264
FOUS30 KWBC 291555
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1155 AM EDT TUE APR 29 2025
DAY 1
VALID 16Z TUE APR 29 2025 - 12Z WED APR 30 2025
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHERN PLAINS...
..SOUTHERN PLAINS
16Z UPDATE: NO MAJOR CHANGE TO THE REASONING OUTLINED BELOW, BUT
THERE WAS AN OVERALL TREND TO SHIFT RISK AREAS SOUTHWARD A BIT.
ALTHOUGH HI-RES MODELS (EVEN THE VERY RECENT 12Z RUNS) ARE
STRUGGLING TO CAPTURE ONGOING CONVECTION IN THE REGION, THEY ALL DO
CONSISTENTLY SHOW ORGANIZED CONVECTION THIS AFTERNOON AND EVENING
GENERATING FAIRLY STRONG COLD POOLS, WHICH IN TURN GRADUALLY PUSHES
THE EFFECTIVE FRONT SOUTH INTO N TX BY THIS EVENING AND OVERNIGHT.
THIS IS SUPPORTED BY RAP ANALYSIS SHOWING HIGHER DCAPE VALUES
ACROSS PORTIONS OF N TX, AS WELL AS THE 12Z FWD SOUNDING WHICH
REVEALED A LAYER OF FAIRLY DRY AIR JUST ABOVE THE BOUNDARY LAYER.
OF THE AVAILABLE HI-RES MODELS, RECENT RUNS OF THE RRFS SEEM TO
BEST REPRESENT THE FORWARD PROPAGATING BOW ECHO IN S MO AND
ADDITIONAL DEVELOPMENT IN SW OK. THEREFORE, THE TWEAKS TO THE
POSITIONING OF THE RISK AREAS LEVERAGED THE RRFS A BIT MORE,
ALTHOUGH SOME DEFERENCE WAS GIVEN TO OTHER GUIDANCE SOURCES AS
WELL. EVEN MODELS THAT AREN'T HANDLING ONGOING CONVECTION VERY WELL
STILL INDICATE THE DEVELOPMENT OF COLD POOLS, AND THE TENDENCY FOR
THE AXIS OF ACTIVE CONVECTION TO SINK SOUTH WITH TIME. THIS LENDS
SOME CONFIDENCE TO THE OVERALL EXPECTATIONS DESCRIBED HERE. THE
SOUTHWARD PROGRESSION OF THE EFFECTIVE FRONT SEEMS TO STALL
OVERNIGHT, WHICH MAY LEAD TO A RAINFALL MAX IN N TX, OR AT LEAST
VERY CLOSE TO THE RED RIVER.
PREVIOUS DISCUSSION: A REPETITIVE SCHEME OF SUCCESSIVE CONVECTIVE
OUTPUTS ACROSS PORTIONS OF WEST TX THROUGH OKLAHOMA WILL RESULT IN
SIGNIFICANT FLASH FLOODING FOR A LARGE PORTION OF THE ABOVE AREAS.
