029
FOUS30 KWBC 070100
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
900 PM EDT WED MAY 6 2026
DAY 1
VALID 01Z THU MAY 07 2026 - 12Z THU MAY 07 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
MISSISSIPPI AND ALABAMA...
01Z UPDATE...
...GULF COAST STATES INTO THE SOUTHERN APPALACHIANS AND INTERIOR
SOUTHEAST...
EVENING ADJUSTMENTS TO THE ERO INCLUDE TRIMMING THE ENTIRE
NORTHWEST FLANKS OF THE MRGL AND SLGT RISK AREAS WHERE THE HEAVIER
CONVECTIVE RAINFALL HAS LARGELY ENDED ACROSS THE MID-SOUTH AND
PORTIONS OF THE TN VALLEY. ALSO, GIVEN THE LATEST TRENDS FROM THE
CAMS, MOST OF TEXAS HAS BEEN TAKEN OUT OF THE MRGL RISK AS A COLD
FRONT CONTINUES TO ADVANCE SOUTH AND ALLOWS FOR A MORE STABLE
AIRMASS TO INCREASINGLY OVERSPREAD THE HILL COUNTRY AND ADJACENT
AREAS OF SOUTH-CENTRAL TEXAS.
THE SLGT AND MDT RISK AREAS HAVE BEEN ADJUSTED SOMEWHAT ACROSS THE
DEEP SOUTH WITH SOME SOUTHWEST TO NORTHEAST ORIENTED REFINEMENT
ACROSS MS/AL/GA THAT TAKES INTO ACCOUNT THE ONGOING SUPERCELL
OUTBREAK AND EXPECTATIONS FOR GENERAL CELL-MERGER AND MCS
CONSOLIDATION GOING INTO THE OVERNIGHT HOURS. THIS INTEGRATES THE
18Z HREF, 12Z EC-AIFS AND RECENT HRRR SOLUTIONS WHICH MAINTAIN
SIGNIFICANT CONVECTIVE ORGANIZATION AND GRADUALLY INTRODUCE
CONCERNS FOR CELL-TRAINING AS THE CONVECTION BECOMES WELL-ALIGNED
WITH THE DEEPER LAYER AND STRONGLY SHEARED STEERING FLOW ACROSS THE
REGION. IT SHOULD BE NOTED THAT GUIDANCE CONTINUES TO SUPPORT
SOMEWHAT HEAVIER RAINFALL TOTALS ACROSS PORTIONS OF NORTHERN
GEORGIA AND ALSO UPDATE SOUTH CAROLINA WITH SOME CONVECTION
BECOMING LOCALLY CONCENTRATED NEAR AND JUST AHEAD OF THE
APPROACHING COLD FRONT FROM THE NORTH. AS SUCH, THE SLGT RISK AREA
HAS BEEN EXPANDING OFF TO THE EAST A BIT.
FOR MS/AL IN PARTICULAR, HIGH PWS LOCALLY REACHING 2 INCHES,
COUPLED WITH MODERATE TO STRONG INSTABILITY (1500 TO 2500+ J/KG OF
MLCAPE) WILL BE KEY PLAYERS ALONG WITH THE SHEAR TO FOSTER RAINFALL
RATES CAPABLE OF REACHING 2+ INCHES/HOUR. THE CELL-TRAINING AND
CELL- MERGER CONCERNS WILL SUPPORT SOME 2 TO 4 INCH RAINFALL TOTALS
WITH ISOLATED HEAVIER AMOUNTS, AND THERE IS SOME HIRES CAM
GUIDANCE THAT SUPPORTS 5+ INCH TOTALS OVERNIGHT. THE THREAT FOR
FLASH FLOODING WILL BE INCREASING OVER THE NEXT SEVERAL HOURS,
WHICH WILL INCLUDE URBAN FLOODING IMPACTS. PLEASE CONSULT THE
LATEST WPC MPDS FOR ADDITIONAL INFORMATION.
ORRISON
DAY 2 VALID 12Z THU MAY 07 2026 - 12Z FRI MAY 08 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL GULF COAST THROUGH SOUTHERN GEORGIA AS WELL AS FOR
PORTIONS OF THE RIO GRANDE VALLEY OF SOUTH TEXAS...
..2030Z UPDATE
..CENTRAL GULF COAST THROUGH SOUTHERN GEORGIA
BY THE START OF THE PERIOD 12Z THURSDAY, THE CLASH OF AIR MASSES
BETWEEN A COOLER, DRY AIR MASS OVER MUCH OF THE INTERIOR SOUTHEAST
AND A VERY WARM, UNSTABLE, TROPICAL AIR MASS OFF THE GULF TO THE
SOUTH WILL BE WANING, WITH THE FORMER AIR MASS WINNING OUT. THE
FRONT WILL BE ON THE MOVE TOWARDS THE SOUTH AND EAST THURSDAY
MORNING. THIS WILL BE COMBINED WITH A FAST MOVING SHORTWAVE AT THE
BASE OF A DEEP LONGWAVE TROUGH TO SUPPORT THE PROGRESSIVE MOVEMENT
OF THE STORMS SOUTH AND EAST ACROSS SOUTHERN ALABAMA, SOUTH
GEORGIA, AND EVENTUALLY THE NORTHERN PANHANDLE OF FLORIDA. AS THE
FRONT MOVES OVER SOUTHERN ALABAMA AND CENTRAL GEORGIA EARLY
THURSDAY MORNING, SOME BACKBUILDING DUE TO SOUTHWESTERLY MOISTURE
ADVECTION COULD STILL RESULT IN LOCALIZED AREAS OF TRAINING BETWEEN
STORMS AS THE ENTIRE SYSTEM MOVES SOUTHEASTWARD. COMBINED WITH A
FEW BURN SCARS ACROSS FAR SOUTH GEORGIA DUE TO RECENT WILDFIRES,
THE MARGINAL RISK INHERITED WAS LARGELY LEFT UNCHANGED, OTHER THAN
TRIMMING IT BACK FROM THE SOUTH CAROLINA COAST DUE TO NATURAL FLOOD
RESISTANCE AND LESS EXPECTED RAINFALL THERE. THE FLOOD THREAT WILL
RAPIDLY DIMINISH THURSDAY AFTERNOON AS THE FRONT DISSIPATES ACROSS
NORTH FLORIDA.
