510
FOUS30 KWBC 242008
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
408 PM EDT FRI OCT 24 2025
DAY 1
VALID 16Z FRI OCT 24 2025 - 12Z SAT OCT 25 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN PLAINS...
..16Z UPDATE
THE MARGINAL AND SLIGHT RISK AREAS WERE EXPANDED SLIGHTLY OVER
PORTIONS OF TEXAS AND OKLAHOMA FOR THIS AFTERNOON AND EVENING'S
HEAVY RAINFALL THREAT. THE OVERALL SETUP DESCRIBED IN THE PREVIOUS
DISCUSSION REMAINS MOSTLY IN PLACE WITH A LINE OF CONVECTION MOVING
THROUGH A FAVORABLE ENVIRONMENT FOR PRODUCING HEAVY TO EXCESSIVE
RAINFALL. THERE'S AN INCREASING RISK (AT LEAST 25% CHANCE) OF
EXCESSIVE RAINFALL OVER PORTIONS OF THE DALLAS FORT- WORTH METRO
AREA DUE, IN PART, TO ANTECEDENT CONDITIONS FROM RECENT RAINFALL
(1-3" OVER THE PAST 12 HOURS). HREF 40KM NEIGHBORHOOD PROBABILITIES
OF EXCEEDING 3" ARE BETWEEN 20-50%, WHICH SUPPORTS THE DRAWN 25%
AREA. ERO FIRST GUESS FIELDS BETWEEN 25-40% ACROSS MUCH OF THE
SLIGHT RISK AREA ALSO SUPPORT INCREASED CONFIDENCE IN THE POTENTIAL
FOR FLASH FLOODING.
THE MARGINAL RISK AREA OVER THE NORTHWEST COAST REMAINS MOSTLY
UNCHANGED. THE STRONGEST IVT REMAINS LIKELY TO BE DIRECTED AT
PORTIONS OF THE PACIFIC NORTHWEST AND GRADUALLY WEAKEN AS IT WORKS
ITS WAY SOUTH ALONG A COLD FRONT INTO NORTHERN CALIFORNIA.
KEBEDE
..PREVIOUS DISCUSSION
THE LARGE SCALE PATTERN STILL FAVORS AN ACTIVE DAY FOR CONVECTION
THROUGH EARLY SATURDAY MORNING OVER PORTIONS OF THE SOUTHERN
PLAINS AS STRONG HEIGHT FALLS ASSOCIATED WITH AN UPSTREAM SOUTHWEST
U.S. CLOSED LOW/TROUGH EJECTS OUT INTO THE HIGH PLAINS ALONG WITH
A COLD FRONT. LOW LEVEL MOISTURE AND STABILITY WILL BE IN PLACE
ACROSS MUCH OF CENTRAL AND NORTHERN TX AS THE NOSE OF A 30 TO 40+
KTS SOUTHERLY LOW-LEVEL JET RIDES UP INTO THE RED RIVER VALLEY
REGION. THE EXPECTATION IS THAT ORGANIZED CONVECTION SHOULD DEVELOP
INITIALLY ACROSS AREAS OF WEST TX AND ADVANCE EAST BY LATER IN THE
AFTERNOON/EVENING WHICH WILL BE CAPABLE OF PRODUCING HIGH RAINFALL
RATES UPWARDS OF 2 INCHES/HOUR WITH THE STRONGER CELLS. HOWEVER,
THE ORGANIZED NATURE OF THE CONVECTION SUGGESTS SOME FORWARD
PROPAGATION POTENTIAL THAT COULD MITIGATE THE OVERALL STORM TOTAL
AMOUNTS. IN FACT, MOST OF THE GUIDANCE SUPPORTS A FAIRLY WELL-
ORGANIZED MCS EVOLUTION INTO SOUTHEAST TX AND NEAR THE NORTHWEST
GULF COAST REGION BY EARLY SATURDAY MORNING. MAINTAINED THE SLIGHT
RISK AREA WITH ONLY SOME MINOR ADJUSTMENTS TO THE WESTERN AND
NORTHERN PERIPHERY OF THE AREA TO ACCOUNT FOR WHERE THE AXIS OF
BETTER INSTABILITY SHOULD BE ALONG WITH CORRIDORS OF CONVECTIVE
INITIATION. THIS IS ALSO IN BETTER ALIGNMENT WITH THE CONSENSUS OF
THE 24/00Z HREF AND 23/18Z REFS GUIDANCE. SCATTERED AREAS OF FLASH
FLOODING, ESPECIALLY FOR THE MORE URBANIZED LOCATIONS, WILL BE A
CONCERN.