THE COMBINATION OF SEVERAL MID-LEVEL IMPULSES EJECTING NORTHEAST
WITHIN A LARGE SCALE DIFFLUENT PATTERN WILL INTERACT WITH A QUASI-
STATIONARY FRONT ALIGNED FROM THE WESTERN ROLLING PLAINS OF TX UP
TOWARDS THE RED RIVER BASIN MAINLY WEST OF I-35. FAVORABLE MID-
LEVEL ASCENT WILL ALLOW FOR WAVES OF CONVECTIVE INITIATION
BEGINNING LATE-MORNING AND AFTERNOON TUESDAY WITH A SECONDARY PULSE
AROUND 00Z WEDNESDAY WITH A FINAL PULSE FORECAST AFTER 06Z AS THE
MEAN TROUGH FINALLY STARTS PIVOTING EAST OUT OF THE SOUTHWESTERN
CONUS. INSTABILITY WITHIN THE CONFINES OF WEST TX UP TO THE RED
RIVER WILL ALLOW FOR RAPID DEVELOPMENT OF CONVECTIVE CLUSTERS WITH
SOME SUPERCELLULAR MODES PLAUSIBLE PRIOR TO NIGHTFALL, EVENTUALLY
MERGING INTO A MORE MULTI-CELLULAR SCHEME WITH BACKBUILDING FAVORED
WITHIN THE CONFINES OF THE FRONT DENOTED PRETTY WELL WITHIN THE
THETA_E GRADIENT OUTPUT IN EACH DETERMINISTIC. ALL CAMS ARE WELL
SUPPORTIVE OF THE 3-WAVE CONVECTIVE EVOLUTION WITH HEAVY RAINFALL
SITUATED ACROSS THE SOUTHERN HIGH PLAINS NEAR THE EASTERN PERMIAN
BASIN WITH A GENERAL QPF MAXIMA ALIGNED SOUTHWEST TO NORTHEAST
ACROSS THE NORTHERN EXTENSION OF THE ROLLING PLAINS IN TX, UP
THROUGH THE RED RIVER AND INTO THE SOUTHERN PORTION OF THE OKC
METRO. THIS AREA HAS BEEN THE BENEFACTOR OF MULTIPLE CONVECTIVE
EPISODES ALREADY, LEADING TO FLASH FLOODING WITHIN THE CORRIDOR
EXTENDING FROM LAWTON DOWN TO THE RED RIVER. THIS AREA WILL BE THE
MOST PRIMED LOCATION FOR NOT ONLY WIDESPREAD FLASH FLOODING, BUT
SIGNIFICANT LIFE-THREATENING FLASH FLOOD PROSPECTS DUE TO THE WELL
ABOVE NORMAL SOIL MOISTURE ANOMALIES LIKELY CURBING ANY POTENTIAL
FOR RAINFALL TO SOAK INTO THE TOP SOIL LAYER.
LATEST 00Z HREF PROBABILITY FIELDS ARE OVERWHELMINGLY INDICATIVE OF
THE THREAT WITH ONE OF THE MORE ROBUST INDICATIONS OCCURRING
WITHIN THE 6-HR FFG EXCEEDANCE PROBABILITY MARKER RUNNING BETWEEN
70-90% ACROSS THE AREA EXTENDING FROM FOARD COUNTY IN TX UP TO
WESTERN CLEVELAND COUNTY IN OK. NEIGHBORHOOD PROBABILITIES OF >5"
TOTAL RAINFALL ARE RUNNING BETWEEN 50-80% IN THE SAME LOCATION WITH
>8" BETWEEN 20-30% ACROSS SOUTHWEST OK BETWEEN LAWTON TO THE RED
RIVER. NEIGHBORHOOD PROBS FOR >3" ARE SIGNIFICANT ACROSS MUCH OF OK
BACK INTO NORTH TX WITH THE SOUTHWEST EXTENSION BACK INTO THE
SOUTHEAST CORNER OF THE LUB CWA. CONSIDERING THE NASA SPORT SOIL
MOISTURE PERCENTILES RUNNING BETWEEN 70-99% FOR THE 0-40CM LAYER
ACROSS THE ENTIRE AREA ABOVE, THE PROPENSITY FOR FLOODING, EVEN IN
RURAL ZONES WILL BE HIGHER THAN NORMAL. GIVEN EXPECTED RATES
BETWEEN 1-2"/HR DURING PEAK STORM CYCLES AND THE EXPECTATION FOR
>3" OF RAINFALL...THE THREAT WILL BE OF THE HIGHER MAGNITUDE IN
TERMS OF IMPACT PROSPECTS. THE PREVIOUS MDT RISK INHERITED WAS NOT
ONLY MAINTAINED, BUT EXPANDED A BIT FURTHER SOUTHWEST TO ALIGN WITH
THE HIGHER PROBABILITIES WITH THE NEIGHBORHOOD >5" POTENTIAL AND
THE ELEVATED HREF EAS >2" PROBABILITIES THAT HAVE BEEN DEPICTED. A
HIGH-END MDT RISK IS FORECAST ACROSS THE RED RIVER BASIN WEST OF
WICHITA FALLS UP INTO THE SOUTHERN FRINGES OF THE OKC METRO,
INCLUDING THE TOWN OF NORMAN. LOWER END PROBABILITIES FOR FLASH
FLOODING WILL EXIST ACROSS AREAS OF THE EASTERN PERMIAN BASIN OUT
THROUGH THE CONCHO VALLEY AS WELL AS ACROSS MUCH OF OKLAHOMA NOT
INCLUDED IN THE MDT.
