755
FOUS30 KWBC 252057
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
457 PM EDT SAT JUL 25 2026
DAY 1
VALID 16Z SAT JUL 25 2026 - 12Z SUN JUL 26 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE EASTERN
CAROLINAS AND THE SOUTHWEST...
..SOUTHEAST THROUGH THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS
DEEP MOISTURE WILL CONTINUE TO POOL ALONG AND NEAR A STALLED
FRONTAL BOUNDARY, WHICH LEADS TO PRECIPITABLE WATER VALUES REACHING
NEARLY 3 STANDARDIZED ANOMALIES ABOVE CLIMATOLOGY FOR LATE JULY
AND IN EXCESS OF THE 95TH PERCENTILE OF CLIMATOLOGY EXTENDING
EASTWARD FROM THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS TO THE
CAROLINAS. RECENT CAMS CONTINUE TO POINT TO HEAVY RAINFALL
POTENTIAL, WITH LOCALIZED 2-4 INCH TOTALS WITH HIGHER INSTANTANEOUS
RAINFALL RATES, ESPECIALLY IN THE EASTERN CAROLINAS WHERE THE
SLIGHT RISK REMAINS. REFER TO MPD 846 FOR MORE ON THE THREAT INTO
THIS AFTERNOON. TRIMMED OFF THE NORTHERN SIDE OF THE SLIGHT GIVEN
LESS INSTABILITY TO THE NORTH OF THE FRONT IN THIS ISSUANCE.
HOWEVER, DID EXPAND THE MARGINAL NORTHWARD A BIT FARTHER WEST TO
COVER THE SOUTHERN APPALACHIANS, WHERE LOCALIZED CONVECTION COULD
BE PRESENT THIS EVENING AND TONIGHT OVER AREAS WITH WETTER
ANTECEDENT CONDITIONS AND LOWER FFG.
FARTHER WEST, RECENT GUIDANCE REMAINS LESS ENTHUSIASTIC COMPARED
TO A DAY AGO REGARDING HEAVY RAINFALL IN AND AROUND ARKANSAS. WITH
THE 00Z AND 12Z CAM/HREF CYCLES BOTH LAYING OFF ON HEAVY RAIN, FELT
CONFIDENT ENOUGH TO REMOVE THE SLIGHT RISK THERE. THE 12Z HREF
DOES SHOW SOME 30-40 PERCENT PROBABILITIES OF QPF EXCEEDING FFG
NEAR THE MISSISSIPPI/WESTERN TENNESSEE BORDER THAT COULD BE A
RELATIVELY HIGHER RISK, BUT WITH TOO LOW CONFIDENCE IN IMPACTS TO
UPGRADE TO A SLIGHT THERE.
SCATTERED THUNDERSTORMS ACROSS FLORIDA COULD ALSO CAUSE LOCALIZED
HEAVY RAIN, BUT CURRENTLY CONSIDER THAT TO BE SUB-MARGINAL AS EAS
PROBABILITIES OF EXCEEDING 2 INCHES IS ONLY AROUND 10 PERCENT, AND
OVER THE EVERGLADES RATHER THAN THE MORE SENSITIVE URBAN CORRIDOR.
..SOUTHWEST
THE MONSOON WILL GET RE-INVIGORATED ACROSS THE FOUR CORNERS TODAY
WITH AN UPTICK IN COVERAGE AND INTENSITY OF RAINFALL EXPECTED IN
THE REGION. INSTABILITY COULD BE 1000-2000 J/KG WHILE PRECIPITABLE
WATER VALUES ARE FORECAST TO BE ABOVE THE 90TH PERCENTILE. AN MCV
IN THE VICINITY COULD BECOME A KEY PLAYER IN ENHANCING THE RAINFALL
WHICH LEADS TO GREATER/HIGHER RAIN RATES. CONCERN IS HEIGHTENED
GIVEN THE POSSIBILITY THAT THE HIGHER RAINFALL RATES/AMOUNTS
OVERLAPS WITH AREAS WHICH HAVE RECENTLY DEALT WITH HEAVY RAINFALL
AND WHERE SOILS WILL BE LESS CAPABLE OF HANDLING THE INFLUX OF RAIN
WATER. THE MARGINAL AND SLIGHT RISKS STILL LOOK ON TRACK AND WERE
ADJUSTED ONLY MINIMALLY FROM THE PREVIOUS ISSUANCE.
TATE/BANN
DAY 2
VALID 12Z SUN JUL 26 2026 - 12Z MON JUL 27 2026
...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL ACROSS THE FOUR
CORNERS REGION...MIDWEST...AND PORTIONS OF THE SOUTHEAST/FLORIDA...
