088
FOUS30 KWBC 311558
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1158 AM EDT FRI JUL 31 2026
DAY 1
VALID 16Z FRI JUL 31 2026 - 12Z SAT AUG 01 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
MID TO UPPER MISSISSIPPI VALLEY, AND THE UPPER PENINSULA OF
MICHIGAN...
..CENTRAL US SYSTEM
A POTENT SHORTWAVE DIVING ACROSS THE NORTHERN PLAINS THIS MORNING
WILL DEEPEN AS IT EJECTS SOUTHEAST INTO THE UPPER MIDWEST BY
SATURDAY MORNING. THIS DEEPENING WILL CREATE AN EXTREMELY ANOMALOUS
MID-LEVEL LOW FOR LATE JULY, REFLECTED BY NAEFS HEIGHT ANOMALIES
FALLING TO BELOW THE MINIMUM CLIMATOLOGICAL VALUES AT 700MB, AND TO
BELOW THE 10TH PERCENTILE AT 500MB. AN IMPRESSIVELY DEEP SYSTEM
OVERLAPPING LATE JULY THERMODYNAMICS IS A CLEAR INDICATOR OF
EXCESSIVE RAINFALL POTENTIAL, AND THIS EVENT IS NO DIFFERENT.
AS THE MID-LEVEL LOW DIVES SOUTHEAST, IT WILL DRIVE INCREASING
DOWNSTREAM ASCENT THROUGH DIVERGENCE AND HEIGHT FALLS, WITH THE
SUBSEQUENT SURFACE LOW OCCLUDING ACROSS IOWA. WITHIN THIS
OCCLUSION (AND FARTHER DOWNSTREAM WARM SECTOR) PWS WILL CLIMB TO
1.75 TO 2.00 INCHES, ABOVE THE 90TH PERCENTILE FOR THE DATE, AND
OVERLAP WITH MUCAPE AROUND 1000 J/KG. THE ACCOMPANYING 850MB INFLOW
WILL BE LOCALLY ACCELERATED TO 30-40 KTS, DRAWING THESE PRONOUNCED
THERMODYNAMICS NORTHWARD TO SUPPORT HEAVY RAIN PRODUCTION WITHIN
THUNDERSTORMS. AT THE SAME TIME, THE ASSOCIATED THETA-E RIDGE IS
PROGGED TO LIFT CYCLONICALLY, CREATING AN IMPRESSIVE (ESPECIALLY
FOR THE END OF JULY) TROWAL WHICH WILL PIVOT ATOP THE UPPER
MIDWEST. THIS WILL NOT ONLY RESULT IN ENHANCED ELEVATED
INSTABILITY, BUT ALSO SUPPORT ADDITIONAL MOISTURE TO FUEL HEAVY
RAINFALL.
BOTH THE HREF AND REFS NEIGHBORHOOD PROBABILITIES INDICATE A 40-70%
CHANCE FOR AT LEAST HOURLY RAINFALL OF 1", AND ALTHOUGH THERE
CONTINUES TO BE SOME LATITUDINAL UNCERTAINTY TO THE PLACEMENT, THE
CONSENSUS OF THE AVAILABLE HIGH-RES CAMS IS FOR LOCALLY HEAVY RAIN
RATES WITHIN A PROGRESSIVE BAND THIS MORNING, BECOMING MORE ALIGNED
FOR TRAINING LATER TODAY. THIS IS MOST LIKELY BENEATH THE TROWAL
WHERE CORFIDI VECTORS AND MEAN 0-6KM WINDS BECOME ANTI-PARALLEL
LEADING TO BACKBUILDING/REPEATING HEAVY RAIN RATES. THE GREATEST
RISK FOR 3"/24HRS FROM THE HIGH-RES ENSEMBLES IS FROM NEAR ST.
LOUIS, MO NORTHWARD THROUGH SOUTHERN WI, WHICH IS ALSO WHERE THERE
ARE NOTABLE PROBABILITIES FOR 5"/24 HRS (30-60%), ESPECIALLY NEAR
THE QUAD CITIES OF IA. THIS IS ALSO WHERE THE CSU FIRST-GUESS ERO
FIELD IS MOST AGGRESSIVE, SO DESPITE SOME DRYNESS IN THE ANTECEDENT
SOILS, AN ELEVATED SLGT RISK IS WARRANTED FOR THIS REGION.
OTHERWISE, COSMETIC ADJUSTMENTS WERE MADE TO BOTH THE SLGT AND MRGL
RISKS ACROSS THE REGION.
