254
FOUS30 KWBC 080829
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
429 AM EDT WED JUL 8 2026
DAY 1
VALID 01Z WED JUL 08 2026 - 12Z WED JUL 08 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE CENTRAL PLAINS THROUGH THE UPPER GREAT LAKES...
..CENTRAL PLAINS TO THE UPPER GREAT LAKES
EMBEDDED UPPER-LEVEL SHORTWAVES ROUNDING AN UPPER-HIGH OVER THE
SOUTHWESTERN U.S. WILL LEAD TO INCREASINGLY NORTHWESTERLY FLOW OVER
A QUASI-STATIONARY FRONTAL BOUNDARY ACROSS THE UPPER GREAT
LAKES/MIDWEST. AN OVERNIGHT MCS MAY STILL BE ONGOING THROUGH THE
START OF THE DAY 1 PERIOD ACROSS THE MICHIGAN UP/NORTHERN WISCONSIN
WEST-SOUTHWEST THROUGH SOUTHERN MINNESOTA, WITH THE OUTFLOW FROM
THESE STORMS LIKELY HELPING TO DELINEATE THIS AS THE EVENTUAL
POSITION OF THE FRONTAL BOUNDARY LATER THIS AFTERNOON. THIS WILL
FAVOR RENEWED DEVELOPMENT OF STORMS ALONG AND JUST TO THE SOUTH OF
THE BOUNDARY FROM THE UP/NORTHERN LP OF MICHIGAN SOUTHWEST THROUGH
CENTRAL WISCONSIN AND INTO SOUTHERN MINNESOTA/NORTHERN IOWA.
SEASONABLY HIGH PWAT VALUES 1.5-2 STANDARD DEVIATIONS ABOVE THE
MEAN WILL SUPPORT RAIN RATES OF 1-2"+ PER HOUR. THE LATEST HI-RES
GUIDANCE SHOWS THE POTENTIAL FOR LOCALLY HEAVY RAINFALL TOTALS OF
3"+, BACKED BY MODERATE (40-60%) HREF PROBABILITIES OF TOTALS
EXCEEDING 3", SUPPORTING THE RISK FOR SCATTERED FLASH FLOODING.
THE SLIGHT RISK HAS BEEN EXTENDED FURTHER TO SOUTHWEST WHERE HEAVY
RAINFALL IS ALSO EXPECTED AHEAD OF A DEVELOPING SURFACE WAVE ALONG
THE COLD FRONT OVER NEBRASKA. THIS WILL HELP FOCUS CONVERGENCE
ALONG THE FRONT PROMOTING MORE WIDESPREAD STORM DEVELOPMENT WITH
STORM CLUSTERING/COLD POOL MERGERS IN THE PRESENCE OF NORTHWESTERLY
FLOW LEADING TO THE POTENTIAL FOR UPSCALE GROWTH INTO AN ORGANIZED
CONVECTIVE SYSTEM. SEASONABLY HIGH MOISTURE FLOWING NORTHWARD ON
THE WEST SIDE OF SURFACE HIGH PRESSURE TO THE EAST WILL POOL AHEAD
OF THE BOUNDARY WITH DAYTIME SURFACE HEATING LEADING TO MODERATE TO
STRONG INSTABILITY SUPPORTING HEAVY RAINFALL RATES OF 1-2"+. A
DEVELOPING LOW LEVEL JET OVER THE CENTRAL PLAINS WILL ALSO HELP TO
MAINTAIN STORMS INTO THE EVENING HOURS. SIMILAR TO THE UPPER GREAT
LAKES/MIDWEST, THE LATEST HI-RES GUIDANCE SUPPORTS THE POTENTIAL
FOR LOCALLY HEAVY RAINFALL OF 3"+ AND SCATTERED INSTANCES OF FLASH
FLOODING
THERE MAY BE A RELATIVE MINIMA BETWEEN THESE TWO REGIONS THAT
WOULD NOT QUITE RISE TO THE LEVEL OF A SLIGHT RISK. HOWEVER,
THERE'S ENOUGH AGREEMENT AMONGST THE GUIDANCE THAT THIS REGION
WOULD BE LIMITED IF PRESENT AT ALL SO FELT A FULL EXTENSION OF THE
SLIGHT RISK SOUTHWESTWARD WAS WARRANTED RATHER THAN INTRODUCING A
SEPARATE RISK AREA.
