519  
FXUS63 KARX 171111  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
611 AM CDT SUN AUG 17 2025  
   
KEY MESSAGES  
 
- HEAVY RAIN BAND THIS MORNING WEAKENS THROUGH THE LATE MORNING  
WITH A MOSTLY DRY FORECAST UNTIL TONIGHT.  
 
- WIDESPREAD HEAVY RAIN PROGRESSES FROM WEST TO EAST OVERNIGHT  
THROUGH MONDAY. AN ADDITIONAL 1" TO 1.5"+ IS EXPECTED FOR MUCH  
OF THE AREA.  
 
 
   
DISCUSSION  
 
ISSUED AT 304 AM CDT SUN AUG 17 2025  
 
A NARROW CORRIDOR OF ONGOING HEAVY RAINFALL IS EXPECTED TO  
CONTINUE THROUGH THE EARLY MORNING HOURS, SITUATED ALONG AN AXIS  
OF DILATATION AND PRESSURE SADDLE VISIBLE ON VWPS ACROSS THE  
UPPER MIDWEST. ADDITIONAL STORM INITIATION UPSTREAM OVER  
SOUTHWESTERN MINNESOTA EARLY THIS MORNING ON THE NOSE OF THE LOW  
LEVEL JET IS EXPECTED TO REMAIN WEST OF THE LOCAL FORECAST AREA  
AS PRECIPITATION CHANCES RETURN TONIGHT, BECOMING WIDESPREAD  
OVERNIGHT.  
 
BREAK IN HEAVIER PRECIPITATION THIS AFTERNOON:  
 
SLIGHT REGRESSION IN THE UPPER LEVEL SYNOPTIC HIGH OFF THE  
SOUTHERN CONUS WILL PASS A WEAKENING RIDGE AXIS ACROSS THE UPPER  
MIDWEST TODAY AND SUBSEQUENTLY POINT MID-UPPER LEVEL SOUTHWEST  
FLOW DIRECTLY FROM THE SOUTHERN CALIFORNIA COAST THROUGH THE  
UPPER MISSISSIPPI RIVER VALLEY TONIGHT. A SLIGHT BREAK IN  
PRECIPITATION THROUGH THE EARLY AFTERNOON LOCALLY WILL  
ACCOMPANY THIS SYNOPTIC PROGRESSION BEFORE PERTURBATIONS ALONG  
THE SOUTHWEST FLOW AND ASSOCIATED AGEOSTROPHIC ASCENT DEEPEN AND  
ADVECT A SURFACE LOW NORTHEAST THROUGH THE NORTHERN PLAINS  
PERPETUATING HEAVY RAIN CONCERNS LOCALLY TONIGHT THROUGH MONDAY.  
 
INITIAL RAINFALL TONIGHT:  
 
AS A LOW STRENGTHENS ACROSS THE NORTHERN PLAINS TODAY,  
INVIGORATION OF A SOUTHWEST LOW LEVEL JET TIGHTENS THE  
ANOMALOUS (SPC CLIMATOLOGY) RIBBON OF MOISTURE (1.5"-2" PWATS  
17.00Z RAOBS) LINGERING ACROSS THE FORECAST AREA FOR TONIGHT.  
RESULTANT INITIAL PRECIPITATION CHANCES (20-40%) EXPECTED IN A  
NARROW NORTHWEST TO SOUTHEAST ORIENTED BAND PRIMARILY ACROSS OUR  
WESTERN PERIPHERAL COUNTIES FROM NORTHEAST IOWA INTO SOUTHEAST  
MINNESOTA. HIGHEST CONFIDENCE IN PRECIPITATION WILL REMAIN  
NORTHWEST OF THE LOCAL FORECAST AREA TIED TO FORCING FROM THE  
SURFACE LOW WHILE FRONTAL FORCING REMAINS SUPERFLUOUS,  
INHERENTLY DEPENDENT ON EXACT LOCATION OF THE FRONT. EVENTUALLY,  
PRECIPITATION POTENTIAL (30-50%) INCREASES FROM WEST TO EAST  
WITHIN THIS BAND AS ISENTROPIC ASCENT INCREASES TONIGHT.  
 