..UPPER PENINSULA OF MICHIGAN
THE IMPRESSIVE SYSTEM MOVING THROUGH THE UPPER MIDWEST WILL RESULT
IN INCREASED DEFORMATION BETWEEN 700-500MB PIVOTING INTO THE UPPER
PENINSULA THIS AFTN/EVE. THIS WILL ENCOURAGE ENHANCED ASCENT ACROSS
THE REGION, DESPITE A SLOW WANE IN MUCAPE NOTED VIA THE VARIOUS
MODELS. THE ACCOMPANYING ASCENT WITHIN THIS PERSISTENT DEFORMATION
AXIS WILL SUPPORT WIDESPREAD SHOWERS AND THUNDERSTORMS TODAY, WHICH
DESPITE THE WANING INSTABILITY WILL BE FUELED BY PWS AS HIGH AS
1.5 INCHES, OR ABOVE THE 90TH CLIMATOLOGICAL PERCENTILE. THIS WILL
SUPPORT RAINFALL RATES THAT ARE PROGGED BY BOTH HREF AND REFS
NEIGHBORHOOD PROBABILITIES TO HAVE A 30-60% CHANCE OF EXCEEDING
1"/HR, WHICH WILL OCCUR WITHIN ALIGNED CORFIDI VECTORS/MEAN 0-6KM
WINDS TO SUPPORT TRAINING.
3-HR FFG ACROSS THE AREA IS GENERALLY 1.5 TO 2.5 INCHES WHICH HAS
20-40% CHANCE OF EXCEEDANCE. THIS SUGGESTS AT LEAST SCATTERED
INSTANCES OF FLASH FLOODING ARE POSSIBLE, BUT WILL BE MOST LIKELY
WHERE ANY MORE PROLONGED TRAINING CAN RESULT IN 3 INCHES (50-60%
CHANCE) TO AS MUCH AS 5 INCHES (10-20% CHANCE) OF RAIN. AFTER
COORDINATION WITH WFO MQT, A SLGT RISK WAS ADDED FOR THE INCREASED
EXCESSIVE RAINFALL POTENTIAL TODAY AND TONIGHT.
..NORTHERN FLORIDA THROUGH THE CENTRAL GULF COAST
ROBUST LATE-JULY THERMODYNAMICS CHARACTERIZED BY PWS OF 2-2.25
INCHES AND MUCAPE ABOVE 2000 J/KG WILL SPREAD ACROSS THE AREA TODAY
AND TONIGHT AHEAD OF A QUASI-STATIONARY FRONT. THIS WILL LIKELY
RESULT IN TWO PERIODS OF CONVECTION CAPABLE OF PRODUCING HEAVY
RAINFALL.
THE FIRST WILL BE DURING PEAK HEATING WHEN AIRMASS
THUNDERSTORMS WILL DEVELOP, AIDED BY A MODEST VORTICITY IMPULSE
DIGGING INTO MS/AL AROUND THE LARGE MID-LEVEL RIDGE TO THE WEST.
WEAK SHEAR (LESS THAN 20 KTS) DURING THIS TIME SUGGESTS STORMS THAT
DEVELOP WILL BE GENERALLY OF THE PULSE VARIETY WITH LIMITED
ORGANIZATION AND LIFESPANS, BUT STORM MERGERS, BOUNDARY
COLLISIONS, AND ANY LOCALLY ENHANCED ASCENT IN THE VICINITY OF THIS
SHORTWAVE COULD INCREASE THE OVERAGE AND INTENSITY OF STORMS DURING
THE AFTN/EVE.
THESE STORMS SHOULD WANE WITH CONVECTIVE OVERTURNING DURING THE
EVENING, BUT A SECONDARY SIGNAL HAS SHOWN UP IN THE GUIDANCE FOR
LATE TONIGHT INTO EARLY SATURDAY, ESPECIALLY ACROSS THE FLORIDA
PANHANDLE AND INTO THE BIG BEND AREA. HERE, THE AFOREMENTIONED
SHORTWAVE WILL SLOW WITHIN AN AREA OF THICKNESS DIFFLUENCE, LEADING
TO A LONGER PERIOD OF ENHANCED SYNOPTIC LIFT AIDED BY MODEST JET-
LEVEL DIFFLUENCE. THIS ASCENT ACTING UPON ANY RESIDUAL BOUNDARIES
AND THE LAND BREEZE COULD REIGNITE THUNDERSTORMS AS THE LLJ
ATTEMPTS TO BACK SUBTLY MORE TO THE WSW FROM W AS THE FRONT
APPROACHES, DRAWING EVEN MORE IMPRESSIVE PWS ALONG THE COAST.
