082
FOUS30 KWBC 270039
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
839 PM EDT SUN JUL 26 2026
DAY 1
VALID 01Z MON JUL 27 2026 - 12Z MON JUL 27 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN & NEAR THE
LOWER SAVANNAH RIVER BASIN, WESTERN KENTUCKY, & MIDDLE TENNESSEE...
..SOUTH CAROLINA THROUGH THE ATLANTIC COAST OF FLORIDA
ABOVE AVERAGE MOISTURE REMAINS OVER SOUTH CAROLINA INTO GA WITH
LOW LEVEL FLOW NEAR A LINGERING QUASI- STATIONARY FRONT CONTINUING
TO FEED MOISTURE INTO THE AREA WHILE POORLY DEFINED WAVES OF LOW
PRESSURE STRETCHING ACROSS THE BASE OF AN EASTERN U.S. TROUGH
SHOULD FOCUS/ENHANCE THE CONVECTION NEAR COASTAL SOUTH
CAROLINA/GEORGIA EARLY ON. MAINTAINED/TRIMMED SLIGHT RISK BASED ON
RECENT CONVECTIVE EVOLUTION AND MESOSCALE GUIDANCE.
A MARGINAL RISK AREA EXTENDS SOUTHWARD THROUGH PORTIONS OF THE FL
PENINSULA, WITH SOME UPTICK EXPECTED OVERNIGHT INTO THE EARLY
MORNING. THERE IS ABUNDANT DEEP- LAYER MOISTURE IN PLACE AS SHOWN
BY THE 90+ PERCENTILE VALUES OF PRECIPITABLE WATER WHICH SUGGESTS
CELLS SHOULD BE EFFICIENT RAINFALL PRODUCERS WITH LOCALIZED
RAINFALL RATES IN EXCESS OF 3 INCHES POSSIBLE AND RAINFALL TOTALS
GENERALLY 2 TO 4 INCHES.
..FOUR CORNERS STATES
MONSOONAL SHOWERS AND THUNDERSTORMS APPEARED TO HAVE PEAKED FOR THE
DAY AND SHOULD BE ON DECLINE THIS EVENING INTO TONIGHT. HAVE
MAINTAINED THE MARGINAL RISK TO ACCOMMODATE THE ONGOING ACTIVITY.
..PORTIONS OF THE MIDWEST-UPPER GREAT LAKES-LOWER OHIO VALLEY
PROGRESSIVE, ORGANIZED ACTIVITY HAS BEGUN TO DEVELOP WITHIN AND
DOWNWIND OF A HIGHLY UNSTABLE AIRMASS (3000-6000 J/KG OF ML CAPE)
WHICH SHOULD CONTINUE OVERNIGHT, PARTICULARLY FROM THE LOWER OHIO
VALLEY THROUGH MIDDLE TN INTO NORTHERNMOST AL. THE INSTABILITY
GRADIENT THUNDERSTORMS RIDE DOWN SHOULD SHIFT WESTWARD WITH TIME AS
CONVECTION AND RELATED OUTFLOW BOUNDARIES SLOWLY STABILIZE THE
ATMOSPHERE. THE CONCERN IS FOR EMBEDDED MESOCYCLONES AND CELL
TRAINING BRINGING HOURLY RAIN AMOUNTS TO 2.5" WITHIN AN AREA OF
MODEST FLASH FLOOD GUIDANCE. RAISING A SLIGHT RISK ON THIS UPDATE
TO ACCOUNT FOR THE DEVELOPING SCENARIO. LOCAL TOTALS COULD REACH 6"
WHERE CELLS REPEAT/TRAINING THE LONGEST. THE UPGRADE TO SLIGHT
RISK WAS COORDINATED WITH THE MEMPHIS TN, NASHVILLE TN, AND
HUNTSVILLE AL FORECAST OFFICES.
..NORTH-CENTRAL VIRGINIA INTO CENTRAL NORTH CAROLINA
STRONG AGREEMENT AMONG 18Z HREF/12Z REFS GUIDANCE ON LEE-SIDE
TROUGH ACTIVITY DEVELOPING THIS EVENING OVER NORTH-CENTRAL VA UNDER
A REINFORCING IMPULSE ON THE MAIN TROUGH AXIS OVER THE EASTERN
SEABOARD. THIS ACTIVITY SHIFTS/PROPAGATES SOUTH AHEAD OF THE MID-
LEVEL IMPULSE REACHING CENTRAL NC LATE TONIGHT. PWS AROUND 1.75",
ML CAPE OF 1000+ J/KG, AND EFFECTIVE BULK SHEAR COULD ALLOW FOR
HOURLY RAIN AMOUNTS TO 2.5" WHERE CELLS TRAIN OR MESOCYCLONES FORM.
