textproduct: La Crosse

KEY MESSAGES

- Shower and storm chances increase for this morning. While the potential is low (under 10%), some of these storms may be strong to severe with large hail.

- Uncertainty remains on if a secondary round of storms will develop later into the evening. If this round of storms does manifest, a potential convective system may bring the risk for damaging wind gusts this evening/overnight for the area.

- Periodic chances for showers and storms persist for Friday and through the holiday weekend.

DISCUSSION

Issued at 1200 AM CDT Thu Sep 3 2026

This Morning - Overnight: Uncertain Storm Chances and Severe Potential

A very complex forecast is in store for our area over the next 24 hours as hi-res guidance continues to struggle with how to capture potential convective evolution this morning and into the evening. Currently, confidence is increasing for storms to develop across the region during the morning hours as an axis of 850mb moisture transport and sfc theta-e advection overrides a quasi-stationary boundary across the region. Consequently, expecting showers and storms to quickly increase in coverage and push northeast with this forcing regime. Overall, the environment for this morning convection is not overly impressive as the nocturnal inversion will be firmly in place as convection is ongoing which should trend more elevated in nature. However, cannot rule out some large hail with stronger cores as both elongated hodographs in the recent RAP and modest mid- level lapse rates of 6.5-7 C/km are present during the morning.

The key question will be exactly how long morning convection will linger across the area and if it will inhibit the potential for convection during the evening and into the overnight. Currently, 00z CAMs have generally shifted towards a more limited convective scenario which would suggest morning convection staying present across the local area later into the morning, perhaps even early afternoon. If this is the case, destabilization would be limited in nature and a shortwave impulse that would be responsible for organizing a potential MCS later into the evening would not have much instability to work with. However, in the event that destabilization does occur, ample instability and somewhat favorable shear profiles would allow for robust cold pool organization and a subsequent damaging wind risk. Another scenario that some of the recent 00z CAMs have also picked up on is a pronounced 850mb moisture transport axis later into the overnight interacting with the aforementioned quasi-stationary boundary. This coupled with any lingering instability would be enough for convective development to occur in a focused corridor leading to the potential for training storms which is currently depicted in the 00z HRRR. Cannot rule out some heavy rain potential if this scenario pans out given warm cloud depths in excess of 4km and precipitable waters over 1.75".

In all, there appears to be multiple scenarios for this evening/overnight, all of which are fairly low confidence at this point. Confidence will likely increase in light of morning convective trends. The main takeaways from guidance at this point is that some severe potential is in play and that the MCS scenario later into the is fairly low confidence but could have some potential for higher wind gusts (over 70 mph) if it manifests.

Friday: Shower & Storm Chances, Low-End Severe Potential

The pattern for Friday really does not change all that much with there being some question with how prior storm activity may affect any potential for storms on Friday. However, given fairly robust instability profiles with MLCAPE values approaching 4000 J/kg could suggest substantial buoyancy for quick developing updrafts. This coupled with robust DCAPE values in the RAP would suggest any collapsing cores could have a damaging wind gust risk and perhaps some large hail with mid-level lapse rates hovering around 6.5C/km. However, given the fairly unimpressive shear profiles with minimal hodographs elongation, thinking that any updrafts that do get going would be short-lived.

Holiday Weekend & Early Next Week: Persisting Shower and Storm Chances

As we head into the weekend and early next week, upper-level ridging remains to our west with the local area subjected to a northwesterly flow regime. Consequently, additional shortwave impulses may move into the region this weekend and early next week. Overall the grand ensemble (GEFS/EC/Canadian ensemble) has respectable probabilities (40-60%) for measurable precipitation throughout the weekend and into early next week, so thinking off and on storm chances are feasible. As far as any severe potential, AI/ML guidance highlights some low-end potential (5% chance) over the weekend, however likely any severe potential would be dictated by mesoscale factors so would be challenging to hone in on any definitive severe potential at this point.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 546 AM CDT Thu Sep 3 2026

Widespread showers embedded with scattered storms shifting northeast on early morning RADAR imagery will affect both TAF sites (KLSE/KRST) through the morning hours. While storm and shower chances lower through the late morning, probabilities return and increase into the nighttime hours. Have included PROB30 TSRA given current confidence at both TAF sites but will require additional fine tuning as forecast hour nears.

ARX WATCHES/WARNINGS/ADVISORIES

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