DURING THIS TIME, CORFIDI VECTORS ARE PROGGED TO COLLAPSE TO 5 KTS
OR LESS AND BECOME INCREASINGLY ANTI-PARALLEL TO THE MEAN WIND
SUGGESTING SOME GREATER BACKBUILDING/TRAINING POTENTIAL WITH RAIN
RATES POTENTIALLY REACHING 3"/HR (10-20% CHANCE). BOTH THE HREF AND
REFS INDICATE A 20-40% CHANCE FOR 5" OF RAINFALL FROM THIS
NOCTURNAL EVENT, BUT THE DETERMINISTIC MODELS ARE QUITE DIFFERENT
IN THE COVERAGE AND PLACEMENT. AT THIS TIME, AFTER COORDINATION
WITH WFO TAE, THE MRGL RISK WAS LEFT UNCHANGED FOR THIS AREA, BUT
AN UPGRADE TO A TARGETED SLGT RISK MAY BE NEEDED WITH LATER
UPDATES, WITH THE SLGT POTENTIALLY EXTENDING (OR BEING MORE NEEDED)
THROUGH D2.
..FOUR CORNERS STATES INTO THE SOUTHERN-CENTRAL HIGH PLAINS
THE MONSOON RIDGE WILL GET SUPPRESSED TO THE SOUTH AND WEST IN
RESPONSE TO THE POTENT SYSTEM MOVING THROUGH THE PLAINS/MIDWEST,
WITH A SECONDARY PIECE OF VORTICITY ENERGY DROPPING ACROSS THE
SOUTHERN HIGH PLAINS INTO THE TEXAS PANHANDLE. THIS WILL HELP PUSH
A COLD FRONT THROUGH THE SOUTHERN PLAINS AND BANK AGAINST THE
TERRAIN OF NEW MEXICO LATER THIS EVENING. THE OVERLAPPING ASCENT
FROM THE COLD FRONT AND SHORTWAVE WILL ACT UPON FAVORABLE
THERMODYNAMICS AS A RIBBON OF PWS ABOVE 1.5 INCHES AND POOLED
MUCAPE OF 1000-1500 J/KG GET DRAWN WESTWARD AHEAD OF THE FRONT.
COVERAGE OF MONSOONAL THUNDERSTORMS MAY BE SOMEWHAT LESS THAN
PREVIOUS DAYS TODAY DUE TO THE RE-CENTEREING OF THE RIDGE. BUT AT
LEAST SCATTERED DIURNAL THUNDERSTORMS ARE EXPECTED FROM EASTERN AZ,
THROUGH NM, AND INTO EASTERN CO WITH HOURLY RAINFALL UP TO 1 INCH
AT TIMES. THE FOCUS FOR HEAVIEST RAIN IS LIKELY WHERE THE
SHORTWAVE/FRONT MOVE INTO NM/TX PANHANDLE WHERE SOME ORGANIZED
CLUSTERS AND BETTER TRAINING POTENTIAL EXISTS. THIS IS REFLECTED BY
BOTH HREF AND REFS EXCEEDANCE PROBABILITIES REACHING 15-25% (FFG)
AND 30-50% (3"/24HRS). THIS STILL SUPPORTS THE INHERITED MRGL RISK,
AND ONLY COSMETIC ADJUSTMENTS WERE MADE BASED ON THE NEW GUIDANCE.
WEISS/MILLER
DAY 2
VALID 12Z SAT AUG 01 2026 - 12Z SUN AUG 02 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FRIDAY ACROSS
PARTS OF THE UPPER MIDWEST TO MID MISSISSIPPI VALLEY...
..OHIO/TENNESSEE VALLEY
A POTENT LOW PRESSURE SYSTEM WILL SUPPLY PLENTIFUL INSTABILITY TO
THE GREAT LAKES/OHIO AND TENNESSEE VALLEYS REGION BENEATH A
DEEPENING POSITIVELY TILTED MID-LEVEL LOW. PW VALUES OF 2+ STANDARD
DEVIATIONS ABOVE AVERAGE (2-2.25 INCHES) WILL BE ADVECTING INTO
THE REGION TO SUPPORT ENHANCED RAINFALL. A SLIGHT RISK REMAINS IN
EFFECT FROM EASTERN ILLINOIS TO OHIO AND SOUTHWARD TO ALABAMA AND
GEORGIA. A BROAD MARGINAL RISK SPANS FROM WISCONSIN TO WESTERN NEW
YORK SOUTH TO THE EASTERN GULF COAST AND SOUTHEAST.