SINCE COVERAGE IS NOT EXPECTED TO BE SIGNIFICANT, LEFT THE RISK
LEVEL AS MARGINAL HERE.
ROTH
DAY 2
VALID 12Z MON JUL 27 2026 - 12Z TUE JUL 28 2026
...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL ACROSS THE FOUR
CORNERS STATES ONTO THE CENTRAL PLAINS AND GREAT LAKES/OHIO VALLEY
INTO THE NORTHEAST...
..FOUR CORNERS STATES ONTO THE CENTRAL PLAINS
CENTER OF UPPER HIGH SHIFTS SOUTH FROM CO TO NM THROUGH TONIGHT
WHICH WILL DIRECT MORE RIDGE TOPPING DIURNALLY-DRIVEN ACTIVITY FROM
THE CENTRAL ROCKIES ONTO THE CENTRAL PLAINS ON MONDAY COMPARED TO
TODAY. MEANWHILE CONTINUED MONSOONAL ACTIVITY IS EXPECTED ACROSS
THE FOUR CORNERS STATES AGAIN. FAVORED FOCUS AREAS FOR QPF ARE
AGAIN ALONG THE MOGOLLON RIM IN AZ AND IN CO, THOUGH THIS TIME IT'S
EAST FROM THE CONTINENTAL DIVIDE INSTEAD OF WEST LIKE TODAY. ONLY
A MINOR EXPANSION TO THE MARGINAL RISK IS NOTED WITH THE HREF
FAVORING CENTRAL PLAINS ACTIVITY INTO SOUTHWESTERN SOUTH DAKOTA.
..GREAT LAKES AND OHIO VALLEY INTO THE NORTHEAST US
A SHORTWAVE TROUGH SHIFTS SOUTHEAST OVER NORTHERN MINNESOTA MONDAY
MORNING AND THROUGH THE UPPER GREAT LAKES MONDAY
AFTERNOON/EVENING. THIS IS IN NORTHWEST FLOW DOWNSTREAM OF THE
UPPER LEVEL RIDGE AXIS STALLED OVER THE WESTERN DAKOTA BORDER.
INCREASINGLY DIFLUENT FLOW AHEAD OF THE SHORTWAVE WILL LEAD TO THE
CONSOLIDATION/ STRENGTHENING OF A LOW PRESSURE SYSTEM MONDAY NIGHT
WHICH INCREASES FORCING FOR HEAVIER RAINFALL OVER THE GREAT
LAKES/OHIO VALLEY. THE MARGINAL RISK WAS EXPANDED WEST ALONG THE
WI/UP OF MI BORDER FOR MORNING ACTIVITY, DOWN THROUGH EASTERN IL
FOR DOWNSTREAM EFFECTS FROM TONIGHT, AND FARTHER DOWNSTREAM INTO
NEW JERSEY FOR MONDAY NIGHT ACTIVITY BEGINNING BEFORE IT BECOMES
MORE SIGNIFICANT ON TUESDAY.
..TAMPA BAY
TROUGHING CURRENTLY ON THE EAST SIDE OF THE FL PENINSULA SHIFTS TO
THE GULF SIDE TOMORROW. EXCELLENT AGREEMENT AMONG 12Z HREF/REFS
GUIDANCE FOR REPEATING HEAVY THUNDERSTORMS ACROSS GREATER TAMPA BAY
MONDAY MORNING INTO THE AFTERNOON. CONSENSUS AVERAGE QPF IS 2-4"
WITH POTENTIAL FOR 6" FROM BOTH THE HREF AND RRFS. A MARGINAL RISK
FOR FLASH FLOODING IS WARRANTED IN THIS SCENARIO, ESPECIALLY FOR
URBANIZED DRAINAGE CONCERNS.