..PACIFIC NORTHWEST INTO NORTHWEST CALIFORNIA
ONLY SMALL LOCALIZED ADJUSTMENTS WERE MADE TO THE MARGINAL RISK
AREA AS A MODEST ATMOSPHERIC RIVER (AR) PUSHES ACROSS THE COASTAL
AND CASCADE RANGES OF WASHINGTON AND OREGON. THE PLUME OF DEEPEST
MOISTURE AND ASSOCIATED RAINFALL WILL SLIDE SOUTHWARD WITH RESPECT
TO THE COASTLINE INTO NORTHWEST CALIFORNIA BY EARLY SATURDAY
MORNING. STRONG HEIGHT FALLS AND PRECIPITABLE WATER VALUES OVER 1
INCH TOTAL PWATS INTO THE COASTAL RANGE SET UP THE POTENTIAL FOR
RAINFALL RATES OF 0.75 INCHES TO 1 INCH THROUGH THE COLUMBIA VALLEY
INTO CENTRAL WA WITH HIGHER RAINFALL RATES REMAINING OFF- SHORE.
WINDS OF 45-50KTS THROUGH 850-700MB WILL RESULT IN PEAK IVT VALUES
OF 700-750 KG/M/S. STILL AGREE THAT THE DURATION OF HEAVIEST
RAINFALL IS GOING TO BE VERY LIMITED GIVEN THE STRENGTH OF THE
HEIGHT FALLS AND FORWARD PROPAGATION OF THE COLD FRONT. QPF SIGNALS
REMAIN AT THE 2-4" RANGE WITHIN THE FAVORED SOUTHWEST FACING
OROGRAPHY WITH AN OCCASIONAL RATE UP TO .5" THOUGH FLEETING; ALL IN
LINE WITH A BROAD MARGINAL RISK OF EXCESSIVE RAINFALL.
BANN
DAY 2
VALID 12Z SAT OCT 25 2025 - 12Z SUN OCT 26 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST TEXAS INTO SOUTHERN ARKANSAS AND WESTERN LOUISIANA...
..2030Z UPDATE
THE SLIGHT RISK AREA OVER THE SOUTH WAS EXPANDED EASTWARD INTO
PORTIONS OF SOUTHEASTERN LOUISIANA AND WESTERN MISSISSIPPI, WHERE A
NOTABLE NEIGHBORHOOD PROBABILITY SIGNAL OF EXCEEDING 3" EXISTS. THE
HIGH QPF SIGNAL SHIFTED SOUTH AND EAST SINCE THE PREVIOUS ISSUANCE
AS A RESULT. A ROUND OF CONVECTION IN THE MORNING COULD PRIME
SOILS FOR ANOTHER ROUND IN THE EVENING, WHICH WOULD CARRY HIGHER
RAIN RATES DUE TO A RECHARGED INSTABILITY AND MOISTURE PLUME. ERO
FIRST GUESS FIELDS INDICATE A 15-40% PROBABILITY OF ARI EXCEEDANCE
OR UFVS-VERIFIED FLASH FLOODING ACROSS MUCH OF THE HIGHLIGHTED
AREAS.
THE MARGINAL RISK OVER THE NORTHWEST REMAINS IN PLACE WITHOUT ANY
CHANGES DUE TO A LACK OF SIGNIFICANT CHANGES IN THE QPF GUIDANCE.
THE HEAVIEST RAIN ASSOCIATED WITH AN ATMOSPHERIC RIVER EVENT WILL
OCCUR LATE SATURDAY MORNING INTO THE AFTERNOON.
KEBEDE
..PREVIOUS DISCUSSION
MULTIPLE ROUNDS OF HEAVY SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
IMPACT THE BROADER NORTHWEST GULF COAST REGION THIS PERIOD, WITH
ONE INITIAL AXIS OF CONVECTION LIKELY ONGOING SATURDAY MORNING
ACROSS AREAS OF SOUTHEAST TO EAST-CENTRAL TX AND ADVANCING ACROSS
WESTERN LOUISIANA AND SOUTHERN ARKANSAS. THIS WILL BE THE
CARRYOVER OF ORGANIZED CONVECTION FROM THE DAY 1 PERIOD WHICH
SHOULD BE INTERACTING AT LEAST INITIALLY WITH A 40+ KT SOUTHERLY
LOW-LEVEL JET OFF THE WESTERN GULF. PRECIPITABLE WATER VALUES AT OR
ABOVE 1.75 INCHES AND MUCAPE VALUES LOCALLY OF 2000+ J/KG WILL
SUPPORT HIGH RAINFALL RATES POTENTIALLY EXCEEDING 2 INCHES/HOUR
WITH THE STRONGER STORMS.
