336  
FXUS63 KARX 161746  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
1246 PM CDT SAT AUG 16 2025  
   
KEY MESSAGES
 
 
- PERIODIC STORMS CAPABLE OF HEAVY RAIN THROUGH MONDAY. HIGHER  
CONFIDENCE FOR STORMS THIS MORNING, OVERNIGHT THROUGH SUNDAY  
MORNING, AND SUNDAY NIGHT THROUGH MONDAY MORNING.  
 
- LOCALIZED FLASH FLOODING AND RIVER RISES REMAIN A CONCERN  
THROUGH THE WEEKEND WITH 2"+ RAINFALL POSSIBLE PRIMARILY NORTH  
OF INTERSTATE 90.  
 
- HOT TODAY WITH HEAT INDICES FROM 90 TO 105 DEGREES. HEAT  
ADVISORY ISSUED FOR COUNTIES IN NORTHEAST IOWA WITH HEAT  
INDICES ABOVE 100.  
 

 
   
DISCUSSION
 
 
ISSUED AT 339 AM CDT SAT AUG 16 2025  
 
HOT TODAY, HEAT ADVISORY ISSUED IN NORTHEAST IOWA:  
 
LITTLE CHANGE IN THE MOIST AIRMASS FROM YESTERDAY MEANS ANOTHER  
HOT DAY IS EXPECTED. WARMEST TEMPERATURES WILL BUILD THROUGH  
IOWA TODAY, BRINGING UPPER 80 DEGREE SURFACE TEMPERATURES  
LOCALLY. THEREFORE, HIGHEST CONFIDENCE FOR 100 DEGREE HEAT  
INDICES IN NORTHEAST IOWA RESULTED IN HEAT ADVISORY ISSUED FROM  
NOON TO 8PM TONIGHT.  
 
LINE OF STORMS THIS MORNING:  
 
A LOW LEVEL JET THROUGH THE CENTRAL PLAINS, CONFINED TO TIGHTENING  
ISOHEIGHT GRADIENT BETWEEN A ROCKY MOUNTAIN LOW OVER EASTERN COLORADO  
AND ANTICYCLONIC SYNOPTIC FLOW OVER THE SOUTHEAST CONUS, INITIATED  
STORMS OVER SOUTHWEST MINNESOTA EARLY THIS MORNING. INTERACTION  
BETWEEN THIS MOST RECENT STORM INITIALIZATION AND AN UPSTREAM ONGOING  
MCS QUICKLY PROGRESSING EAST THROUGH SOUTH DAKOTA ON EARLY MORNING  
RADAR IMAGERY IS CAUSING FORECAST CHALLENGES LOCALLY. PREVIOUS FORECASTS  
CALLED FOR THIS MCS TO CONTINUE THROUGH MINNESOTA INTO WEST-CENTRAL  
WISCONSIN THIS MORNING HOWEVER THE NEWEST STORM INITIALIZATION STANDS  
BETWEEN THE LOCAL FORECAST AREA AND THE MCS.  
 
EXPECT STORMS TO CONTINUE ALONG AN EASTERLY TRAJECTORY WITH MEAN MID  
LEVEL FLOW, PLACING THE NEWEST STORMS POTENTIALLY IN THE CROSSHAIRS  
OF THE MCS THROUGH THE EARLY MORNING. THE MORE NORTHEASTERLY TRAJECTORY  
INITIALLY TO THE RECENT STORMS WILL EVENTUALLY LOCALLY INFLUENCE SOUTHERN  
EXTENT OF STORMS.  
 
STORM STRENGTH IS EXPECTED TO PEAK UPSTREAM OF THE LOCAL FORECAST  
AREA, LOCALLY DEPENDENT ON LOCATION OF EVENTUALLY OUTGOING COLD  
POOL. A SLOWER STORM MOTION OR STUTTER STEP IN PROGRESSION FROM THE  
EARLY MORNING COULD ALSO ALLOW ADDITIONAL DIURNALLY-FED INSTABILITY  
TO BRING STRONGER STORMS. DAMAGING WINDS WILL BE THE MAIN  
THREAT IN PART DUE TO A STORM MOTION OF 50+ KTS. LARGE HAIL OR  
AN ISOLATED TORNADO CANNOT BE RULED OUT HOWEVER AS STORMS BOW.  
 