..FOUR CORNERS STATES ONTO THE CENTRAL PLAINS
MONSOONAL FLOW FROM THE DESERT SOUTHWEST TO THE CENTRAL ROCKIES
CONTINUES INTO EARLY NEXT WEEK. ABOVE AVERAGE PRECIPITABLE WATER
VALUES AND AVAILABLE INSTABILITY WILL AGAIN SUPPORT ISOLATED TO
WIDELY SCATTERED THUNDERSTORMS CAPABLE OF PRODUCING INTENSE RAIN
RATES CAPABLE OF PRODUCING FLASH FLOODING. THERE MAY BE A GENERAL
FOCUS FOR MOISTURE/INSTABILITY AXIS TO EXTEND FARTHER NORTH THAN
SATURDAY, AND THERE IS SOME SIGNAL IN THE CAMS AND GLOBAL GUIDANCE
TO FOCUS THE GREATEST COVERAGE OF HEAVY RAIN INTO WESTERN/CENTRAL
COLORADO. WILL HOLD OFF ON ANY SLIGHT RISK UPGRADE THOUGH DUE TO
UNCERTAINTIES IN THE IMPACTS, AS WELL AS UNCERTAINTIES WITH
INSTABILITY AFTER AN ACTIVE MONSOON SATURDAY.
..UPPER MIDWEST-UPPER GREAT LAKES-OHIO VALLEY
GLOBAL, CAM, AND AI GUIDANCE CONTINUE TO SHOW CONVECTIVELY-AIDED
SHORTWAVE ACTIVITY RIDING DOWN THE TOP SIDE OF THE UPPER RIDGE AXIS
IN NORTHWEST FLOW. A NORTHWEST TO SOUTHEAST ORIENTED STATIONARY
FRONT COULD ALSO PROVIDE A CONVECTIVE FOCUS AS SLIGHTLY ABOVE
NORMAL PWS BUT VERY STRONG INSTABILITY COME IN. HOWEVER, MODELS
SHOW QUITE A BIT OF SPREAD IN POSITION OF THESE RIDGE RIDERS
ESPECIALLY FOR A SHORT RANGE FORECAST. THE LOCATION OF CONVECTION
WILL BE AFFECTED BY PLACEMENT OF UPPER LEVEL CONVERGENCE ASSOCIATED
WITH A BROAD ARCHING ANTICYCLONIC FLOW AT THE JET LEVEL. ADJUSTED
THE MARGINAL RISK TO FIT WITH A MIDDLE GROUND MODEL "CONSENSUS,"
BUT IT DOES NOT COVER ALL THE CAM AND GLOBAL MODEL SCENARIOS, SO
MAY NEED TO BE ADJUSTED FURTHER. FAST MOVEMENT WILL BE A MITIGATING
FACTOR FOR FLOODING THOUGH.
..SOUTHEAST INTO FLORIDA
ABOVE AVERAGE MOISTURE WILL CONTINUE TO FLOW INTO THE SOUTHEASTERN
U.S. INTO A QUASI-STATIONARY FRONT WITH POSSIBLE WAVES OF LOW
PRESSURE STRETCHING ACROSS GEORGIA AND SOUTH CAROLINA AT THE BASE
OF AN EASTERN U.S. TROUGH. THIS FRONT AND A SURFACE TROUGH ACROSS
FLORIDA SHOULD FOCUS THE MOISTURE FOR CONVECTION. 90+ PERCENTILE
PWS ARE PRESENT ALONG THE EASTERN COAST OF FLORIDA, WHERE URBAN
CORRIDORS CAN INCREASE SENSITIVITY TO HIGH RAINFALL RATES. A
MARGINAL RISK COVERS THE THREAT OF ISOLATED FLASH FLOODING WITH
THIS ACTIVITY.
TATE/BANN
DAY 3
VALID 12Z MON JUL 27 2026 - 12Z TUE JUL 28 2026
...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL MONDAY ACROSS
THE FOUR CORNERS STATES TO CENTRAL PLAINS AND GREAT LAKES/OHIO
VALLEY...
..FOUR CORNERS STATES INTO THE CENTRAL PLAINS
ELEVATED AMOUNTS OF MOISTURE WILL LINGER OVER THE FOUR CORNERS
REGION GIVEN A PERSISTENT MONSOON PATTERN, ALTHOUGH GUIDANCE STILL
POINTS TO A GRADUAL SOUTHWARD SHIFT IN THE PLACEMENT OF THE UPPER
HIGH CENTER. THIS MAY SLIGHTLY REDUCE THUNDERSTORM COVERAGE IN
AREAS LIKE UTAH TO THE FOUR CORNERS THEMSELVES, BUT A WEAK
SHORTWAVE LOOKS TO MOVE ACROSS COLORADO AND VICINITY MONDAY INTO
MONDAY NIGHT AND ENHANCE CONVECTION THERE AND SPREADING INTO THE
CENTRAL PLAINS OVERNIGHT. MAINTAINED A MARGINAL RISK AREA IN THE
FOUR CORNERS STATES AND EXTENDING EASTWARD INTO THE CENTRAL HIGH
PLAINS TO COVER THE ISOLATED FLASH FLOODING THREAT. PLOTS OF ECMWF
PW ANOMALY PLOTS CONTINUE TO PROVE HELPFUL IN HIGHLIGHTING AREAS OF
INCREASED CONCERN.
