393
FOUS30 KWBC 090042
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
842 PM EDT FRI MAY 8 2026
DAY 1
VALID 01Z SAT MAY 09 2026 - 12Z SAT MAY 09 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE DEEP SOUTH AND SOUTHERN TEXAS...
...01Z UPDATE..
MUCH OF THE DAY'S EXPECTED RAINFALL FROM THE UPPER TEXAS GULF COAST
THROUGH COASTAL LOUISIANA HAS ENDED. THUS, THE INHERITED SLIGHT
RISK WAS DROPPED AS WELL AS THE MARGINAL FOR COASTAL AREAS. THE
MARGINAL REMAINS FOR COASTAL MISSISSIPPI, ALABAMA, AND THE FAR
WESTERN FLORIDA PANHANDLE FOR THE REMAINING SHOWERS AND STORMS OVER
THE GULF THAT ARE QUICKLY SHIFTING EAST OVER THOSE AREAS AND COULD
CAUSE ISOLATED INSTANCES OF FLASH FLOODING, PARTICULARLY IN URBAN
AREAS.
THE NORTHERN HALF OF THE INHERITED MARGINAL RISK FROM FAR EASTERN
TEXAS THROUGH CENTRAL ALABAMA WAS LEFT LARGELY UNCHANGED, WITH
MINOR TWEAKS. CONVECTION CURRENTLY OVER OKLAHOMA ASSOCIATED WITH
ANOTHER FRONT WILL MAKE ITS WAY SOUTHEAST IN SOME FORM VERY LATE
TONIGHT. MUCH OF THE CAMS GUIDANCE SUGGESTS THESE STORMS MAY HAVE
THE OPPORTUNITY TO TRAIN AS THE LINE ITSELF PUSHES SOUTHEASTWARD,
AND OVER PORTIONS OF LOUISIANA, MISSISSIPPI, AND ALABAMA THAT WERE
HARD HIT WITH HEAVY RAINS EARLIER TODAY. THUS, WHILE THESE STORMS
ARE LIKELY TO BE MORE SCATTERED AND FAR MORE PROGRESSIVE, THE
SENSITIVE SOILS COULD SUPPORT AN ISOLATED INSTANCE OF FLASH
FLOODING OR TWO IN THE PREDAWN HOURS TONIGHT.
THE MARGINAL ACROSS SOUTH TEXAS WAS LEFT UNCHANGED WITH THIS
UPDATE. AS A SHORTWAVE CURRENTLY OVER THE BIG BEND APPROACHES SOUTH
TEXAS OVER THE NEXT FEW HOURS, STORMS INITIATING OVER THE MOUNTAINS
OF MEXICO ARE LIKELY TO DRIFT EAST OFF THE MOUNTAINS AND ACROSS THE
RIO GRANDE. FLOOD-SENSITIVE SOILS COULD ALLOW FOR ISOLATED FLASH
FLOODING AS A RESULT OF THESE STORMS, WHICH ARE LIKELY TO REMAIN
ISOLATED TO VERY WIDELY SCATTERED, AND THEREFORE WILL NOT POSE
MUCH OF A THREAT AREALLY, JUST WHERE THE HEAVIEST RAINS OCCUR.
WEGMAN
..PREVIOUS DISCUSSIONS
..16Z UPDATE
THE OVERNIGHT SLIGHT RISK AREA WAS MAINTAINED AS AN AREA OF
TRAINING SHOWERS AND THUNDERSTORMS TAKE SHAPE ACROSS LOUISIANA AND
MISSISSIPPI. 12Z HREF AND RRFS EAS NEIGHBORHOOD PROBABILITIES
CONTINUE TO DEPICT A HIGH PROBABILITY OF RAINFALL EXCEEDING 2
INCHES IN THE HIGHLIGHTED AREA. THIS ALIGNS WITH THE LOCATION OF
AN INSTABILITY GRADIENT/STATIONARY FRONT ANALYZED NEAR THE GULF
COAST WHICH WILL FOCUS CONVECTION TODAY.
OTHERWISE, THE FORECAST IN SOUTH TEXAS REMAINS SOMEWHAT UNCERTAIN,
WITH SOME 12Z CAM GUIDANCE TRENDING MORE DRY IN THE AREA. HOWEVER,
BASED OFF OF THE SYNOPTIC SETUP AND MOISTURE PROFILES OUTLINED
PREVIOUSLY, THUNDERSTORM CLUSTERS CAPABLE OF PRODUCING ISOLATED
FLASH FLOODING CERTAINLY REMAIN PLAUSIBLE. THUS, THE MARGINAL RISK
WAS KEPT IN FOR THIS UPDATE.