..MISSISSIPPI AND OHIO VALLEYS
16Z UPDATE: NO MAJOR CHANGES WERE MADE TO THE RISK AREAS HERE.
PREVIOUS DISCUSSION: MID-LEVEL IMPULSES THAT EJECT OUT OF THE
SOUTHERN PLAINS WILL CONTINUE TO PRESS NORTHEAST TOWARDS THE
MISSISSIPPI AND OHIO VALLEYS WITH A PROGRESSIVE COLD FRONT MOVING
SOUTHEAST OUT OF THE MIDWEST DURING THE SAME TIME FRAME. AFTERNOON
DESTABILIZATION COUPLED WITH THE FAVORABLE ADDITION OF MID-LEVEL
FORCING AND SURFACE FRONTOGENESIS WILL LEAD TO SCATTERED CONVECTIVE
PULSES ACROSS THE REGION WITH SOME ORGANIZED ELEMENTS FOCUSED
WITHIN THE CONFINES OF THE FRONT AND UNDER THE SHORTWAVE
PROPAGATION. SOILS REMAIN MOIST ACROSS MUCH OF THE REGION EXTENDING
FROM MO THROUGH THE OHIO RIVER BASIN WITH AN EASTERN EXTENSION TO
THE CENTRAL APPALACHIANS AND WESTERN PA HIGHLANDS. PWAT ANOMALIES
ON THE ORDER OF +1 TO AS HIGH AS +2.5 DEVIATIONS CEMENTS A
FAVORABLE DEEP MOIST ENVIRONMENT CONDUCIVE FOR HEAVY RAINFALL
PROSPECTS WITHIN ANY CONVECTIVE SCHEME. THE GREATEST CONCENTRATION
OF HEAVY RAIN WILL LIKELY BE BACK OVER SOUTHERN AND CENTRAL MO
TOWARDS THE 3 RIVER CONFLUENCE ZONE NEAR KY/MO/IN/IL. HREF PROBS
FOR >1" ARE VERY HIGH (70-90+%) ACROSS MUCH OF THE MISSISSIPPI AND
OHIO VALLEY AREAS WITH >2" PROBS RELATIVELY HIGH (50-70%) IN-OF THE
OHIO RIVER BASIN OVER SOUTHERN IL THROUGH MUCH OF EASTERN KY. THE
COMBINATION OF CONVECTION OVER AREAS THAT ARE STILL IN RECOVERY
FROM PREVIOUS RAINFALL EPISODES AND COMPLEX TERRAIN WILL CREATE A
THREAT FOR ISOLATED TO PERHAPS SCATTERED FLASH FLOOD INSTANCES OVER
A LARGE AREA DURING THE AFTERNOON AND EVENING HOURS TUESDAY. A
SLGT RISK REMAINS FIRMLY IN PLACE ACROSS MUCH OF MO ALONG AND SOUTH
OF I-70 UNTIL THE 3 RIVER CONFLUENCE ZONE REFERENCED ABOVE. A MRGL
RISK ENCOMPASSES ALL OTHER AREAS EAST THROUGH WESTERN PA AND EVEN
THE SOUTHWEST CORNER OF NY STATE.
LAMERS/KLEEBAUER
DAY 2
VALID 12Z WED APR 30 2025 - 12Z THU MAY 01 2025
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE ARKLATEX, EASTERN OKLAHOMA, AND WESTERN OZARKS...
THE PATTERN REMAINS VERY ACTIVE AS WE MOVE INTO WEDNESDAY AS THE
MEAN TROUGH SLOWLY SLIPS EASTWARD WITH AMPLE MID-LEVEL ENERGY
ACCOMPANYING, CREATING AN ENVIRONMENT FAVORABLE FOR ORGANIZED
CONVECTIVE CLUSTERS THROUGH THE ENTIRE D2 TIME FRAME. RICH GULF AIR
WILL BE PULLED POLEWARD AHEAD OF THE ADVANCING TROUGH WITH SEVERAL
MID-LEVEL PERTURBATIONS EJECTING OUT OF THE AHEAD OF THE PRIMARY
SHORTWAVE TROUGH. THIS IN COMBINATION WITH SUFFICIENT BUOYANCY
ACROSS CENTRAL AND EAST TX THROUGH THE MISSISSIPPI VALLEY WILL
MAINTAIN A WIDESPREAD CONVECTIVE ZONE OF IMPACT WITH STRONG, HEAVY
THUNDERSTORM CORES AND CLUSTERS CAPABLE OF PRODUCING PROLIFIC
RAINFALL TOTALS.