THE ARRIVAL OF AN UPPER- LEVEL JET STREAK IN THE SUBTROPICAL
STREAM COMBINED WITH THE INTERACTION WITH THE SOUTHERN STREAM
CLOSED LOW/TROUGH AXIS CROSSING THE SOUTHERN PLAINS WILL FAVOR A
RENEWED CONVECTIVE OUTBREAK ACROSS AREAS OF EASTERN TEXAS THROUGH
PORTIONS OF WESTERN AND SOUTHERN LOUISIANA SATURDAY AFTERNOON
THROUGH EARLY SUNDAY. EVEN THOUGH ANTECEDENT CONDITIONS ARE QUITE
DRY, THE CONCERN FOR MULTIPLE ROUNDS OF CONVECTION WHICH COMBINED
MAY YIELD SOME 3 TO 5+ INCH TOTALS, WILL PROBABLY BE ENOUGH TO
SUPPORT A THREAT FOR SCATTERED AREAS OF FLASH FLOODING. THE MORE
SENSITIVE URBANIZED LOCATIONS WILL BE AT GREATEST RISK FOR IMPACTS.
FOR THIS UPDATE, THE SLIGHT RISK AREA WAS EXPANDED GIVEN THE
FOOTPRINT OF 2+ INCH RAINFALL AMOUNTS WITHIN A BROADENED REGION OF
INSTABILITY SHOWN BY THE MODELS. THIS IS ALSO CONSISTENT WITH THE
LATEST DETERMINISTIC QPF FROM WPC.
..PACIFIC NORTHWEST AND NORTHWEST CALIFORNIA
MULTIPLE ROUNDS OF MOISTURE TRANSPORT INTO THE COASTAL RANGES WILL
CONTINUE FOR THE PERIOD AS ATMOSPHERIC RIVER ACTIVITY CONTINUES.
LOCALLY A FEW ADDITIONAL INCHES OF RAIN WILL BE POSSIBLE FOR THE
WINDWARD SLOPES OF THE TERRAIN, BUT GIVEN THE EARLY-SEASON AND
RELATIVELY MODEST NATURE OF THIS ATMOSPHERIC RIVER ACTIVITY, ANY
FLOODING CONCERNS ARE EXPECTED TO BE ISOLATED AT BEST. THEREFORE,
THE MARGINAL RISK AREA IS MAINTAINED WITH NO CHANGES FOR THIS
UPDATE CYCLE.
BANN
DAY 3
VALID 12Z SUN OCT 26 2025 - 12Z MON OCT 27 2025
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID-AND LOWER-MISSISSIPPI VALLEY AND ALONG THE PACIFIC
NORTHWEST COAST...
..2030Z UPDATE
SEPARATE AXES OF PRECIPITATION WILL IMPACT DIFFERENT PARTS OF THE
MARGINAL RISK AREA ON SUNDAY. CONVECTION ASSOCIATED WITH THE MID-
LEVEL LOW WILL SPREAD ACROSS THE TENNESSEE VALLEY GENERATING
QUARTER TO HALF INCH RAIN RATES WITHIN A WEAKLY DESTABILIZED
ENVIRONMENT (200-400J/KG MUCAPE). ANOTHER LINE OF STORMS WILL
SPREAD ACROSS THE CENTRAL GULF COAST BENEATH RIPPLES OF SHORTWAVE
ENERGY BREAKING AWAY FROM THE PARENT MID-LEVEL LOW TO ITS NORTH.
PWATS OF 1-2" MAY SUPPORT ANY ISOLATED INSTANCES OF EXCESSIVE
RAINFALL/FLASH FLOODING WITHIN THE MARGINAL RISK AREA. MODELS ARE
TRENDING TOWARD A HIGHER QPF SOLUTION ALONG THE CENTRAL GULF COAST,
BUT THERE'S STILL ENOUGH UNCERTAINTY ON THE EXACT PLACEMENT (READ:
EURO OUTLIER) TO MITIGATE ANY UPGRADES AT THIS TIME.
KEBEDE
..PREVIOUS DISCUSSION
MAINTAINED A MARGINAL RISK AREA ACROSS PORTIONS OF THE SOUTHERN AND
MIDDLE MISSISSIPPI VALLEY. THE RISK ACROSS THE SOUTHERN SHOULD
DIMINISH ONCE A COLD FRONT PASSES THROUGH THE AREA EARLY IN THE
PERIOD AND THE DEEPER MOISTURE/INSTABILITY GET SHUNTED EASTWARD.
FARTHER NORTH WHERE THE MOISTURE IS NOT AS DEEP...CONCERN IS MORE
FROM MID-LEVEL FRONTOGENESIS AND UPPER LEVEL DIVERGENCE LEADING TO
LOCALLY ENHANCED RAINFALL RATES WHERE ANTECEDENT CONDITIONS HAVE
BEEN SOMEWHAT WETTER THAN OTHER LOCATIONS. THERE IS PLENTY
UNCERTAINTY AS TO WHETHER THERE WILL BE A SECOND ROUND OF STORMS
CAPABLE OF PRODUCING LOCALLY HEAVY RAINFALL...SO OVERALL CONFIDENCE
IS BELOW AVERAGE WHICH PRECLUDES ANYTHING HIGHER THAN A MARGINAL
RISK.
BANN
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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