..CENTRAL/NORTHERN HIGH PLAINS
A COLD FRONT PUSHING INTO THE CENTRAL/NORTHERN HIGH PLAINS WILL
PROVIDE A FOCUS FOR CONVERGENCE AS WELL AS MOIST, POST-FRONTAL
UPSLOPE FLOW TO SUPPORT SCATTERED AFTERNOON THUNDERSTORMS OFF THE
HIGHER TERRAIN. LOCALLY HIGHER PWAT VALUES OF 1"+ WILL SUPPORT
HEAVIER DOWNPOURS WITH AN ISOLATED RISK FOR FLASH FLOODING.
...EASTERN TEXAS/LOWER MISSISSIPPI VALLEY TO THE TENNESSEE/OHIO
VALLEY AND THE MID-ATLANTIC...
A MARGINAL RISK WAS MAINTAINED FOR THIS REGION. A SHORTWAVE MOVING
ACROSS KENTUCKY/TENNESSEE AND A LINGERING FRONT SHOULD BOTH ACT AS
A FOCUS FOR CONVECTIVE DEVELOPMENT. ADDITIONAL DAY TIME STORMS ARE
LIKELY FURTHER EAST ALONG THE FRONT INTO THE SOUTHERN MID-
ALANTIC/NORTH CAROLINA AS WELL AS SOUTHWEST ALONG THE FRONT THROUGH
THE LOWER MISSISSIPPI VALLEY AND THEN SOUTH THROUGH THE NORTHWEST
GULF COAST. NOT EXPECTING ANYTHING TOO ORGANIZED OR WIDESPREAD, BUT
ENOUGH MOISTURE AND INSTABILITY WILL BE AROUND TO SUPPORT LOCALLY
HEAVY RAINFALL RATES.
PUTNAM
DAY 2
VALID 12Z WED JUL 08 2026 - 12Z THU JUL 09 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS...
..MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS
EMBEDDED SHORTWAVES ROUNDING THE UPPER-RIDGE WILL EVENTUALLY LEAD
TO DEEPENING TROUGHING ACROSS THE THE MIDWEST AND ADJACENT AREAS ON
THURSDAY. THE SOUTHWARD SHIFT OF STRONGER FLOW ALOFT OVERTOP A
SOUTHWARD PROGRESSING COLD FRONT WILL BRING BROADENING SCATTERED
THUNDERSTORM CHANCES FROM THE CENTRAL PLAINS EAST THROUGH THE
MIDWEST AND INTO THE LOWER GREAT LAKES/INTERIOR NORTHEAST.
SEASONABLY HIGH MOISTURE AND INSTABILITY AHEAD OF THE FRONT WILL
SUPPORT THE THREAT FOR LOCALLY HEAVY DOWNPOURS AND ISOLATED FLASH
FLOODING. TO THE SOUTH, A LINGERING FRONTAL BOUNDARY WILL LIFT BACK
NORTHWARD AS A WARM FRONT TOWARDS THE MIDDLE MISSISSIPPI/LOWER
OHIO VALLEYS AHEAD OF THE APPROACHING COLD FRONT, HELPING TO FOCUS
STORM DEVELOPMENT THROUGH THIS CORRIDOR. EMBEDDED WAVES LOCALLY
SLOWING THE PROGRESSION OF THE COLD FRONT AS WELL AS GENERALLY MEAN
WESTERLY FLOW OVER THE WEST-TO-EAST ORIENTED BOUNDARY WILL PROMOTE
POTENTIAL REPEATED/TRAINING STORMS, INCREASING RAINFALL TOTALS.
THE MOST RECENT DETERMINISTIC GLOBAL AND HI-RES GUIDANCE HAVE SHOWN
AN INCREASING POTENTIAL FOR MULTI-INCH RAINFALL TOTALS, WITH THE
AI GUIDANCE ALSO FAVORING A HEAVIER RAINFALL AXIS THROUGH THIS
CORRIDOR. FOR THESE REASONS, A SLIGHT RISK HAS BEEN INTRODUCED WITH
THIS OUTLOOK.