TWO PRIMARY PERIODS OF INTEREST HAVE BECOME FAIRLY WELL DOCUMENTED
WITHIN THE RECENT DETERMINISTIC CYCLES. THE FIRST IS THE
CONTINUATION OF THE CONVECTIVE COMPLEX THAT WILL DEVELOP OVERNIGHT
TUESDAY INTO WEDNESDAY MORNING OVER THE WESTERN RED RIVER BASIN AND
SLOWLY TRUDGE EASTWARD AS IT MANEUVERS IN TANDEM WITH THE PRIMARY
SHORTWAVE ENERGY, AND ACROSS THE REMAINING THETA_E GRADIENT RUNNING
PARALLEL TO THE RIVER. 00Z HREF ON THE BACK END OF ITS RUN IS
SIGNALING SOME VERY IMPRESSIVE RAINFALL TOTALS (2-5") WITHIN THE
FIRST 12 HR. PERIOD IN THE FORECAST CYCLE (12Z WED TO 00Z THU)
ACROSS PLACES ALONG THE RED RIVER UP THROUGH CENTRAL AND EASTERN OK
AS THE MULTI-CELL CLUSTER ADVANCES. PROB FIELDS FOR >3" WITHIN
THAT FIRST 12 HRS. ARE BETWEEN 50-90% ACROSS SOUTH-CENTRAL OK,
ALONG AND EAST OF THE I-35 CORRIDOR WITH 25-40% PROBS FOR EVEN >5".
CONSIDERING THIS IS ONLY FOR THE FIRST 12 HRS., THE PROBS ARE
PRETTY IMPRESSIVE AND REALLY HIGHLIGHT THE THREAT ON THE INITIAL
HEAVY QPF CORE.
THE SECOND PERIOD OF INTEREST WILL OCCUR IN THE AFTERNOON AND
EVENING HRS. AS DIURNALLY DRIVEN CONVECTION WILL FLARE UP OVER
EASTERN TX WITHIN A BROAD MOISTURE RICH ENVIRONMENT AS NAEFS
ANOMALIES CONTINUE TO POINT TO +2 TO +3 DEVIATIONS FOR PWATS
(1.5-2") SITUATED OVER THE AREA. LLJ INTRODUCTION BY EARLY EVENING
WILL ONLY EXACERBATE THE POTENTIAL WITH INCREASING LOW-LEVEL SHEAR
CAPABLE OF PERSISTING UPDRAFTS AND EVENTUAL CELL CLUSTERS THAT WILL
ORIGINATE FROM CELLS MOVING NORTHEAST WITHIN THE MEAN FLOW. SEVERAL
MID-LEVEL PERTURBATIONS WILL BE IN THE VICINITY ACROSS NORTHEAST TX
TO TRULY ENHANCE AND MAINTAIN CONVECTIVE CORES SUCH THAT IT BECOMES
A FAIRLY FAVORABLE PROSPECT FOR HEAVY RAINFALL EXTENDING INTO THE
LOWER MISSISSIPPI VALLEY. TOTALS BETWEEN 2-4" WITHIN AN AREAL
EXPANSE ARE FORECAST ACROSS THE ARKLATEX UP THROUGH WESTERN AR TO
JUST BEFORE THE MO OZARKS. LOCALLY HIGHER TOTALS WILL BE POSSIBLE
ACROSS THAT ENTIRE AREA GIVEN THE FAVORABLE RATES BETWEEN 1-2.5"/HR
FORECAST CURRENTLY WITHIN GLOBAL DETERMINISTIC. PENDING OUTFLOW
PROPAGATION WITHIN THE SETUP, HEAVIER TOTALS COULD ADVANCE FURTHER
EAST TOWARDS CENTRAL AR, BUT AT THIS JUNCTURE, THE PRIMARY AREA OF
FOCUS ALIGNS OVER EAST TX UP THROUGH EASTERN OK AND WESTERN AR.
