540
FXUS63 KARX 131722
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1222 PM CDT SUN SEP 13 2026
KEY MESSAGES
- SHOWER CHANCES MOVE WEST TO EAST THIS MORNING INTO THE
AFTERNOON, MINIMAL OVERALL ACCUMULATIONS EXPECTED.
- HEAVY RAIN LIKELY MONDAY THROUGH MONDAY NIGHT WITH FLOODING
CONCERNS WHERE HEAVY RAIN BANDS SET UP.
- RAIN CHANCES RETURN WEDNESDAY, POTENTIALLY LASTING INTO THE
WEEKEND.
DISCUSSION
ISSUED AT 1245 AM CDT SUN SEP 13 2026
TODAY:
SHOWER CHANCES THROUGH TODAY WILL BE TIED TO A MID LEVEL TROUGH
PASSAGE AND POSITIVE MID LEVEL VORTICITY ADVECTION THROUGH THE
UPPER MIDWEST. OVERALL LIMITING FACTOR FOR COVERAGE AND AMOUNTS
WILL BE AVAILABLE MOISTURE.
RAINFALL CHANCES MONDAY NIGHT:
HEAVY RAINFALL SPREADS NORTHEAST THROUGH MONDAY MORNING, BECOMING
WIDESPREAD THROUGH OF THE REST OF MONDAY AND MONDAY NIGHT. THE
RESPONSIBLE CLOSED UPPER LEVEL ANTICYCLONE ON UPPER LEVEL WATER
VAPOR IMAGERY LOOPS OVER THE PACIFIC NORTHWEST WILL RAPIDLY ADVECT
EAST INTO SOUTHERN CANADA, DRAWING 90TH PERCENTILE (TOP 13.00Z RAOB -
CLIMATOLOGY) NORTH THROUGH THE CENTRAL TO NORTHERN PLAINS.
RESULTANT LOCAL PWATS EXPECTED TO NEAR 2" BY MONDAY NIGHT (GEFS
12.18Z 30-60% ; EPS 12.18Z 50-90%). INITIAL, MORE WIDESPREAD
RAINFALL EXPECTED TO PROGRESS EAST WITHIN THE CLOSING WARM, MOIST
SECTOR ADVECTING EAST ACROSS THE UPPER MIDWEST THROUGH MONDAY.
SOLIDIFICATION OF THE LOW LEVEL FRONTAL BOUNDARY AND INTENSIFICATION
OF THE LOW LEVEL JET WITH ANOMALOUS LEVEL MOISTURE INCREASES
FLOODING CONCERN PRIMARILY ACROSS THE SOUTHERN HALF OF THE FORECAST
AREA MONDAY NIGHT. EXACT LOCATION OF THE FRONTAL BOUNDARY FOCUSING
THE HEAVIER RAINFALL RATES AS THE PARENT LOW EXITS EAST WILL
DETERMINE LOCATION OF HIGHEST CONCERN, VARYING FROM WEST-CENTRAL
WISCONSIN, EAST-CENTRAL MINNESOTA, AND NORTHEAST IOWA IN THE
AVAILABLE LREF (12.12Z). LREF (12.12Z) MEMBER MEAN PRECIPITATION
SPREADS FROM 0.6" (GEFS) TO 1.4" (EPS) WITH INTERMEMBER
INTERQUARTILE SPREAD FROM 0.25" (GEFS) TO 1.2" (EPS), OUTLINING THE
CURRENT FORECAST CHALLENGE IN FINE TUNING LOCATION OF HIGHEST
IMPACTS.
RAINFALL RETURNS WEDNESDAY:
MONDAY'S FRONTAL BOUNDARY EXPECTED TO REMAIN JUST SOUTH OF THE
LOCALE FORECAST AREA AS PASSING ANTICYCLONIC LOW LEVEL FLOW MOSTLY
DRYING THINGS OUT FOR TUESDAY BEFORE A SIMILAR TRAJECTORY EJECTING
UPPER LEVEL LOW LIFTS NORTHEAST THROUGH THE NORTHERN PLAINS FOR
WEDNESDAY. WHILE THE ANOMALOUS MOISTURE WILL REMAIN ON THE SOUTHERN
DOORSTEP OF THE LOCAL FORECAST AREA, MERIDIONAL EXTENT OF THE LOW'S
PATH LEAVES DISCREPANCIES AND LOWER CONFIDENCE FOR NORTHERN SURGE OF
MOIST AIR. THEREFORE, HAVE KEPT NBM PRECIPITATION PROBABILITIES
WEDNESDAY THROUGH SATURDAY. THE LONG DURATION OF RAINFALL POTENTIAL
WOULD INCREASE ADDITIONAL FLOODING CONCERNS THROUGH THE WEEK.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1220 PM CDT SUN SEP 13 2026
WHILE VFR CONDITIONS ARE FAVORED TO CONTINUE OVER THE NEXT 24
HOURS, REDUCTIONS DUE TO APPROACHING WIDESPREAD SHOWERS AND
THUNDERSTORMS MAY LEAD TO REDUCTIONS AT RST NEAR THE TAIL END OF
THE PERIOD. OTHERWISE, ONLY ISSUES LOOK TO BE AROUND OVS
OVERNIGHT WHEN THE USUAL WISCONSIN AND KICKAPOO VALLEY FOG/STRATUS
LOOK TO DEVELOP. WIDESPREAD REDUCTIONS ARE LIKELY AFTER 18Z
MONDAY.
ARX WATCHES/WARNINGS/ADVISORIES
WI...FROST ADVISORY FROM 2 AM TO 8 AM CDT MONDAY FOR WIZ034-042.
MN...NONE.
IA...NONE.
DISCUSSION...JAR
AVIATION...FERGUSON
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