ASHERMAN
..LOWER MISSISSIPPI VALLEY/CENTRAL GULF COAST
A ROBUST MOISTURE POOL IS EXPECTED TO DEEPEN ALONG THE CENTRAL
GULF COAST TODAY AS SOUTHWESTERLY WINDS AMPLIFY AHEAD OF ENERGY
MOVING OUT OF EASTERN TEXAS AND THE NORTHWESTERN GULF. THIS FLOW
WILL SUPPORT PWS CLIMBING TO AROUND 2 INCHES ALONG A SLOW-MOVING
FRONT, OR MORE THAN 2.5 STD DEV ABOVE NORMAL. THE MAJORITY OF THE
CAMS ARE IN GOOD AGREEMENT INDICATING A CORRIDOR OF TRAINING
CONVECTION DEVELOPING BY THE AFTERNOON ACROSS SOUTHEASTERN
LOUISIANA AND SOUTHERN MISSISSIPPI. GIVEN THE HIGH MOISTURE CONTENT
AND POTENTIAL FOR TRAINING, LOCALIZED TOTALS OF 2-3+ INCHES ARE
POSSIBLE. HIGH HOURLY RATES WITHIN THESE TRAINING STORMS WILL POSE
A RISK FOR FLASH FLOODING, PARTICULARLY IN LOW-LYING AND URBAN
AREAS, WITH THE HIGHEST POTENTIAL IMPACT CENTERED ALONG THE I-10
CORRIDOR. THE INTRODUCED SLIGHT RISK AREA REFLECTS HIGH
NEIGHBORHOOD PROBABILITIES SHOWN BY BOTH THE HREF AND RRFS FOR
AMOUNTS EXCEEDING 2 INCHES.
..SOUTH TEXAS
FARTHER WEST, A WELL-DEFINED MID-TO-UPPER LEVEL SHORTWAVE/LOW
MOVING THROUGH NORTHERN MEXICO INTO WEST TEXAS WILL PROVIDE
INCREASING ASCENT. MOIST SOUTHERLY FLOW INTERACTING WITH THIS
FEATURE AND UPSLOPE INTO THE SIERRA MADRE ORIENTAL WILL SUPPORT
STORMS DEVELOPING OVER NORTHEASTERN MEXICO. WHILE MUCH OF THIS
ACTIVITY MAY REMAIN SOUTH OF THE INTERNATIONAL BORDER, THERE ARE
SOME HI-RES MEMBERS THAT SHOW SOME OF THESE CONVECTIVE CLUSTERS
MOVING INTO SOUTH TEXAS. THOUGH MODEL SPREAD IS HIGHER IN THIS
REGION, BOTH THE HREF AND RRFS INDICATE THAT LOCALIZED TOTALS
EXCEEDING 2 INCHES ARE POSSIBLE. THEREFORE, A MARGINAL RISK WAS
MAINTAINED TO ACCOUNT FOR THIS POTENTIAL.
PEREIRA
DAY 2
VALID 12Z SAT MAY 09 2026 - 12Z SUN MAY 10 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
SOUTHEAST LOUISIANA AND EXTREME SOUTHWEST MISSISSIPPI...
AFTER COORDINATION WITH LIX, A SLIGHT RISK WAS HOISTED OVER
SOUTHEAST LOUISIANA ROUGHLY ALONG THE I-10 CORRIDOR. BY 12Z
TOMORROW MORNING, CAM GUIDANCE SHOWS FAIRLY GOOD AGREEMENT IN
DEPICTING A TRAINING SIGNAL WITHIN AN OVERNIGHT MCS FORECAST TO
TRACK TOWARDS THE CENTRAL GULF COAST. AHEAD OF THE COMPLEX, A MOIST
AND UNSTABLE AIRMASS CHARACTERIZED PW VALUES NEAR 1.75-2" AND
MUCAPE OF 1500-2000 J/KG SHOULD FAVOR RAINFALL RATES EXCEEDING
2"/HR WITHIN THE MOST INTENSE CELLS -- LOCALLY EVEN HIGHER WHERE
CELL MERGERS OCCUR. AS THIS ACTIVITY OVERLAPS WITH ONGOING HEAVY
RAINFALL IN SOUTHEAST LOUISIANA, ADDITIONAL SCATTERED FLASH
FLOODING COULD RESULT WITH 2-4" EXPECTED IN THE MAIN TRAINING AXIS.
ASHERMAN
DAY 3
VALID 12Z SUN MAY 10 2026 - 12Z MON MAY 11 2026
...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF NORTHEASTERN TEXAS, SOUTHEASTERN OKLAHOMA, SOUTHERN ARKANSAS,
AND NORTHERN LOUISIANA...
LITTLE CHANGE WAS MADE TO THE OUTLOOK AS A SHORTWAVE DIVES INTO
THE BASE OF BROADER SCALE TROUGH AND DRIVES A COLD FRONT SOUTHWARD
ACROSS THE REGION. SOUTHERLY FLOW AHEAD OF THE BOUNDARY WILL BOOST
PWS TO OVER 1.5 INCHES. THIS MOISTURE, COMBINED WITH FAVORABLE
RIGHT ENTRANCE REGION ASCENT, WILL SUPPORT STORMS DEVELOPING ALONG
AND AHEAD OF THE FRONT. MODEL SPREAD REMAINS TOO HIGH TO SUPPORT A
HIGHER RISK CATEGORY WITHIN THE BROAD MARGINAL RISK, WHILE
ANTECEDENT CONDITIONS IN THE REGION ARE QUITE DRY. THAT SAID, THERE
REMAINS A SIGNAL IN THE GLOBAL AND AI GUIDANCE FOR SOME AREAS OF
TRAINING AND REPEATING CELLS TO DEVELOP IN ANY MCS THAT FORMS ON
DAY 3. LOCALLY INTENSE RATES WITHIN SOME AREAS OF REPEATING CELLS
COULD RESULT IN ISOLATED FLASH FLOODING.
ASHERMAN/PEREIRA
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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