIGNIFICANT SPREAD WITH
RESPECT TO QPF. THE GENERAL CONSENSUS OF THE 12Z HREF GUIDANCE
KEEPS THE HEAVIEST PRECIPITATION CONFINED OVER EASTERN NORTH
CAROLINA AND FAR SOUTHEASTERN VIRGINIA, WHILE SOME OTHER MODELS,
MOST NOTABLY THE CANADIAN REGIONAL AND GLOBAL, SPREAD HEAVY
AMOUNTS FARTHER WEST, CLOSER TO THE MID-LEVEL CENTER. MODELS
GENERALLY AGREE THAT EASTERN NORTH CAROLINA AND SOUTHEASTERN
VIRGINIA WILL BECOME THE FOCUS FOR A STRONG EASTERLY LOW LEVEL JET
AND DEEPENING MOISTURE (PWS INCREASING TO 1.5-2 INCHES). WHILE THE
PRIMARY SOIL TYPES AND PRE-EXISTING DRY CONDITIONS MAY INITIALLY
LIMIT THE THREAT FOR RUNOFF CONCERNS, EMBEDDED CONVECTION MAY RAISE
RAINFALL RATES, RESULTING IN AT LEAST ISOLATED EXCESSIVE RUNOFF,
ESPECIALLY ACROSS URBANIZED AREAS. THEREFORE, A MARGINAL RISK WAS
INTRODUCED. THE HIGHLIGHTED AREA LEANS CLOSER TO THE 12Z HREF
CONSENSUS AND ITS HIGHER NEIGHBORHOOD PROBABILITIES. PROBABILITIES
OF AMOUNTS EXCEEDING 3 INCHES ARE ABOVE 50 PERCENT WITHIN MUCH OF
THE RISK AREA. GIVEN THE NOTED UNCERTAINTY, ADJUSTMENTS INCLUDING
AN INCREASE IN CATEGORY CANNOT BE RULED OUT.
PEREIRA
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/NORTH CAROLINA...
20Z UPDATE...
BROADENED THE MARGINAL RISK OVER SOUTHEASTERN VIRGINIA TO ALSO
INCLUDE PORTIONS OF NORTHEASTERN NORTH CAROLINA. SOME MODELS,
INCLUDING THE ECMWF, SHOW ADDITIONAL HEAVY AMOUNTS CARRYING OVER
INTO DAY 3 ACROSS THE REGION -- WHICH GIVEN THE ANTICIPATION OF
HEAVY AMOUNTS IMPACTING THIS REGION ON DAY 3, MAY PROLONG RUNOFF
CONCERNS. AS ON DAY 2, CONTINUED TO LEAN TOWARD THE MORE EASTERLY
GUIDANCE. HOWEVER, GIVEN THE UNCERTAINTY, ADDITIONAL ADJUSTMENTS
MAY BE FORTHCOMING.
FURTHER WEST, THE UPPER TROUGH MOVING ACROSS THE ROCKIES HAS
TRENDED SLOWER. THE GENERAL CONSENSUS OF THE MODELS SHOWS THE AXIS
OF ASSOCIATED PRECIPITATION SHIFTING FURTHER WEST, WITH MANY OF THE
MODELS SHOWING THEIR HEAVIEST AMOUNTS CENTERED OVER THE FLOOD-RESISTENT
NEBRASKA SANDHILLS. THEREFORE, SHIFTED THE PREVIOUS OUTLOOK
FURTHER WEST, CONFINING THE FOOTPRINT TO THE MORE SENSITIVE AREAS
FROM THE SOUTHERN NEBRASKA PANHANDLE TO NORTHWESTERN KANSAS.
PEREIRA
PREVIOUS DISCUSSION...
..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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