textproduct: La Crosse

KEY MESSAGES

- Showers move through western Wisconsin this afternoon before exiting to the east this evening.

- Additional showers and storms possible Sunday night (20-50% chance) and Monday afternoon/evening (15-25% chance). If storms do develop on Monday afternoon/evening they may become strong with strong wind gusts and small hail.

- Much warmer and drier for Tuesday through Friday with high temperatures in the 80s areawide.

DISCUSSION

Issued at 155 PM CDT Sat May 23 2026

Rest of Today - Sunday Night: Warming Trend, Shower/Storm Chances

GOES-19 water vapor imagery and 23.15z RAP 500mb heights depict a fairly pronounced trough situated over the Great Plains with a low attempting to close off across southern Canada. In general this feature is expected to move eastward with time as our area gets subjected into zonal flow into Sunday. However, prior to this occurring, a weak frontal passage combined with very weak instability has resulted in some showers this afternoon along and east of the Mississippi River as highlighted in much of the CAMs. Given fairly weak instability (around 250 J/kg) think that these cells along the front in western WI will not be overly robust of which the CAMs generally agree.

As we head into Sunday, zonal to slightly northwesterly flow is anticipated for the daytime hours, however with southwesterly flow in the low-levels push into the area with an increasing axis of 850mb moisture transport, warm advection gets pushed into the region with the inter-quartile range for high temperatures in the NBM ranging from the upper 70s to lower 80s across the local area. By the time the evening and overnight rolls around, this 850mb moisture transport axis becomes more robust overnight and into the early morning hours on Monday as it interacts with the nocturnal low-level jet. As a result, CAMs generally agree on some convective development across southern MN that pushes east/northeast through the overnight and into the early morning hours on Monday. Overall, while instability during the overnight reaches around 1500-2000 J/kg of MUCAPE in the recent RAP, shear profiles are not all that impressive with lots of looping in the 0-6km hodographs which would not favor organized storm structures. Additionally, a fairly pronounced nocturnal capping inversion would be in place as well. Consequently, any severe potential seems unlikely during this overnight period with any storms that push into our area.

Monday: Warmer, Outside Chance for Storm on Monday Afternoon & Evening

By the time Monday rolls around, continued low-level south to southwesterly flow will allow our temperatures to continue to warm further as an upper-level ridge begins to push into the Great Plains. As a result, the inter-quartile range for high temperatures in the grand ensemble (GEFS/EC/Canadian ensemble) ranging from the upper 70s to lower 80s. Granted with fairly pronounced inverted-v soundings and the ridge over the area, temperatures will likely overachieve this.

Later into the afternoon and evening, a ribbon of theta-e advection pushes through the area within a weak 850mb moisture transport regime. As a result, the GFS/NAM has corridor of relatively robust MLCAPE of around 2000-3000 J/kg. This coupled with the aforementioned inverted-v soundings would suggest some potential for a surface-based environment (although this is heavily dependent on if we heat enough to break the cap) that could support strong wind gusts with any storms that get going in addition to small hail. However, this is relatively conditional scenario given the lack of surface convergence present in this theta-e advection regime so it is questionable if the forcing is even there during the afternoon and early evening for anything to get going. Consequently, have decided to add some low-end precipitation chances (15-20%) during this period to account for this low confidence scenario.

Tuesday - Friday: Staying Warm with Minimal Precipitation Chances

As we head into mid-week, the upper-level ridge amplifies over the region with continued weak southerly low-level flow into the region on Tuesday. As a result, Tuesday and Wednesday appear to be our warmest period with some notable differences in guidance between the NBM and grand ensemble (GEFS/EC/Canadian). Overall, NBM is running around 5-10 degrees warmer than other guidance due to its bias correction and while it would seem fairly likely that we will overachieve on temperatures from ensemble guidance due to the more favorable mixing and lack of sky cover under the ridge, it is unclear if we will reach the lower 90s that the NBM portrays near I- 90 on Tuesday.

Otherwise, temperatures will remain on the warm side throughout the remainder of the week with highs in the 80s as guidance continues to keep the upper-level ridge sitting near or just west of the local area. The GEFS and operational GFS tries to bring some stronger upper-level northerly flow into the region later into the week which may aid in returning precipitation chances and cooling our temperatures. However, this is not reflected in either the EC or Canadian operational runs. Additionally with surface high pressure situated over the northern Great Lakes, the grand ensemble (GEFS/EC/Canadian) keeps the bulk of the measurable precipitation chances to our south and west with only low to medium probabilities (20-40%) for measurable precipitation Wednesday through Friday.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1225 PM CDT Sat May 23 2026

Main taf concerns will be the potential for a brief period of MVFR conditions at LSE taf early in the taf period. Latest visible satellite imagery shows narrow band of stratus north to south mainly along the Mississippi River and western Wisconsin. Ceiling heights are in the MVFR conditions per latest metars under the stratus deck. With daytime heating and high pressure building in...stratus will become open cellular and MVFR conditions at LSE taf site would be very brief early in the taf period. At this time...will continue MVFR conditions for a couple of hours early in the taf period at LSE. Then...VFR conditions to prevail through the rest of the taf period at both RST/LSE taf sites.

ARX WATCHES/WARNINGS/ADVISORIES

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