319
FOUS30 KWBC 050051
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
851 PM EDT SAT JUL 4 2026
DAY 1
VALID 01Z SUN JUL 05 2026 - 12Z SUN JUL 05 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHEAST KANSAS
INTO OKLAHOMA AND PORTIONS OF INDIANA AND OHIO...
SCATTERED AREAS OF CONVECTION CONTINUE TO POSE AT LEAST A
LOCALIZED FLASH FLOOD RISK ACROSS PORTIONS OF THE CENTRAL AND
EASTERN PART OF THE COUNTRY. EMBEDDED WITHIN THIS WE WILL CARRY TWO
SLIGHT RISK AREAS INTO THE OVERNIGHT HOURS. ONE ACROSS PORTIONS OF
IN AND OH WHERE AN MCV IS FOCUSING CONVECTION THIS EVENING. STILL
SEEING ENOUGH CELL MERGERS TO DRIVE SOME FLASH FLOOD RISK OVER THE
NEXT FEW HOURS. WHILE ACTIVITY MAY GENERALLY WEAKEN THEREAFTER,
THE HRRR HAS BEEN CONSISTENT AT INDICATING A POTENTIAL FOR
CONTINUED CONVECTION NEAR THE MCV CENTER AS IT TRACKS FROM
NORTHERN IN INTO NORTHERN OH TONIGHT. SOME FLASH FLOOD RISK COULD
THUS CONTINUE THROUGH MUCH OF THE NIGHT OVER THIS REGION.
THE OTHER SLIGHT RISK IS ACROSS PORTIONS OF CENTRAL/NORTHERN OK
INTO SOUTHEAST KS AND IMMEDIATE ADJACENT AREAS OF SOUTHWEST MO AND
NORTHWEST AR. GENERALLY EXPECT THIS ACTIVITY TO START FORWARD
PROPAGATING OFF TO THE SOUTHEAST, WHICH SHOULD LIMIT THE EXTENT OF
THE FLASH FLOOD RISK. NONETHELESS, HIGH RAINFALL RATES ARE LIKELY,
AND BRIEF CELL MERGERS COULD BE ENOUGH TO RESULT IN SOME FLASH
FLOOD IMPACTS, ESPECIALLY ACROSS ANY MORE SENSITIVE URBAN AREAS.
ALSO, AS THE SYSTEM TRANSITIONS INTO AN MCS, A COMMA HEAD FEATURE
ON THE NORTHERN EXTENT COULD SLOW AND LOCALLY INCREASE RAINFALL
TOTALS ACROSS THE NORTHEASTERN PORTION OF THE SLIGHT RISK AREA.
CHENARD
DAY 2
VALID 12Z SUN JUL 05 2026 - 12Z MON JUL 06 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE MID-ATLANTIC...
THE EAST TO WEST ORIENTED FRONTAL BOUNDARY WILL SLOWLY DROP
SOUTHWARD INTO THE MID-ATLANTIC DURING THE PERIOD. THE WARM, MOIST,
AND UNSTABLE AIRMASS IS EXPECTED TO PRODUCE WIDESPREAD SLOWER
MOVING THUNDERSTORMS. THE ATMOSPHERE WILL BE QUITE FAVORABLE FOR
HEAVY RAINFALL AND FLASH FLOODING, BOTH FOR INTENSE RAIN RATES AND
REPEATING/BACK-BUILDING THUNDERSTORMS.
