934
FOUS30 KWBC 010041
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
841 PM EDT THU JUL 31 2025
DAY 1
VALID 01Z FRI AUG 01 2025 - 12Z FRI AUG 01 2025
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE EAST, SOUTH, SOUTHERN PLAINS, HIGH PLAINS, & NORTHERN
INTERMOUNTAIN WEST...
..MID-ATLANTIC INTO NEW ENGLAND
THE LAST OF THE ORGANIZED CONVECTION WITH HEAVY RAINFALL IS IN THE
PROCESS OF FADING ACROSS PORTIONS OF THE EASTERN SHORE OF THE
CHESAPEAKE AND PORTIONS OF SOUTHERN LONG ISLAND NY, WHILE A BRIEF
UPTICK WAS NOTED CLOSER TO NORFOLK VA. ACROSS PORTIONS OF SOUTHERN
NEW ENGLAND AND THE COASTAL MID- ATLANTIC STATES, A NON-ZERO
CHANCE OF HEAVY RAINFALL EXISTS FOR ANOTHER FEW HOURS/INTO TONIGHT
PER THE 18Z HREF AND 12Z REFS PROBABILITIES OF 0.5"+, WHILE AREAS
NEAR WV HOLD ON TO A MINIMAL HEAVY RAINFALL RISK OVERNIGHT AS THE
FRONT DROPS SOUTHWARD. DOWNGRADED THE EXISTING RISK AREAS AND
THREAT LEVEL TO A MARGINAL TO ACCOMMODATE RADAR REFLECTIVITY AND
18Z HREF/12Z REFS TRENDS.
..GULF COAST & SOUTHEAST
EXISTING STORMS ARE EXPECTED TO FADE OVER THE NEXT SEVERAL HOURS
UNTIL CIN SETS IN, SO THE MARGINAL RISK FOR EXCESSIVE RAINFALL WILL
BE MAINTAINED THROUGH THIS EVENING.
..PORTIONS OF OKLAHOMA
AN AREA OF HIGH MOISTURE DRIFTS THROUGH PORTIONS OF OK OVERNIGHT.
THE 18Z HREF/12Z REFS SHOWS AN INCREASING CHANCE OF HEAVY RAINFALL
OVER THE EASTERN HALF OF THE STATE, BUT WITHOUT THE BENEFIT OF A
NOCTURNAL LOW-LEVEL JET. HOWEVER, INCREASING EFFECTIVE BULK SHEAR
IS MOVING INTO THE REGION FROM THE NORTHWEST AS A SHORTWAVE NOTED
ON WATER VAPOR IMAGERY ACROSS PORTIONS OF THE CENTRAL PLAINS MOVES
BY. HOURLY RAIN AMOUNTS TO 2.5" WITH LOCAL AMOUNTS TO 4" ARE
POSSIBLE IN THIS AREA. WHILE THE 12Z REFS SHOWS A BROAD ENOUGH
SIGNAL TO POTENTIALLY SUPPORT A SLIGHT RISK IN THIS REGION, THE 18Z
HREF IMPLIES THAT SUCH A RISK EXISTS AT ONE SPECIFIC SPOT. KEPT
THE RISK AS MARGINAL FOR THE TIME BEING PER COORDINATION WITH THE
TSA/TULSA OK AND OUN/NORMAN OK FORECAST OFFICES. LOCALIZED SLIGHT
RISK IMPACTS CAN'T BE RULED OUT, DEPENDING UPON HOW THE CONVECTIVE
EVOLUTION OCCURS OVERNIGHT.
..ROCKIES INTO THE PLAINS
SCATTERED THUNDERSTORMS EXPECTED TO CONTINUE FROM EASTERN
ARIZONA/NEW MEXICO NORTHWARD TO MONTANA. WHILE IN MOST AREA IN
GENERAL, THE STORMS WILL LIKELY LACK ORGANIZATION FOR A MORE
ELEVATED THREAT FOR FLASH FLOODING. IN MOST SPOTS, THE THREAT
SHOULD CONTINUE THROUGH 06Z, THOUGH IN THE NORTHERN PLAINS, THE
HEAVY RAIN THREAT COULD HANG ON INTO THE EARLY MORNING HOURS AS A
LOW-LEVEL JET INCREASES AVAILABLE MOISTURE AND MAINTAINS
INSTABILITY OVERNIGHT.
ROTH
DAY 2
VALID 12Z FRI AUG 01 2025 - 12Z SAT AUG 02 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE CAROLINAS AND NORTH/NORTHEAST TEXAS...
