180
FOUS30 KWBC 091559
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1059 AM EST FRI JAN 9 2026
DAY 1
VALID 16Z FRI JAN 09 2026 - 12Z SAT JAN 10 2026
..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF SOUTHERN MISSISSIPPI AND ADJACENT LOUISIANA...
..16Z UPDATE
THE OSPO ADVECTED LPW PRODUCT SHOWED THE AXIS OF ANOMALOUS MOISTURE
IN PLACE OVER THE LOWER MISSISSIPPI VALLEY (2 TO 4 STANDARD
DEVIATIONS ABOVE THE MEAN) WITH ORIGINS IN THE MIDDLE AND UPPER
LEVELS TO THE TROPICAL EASTERN PACIFIC, WHILE LOW LEVEL MOISTURE
WAS ORIGINATING FROM THE GULF. THE DUAL CONNECTION OF MOISTURE HAS
RESULTED IN HIGHER END RAINFALL EVENTS IN THE PAST SO SEVERAL OF
THE 12Z CAMS SHOWING 7+ INCHES OVER THE 24 HOUR WINDOW ENDING
SATURDAY MORNING LOOK BELIEVABLE.
ONGOING AXES OF HEAVY RAIN WERE OBSERVED ALONG THE EASTERN LA/MS
BORDER BETWEEN BATON ROUGE AND HATTIESBURG EARLY THIS MORNING WITH
HOURLY RAINFALL OF 1 TO 2+ INCHES AND 2 TO 4 INCHES THROUGH JUST
PRIOR TO 16Z. SIMILAR POTENTIAL WILL EXIST OVER THE NEXT 12-24
HOURS WITH THE LIKELIHOOD FOR SEVERAL TRAINING AXES TO DEVELOP
ACROSS THE LOWER MISSISSIPPI VALLEY. THE GREATEST PROBABILITY OF
OVERLAP OF HEAVY RAINFALL AXES LOOKS TO BE WITHIN THE MODERATE RISK
WHICH WAS EXPANDED NORTHEASTWARD INTO WESTERN ALABAMA WHERE 24 HOUR
RAINFALL OF AT LEAST 3 TO 6 INCHES LOOKS LIKELY.
OTHER ADJUSTMENTS FOR THE 16Z UPDATE INCLUDED A SMALL SOUTHWESTERN
SHIFT TO THE MARGINAL, SLIGHT AND 25% CONTOUR ACROSS EASTERN TEXAS
INTO LOUISIANA, IN LINE WITH THE LATEST 12Z HREF.
OTTO
..PREVIOUS DISCUSSION FOLLOWS
THE CLASSIC SYNOPTIC SETUP FOR A WINTER FLASH FLOODING EVENT
CONTINUES TO SLOWLY ADJUST TO THE TIMING/ORIENTATION OF THE
UPSTREAM SHORTWAVE OVER THE SOUTHWEST U.S. THE VERY STRONG LEADING
CYCLONE ACROSS THE GREAT LAKES WILL CONTINUE TO ZIP ALONG TO THE
EAST-NORTHEAST WITH WELL ABOVE NORMAL (4 STANDARD ANOMALY/99TH
PERCENTILE) MOISTURE AND FLUX STILL STREAMING ACROSS THE OHIO AND
TENNESSEE VALLEY. ONGOING THUNDERSTORMS ARE EXPECTED ACROSS THE
LOWER MS VALLEY AS MORNING SURGE OF GULF AIR STREAMS NORTHWARD
BECOMING INCREASINGLY CONFLUENT/CONVERGENT WELL AHEAD OF THE
UPSTREAM SYNOPTIC FRONT IN THE PLAINS.
THE STRONG UPSTREAM BASE OF THE POSITIVE TILT TROF WILL BE
ADVANCING THROUGHOUT THE DAY INTO THE PLAINS, THOUGH THE UPPER-
LEVEL JET STREAK ALSO BE EXPANDING AND STRENGTHENING ACROSS THE
OZARK PLATEAU INTO THE OHIO RIVER VALLEY FROM 110KTS TO OVER 150KTS
BY THE END OF THE FORECAST PERIOD. THE TROUGH WILL ALSO BE SHEARING
INTO THE CONFLUENT, INCREASINGLY UNIDIRECTIONAL LOW TO MID-LEVEL
FLOW ALLOWING FOR A DEEP SOUTHWEST TO NORTHEAST ATMOSPHERIC RIVER
FROM THE WESTERN GULF UP THE LOWER MISSISSIPPI AND THROUGH THE
TENNESSEE RIVER VALLEY INTO THE SOUTHERN APPALACHIANS/CUMBERLAND
PLATEAU THROUGH THE MAJORITY OF THE DAY. WHILE THE LOW LEVEL FLOW
WILL BE WEAKER THAN THURSDAY, 850-700MB 40-45KTS AND 1.5-1.75"
TOTAL PWAT VALUES WILL ALLOW FOR HIGH MOISTURE FLUX CONVERGENCE AND
SUPPORT EFFICIENT RAINFALL PRODUCTION.