THE LATEST GUIDANCE HAS COME INTO BETTER AGREEMENT FOCUSING THE
HIGHEST PROBABILITIES FOR THE INTENSE RAIN RATES AND HIGHER QPF
OVER CENTRAL TO EASTERN PA, PORTIONS OF CENTRAL TO NORTHERN NJ, AND
FAR NORTHERN MARYLAND. 12Z HREF HAS 30-50 PERCENT PROBABILITIES FOR
LOCALIZED 5" TOTALS, WITH A BROADER FOOTPRINT FOR 3" AMOUNTS. THE
COMBINATION OF SOME TERRAIN AREAS AND THE HIGHLY URBANIZED CORRIDOR
MAKES THIS AREA MUCH MORE VULNERABLE TO FLASH FLOODING. WHILE
THERE REMAINS SOME SPATIAL UNCERTAINTY TO EXACTLY WHERE THE
GREATEST RAINFALL WILL OCCUR, THE SETUP FAVORS SOME LOCALLY
SIGNIFICANT FLASH FLOODING WILL BE POSSIBLE. THE SLIGHT RISK WAS
MAINTAINED BUT A FUTURE UPGRADE TO A MODERATE RISK MAY BE NEEDED
OVER PORTIONS OF PA IF TRENDS CONTINUE. A BROAD MARGINAL RISK AREA
SPANS FROM EASTERN OKLAHOMA/KANSAS EASTWARD TO THE MID-
ATLANTIC/SOUTHERN PORTIONS OF THE NORTHEAST.
TAYLOR
DAY 3
VALID 12Z MON JUL 06 2026 - 12Z TUE JUL 07 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE MID-ATLANTIC/NORTHEAST ON MONDAY...
THE THREAT FOR EXCESSIVE RAINFALL AND SCATTERED AREAS OF FLASH
FLOODING WILL REMAIN FOR PORTION OF THE MID-ATLANTIC FOR THIS
PERIOD. RAINFALL OCCURRING DURING THE DAY 1 AND DAY 2 PERIODS MAY
LEAD TO INCREASED SOIL SATURATION AND LOWERED FLASH FLOOD GUIDANCE
FOR THIS REGION, THUS MAKING IT MORE SENSITIVE FOR ADDITIONAL HEAVY
RAINFALL. NEAR AND JUST SOUTH OF THIS FRONT INSTABILITY OF 2000
J/KG OR GREATER AND PWS OVER 2" ARE FORECAST, AN ENVIRONMENT
SUPPORTING EFFICIENT RAINFALL AND HIGH HOURLY RATES. THE SLIGHT
RISK WAS ADJUSTED MINIMALLY WITH THE LATEST GUIDANCE, FOCUSING
PRIMARILY ON THE MID-ATLANTIC FROM NORTHERN VIRGINIA TO SOUTHERN
NEW YORK.
STRONGER LOW LEVEL CONVERGENCE WILL BE CAPABLE OF PRODUCING A
BROADER AREA OF MODERATE TO LOCALLY HEAVY RAINFALL ACROSS NEW YORK
INTO SOUTHERN NEW ENGLAND.; HOWEVER, WITH LESS AVAILABLE
INSTABILITY RAINFALL RATES WILL LIKELY NOT PEAK AS HIGH AS THOSE
FURTHER SOUTH. THUS, THIS AREA IS COVERED BY A BROAD MARGINAL RISK
FROM PORTIONS OF UPSTATE NEW YORK TO THE CAPE, SOUTH TO THE
CAROLINAS AND THEN SOUTHWEST INTO ARKANSAS AND NORTHERN LOUISIANA.
..MONTANA
ALONG AND AHEAD OF FRONTAL SYSTEM, ISOLATED INSTANCES OF HEAVY
RAINFALL WILL BE POSSIBLE CAPABLE OF PRODUCING LOCALIZED FLASH
FLOODING. FIRST WILL BE ACROSS PORTIONS OF NORTHEASTERN MONTANA AS
A SHORTWAVE TROUGH ROUNDS THE BASE OF THE BUILDING SOUTHWESTERN
RIDGE. STORMS WILL BE CAPABLE OF PRODUCING INTENSE RAIN RATES, SO
A MARGINAL RISK WAS ADDED.
CHENARD/CAMPBELL/TAYLOR
DAY 4 AND DAY 5
VALID 12Z TUE JUL 07 2026 - 12Z THU JUL 09 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE NORTHERN PLAINS TO UPPER GREAT LAKES TUESDAY AND WEDNESDAY...