..CENTRAL GULF COAST REGION INTO PARTS OF THE SOUTHEAST
HEAVY RAINFALL THREAT WILL CONTINUE OVER THIS REGION ALONG THE
SOUTHERN PERIPHERY OF THE FULL-LATITUDE TROUGH, SOUTH OF THE
QUASI-SATIONARY FRONT. DEEP-LAYER MOISTURE AND INSTABILITY SHOULD
BE MORE THAN SUFFICIENT, ESPECIALLY WHEN COINCIDING WITH THE WEAK
UPPER FORCING (UPSTREAM UPPER TROUGH W/ EMBEDDED CONVECTIVELY-AIDED
SHORTWAVES), FOR MORE ORGANIZED/PERSISTENT CONVECTIVE
ORGANIZATION.
..NEW MEXICO
DURING THIS PERIOD GENERAL STORM MOTION IS EXPECTED TO BE FROM
NORTH TO SOUTH INTO AN INCREASINGLY MOIST ENVIRONMENT (1"+ AND
97.5TH PERCENTILE PWATS) AND RELATIVELY SATURATED SOILS FROM FRIDAY
STORMS WILL CONTRIBUTE TO THE FLASH FLOODING THREAT. A SLIGHT RISK
WAS MAINTAINED FOR PORTIONS OF CENTRAL/EASTERN NEW MEXICO WITH A
MARGINAL RISK AREA STRETCHING FROM SOUTHEAST ARIZONA TO WESTERN
TEXAS AND NORTHWARD TO SOUTHERN COLORADO.
CAMPBELL/KEBEDE
DAY 3
VALID 12Z SUN AUG 02 2026 - 12Z MON AUG 03 2026
..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE NORTHEAST...
..UPPER MIDWEST TO NORTHEAST AND MID-ATLANTIC REGION
THE POTENT MID-LEVEL CYCLONE WILL CONTINUE TO TRACK TO THE EAST
DURING THIS PERIOD USHERING THE SHOWERS AND THUNDERSTORMS ALONG
WITH IT INTO THE LOWER GREAT LAKES AND NORTHEAST REGION. STREAKS OF
HEAVY RAINFALL ARE ALSO EXPECTED TO DEVELOP ACROSS PARTS OF THE
MID-ATLANTIC/NORTH CAROLINA REGION. SOME OF THESE CELLS WILL HAVE THE
POTENTIAL TO YIELD 2 INCHES OVER A SHORT PERIOD DURING THE
AFTERNOON AND EVENING HOURS. A BROAD MARGINAL RISK SPANS FROM THE
NORTH/SOUTH CAROLINA BORDER NORTHWARD TO NEW YORK AND LOWER
MICHIGAN. A SLIGHT RISK AREA COVERS EXTREME SOUTHEAST MICHIGAN,
NORTHEAST OHIO, NORTHERN WEST VIRGINIA, WESTERN PENNSYLVANIA AND
WESTERN NEW YORK.
..SOUTHEAST
SHOWERS AND THUNDERSTORMS WILL PERSIST ALONG THE STALLED FRONTAL
BOUNDARY THUS MAINTAINING AN ELEVATED THREAT FOR HEAVY RAINFALL AND
POTENTIAL FOR LOCAL FLASH FLOODING. THEREFORE, A MARGINAL RISK AREA
WAS MAINTAINED FOR EASTERN GULF COAST/NORTHERN FLORIDA AND SOUTHERN
GEORGIA.
..SOUTHWEST
MONSOONAL MOISTURE WILL CONTINUE TO DRIVE CONVECTION ACROSS
PORTIONS OF NEW MEXICO AND ARIZONA. LOCALLY HEAVY RAINFALL MAY
CONTINUE TO RESULT IN ISOLATED FLASH FLOODING ACROSS THE REGION. A
MARGINAL RISK AREA IS IN EFFECT FOR SOUTHERN ARIZONA AND SOUTHWEST
NEW MEXICO.
CAMPBELL
DAY 4 AND DAY 5
VALID 12Z MON AUG 03 2026 - 12Z WED AUG 05 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE NORTHERN
MID ATLANTIC INTO SOUTHERN NEW YORK STATE AND SOUTHERN NEW
ENGLAND...
