textproduct: La Crosse

KEY MESSAGES

- Showers and storms likely (70-90% chance) this morning and early afternoon with the risk for some storms to become strong to severe, mainly south of I-90. Damaging wind gusts and locally heavy rainfall will be the primary threats with these storms.

- Additional storm chances Monday through Wednesday with some severe potential, however confidence in details remains low at this time.

- Seasonable temperatures through mid-week with highs in the upper 70s to middle 80s.

DISCUSSION

Issued at 1152 PM CDT Sat Aug 8 2026

This Morning - Early Afternoon: Storms Likely, Some Strong to Severe

Initial forecast concerns this morning will feature likely storm development as a 700mb shortwave moves through the Dakotas and into the Upper Mississippi Valley. As this occurs, increasing warm air advection and instability aloft will allow for a profound instability gradient to setup across portions of the region. The overall evolution manifests as discrete convection develops west of the local area and progresses eastward during the overnight and early morning hours. As this occurs, cold pools with widespread discrete convection associated with the wave will likely result in upscale growth with much of the CAMs agreeing on pushing an MCS/MCV through the region with some differences on exact timing but generally during the mid-morning hours.

Overall, the main question during this period will be exactly how much storms maintain as they move through the local area since they will be pushing into a lower instability environment, especially near the Mississippi River. The primary threat with these storms would be damaging winds with the organized cold pools and favorably oriented 0-3km shear vector. If a more coherent MCV with embedded bowing structures can manifest (as shown in the very recent 09.02z HRRR and 09.00z RRFS), would not be shocked to see some gusts approaching 70 mph. An embedded tornado cannot be fully ruled out with this given the aforementioned 0-3km shear vector, however fairly respectable capping present over the region would make this fairly unlikely. This complex would generally be progressive in nature with much of the CAMs generally having it exiting east of the local area by early afternoon.

This Evening - Overnight: Slight Chance for Redeveloping Storms

Additional storm development later into the evening will heavily hinge on how quickly convection during the morning and early afternoon pushes through the region. Based on the current state of the CAMs, convection later into the evening would seem less favorable as the cold pool from this MCS would likely push the instability gradient further south of the area. This being said, if we can recover instability quick enough and convect by evening, the environment would favor some multi-cellular clusters with embedded supercells. In this scenario, large hail, damaging wind gusts and locally heavy rainfall would be the primary threats with continued development along the instability gradient. Again, need to emphasize though that this is heavily contingent on if we can recover any instability back into the region in light of the morning and early afternoon convection.

Monday - Wednesday: Additional Storm Chances, Severe Storms and Locally Heavy Rainfall Possible

As we head into the start of the work week, persistent zonal to northwesterly flow will allow occasional shortwave perturbations to move through the region. Consequently, expecting additional chances for showers and storms. However, much of this will be contingent on how storms for previous days modify the instability gradient which will be the primary focus for where storms form. Deterministic guidance (GFS/NAM/EC) generally wants to highlight an additional shortwave perturbation that moves through the region later Monday evening and into the overnight. With fairly steep mid-level lapse rates and some stronger flow aloft, wouldn't be surprised if initial development could trend supercellular before organizing cold pools would trend towards a damaging wind threat. The trouble with this again is where storms form will be contingent on where the instability gradient is during this timeframe, which could very likely remain south of the local area.

Heading into Tuesday and Wednesday, the aforementioned zonal to northwesterly flow will persist over the local area. Consequently, shower and storm chances (15-30% in the recent NBM) will remain across the local area, however exact details at this point remain largely uncertain due to evolution of how earlier days storms may manifest. In any case, will need to watch for if repeated rounds of storms may track over the same locations through mid-week as precipitable waters remaining around 1.5-2" and deep warm cloud depths would suggest storms from today through mid-week will likely be efficient rainfall producers. Consequently, flooding concerns would increase if multiple rounds of storms occur over the same locations through mid-week.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 618 AM CDT Sun Aug 9 2026

A large cluster of storms currently stretching from South Central Minnesota down into Central Iowa is starting to track east towards the local region. These storms will impact the terminals over the coming hours with transient MVFR CIGs and MVFR/IFR visibilities from heavy rainfall. These storms should push off to the east through the morning and into the earlier afternoon, leaving VFR conditions in their wake. Another round of storms is possible this evening (a low confidence scenario that will depend on the timing of the departure of the morning storms and how quickly the atmosphere can recover) across NE Iowa and SW Wisconsin but this should remain south of the terminals. Southerly winds will prevail through the day with speeds generally at or below 10 kts, becoming light and variable overnight. This will allow for patchy fog development overnight across much of the region. Low stratus is also expected to build in for areas along and east of the Mississippi River with CIGs dropping into the MVFR/IFR range.

ARX WATCHES/WARNINGS/ADVISORIES

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