WIDESPREAD PRECIPITATION OVERNIGHT THROUGH MONDAY:  
 
SUBSEQUENT STRENGTHENING TO THE SURFACE LOW OVERNIGHT  
FROM A SHORTWAVE PROVIDING MORE WESTERLY MID LEVEL FLOW RESULTS  
IN AN EASTERLY ADVECTION TO THE LOW NEAR THE INTERNATIONAL  
BORDER AND INCREASED PRECIPITATION CHANCES LOCALLY THROUGH  
MONDAY. CURRENT CONFIDENCE KEEPS HIGHEST PRECIPITATION  
POTENTIAL CONSTRAINED TO THE NORTHERN 2/3 OF THE FORECAST AREA,  
CLOSER TO THE SURFACE LOW. GIVEN THE HIGHER CONFIDENCE, HAVE  
COLLABORATED WITH WPC AND NEIGHBORING WFOS TO INCLUDE A SLIGHT  
ERO THROUGH DAY 2 IN WISCONSIN COUNTIES WHERE HEAVIEST  
PRECIPITATION HAS BEEN REALIZED OVER THE LAST 48 HOURS.  
 
ADDITIONAL CYCLOGENESIS ALONG A POTENTIAL TRIPLE POINT NEAR  
SD/MN/IA COULD ALSO INCREASE HEAVY PRECIPITATION AND STORM  
IMPACTS FARTHER SOUTH, ACROSS THE LOCAL FORECAST AREA.  
 
COOLER & DRIER THROUGH MIDWEEK:  
 
TODAY'S REGRESSIVE SYNOPTIC UPPER LEVEL HIGH SETS UP OVER THE  
DESERT SOUTHWEST INTO MIDWEEK USHERING IN UPPER LEVEL DIFFLUENCE  
AND BACK DOOR COOLER AIR LOCALLY WITH NORTHEAST WINDS KEEPING  
THE PATTERN DRIER AND COOLER WITH DAYTIME HIGHS MOSTLY IN THE  
70S. AS THIS WEEKEND'S MOISTURE BECOMES TRAPPED AGAINST ACTIVITY  
IN THE ATLANTIC, RETURN FLOW RAMPS UP INTO THE NORTHERN PLAINS,  
RESULTING IN THE LOCAL FORECAST AREA SURROUNDED BY WARMTH AND  
WEAKENING PRECIPITATION CHANCES INTO NEXT WEEKEND.  
 
 
   
AVIATION /12Z TAFS THROUGH 12Z MONDAY/  
 
ISSUED AT 558 AM CDT SUN AUG 17 2025  
 
EARLY MORNING STORMS SLOWLY WEAKENING OVER SOUTHEAST MINNESOTA,  
EVENTUALLY CLEARING THROUGH THE LATE MORNING HOURS. LIMITED  
LIGHTNING ACTIVITY AT 17.12Z TAF ISSUANCE RESULTED IN KEEPING  
VCTS MENTION AT KRST TAF SITE WITH INCREASED ACTIVITY REMAINING  
WEST OF KAUM. DO NOT EXPECT ADDITIONAL STORM INITIATION FARTHER  
EAST THROUGH THE LATE MORNING.  
 
LOW CONFIDENCE IN SUBSEQUENT CEILING RESTRICTIONS AFFECTING MOST  
OF THE FORECAST AREA FROM NORTHEAST IOWA, SOUTHEAST MINNESOTA,  
AND WESTERN INTO CENTRAL WISCONSIN. FORECAST MODEL GUIDANCE  
VARIES FROM LIFR TO VFR CEILINGS INTO THE AFTERNOON. THEREFORE,  
WHILE MVFR CEILINGS ARE IN BOTH TAFS THROUGH THE MORNING HOURS,  
MAY NEED TO BE ADJUSTED AS OBSERVATIONS ARRIVE.  
 
STORM CHANCES INCREASE AGAIN TONIGHT, PROGRESSING FROM WEST-  
NORTHWEST TO EAST-SOUTHEAST THROUGH MONDAY. INITIALLY EXPECT  
MVFR-IFR CEILINGS WITH INCOMING PRECIPITATION FOLLOWED BY  
POTENTIAL FOR VLIFR-IFR VISIBILITIES DURING HEAVY RAIN IN  
PASSING STORMS. WIDESPREAD AVIATION IMPACTS EXPECTED THROUGH  
MONDAY, LIKELY LINGERING IN CENTRAL WISCONSIN THROUGH MONDAY  
NIGHT.  
 