..MID-ATLANTIC
FURTHER EAST, SOME OF THE 00Z HI-RES GUIDANCE NOW STRETCHING AT
LEAST PARTIALLY INTO THE DAY 2 PERIOD IS RATHER BULLISH ON LOCALLY
HEAVY RAINFALL ACROSS THE MID-ATLANTIC WITH TOTALS OF 2-3"+. AN
EMBEDDED UPPER-LEVEL SHORTWAVE AND ACCOMPANYING SURFACE WAVE ALONG
THE LINGERING SOUTHERN FRONTAL BOUNDARY COULD LEAD TO MORE
WIDESPREAD THUNDERSTORMS THROUGH THIS REGION WITH PLENTIFUL
MOISTURE TO SUPPORT HEAVY RAINFALL. FOR NOW, HAVE EXTENDED THE
MARGINAL RISK EASTWARD TO COVER THIS REGION, BUT ANOTHER EMBEDDED
SLIGHT RISK MAY BE NEEDED WITH MORE CONFIDENCE IN THIS SCENARIO.
..CENTRAL HIGH PLAINS
A FAMILIAR SET-UP WILL REMAIN IN PLACE THURSDAY AS A FRONTAL
BOUNDARY BECOMES QUASI-STATIONARY THROUGH THE REGION. MOIST/POST-
FRONTAL UPSLOPE FLOW AND CONVERGENCE ALONG THE BOUNDARY WILL
CONTINUE TO SUPPORT STORMS WITH LOCALLY HEAVY DOWNPOURS AND AN
ISOLATED RISK FOR FLASH FLOODING.
PUTNAM
DAY 3
VALID 12Z THU JUL 09 2026 - 12Z FRI JUL 10 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE MIDDLE MISSISSIPPI/OHIO/TENNESSEE VALLEYS AND CENTRAL
APPALACHIANS...
..MIDDLE MISSISSIPPI VALLEY TO THE CENTRAL APPALACHIANS
A SIMILAR SET UP TO DAY 2/THURSDAY WILL BE IN PLACE BROADLY FROM
THE CENTRAL PLAINS EAST THROUGH THE MIDDLE MISSISSIPPI/OHIO VALLEYS
TO THE APPALACHIANS AND MID-ATLANTIC AS EMBEDDED SHORTWAVES HELP
TO MAINTAIN GRADUAL UPPER-TROUGHING AND STRONGER FLOW OVER THE
REGION. MOISTURE WILL CONTINUE TO POOL AHEAD OF THE SLOWLY
PROGRESSING COLD FRONT WITH PWAT VALUES REACHING AS HIGH AS 2"+
THROUGH THE MIDDLE MISSISSIPPI/OHIO/TENNESSEE VALLEYS, CONTINUING
THE THREAT FOR HIGH RAIN RATES WITH STORMS. THE SLOW PROGRESSION OF
THE WAVY FRONTAL BOUNDARY WILL ALSO KEEP THE FOCUS FOR STORMS OVER
A SIMILAR AREA TO DAY 2, PARTICULARLY ACROSS THE MIDDLE
MISSISSIPPI TO OHIO VALLEYS, LEADING TO INCREASINGLY WET ANTECEDENT
CONDITIONS AND RISK FOR FLASH FLOODING WITH ADDITIONAL RAINFALL.
THE SOUTHWARD PROGRESSION OF THE FRONT WILL ALSO BRING STORMS
FURTHER INTO THE CENTRAL APPALACHIANS AND TENNESSEE VALLEY. THE
DETERMINISTIC GUIDANCE CONTINUES TO SHOW AREAL AVERAGE RAINFALL OF
1-2" WITH LOCALLY HIGHER AMOUNTS, AND THE AI GUIDANCE ALSO LINES UP
FAVORABLY THROUGH THIS CORRIDOR. A HIGHER CATEGORICAL RISK AREA
MAY EVENTUALLY BE NEEDED AS CONFIDENCE GROWS IN THE HEAVY RAINFALL
POTENTIAL THURSDAY AND OVERLAP OF THIS REGION INTO FRIDAY.