..SOUTHEAST AND MID-ATLANTIC
DURING THIS PERIOD A POTENT COLD FRONT WILL BE DROPPING SOUTH
THROUGH THE REGION IN RESPONSE TO A VERY STRONG SURFACE HIGH
PRESSURE (ABOVE THE 99.5TH CLIMATOLOGICAL PERCENTILE PER THE
NAEFS) OVER THE GREAT LAKES/MIDWEST. THIS WILL ALLOW FOR MOISTURE
TO POOL ALONG THE FRONT AND THUNDERSTORMS TO DEVELOP ACROSS THE
CAROLINAS ON FRIDAY AND FRIDAY NIGHT. MEANWHILE BOTH TERRAIN AND
COASTAL INFLUENCE ARE ALSO LIKELY, WHICH MAY LEAD TO SLOWER STORM
MOTIONS AND HEAVIER RAINFALL AMOUNTS. THIS COMBINATION WILL ALSO RESULT
IN GOOD CONVECTIVE COVERAGE, WHICH WILL ULTIMATELY LIKELY LEAD TO
A DECENT DEGREE OF CELL MERGER ACTIVITY. MUCH OF THE AREA WILL HAVE
PW VALUES NEARING 2.5 INCHES ALONG WITH ABUNDANT INSTABILITY,
RESULTING IN VERY HEAVY RAINFALL RATES OVER 2"/HR IN THIS
THERMODYNAMIC ENVIRONMENT. GIVEN THE LIKELIHOOD OF CELL MERGERS
AND WESTERLY MEAN LAYER FLOW NEARLY PARALLEL TO THE FRONT, THIS
SHOULD DRIVE AN ISOLATED TO SCATTERED FLASH FLOOD RISK. 12Z HREF
GUIDANCE DEPICTED HIGH NEIGHBORHOOD PROBABILITIES (60-90%) FOR AT
LEAST 3" IN 6-HRS ALONG THE COASTAL CAROLINAS, WHERE FFG IS ALSO
HIGHEST. ADDITIONALLY, ALONG THE COMPLEX TERRAIN OF THE WESTERN
CAROLINAS 12Z HREF NEIGHBORHOOD PROBABILITIES FOR EXCEEDING 3" IN
6-HRS ARE 40-50%.
ONLY MINOR ADJUSTMENT TO THE PREVIOUS OUTLOOK WAS TO REDUCE THE
NORTHERN PORTION OF THE SLGT AND MRGL BASED ON SOUTHERN TRENDS IN
THE PROGRESSION OF THE COLD FRONT. URBAN AREAS AND THE COMPLEX
TERRAIN OF THE SOUTHERN APPALACHIANS REMAIN MOST AT RISK TO
SCATTERED INSTANCES OF FLASH FLOODING, WITH THE REMAINDER OF THE
CAROLINAS FLAT AND SANDY SOILS CAPABLE OF SOAKING IN MOST OF THE
INTENSE RAINFALL. THE FRONTAL BOUNDARY WILL ALSO LINGER ACROSS THE
REMAINDER OF THE SOUTHEAST AND INTO THE LOWER MS VALLEY, WHERE
ADDITIONAL INSTANCES OF FLASH FLOODING ARE POSSIBLE GIVEN WEAK
STEERING FLOW AND 2-2.25" PWS. HOWEVER, MOST STORMS SHOULD BECOME
OUTFLOW DOMINANT AND BE SHORT-LIVED AFTER A BRIEF PERIOD OF INTENSE
RAINFALL AND RATES UP TO 3"/HR.
..SOUTHERN PLAINS
THE COLD/STATIONARY FRONT CONTINUES TO STRETCH WESTWARD TOWARDS THE
SOUTHERN PLAINS ALONG WITH PW VALUES NEAR 2" FRIDAY INTO FRIDAY
NIGHT. WHILE MOST ACTIVITY SHOULD REMAIN PULSE-LIKE, A SURFACE WAVE
AND MEANDERING MCV COULD TRIGGER LOCALLY HEAVY RAIN IN
NORTHERN/NORTHEAST TX FRIDAY NIGHT. THE LOCATION REMAINS SOMEWHAT
UNCERTAIN, BUT THIS AREA IS HIGHLIGHTED BY THE 12Z HREF AS HAVING
6-HR PROBABILITIES FOR >5" AT 30-40%. ADDITIONALLY, THE RGEM AND
ECMWF INCLUDED ELEVATED QPF VALUES ABOVE 2-3" WITH THE 12Z RUNS IN
A VERY SIMILAR LOCATION. THIS POTENTIAL COLLOCATED WITH THE
DALLAS- FORT WORTH METRO LED TO ENOUGH CONFIDENCE FOR A TARGETED
SLIGHT RISK. EXPECT REFINEMENTS IN FUTURE OUTLOOKS AS MORE CAM RUNS
BECOME AVAILABLE AND/OR THE MCV AT PLAY BECOMES MORE TRACKABLE.