..GREAT LAKES AND OHIO VALLEY INTO THE NORTHEAST US
BY MONDAY A MORE POTENT SHORTWAVE WILL MOVE SOUTHEASTWARD THROUGH
THE UPPER GREAT LAKES REGION ROUNDING THE ROCKIES/HIGH PLAINS HIGH.
DIFLUENT FLOW AHEAD OF THE SHORTWAVE WILL EVENTUALLY LEAD TO THE
CONSOLIDATION/STRENGTHENING OF A LOW PRESSURE SYSTEM DURING THE
PERIOD. THIS LOW IS EXPECTED TO HELP FORCING FOR HEAVIER RAINFALL
OVER THE GREAT LAKES/OHIO VALLEY, WITH LESS MODEL SPREAD THAN THE
SUNDAY CONVECTION LIKELY DUE TO GREATER FORCING. A MARGINAL RISK
REMAINS IN PLACE, BUT CONVECTIVE ACTIVITY SHOULD BE RELATIVELY
PROGRESSIVE, WHICH IS STILL EXPECTED TO MITIGATE ANY HIGHER RISKS
OF EXCESSIVE RAINFALL.
TATE/BANN
DAY 4 AND DAY 5
VALID 12Z TUE JUL 28 2026 - 12Z THU JUL 30 2026
...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE WEST, PLAINS, & EAST...
..FOUR CORNERS STATES INTO THE CENTRAL/NORTHERN PLAINS
MONSOONAL FLOW, LIKELY TO BE ENHANCED BY GENEVIEVE MOVING OFFSHORE
BAJA CALIFORNIA, BRINGS ELEVATED MOISTURE OVER THE DESERT
SOUTHWEST THROUGH THE CENTRAL ROCKIES AND INTO THE CENTRAL AND
NORTHERN PLAINS. THE MORE SUPPRESSED RIDGE WILL ALLOW MULTIPLE
MESOSCALE/CONVECTIVELY AIDED SHORTWAVES TO PUSH OVER THE TOP/ACROSS
THE ROCKIES INTO THE PLAINS.
..CENTRAL APPALACHIANS-MID ATLANTIC THROUGH NEW ENGLAND
UPPER LEVEL JET STREAK RIDING DOWN THE NORTHEAST SIDE OF A WARM
CORE RIDGE ON TUESDAY WILL LEAD TO AMPLIFICATION OF THE LONGWAVE
TROUGH ACROSS THE EASTERN U.S. BY THE MIDDLE-LATER PART OF NEXT
WEEK, LEADING TO A DEEP LAYER, EVENTUALLY COASTAL, LOW. WHENEVER
FAVORABLE (TYPICAL) WARM- SEASON THERMODYNAMICS (DEEP- LAYER
INSTABILITY AND MOISTURE) ARE PRESENT AHEAD OF A MORE ROBUST,
COOLER-SEASON TROUGH WITH STRONG DEEP- LAYER SHEAR, CHANCES FOR
MORE WIDESPREAD CONVECTION ARE MUCH HIGHER. THOUGH A SLIGHT RISK
WAS CONTEMPLATED FROM EASTERN LONG ISLAND THROUGH SOUTHERN NEW
ENGLAND AS FAR NORTH AS PORTLAND ME WHERE A FEW PIECES OF GUIDANCE
ADVERTISE 2-4" ON DAY 5/WEDNESDAY INTO WEDNESDAY NIGHT,
COORDINATION WITH THE LOCAL FORECAST OFFICES MAINTAINED THE
MARGINAL RISK FROM CONTINUITY. SOONER OR LATER, A SLIGHT RISK WILL
PROBABLY BE NEEDED, ESPECIALLY ONCE THE EVENT MOVES INTO THE HIGH
RES (CAM) WINDOWS AND THE QPF SIGNAL BECOMES LESS VARIABLE AND MORE
ROBUST.
..SOUTHEAST
HEAVY RAINFALL IS EXPECTED ALONG THE NEW ENGLAND CYCLONE'S TRAILING
FRONT NEAR THE FL/GA BORDER. MOISTURE SHOULD BE AMPLE AND THERE
COULD BE ENOUGH EFFECTIVE BULK SHEAR FOR CONVECTIVE ORGANIZATION.
SINCE TO SOME SIGNAL SEEN IN THE MODEL GUIDANCE IN THIS REGION,
ADDED A MARGINAL RISK AREA.
ROTH
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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