20Z UPDATE: ONLY MINOR CHANGES MADE TO THE INHERITED SLIGHT RISK
ON DAYS 4 AND 5, AS THE AREAS ARE STILL ALIGNED WITH THE OVERALL
MODEL CONSENSUS. HIGHER CONFIDENCE ON THE DAY 4 (TUESDAY) AREA,
WITH MORE SPREAD AND UNCERTAINTY ON THE HEAVY RAINFALL AXIS BY DAY
5 (WEDNESDAY).
DID GO AHEAD AND ADD A MARGINAL RISK FOR PORTIONS OF THE MID-
ATLANTIC ON TUESDAY. QUITE A BIT OF UNCERTAINTY ON CONVECTIVE
DETAILS, BUT TROUGHING SHOULD PERSIST INTO TUESDAY, WITH PWS OVER
2" AND INSTABILITY REMAINING IN PLACE. THE THREAT OF ORGANIZED
HEAVY RAINFALL LOOKS LOWER THAN SUNDAY AND MONDAY, BUT THE
INGREDIENTS IN PLACE STILL SUPPORT ISOLATED TO SCATTERED CONVECTION
CAPABLE OF HEAVY RAINFALL RATES. WESTERLY FLOW WILL TRY TO BRING
IN SOME DRIER AIR, SO THE NORTHERN AND WESTERN EXTENT OF THIS RISK
AREA IS SUBJECT TO CHANGE, BUT AT THE MOMENT PRETTY GOOD MODEL
CONSENSUS THAT HIGHER INSTABILITY/MOISTURE WILL AT LEAST PERSIST
ACROSS THE COASTAL MID-ATLANTIC.
CHENARD
..PREVIOUS DISCUSSION
SLIGHT RISKS OF EXCESSIVE RAINFALL HAVE BEEN INTRODUCED ACROSS
PORTIONS OF THE NORTHERN PLAINS INTO THE UPPER GREAT LAKES TUESDAY-
WEDNESDAY. A SEASONABLY MOIST, UNSTABLE AIRMASS WILL BE IN PLACE
ALONG THE NORTHERN SIDE OF AN UPPER-RIDGE BUILDING OVER THE WESTERN
TO CENTRAL U.S. EARLY NEXT WEEK. AN UPPER-LEVEL WAVE ROUNDING THE
RIDGE WILL HELP TRIGGER SCATTERED TO WIDESPREAD THUNDERSTORM
DEVELOPMENT AT THE LEADING EDGE OF THE DEEPER MOISTURE OVER THE
NORTHERN HIGH PLAINS. PROPAGATION AHEAD OF A DEVELOPING SURFACE
WAVE ALONG A QUASI-STATIONARY FRONTAL BOUNDARY AND DEVELOPING LOW-
LEVEL JET WILL HELP MAINTAIN STORMS INTO THE OVERNIGHT HOURS
THROUGH THE NORTHERN PLAINS WITH THE POTENTIAL FOR AT LEAST
ORGANIZED CLUSTERS OF STORMS IF NOT A MESOSCALE CONVECTIVE SYSTEM.
A SIMILAR SCENARIO WILL PLAY OUT WEDNESDAY AS ONGOING/RENEWED STORM
DEVELOPMENT WILL CONTINUE EASTWARD INTO THE UPPER GREAT LAKES.
TYPICAL UNCERTAINTY ON THE EXACT LOCATION AND COVERAGE OF
CONVECTIVE DEVELOPMENT REMAINS A CONCERN PARTICULARLY AS THE STORM
EVOLUTION TUESDAY WILL LIKELY IMPACT STORM DEVELOPMENT/EVOLUTION
WEDNESDAY. HOWEVER, GOOD CONSENSUS AMONGST THE DETERMINISTIC MODEL
GUIDANCE ON AREAL AVERAGE TOTALS IN THE 1-2" RANGE AND LOCALLY
HIGHER AMOUNTS OF 3-4" SUPPORTS THE THREAT FOR SCATTERED FLASH
FLOODING WITH POTENTIAL AREAL ADJUSTMENT OF THE RISK IN SUBSEQUENT
OUTLOOKS.
PUTNAM
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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