..ROCKIES AND PLAINS
SCATTERED CONVECTION IS EXPECTED TO SPAN FROM MONTANA TO NEW MEXICO
INTO FRIDAY. THE MOST FAVORABLE ENVIRONMENT FOR HEAVY RAINFALL WILL
LIKELY SETUP FROM MONTANA INTO THE DAKOTAS, WHICH IS WHERE MID
LEVEL TROUGHING WILL BE PAIRED WITH THE HIGHEST PW ANOMALIES IN
THE CONUS...ABOVE THE 90TH PERCENTILE CLIMATOLOGICAL EARLY AUGUST
PEAK VALUES. COMBINE THIS WITH CAPE FORECAST AROUND 2000 J/KG AND
THE ENVIRONMENT APPEARS CONDUCIVE TO AREAS OF LOCALIZED FLASH
FLOODING. HOURLY RAINFALL RATES UP TO 1.25-1.5 INCHES/HOUR POSSIBLE
OVER THE NORTHERN ROCKIES/MONTANA AND UP TO 2 INCHES/HOUR ACROSS
THE DAKOTAS. THERE IS ALSO THE POTENTIAL FOR AN MCV ACROSS THE
DAKOTAS TO PROVIDE A FOCUS FOR LOCALLY INTENSE RAINFALL, BUT THE
LOCATION OF THIS HEAVY RAIN REMAINS TOO UNCERTAIN FOR AN UPGRADE TO
A SLIGHT RISK. THIS POTENTIAL WILL BE EVALUATED IN FUTURE OUTLOOKS.
SNELL
DAY 3
VALID 12Z SAT AUG 02 2025 - 12Z SUN AUG 03 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHEAST...
..SOUTH AND SOUTHEAST
THE STRONG FRONT MENTIONED WILL CONTINUE PRESSING SOUTHWARD,
DRAPED FROM THE SOUTHEAST WESTWARD ACROSS THE DEEP SOUTH, LOWER
MISSISSIPPI VALLEY AND OVER TEXAS. HIGH MOISTURE CONTENT AND
INSTABILITY ALONG AND AHEAD OF THE FRONT INTERACTING WITH THE RIGHT
ENTRANCE REGION OF THE UPPER JET WILL PROMOTE HEAVY TO EXCESSIVE
RAINFALL IN THUNDERSTORMS THAT COULD CAUSE LOCALIZED FLASH
FLOODING. VERY HEAVY RAINFALL RATES ARE EXPECTED AND SHOULD DRIVE
AN ISOLATED TO SCATTERED FLASH FLOOD RISK. A SLIGHT RISK REMAINS IN
EFFECT FOR PORTIONS OF THE LOWCOUNTRY SOUTH CAROLINA, SOUTHERN
GEORGIA AND FAR NORTHERN/NORTHEAST FLORIDA. THE FRONT STRETCHING
WEST ACROSS THE GULF COAST STATES IN A MOIST AND UNSTABLE
ENVIRONMENT COULD PROMOTE SCATTERED DIURNAL THUNDERSTORMS INTO
SATURDAY THUS MAINTAINING THE MARGINAL RISK.
..ROCKIES AND PLAINS
SHORTWAVES ROUNDING THE EASTERN EDGE OF THE UPPER RIDGE IN THE
WESTERN U.S. IS FORECAST TO INTERACT WITH THE SAME FRONT THAT BENDS
BACK ACROSS THE GREAT PLAINS, WHERE ROUNDS OF RAIN AND
THUNDERSTORMS ARE LIKELY WITH POSSIBLY MULTIPLE MCSS. HIGH RAIN
RATES SHOULD BE SUPPORTED AT TIMES WITH THE ABOVE NORMAL MOISTURE
AND INSTABILITY WITH SOME AREAS POSSIBLY SEEING REPEATED ROUNDS OF
STORMS AS THE FRONT BEGINS TO LIFT AS A WARM FRONT. LOCATION IN
HEAVIEST RAINFALL REMAINS TOO UNCERTAIN FOR AN UPGRADE TO A SLIGHT
RISK AT THE MOMENT AND MCS ACTIVITY MAY BODE TOO PROGRESSIVE FOR
WIDESPREAD FLASH FLOODING, THUS THE REGION IS COVERED BY A
MARGINAL RISK.
SNELL/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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