FRONTAL BOUNDARY PASSAGE MONDAY NIGHT LIMITS CONFIDENCE FOR ANY  
AVIATION IMPACTS AFTER TUESDAY.  
 
 
   
HYDROLOGY  
 
ISSUED AT 405 AM CDT SUN AUG 17 2025  
 
BESIDES AN ONGOING BAND OF HEAVY RAINFALL FROM SOUTHWEST  
MINNESOTA THROUGH SOUTHWEST WISCONSIN EARLY THIS MORNING,  
ADDITIONAL MORE WIDESPREAD HEAVY RAINFALL WITH 1"+ PER HOUR  
RAINFALL RATES IS EXPECTED OVERNIGHT THROUGH MONDAY. THE  
COMBINATION OF THESE HIGH RATES WITH MANY AREAS HAVING ALREADY  
EXPERIENCED HEAVY RAINFALL OVER THE LAST 48 HOURS, FLASH  
FLOODING CONCERNS PERSIST FOR MUCH OF THE AREA THROUGH MONDAY.  
 
THIS MORNING'S NARROW BAND OF HEAVY RAIN PRODUCED 1" TO 2"  
RAINFALL RATES AND 3"+ ACCUMULATION MAXIMA OVERNIGHT LOCALLY  
FROM FILLMORE COUNTY, MN THROUGH WINNESHIEK COUNTY, IA,  
ALLAMAKEE COUNTY, IA, AND GRANT COUNTY, WI. THE INITIAL TIGHT  
GRADIENT OF STRONGER STORMS THAT CAUSED FLASH FLOODING HAS SINCE  
DISSIPATED THROUGH THE EARLY MORNING HOURS, LESSENING OVERALL  
FLASH FLOODING CONCERNS. EXPECT THIS LINE OF HEAVY RAIN TO  
CONTINUE THROUGH THE MORNING HOURS, PROVIDING ANOTHER 1"+ IN  
SOME SPOTS.  
 
FRIDAY'S HEAVY RAIN OBSERVATIONS OF 1" TO 3"+ OCCURRED IN  
NORTHEAST IOWA, SOUTHEAST MINNESOTA, AND WESTERN THROUGH CENTRAL  
WISCONSIN.  
 
AN ADDITIONAL 1" TO 2"+ OF RAINFALL IS EXPECTED OVERNIGHT  
THROUGH MONDAY MOSTLY NORTH OF INTERSTATE 90 IN SOUTHEAST  
MINNESOTA AND WESTERN INTO CENTRAL WISCONSIN. AN INITIAL NW-SE  
ORIENTED BAND OF RAINFALL MAY FORM ALONG THE WESTERN HALF OF THE  
FORECAST AREA TONIGHT, POTENTIALLY PRECIPITATING ON ALREADY SATURATED  
SOILS IN SOUTHEAST MINNESOTA, NORTHEAST IOWA, AND FAR SOUTHWEST  
WISCONSIN. LOW CONFIDENCE (20%) SCENARIO BUT WILL BE SUBSEQUENT  
DETAIL TO KEEP AN EYE ON. ADDITIONAL HEAVY RAIN OVERNIGHT  
THROUGH MONDAY WILL BE MORE WIDESPREAD. PRECIPITATION EXIT MAY  
LINGER IN CENTRAL WISCONSIN THROUGH MONDAY NIGHT, FURTHER  
EXACERBATING RIVER RISES LOCALLY BEING REALIZED ON THE YELLOW  
RIVER AT NECEDAH, WI. BLACK RIVER HASN'T REALIZED AS HIGH RAIN  
ACCUMULATIONS AND THEREFORE REMAINS 3' BELOW ACTION STAGE AT  
BLACK RIVER FALLS, WI AS OF 17.09Z.  
 
 
   
ARX WATCHES/WARNINGS/ADVISORIES  
 
WI...NONE.  
MN...NONE.  
IA...NONE.  
 
 
 
 
 
DISCUSSION...JAR  
AVIATION...JAR  
HYDROLOGY...JAR  
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