A MORE UNSTABLE AIRMASS ALONG AND SOUTH OF THESE STORMS WILL BE  
CAUSE FOR CONCERN THROUGH THE MORNING HOURS AS WEST-NORTHWEST MID  
LEVEL FLOW CAN ADVECT STRONGER STORMS SOUTHEAST. CURRENT CONFIDENCE  
PLACES LOCAL CONCERNS IN CENTRAL WISCONSIN COUNTIES WITH DAMAGING  
WIND AND LARGE HAIL AS THE POTENTIAL THREATS SHOULD STORMS MANAGE TO  
BECOME SEVERE.  
 
HEAVY RAIN TONIGHT THROUGH SUNDAY MORNING:  
 
REINVIGORATION OF THE NOCTURNAL LOW LEVEL JET OVERNIGHT INCREASES  
LOW LEVEL MOISTURE TRANSPORT TOWARDS THE UPPER MISSISSIPPI RIVER  
VALLEY, INCREASING HEAVY RAIN CHANCES TONIGHT. A CORRIDOR OF 2" PWATS  
EXTENDS ACROSS THE FORECAST AREA, STRUNG BETWEEN A STRENGTHENING  
SURFACE LOW OVER THE NORTHERN PLAINS AND THIS MORNING'S LOW, DOWNSTREAM  
OF THE FORECAST AREA. A STRENGTHENING ANTICYCLONE SAGGING SOUTHEAST  
THROUGH CENTRAL CANADA TIGHTENS THE ACCOMPANYING WEST-NORTHWEST TO  
EAST-SOUTHEAST ORIENTED FRONTAL BOUNDARY ACROSS THE FORECAST AREA,  
TIGHTENING AN ACCOMPANYING AXIS OF DILATATION ALONG THE ANOMALOUS  
(SPC CLIMATOLOGY) MOISTURE AXIS. A NARROW BAND OF HEAVY PRECIPITATION  
IS EXPECTED ALONG THIS WEST-NORTHEAST TO EAST-SOUTHEAST GRADIENT,  
LINGERING OVERNIGHT THROUGH SUNDAY MORNING. EXACT LOCATION OF  
THE AXIS OF DILATATION AND MOISTURE AXIS WILL DETERMINE LOCATION  
OF HIGHEST IMPACTS WITH HIGH RESOLUTION MODEL GUIDANCE FOR QPF  
VARYING FROM 2" IN CENTRAL IOWA IN THE ARW (16.00Z) TO 7" IN  
CENTRAL WISCONSIN IN THE FV3 (16.00Z). OTHER THAN SPATIALLY,  
INTER-MODEL TRENDS EXHIBIT MINIMAL CONTINUITY POINTING TO THE  
LACK OF OVERALL CONFIDENCE IN EXACT LOCATION OF HIGHEST RAINFALL.  
INCREASED RAINFALL RATES OF 1"+ PER HOUR COMBINED WITH MINIMAL  
MEAN FLOW MEANS HEAVY RAIN WILL HAVE LONGER RESIDENCE TIMES,  
QUICKLY EXACERBATING POTENTIALLY DANGEROUS IMPACTS.  
 
HEAVY RAIN SUNDAY NIGHT THROUGH MONDAY MORNING:  
 
HEAVY RAIN AND STORM CHANCES INCREASE AGAIN ON SUNDAY NIGHT AS AN  
UPPER LEVEL WAVE, CURRENTLY PLACED ALONG THE BASE OF THE  
LONGWAVE TROUGH OFF THE CALIFORNIA BAJA COAST, FLATTENS THE  
RIDGE PERIPHERY AND REINVIGORATES LOW LEVEL MOISTURE TRANSPORT  
THROUGH THE CENTRAL PLAINS. THE TERMINUS IS EXPECTED TO BE  
ALONG THE LINGERING NORTHWEST TO SOUTHEAST ORIENTED FRONTAL  
BOUNDARY OVER THE UPPER MISSISSIPPI RIVER VALLEY. MINIMAL  
CHANGE IN THE SYNOPTIC AIRMASS KEEPS PWATS NEAR 1.5" AND HEAVY  
RAIN WITH LOCALIZED FLOODING THE MAIN CONCERNS. CURRENT LREF  
CONFIDENCE KEEPS HEAVIEST RAIN CONFINED CLOSER TO THE SURFACE  
LOW LIFTING NORTHWEST OF THE LOCAL FORECAST AREA, PROVIDING AN  
ADDITIONAL 0.5"+ OF RAINFALL.  
 