THE WELL DEFINED UPPER TROF MOVING THROUGH THE OHIO VALLEY DAY 3,
WILL BEGIN TO SPLIT INTO TWO PIECES DAY 4. WHILE THERE ARE
DIFFERENCES WITH THE DETAILS WITH THIS UPPER TROF EVOLUTION, THERE
IS AGREEMENT THAT AN AXIS OF ANOMALOUS PW VALUES, 2+ STANDARD
DEVIATIONS ABOVE THE MEAN, 2 TO 2.25" PW VALUES, WILL STRETCH FROM
NORTH FLORIDA, NORTHEASTWARD ACROSS THE COASTAL SOUTHEAST, MID-
ATLANTIC AND FROM EASTERN NY STATE INTO NEW ENGLAND. GENERALLY
FAVORABLE RIGHT ENTRANCE REGION JET DYNAMICS WILL ACCENTUATE LIFT
IN THIS ANOMALOUS PW AXIS, SUPPORTING POTENTIAL FOR LOCALLY HEAVY
RAINFALL TOTALS. A SLIGHT RISK WAS ADDED OVER PORTIONS OF THE
NORTHERN MID-ATLANTIC INTO SOUTHERN NY STATE AND SOUTHERN NEW
ENGLAND WHERE RECENT HEAVY RAINS HAVE LOWERED FFG VALUES. A
MARGINAL RISK EXTENDS SOUTHWARD THROUGH THE REMAINDER OF THE MID-
ATLANTIC INTO THE SOUTHEAST WHERE LOCALLY HEAVY RAINS ARE ALSO
LIKELY BUT FFG VALUES ARE HIGHER.
FOR BOTH DAY 4 AND DAY 5...A MARGINAL RISK WAS DEPICTED FOR
MONSOONAL CONVECTION ACROSS SOUTHERN ARIZONA INTO NEW MEXICO. NOT A
LOT OF CONFIDENCE WITH QPF DETAILS HERE, BUT LOCALLY HEAVY RAINS
AND ISOLATED RUNOFF ISSUES POSSIBLE IN THE ABOVE AVERAGE PW VALUES
EXPECTED ACROSS THIS AREA.
DAY 5...THE CLOSED LOW OVER THE UPPER OH VALLEY WILL BECOME NEARLY
STATIONARY DAY 5. AN AREA OF ANOMALOUS PW VALUES WILL REMAIN TO THE
EAST OF THIS CLOSED LOW, ACROSS THE UPPER OH VALLEY INTO THE MID-
ATLANTIC, SOUTHERN NEW ENGLAND AND SOUTH INTO THE COASTAL SOUTHERN
MID-ATLANTIC. A BROAD MARGINAL RISK AREA WAS DEPICTED IN THIS
ANOMALOUS PW AXIS FOR LOCALLY HEAVY RAINS AND ISOLATED RUNOFF
ISSUES. THE SURFACE FRONT MOVING THROUGH NEW ENGLAND DAY 4, MAY
BECOME STATIONARY AND WEST TO EAST ORIENTED ACROSS SOUTHERN NEW
ENGLAND INTO THE NORTHERN MID-ATLANTIC DAY 5. A FEW MODELS ARE
SHOWING MORE DEFINED HEAVY RAINS IN THE VICINITY OF THIS FRONT
WHERE THERE IS POTENTIAL FOR PERSISTENT SOUTH SOUTHWESTERLY INFLOW.
STILL A LOT OF SPREAD WITH QPF DETAILS, WARRANTING ONLY A MARGINAL
RISK AT THIS TIME, WITH CHANGES POSSIBLE WITH FUTURE UPDATES.
A SURFACE FRONT EXPECTED TO PUSH SOUTHEASTWARD DAY 5 FROM THE UPPER
MS VALLEY INTO THE UPPER LAKES AND SOUTH THROUGH THE CENTRAL
PLAINS. THERE IS MODEL CONSENSUS FOR AN AXIS OF POTENTIALLY HEAVY
RAINS FROM NEBRASKA, EASTWARD INTO IOWA AND SOUTHERN MN WHERE THE
FRONT MAY BECOME MORE WEST TO EAST ORIENTED LATE TUE INTO EARLY
WED. MOIST SOUTHERLY LOW LEVEL INFLOW INTO THE FRONT AT THIS TIME
MAY SUPPORT ORGANIZED CONVECTION, HEAVY RAINS AND ISOLATED RUNOFF
ISSUES.
ORAVEC
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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