..RIO GRANDE VALLEY
A WEAK AREA OF SURFACE LOW PRESSURE IS EXPECTED TO DEVELOP THURSDAY
AT THE END OF THE SAME FRONT MOVING ACROSS THE SOUTHEAST. THIS LOW
WILL HAVE ABUNDANT ATMOSPHERIC MOISTURE TO WORK WITH, SOME UPPER
LEVEL SUPPORT IN THE RIGHT ENTRANCE REGION OF A JET, AND AN
APPROACHING SHORTWAVE TROUGH OVER WEST TEXAS. THERMAL HEATING WILL
ALLOW FOR CONVECTIVE DEVELOPMENT OVER THE MOUNTAINS OF MEXICO.
WESTERLY FLOW MAY ALLOW A FEW OF THOSE STORMS TO SURVIVE TRACKING
EAST OFF THE MOUNTAINS AND ACROSS THE RIO GRANDE. WHILE MANY AREAS
OF SOUTH TEXAS HAVE VERY DRY SOILS, THE ABUNDANCE OF MOISTURE
(PWATS OVER 2 INCHES) WILL SUPPORT STORMS THAT WILL BE CAPABLE OF
MULTI-INCH-PER-HOUR RATES. THIS INTENSITY OF RAIN MAY OVERCOME THE
DRY SOILS TO RESULT IN ISOLATED INSTANCES OF FLASH FLOODING. THE
MARGINAL WAS LEFT LARGELY UNCHANGED WITH THIS UPDATE.
WEGMAN
DAY 3
VALID 12Z FRI MAY 08 2026 - 12Z SAT MAY 09 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE UPPER
TEXAS GULF COAST THROUGH THE LOWER MISSISSIPPI VALLEY...
..2030Z UPDATE
RETURN FLOW OFF THE GULF ON FRIDAY WILL RUN INTO THE SAME STALLED
FRONT THAT WILL BE LIFTING NORTH AS A WARM FRONT DURING THE DAY.
AMPLE MOISTURE WITH PWATS OF 1.75 INCHES AND UP WILL SUPPORT
NUMEROUS THUNDERSTORM DEVELOPMENT AS EARLY AS MIDDAY, THEN
CONTINUING THROUGH THE AFTERNOON, WITH ADDITIONAL STORMS IMPACTING
THE AREA LATE FRIDAY NIGHT. THIS WILL SUPPORT A RENEWED FLASH
FLOODING RISK, ESPECIALLY SINCE SEVERAL URBAN AREAS, INCLUDING
HOUSTON, SAN ANTONIO, AND NEW ORLEANS COULD BE INVOLVED. DUE TO THE
ABUNDANCE OF MOISTURE AND CONTINUING SOUTHERLY FLOW OFF THE
WESTERN GULF RESUPPLYING MOISTURE LOST TO RAINFALL, EXPECT
BACKBUILDING AND TRAINING THUNDERSTORMS TO IMPACT THE SLIGHT RISK
AREA, WHICH WILL SUPPORT WIDELY SCATTERED INSTANCES OF FLASH
FLOODING. WHILE SOME AREAS ARE STARTING OUT DRIER THAN NORMAL FOR
SOIL MOISTURE, MOST ARE RIGHT AROUND AVERAGE FOR THIS TIME OF YEAR.
THIS COULD ALLOW FOR THE STORMS TO OVERWHELM LOCAL SOILS,
ESPECIALLY IN URBAN AREAS, A BIT SOONER, CONTRIBUTING TO THE WIDELY
SCATTERED FLASH FLOODING THREAT.
WEGMAN
..PREVIOUS DISCUSSION
THE RISK OF EXCESSIVE RAINFALL WILL BE FOCUSED ALONG THE LOW-LEVEL
BOUNDARY THAT BUILDS INTO THE REGION ON DAY 2 AND STALLS ALONG A
WEST TO EAST AXIS. PRECIPITABLE WATER VALUES IN EXCESSIVE OF 1.5
INCHES SHOULD BE POOLING ALONG THE BOUNDARY ON FRIDAY...WITH HIGHER
PRECIPITABLE WATER VALUES RETURNING NORTHWARD LATER IN THE DAY ON
FRIDAY AND THROUGH FRIDAY NIGHT/EARLY SATURDAY MORNING.
SOUTHERN STREAM SHORTWAVE ENERGY BECOME SOUTHERLY DURING THE DAY
AND INCREASES.
THE MARGINAL RISK AREA IS CONDITIONAL IN THE SENSE THAT A SLIGHT
COULD BE NEEDED DEPENDING ON OBSERVED RAINFALL ON DAY 2, THE
DEGREE OF OVERLAP WITH DAY 3 QPF AND THE AMOUNT OF URBANIZATION.
BANN
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
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