AS THE TRENDS HAVE SLOWED THE UPSTREAM SHORTWAVE, THIS ALLOWS FOR
GREATER FLUX OF UNSTABLE AIR NORTHWARD AND FORCING TO
OVERLAP/INTERSECT WITH 1000-1500 J/KG OF MLCAPE ACROSS THE COASTAL
PLAIN REDUCING TOWARD 500 J/KG NEAR THE SOUTHERN TN BORDER, PULSING
WITH NORTHWARD SURGES AS THE SHORTWAVE LIFTS OUT. THIS WILL PROVIDE
ENOUGH ASCENT AND LOW LEVEL SHEAR FOR ORGANIZED BANDS OF
CONVECTION THAT WILL LIKELY HAVE TRAINING ELEMENTS THROUGHOUT THE
DAY. RAIN-RATES OF 1.5"/HR ARE PROBABLE THOUGH 00Z HI-RES CAMS
SUPPORT OCCASIONAL UP-TICKS TO 2"+/HR LOCALLY. COMBINED WITH THE
TRAINING PROFILES, 00Z HREF SHOWS SOLID 15-25% 3"/3HR PROBABILITY
ACROSS SOUTHERN MS INTO FAR NORTHEAST LA, WITH NEARLY 50%
NEIGHBORHOOD PROBABILITY OF 5". AS SUCH, AND IN COORDINATION WITH
LOCAL FORECAST OFFICES, WPC IS INTRODUCING A SMALL MODERATE RISK OF
EXCESSIVE RAINFALL FOR S MS AND ADJACENT NE LA. IT SHOULD BE
NOTED, THERE IS SOLID AGREEMENT WITHIN THE GUIDANCE SUITE OF 5-8"
TOTAL STREAKS BUT THERE IS LIMITED AGREEMENT IN THE PLACEMENT
PARTICULARLY WEST OR EAST.
THUNDERSTORMS WILL TRAIN, BUT AS THEY MOVE NORTHEAST INTO MIDDLE TO
EASTERN TN AND NORTHERN AND CENTRAL AL, INTENSITY AND RAINFALL
TOTALS ARE LIKELY TO DIMINISH, GIVEN INSTABILITY WILL BE LIMITED
TO 200-300 J/KG. YET, PROLONGED DURATION AND SIZABLE TOTALS OF 2-4"
ARE STILL POSSIBLE AND SO THE SLIGHT RISK CONTINUES TO BE IN PLACE
DOWNSTREAM ACROSS MUCH OF AL, NORTHERN GA, AND SOUTHEAST TN.
UPSTREAM, AS THE MAIN FORCING EXITS, A SECONDARY AXIS OF
CONVERGENCE ALONG INSTABILITY/MOISTURE GRADIENT ACROSS EASTERN
TEXAS WILL PRODUCE ADDITIONAL, SLIGHTLY MORE ELEVATED
THUNDERSTORMS. SIMILAR RATES OF 1.5" TO 2"/HR ARE POSSIBLE WITH
SOME REPEATING/TRAINING TRACKS ACROSS NW LA, THOUGH OVERALL
DURATION AND COVERAGE SHOULD LIMIT RAINFALL TOTALS TO 2-4" RELATIVE
TO THE MODERATE RISK AREA FURTHER SOUTHEAST. AS SUCH, THE SLIGHT
RISK WAS ALSO EXPANDED WESTWARD ALONG THE AXIS OF BEST OVERALL
MODEL AGREEMENT.
GALLINA
DAY 2
VALID 12Z SAT JAN 10 2026 - 12Z SUN JAN 11 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHERN APPALACHIANS...
HEAVY RAINFALL EARLY IN THE PERIOD IS EXPECTED OVER WHAT SHOULD BE
AT LEAST PARTIALLY SATURATED GROUND ACROSS PORTIONS OF THE
SOUTHERN APPALACHIANS BEFORE HEAVY RAINFALL EJECTS INTO THE
SOUTHERN MID-ATLANTIC STATES. ADDED A MARGINAL RISK AS A
PRECAUTION FOR THIS REASON; THE THREAT NOT EXPECTED TO PERSIST PAST
18Z SATURDAY.
ROTH/GALLINA
DAY 3
VALID 12Z SUN JAN 11 2026 - 12Z MON JAN 12 2026
THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS LESS
THAN 5 (FIVE) PERCENT.
GALLINA
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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