LINGERING HEAVY RAIN THOUGH MONDAY, COOLER THROUGH MIDWEEK:  
 
REGRESSIVE UPPER LEVEL HEIGHTS TRAVERSE INTO THE DESERT SOUTHWEST  
THROUGH MONDAY, USHERING IN NORTHWEST FLOW AS THE ANOMALOUSLY MOIST  
AIRMASS EXITS EAST. PRECIPITATION CHANCES ARE SLOW TO EXIT,  
LINGERING ALONG EASTERN PERIPHERAL COUNTIES IN CENTRAL WISCONSIN  
THROUGH MONDAY MORNING.  
 
STRONGEST RETURN FLOW EXPECTED TO REMAIN THROUGH THE CENTRAL PLAINS  
THROUGH MIDWEEK, KEEPING THE LOCAL FORECAST AREA IN THE HIGH 70S TO  
LOW 80S HOWEVER MUCH TO BE IRONED OUT.  
 

 
   
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
 
 
ISSUED AT 1245 PM CDT SAT AUG 16 2025  
 
TRICKY AVIATION FORECAST AS POTENTIAL FOR STORMS CONTINUE  
THROUGH MOST OF THE NEXT 12 HOURS AT ALL TAF SITES. DO EXPECT  
CIGS AND VSBYS TO LOWER INTO THE IFR RANGE TONIGHT AT BOTH  
SITES. TIMING ON STORM ARRIVAL IS DIFFICULT AT THIS TIME SO USED  
ONLY PROB30S FOR THIS EVENING AND OVERNIGHT. REFINEMENTS TO  
THUNDERSTORM TIMING WILL LIKELY BE NEEDED IF/WHEN THEY FORM.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 423 AM CDT SAT AUG 16 2025  
 
PERIODIC STORM CHANCES CAPABLE OF HEAVY RAIN CONTINUE FLASH FLOODING  
CONCERNS THROUGH MONDAY. HEAVIER RAINFALL EXPECTED THIS MORNING,  
TONIGHT THROUGH SUNDAY MORNING, AND SUNDAY NIGHT THROUGH MONDAY  
MORNING.  
 
YESTERDAY'S HEAVY RAIN OBSERVATIONS OF 1" TO 3"+ SEEN IN  
NORTHEAST IOWA, SOUTHEAST MINNESOTA, AND WESTERN THROUGH CENTRAL  
WISCONSIN YESTERDAY (FRIDAY). WHILE STORM PERIODICITY LIMITS  
WIDESPREAD RIVER FLOODING CONCERNS, INTER-STORM DEPENDENCY  
DECREASES CONFIDENCE IN EXACT LOCATION OF HEAVIEST RAINFALL AND  
ACCOMPANYING RIVER FLOODING POTENTIAL.  
 
OVERALL IMPACTS FROM HEAVY RAINFALL RATES THIS MORNING WILL BE  
LIMITED BY QUICK STORM MOTIONS, KEEPING CONFIDENCE FOR FLASH  
FLOODING LOW ENOUGH TO ABSTAIN FROM ISSUING A FLOOD WATCH.  
 
SUBSEQUENT FLASH FLOODING CONCERNS TONIGHT THROUGH SUNDAY  
MORNING LACKS CONFIDENCE IN LOCATION WITH NARROW CORRIDOR OF  
HIGHEST RAINFALL RATES 1"+ REMAINING OVER THE SAME AREAS. A  
NARROW BAND ORIENTED FROM NORTHWEST TO SOUTHEAST IS EXPECTED TO  
DEVELOP TONIGHT WITH LITTLE MOVEMENT THROUGH THE OVERNIGHT  
HOURS. STATIONARY NATURE AND HEAVY RAINFALL RATES CAN RAPIDLY  
EXACERBATE FLOODING IMPACTS. THEREFORE, IN ADDITION TO FLASH  
FLOODING, FLASHIER RIVERS WOULD ALSO BE IMPACTED.  
 

 
   
ARX WATCHES/WARNINGS/ADVISORIES
 
 
WI...NONE.  
MN...NONE.  
IA...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR IAZ008-018-019-  
029-030.  
 

 
 

 
 
DISCUSSION...JAR  
AVIATION...DVN  
HYDROLOGY...JAR  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab WI Page
The Nexlab IA Page
The Nexlab MN Page Main Text Page