..CENTRAL/SOUTHERN HIGH PLAINS
THE LINGERING FRONT THROUGH THE CENTRAL HIGH PLAINS THURSDAY WILL
BEGIN TO PRESS FURTHER SOUTHWARD ON FRIDAY WITH THE ACCOMPANYING
STORM RISK SHIFTING SOUTHWARD INTO THE SOUTHERN HIGH PLAINS.
CONTINUED CONVERGENCE/MOISTURE POOLING ALONG THE BOUNDARY WILL
BRING ANOTHER ROUND OF AFTERNOON THUNDERSTORMS CAPABLE OF LOCALLY
HEAVY RAINFALL LEADING TO ISOLATED FLASH FLOODING.
PUTNAM
DAY 4 AND DAY 5
VALID 12Z SAT JUL 11 2026 - 12Z MON JUL 13 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE OHIO/MID-MISSISSIPPI VALLEYS AND CENTRAL APPALACHIANS ON
SATURDAY...
...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE PLAINS/MID-MISSISSIPPI VALLEY EASTWARD TO THE MID-
ATLANTIC/SOUTHEAST...
..OHIO AND MID-MISSISSIPPI VALLEY'S
EMBEDDED SHORTWAVES ROUNDING THE UPPER-RIDGE WILL DEEPEN TROUGHING
ACROSS THE THE MIDWEST AND ADJACENT AREAS BY THURSDAY. THE
SOUTHWARD SHIFT OF STRONGER FLOW ALOFT WILL BRING INCREASINGLY
WIDESPREAD STORM CHANCES FROM THE CENTRAL PLAINS EAST THROUGH THE
MISSISSIPPI VALLEY INTO THE OHIO/TENNESSEE VALLEYS AND CENTRAL
APPALACHIANS. SEASONABLY HIGH INSTABILITY AND MOISTURE POOLING
ALONG A SOUTHWARD PROGRESSING, WAVY COLD FRONT WILL LEAD TO
MULTIPLE ROUNDS OF HEAVY RAIN- PRODUCING STORMS LATER THIS WEEK AND
INTO THE WEEKEND.
MEAN FLOW GENERALLY PARALLEL TO THE EAST-WEST
ORIENTED FRONT WILL SUPPORT CLUSTERING/TRAINING STORMS INCREASING
THE THREAT FOR LONGER- DURATION RAINFALL AND HIGHER TOTALS. THE
FRONTAL PROGRESSION WILL SLOW AT TIMES WHICH WILL HELP SETUP
TRAINING OF STORMS. WIDESPREAD 1-2 INCHES WILL BE POSSIBLE FOR THE
OHIO/TENNESSEE VALLEYS INTO THE CENTRAL APPALACHIANS, WHERE A
SLIGHT RISK HAS BEEN MAINTAINED. A SIMILAR SETUP FOR HEAVY
RAINFALL WILL BE IN PLACE FOR SUNDAY ACROSS THE TENNESSEE VALLEY TO
THE MID- ATLANTIC/SOUTHEAST. A MARGINAL RISK AREA IS IN EFFECT FOR
D5 SPANNING FROM EASTERN KANSAS/OKLAHOMA TO THE MID-
ATLANTIC/SOUTHEAST.
..SOUTHWEST U.S
MONSOONAL MOISTURE WILL RAMP UP CONVECTION ACROSS THE TERRAIN
OF SOUTHEASTERN AND CENTRAL AZ, MAINLY FOLLOWING THE HUACHUCAS UP
THROUGH THE MOGOLLON RIM IN EAST-CENTRAL AZ. PW VALUES WILL SURGE
NORTH ALONG PREVAILING SOUTHERLY FLOW ON THE WESTERN SIDE OF THE
BROAD UPPER RIDGE CENTERED OVER THE FOUR CORNERS. QPF SIGNATURES
ARE TEXTBOOK IN MONSOONAL CONVECTION BILLOWING UP ACROSS THE
TERRAIN AT LEAD WHICH IS A GOOD INDICATOR OF AT LEAST THE ISOLATED
THREAT OF FLASH FLOODING TO KICK OFF THE MONSOON SEASON ACROSS THE
SOUTHWEST. A MARGINAL RISK WAS MAINTAINED FOR DAY 4.
PUTNAM/CAMPBELL
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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