JACKSON
DAY 3
VALID 12Z TUE JUL 28 2026 - 12Z WED JUL 29 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
NORTHERN MID-ATLANTIC INTO SOUTHERN NEW ENGLAND...
...SOUTHERN APPALACHIANS INTO NEW ENGLAND INCLUDING NORTHERN MID-
ATLANTIC...
SHORTWAVE TROUGH DEVELOPS INTO A LOW PRESSURE SYSTEM OVER THE
EASTERN GREAT LAKES MONDAY NIGHT THAT THEN STALLS OVER INTERIOR
NY/PA TUESDAY. THERE IS GREATER CERTAINLY ON THE INTERIOR POSITION
OF THIS LOW WHICH THEN MAINTAINS THE WARM SECTOR OVER THE NORTHERN
MID-ATLANTIC COAST INTO SOUTHERN NEW ENGLAND. 2 INCH PW IS
HIGHLIGHTED THROUGH THIS WARM SECTOR WHICH SHOULD ALSO HAVE
SUFFICIENT INSTABILITY FOR HIGHER RAINFALL RATES ALONG WITH UPPER
DIVERGENCE TO PROMOTE GROWTH AND REPEATING ACTIVITY. A SLIGHT RISK
REMAINS OVER THE NORTHERN MID-ATLANTIC INTO SOUTHERN NEW ENGLAND
WITH ADDITIONAL FOCUS NOW FOR NORTHERN NJ, SOUTHERN NY (INLAND OF
NYC AS OF NOW) INTO WESTERN CT AS A HIGHER END SLIGHT (AKA
"ENHANCED"). AREAL AVERAGE RAINFALL OF 2-4" WITH LOCALLY HIGHER
AMOUNTS IS CURRENTLY FORECAST FOR THIS "ENHANCED" AREA.
ELSEWHERE, WARM SECTOR MOISTURE AND INSTABILITY IS PRESENT DOWN THE
MID-ATLANTIC THROUGH NORTH CAROLINA WITH POTENTIAL FOR SOUTH MOVING
ACTIVITY TO REPEAT FROM REINFORCING SHORTWAVES ROUNDING THE NEW LOW
OT THE NORTH. TARGETED SLIGHT RISKS MAY BE WARRANTED IN THE
SOUTHERN MID-ATLANTIC EVENTUALLY. OTHERWISE, THE 12Z QPF CONSENSUS
FAVORED THE SOUTHERN APPALACHIANS MORE THAN BEFORE, SO THEY WERE
ADDED TO THE MARGINAL RISK.
..FOUR CORNERS STATES ACROSS THE CENTRAL PLAINS
FURTHER SUPPRESSION OF THE UPPER HIGH CENTER SOUTH THROUGH NEW
MEXICO OPENS FURTHER DOWNSTREAM ACTIVITY FROM THE FOUR CORNERS
STATES ACROSS THE CENTRAL PLAINS. THE MARGINAL RISK WAS EXPANDED
EAST TO THE KC METRO. AS OF NOW THE RRFS AND EC-AIFS HIGHLIGHT THE
HIGH PLAINS OF BOTH NORTHEAST AND SOUTHEAST CO WITH MORE TYPICAL
MONSOONAL ACTIVITY OVER TERRAIN IN THE FOUR CORNERS STATES.
JACKSON
DAY 4 AND DAY 5
VALID 12Z WED JUL 29 2026 - 12Z FRI JUL 31 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
NORTHEAST WEDNESDAY...
..NORTHEAST
A DYNAMIC COASTAL SYSTEM TAKES SHAPE TUE-THU ALONG/NEAR THE NEW
ENGLAND COAST PER MODEL GUIDANCE. STRONG UPPER LEVEL JET ENERGY
UPSTREAM DIVING TOWARD THE TROUGH BASE WILL AMPLIFY THE UPPER
TROUGH -- TO THE TUNE OF 2+ STANDARD DEVIATIONS BELOW LATE JULY
MEANS AT 500 MB-- WHICH ENHANCES THE DOWNSTREAM QG FORCING (UPPER
DIFFLUENCE/DIVERGENCE AND DEEP-LAYER ASCENT). STRENGTHENING
EAST TO SOUTH LOW-LEVEL FLOW WILL DRAW IN MOISTURE-RICH AIR OFF
THE ATLANTIC GULF STREAM, WITH A SWATH OF ~1.75" PWS WITHIN THE
DEEPENING TROWAL PIVOTING AROUND THE SLOW- MOVING COMMA HEAD. GIVEN
THE PERSISTENCE OF FAVORABLE COOL SEASON DYNAMICS WITH WARM SEASON
THERMODYNAMICS (HIGH DEEP- LAYER TPW/THETA-E VALUES), HAVE
MAINTAINED THE DAY 4 SLIGHT RISK AREA ACROSS PARTS OF THE
NORTHEAST, WHICH FITS THE MOST RECENT GLOBAL GUIDANCE RATHER WELL.
