textproduct: La Crosse

KEY MESSAGES

- Warm and muggy for today and Wednesday with highs in the low to mid 80s for today and the low 80s to low 90s for Wednesday. Heat indices largely in the mid to upper 80s for today and the low to mid 90s for Wednesday

- Strong to severe storms are possible tonight into Wednesday morning with large hail and localized damaging winds being the primary threats.

- Severe storms are likely Wednesday afternoon through the evening with large hail, damaging winds, and tornadoes all being possible.

- Another conditional threat for severe weather exists Thursday across northeast Iowa and southwest Wisconsin.

DISCUSSION

Issued at 152 PM CDT Tue Jun 9 2026

Today-Wednesday: Warm and Humid with Showers and Storms Possible Tonight and Wednesday

Dry conditions for today as the Upper Midwest is in an area of shortwave ridging. Warm southwest flow will continue for today and Wednesday bringing in dewpoints in the upper 60s to mid 70s. Highs for today have continued to lower as they have been over the past few days with temperatures staying the low to mid 80s for most locations. Heat indices have also continued to come down with values largely in the mid 80s to low 90s. The temperature forecast for Wednesday is a bit trickier as it depends on when storms initiate as this will impact how warm we get. Right now we have forecasted high temperatures in the low to upper 80s with heat indices largely in the upper 80s to mid 90s.

Shifting gears to the storm potential we begin with a warm front advancing northeastward across the Midwest. A low level jet will also be pushing into the area and this combining with a good moisture push behind this warm front, storms are expected to form, particularly in central and southern Minnesota. There is uncertainty on how far southeast along this front will have storms, but the higher confidence for our forecast area is southeast Minnesota and western Wisconsin north of I-90. These storms look to exit our area by mid morning Wednesday. While we are not expecting widespread severe storms along this line, there is enough instability (1500 to 2500 J/kg of MUCAPE) that some large hail and localized damaging wind gusts with this first line.

Heading into the later morning to early afternoon, we will watch where exactly some potential remnant MCVs and outflows from the storms around the area end up as these would be the areas to watch initially for storm development. Across the CWA, SBCAPE values will be in the 2500 to 3500 J/kg range throughout the afternoon and evening. Deep layer shear gets better for the later afternoon and early evening with 0-6km shear values around 35 to 45 kts. The low level shear also increases during the mid afternoon and evening hours with values in the 25 to 35 kt range. With these values, the tornado potential is highest during the mid afternoon through the evening, however a tornado could occur with any of these storms in the earlier afternoon if they can latch onto another storm's outflow. With the high instability and decent mid level lapse rates, large hail and damaging winds will also be possible with any severe storm. The initial storm mode based on hodographs across the area look to be discrete to semi-discrete increasing the potential for supercells to occur. Now these storms may congeal rather quickly into bowing segments or clusters of storms. This is going to lead to a tricky forecast regarding exact storm mode for this event. Another thing to note is that there could be multiple rounds of storms that occur as we will have limited capping in place from the later morning hours through the evening. This will result in storms having the capability to rapidly form and will lead to a rather quick recovery in the atmosphere allowing for more storms to move through or form over the same areas. By the evening, a cold front sweeps through through and the storm mode is expected to become linear which would indicate the severe threats are mainly damaging winds, potentially in the 75+mph range and embedded tornadoes within the line. All storms are expected to leave the area between 04 and 06Z. Not only is there severe potential, but there is also a heavy rain threat, particularly if these storms go over the same locations multiple times. Overall, this forecast for Wednesday is very tricky and still has uncertainties that may not be resolved until it is the mid morning. Stay tuned for further updates regarding the severe weather potential for tonight and Wednesday. An update section of the AFD may be issued later tonight for those storms along the warm front if they overachieve.

Thursday: Conditional Severe Setup, Heavy Rain Potential

The upper level trough shifts over the the Upper Midwest Thursday afternoon and evening while a surface low ejects out of the southern Rockies Wednesday evening and shifts northeastward during the overnight. By the mid morning hours on Thursday, this low will be somewhere in western to central Iowa. The boundary that the Wednesday night storms form is expected to shift northward as the low moves off to the northeast. Showers and storms are expected to form along this boundary and back build toward the low, however depending on where this boundary ends up will likely be the northern extent of any severe weather concerns. With instability surging northward 1500 to 2500 J/kg of SBCAPE and good deep layer shear associated with the low and trough overhead, all storm hazards will be possible. SPC has introduced a Slight risk (level 2 of 5) for our southeastern half of the CWA, basically south of a Mason City to just south of Wausau line. AI and ML guidance have mixed signals for Thursday for how far north to bring the severe weather threat. Some guidance brings it as far north as the WI/MN/IA line while others keep it south of the local area. The timing for any severe weather is likely going to be Thursday morning into the early afternoon hours. After this the low moves off to the east and we are behind the cold front. Stay tuned for updates regarding the severe weather potential as this a conditional threat.

While the severe weather may or may not occur, heavy rainfall is certainly going to be possible. As the low moves north into the Upper Midwest, a good push of moisture advection comes into the region. PWATs are generally in the 90th percentile of climatology based on the NAEFS for northeast Iowa and far southwest Wisconsin and EFI values for QPF highlights much of northeast Iowa and southwest into central Wisconsin with values of 0.7 to 0.7 indicating that forecasted QPF amounts are on the higher side of climatology. As far as QPF amounts go for Thursday, the newest NBM has between 1.5 to 2" for mean QPF amounts across northeast Iowa and southwest Wisconsin. The 90th percentile does highlight those same areas with values 2.75 and 3.5". Regardless of the severe weather potential, the heavy rain potential will be there.

Friday-Early Next Week: Cooler with Periodic Rain Chances

The upper level pattern shifts from predominantly southwest flow to a mixture of zonal to southwest flow. The Upper Midwest will also be under a longwave trough through this time period. The overall pattern will be cooler with temperatures in the 70s and a few rain chances.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 621 PM CDT Tue Jun 9 2026

Continued presence of a very moist atmosphere should (80%) lead to another breakout of MFVR/IFR ceilings tonight. Broken line of thunderstorms will likely (70%) skirt north of a RST to MFI line after 06z through 15z Wednesday morning but have included a PROB30 at RST to cover that remaining 30 percent. Attention then turns to potential for widespread thunderstorms after 18z, particularly along and east of the Mississippi. For now, have included a PROB30 at LSE, but fully expect this mention to become more definite and over a narrower time frame as details become clearer over the next 2-3 TAF cycles.

ARX WATCHES/WARNINGS/ADVISORIES

WI...None. MN...None. IA...None.