THIS CORRELATES WELL WITH THE THETA_E RIDGE EXTENSION UP THROUGH
THE AREA WHERE CONVECTIVE THREATS WILL BE HIGHEST DURING PEAK
DIURNAL DESTABILIZATION AND BEYOND.
THE PREVIOUS MDT RISK WAS MAINTAINED WITH A WESTWARD EXTENSION BACK
OVER PORTIONS OF SOUTH-CENTRAL OK DOWN ACROSS THE RED RIVER INTO
TX. THE MDT RISK IS NOT WITHIN THE DFW METRO, HOWEVER IT DOES LIE
JUST NORTH, SO WILL HAVE TO MONITOR TRENDS CLOSELY OVER THE NEXT
24-36 HRS. A BROAD SLGT RISK EXTENDS SOUTH INTO EAST TX BUT WELL
NORTH OF THE TX GULF COAST.
KLEEBAUER
DAY 3
VALID 12Z THU MAY 01 2025 - 12Z FRI MAY 02 2025
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE LOWER MISSISSIPPI VALLEY UP THROUGH THE CENTRAL AND EASTERN
GREAT LAKES...
NUMEROUS AREAS OF THUNDERSTORMS WILL DEVELOP ACROSS THE MISSISSIPPI
VALLEY THROUGH THE EAST-CENTRAL CONUS DUE TO THE PROGRESSION OF A
SURFACE LOW OUT OF THE SOUTHERN PLAINS AND ATTENDANT COLD FRONT
TRAILING THE PRIMARY CYCLONE. WESTERN ATLANTIC RIDGING WILL ALLOW
FOR A CONTINUED ADVECTION OF RICH GULF AIR INTO THE EASTERN U.S.
WITH A DEEP MOIST ENVIRONMENT PRETTY MUCH SOLIDIFIED FROM THE GREAT
LAKES DOWN TO THE GULF COAST. AREA PWATS WILL RUN BETWEEN 1.5-2.5
DEVIATIONS ABOVE NORMAL FOR MUCH OF THE CONUS EAST OF THE
MISSISSIPPI, AN ENVIRONMENT VERY FAVORABLE FOR CONVECTIVE SCHEMES
ON THE EASTERN FLANK OF THE SURFACE LOW, AS WELL AS ALONG AND AHEAD
OF THE PROGRESSING COLD FRONT. AREAL QPF WITHIN THE ENSEMBLE MEANS
ARE GENERALLY BETWEEN 0.5 AND 1" WITH SOME LOCALLY HIGHER FORECAST
ACROSS THE ABOVE AREA(S). SOME OF THE DETERMINISTIC OUTPUT IS OF
COURSE HIGHER WITH SOME 2-4" MAXIMA LITTERED OVER THE SOUTHEAST AND
OHIO VALLEY WHERE THE CONVECTIVE SCHEME WILL BE MOST PROMINENT.
THERE'S LITTLE AGREEMENT WITHIN THE SUITE ON EXACTLY WHERE THE
HEAVIEST PRECIP WILL FALL, BUT THERE'S PLENTY OF COVERAGE WHERE ANY
ONE SPOT COULD BE THE BENEFICIARY OF SOME HEAVY PRECIP. AT THIS
LEAD, WOULD PROBABLY LEAN ON THE TENNESSEE VALLEY INTO THE SOUTHERN
OHIO VALLEY TO HAVE THE BEST POTENTIAL DUE TO A COMBO OF ANTECEDENT
MOIST SOILS, AS WELL AS THE GREATEST SURFACE BASED ASCENT LIKELY
WITHIN PROXY TO THE ADVANCING COLD FRONT. A BROAD MRGL RISK EXISTS
OVER PARTS OF THE LOWER MISSISSIPPI UP THROUGH THE CENTRAL AND
EASTERN GREAT LAKES WITH THE FURTHEST EAST EXPANSION OVER WESTERN
NY STATE DOWN TO THE CENTRAL APPALACHIANS.
KLEEBAUER
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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