COORDINATION WITH GYX/GRAY ME AND BTV/BURLINGTON VT FORECAST
OFFICES LED TO SOME RESTRICTION ON ITS NORTH AND NORTHEAST SIDE,
BASED ON THE 3-6 HOURLY FFGS.
OPERATIONAL GUIDANCE SHOWS 2-4" ACROSS THE SLIGHT RISK AREA ON DAY
4/WEDNESDAY INTO WEDNESDAY NIGHT. SOUNDINGS WILL BE MOIST, AND
FRONTOGENESIS OF THE COMMA HEAD COULD ON ITS OWN LEAD TO EFFICIENT
HEAVY RAINFALL; NOT MUCH MU/ML CAPE WILL BE NECESSARY TO LEAD
TO FLASH FLOODING CONCERNS. THERE HAS BEEN A DECIDED BROADENING
TREND IN THE HEAVY RAIN SIGNAL SINCE THIS TIME YESTERDAY, AND
DEPENDING ON THE DEGREE OF HEAVY RAINFALL THAT OCCURS ON
TUESDAY/TUESDAY NIGHT, AN UPGRADE TO A MODERATE SOMEWHERE IN/NEAR
THE SIGHT RISK AREA CAN'T BE RULED OUT. ADDED A MARGINAL RISK FOR
THURSDAY/THURSDAY NIGHT DUE TO SOME SIGNAL FOR CONTINUED HEAVY
RAINFALL ON DAY 5.
..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. THE MARGINAL RISK AREA HERE ONLY
NEEDED SOME COSMETIC CHANGES TO BETTER FIT THE MOST RECENT QPF
GUIDANCE.
..LOWER MISSOURI VALLEY INTO THE UPPER MISSISSIPPI VALLEY
ON DAY 5 (THURSDAY-THURSDAY NIGHT), CONVECTIVELY-AIDED SHORTWAVE
ENERGY PROGRESSING EAST FROM THE CENTRAL-NORTHERN PLAINS WILL
AMPLIFY A BIT (DIG A BIT FARTHER SOUTH) UPON REACHING THE LOWER
MO-MID MS VALLEYS) DURING THIS TIME AS THE ~600DM 500MB HIGH
BECOMES CENTERED FARTHER WEST TOWARD THE FOUR CORNERS. THERE'S NEAR
TO ABOVE AVERAGE DISCREPANCY AMONGST THE GLOBAL GUIDANCE (GFS MOST
VIGOROUS WITH THE DEEP-LAYER FORCING AND LOW-LEVEL MOISTURE
TRANSPORT) ON WHERE THE HEAVY RAIN FALLS, AND HOW MUCH. A WET
SOLUTION WITH THE LIKELIHOOD OF AN MCS/UPSCALE CONVECTIVE GROWTH
WITHIN AN AREA OF EXPANDING PWS OF 2-2.25+ INCHES IS WITHIN THE
REALM OF POSSIBILITY, GIVEN THE INGREDIENTS EXPECTED. COULD
CERTAINLY SEE A BUMP UP TO SLIGHT RISK AT SOME POINT, BUT FOR NOW
GIVEN THE SPREAD IN THE GUIDANCE, HAVE OPTED TO KEEP THE INHERITED
MARGINAL RISK WITH COSMETIC CHANGES TO BETTER FIT THE MOST RECENT
QPF GUIDANCE.
..CENTRAL GULF COAST REGION INTO PARTS OF THE 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. THE INHERITED MARGINAL RISK AREAS FOR WEDNESDAY INTO
THURSDAY NIGHT SAW ONLY A FEW COSMETIC CHANGES TO BETTER FIT THE MOST RECENT
QPF GUIDANCE.
ROTH/HURLEY
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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