textproduct: La Crosse

KEY MESSAGES

- A few rounds of storms this morning and possibly again this afternoon. The overall severe threat is low, but a few storms could produce locally heavy rainfall.

- Severe weather threat for Monday evening hinges on *IF* storms can develop along and south of the warm front. If storms can form in this favorable environment, all hazards are possible.

- Tuesday's severe weather threat looks to be shifting more into Iowa and southern Wisconsin, impacting northeast Iowa and southwest Wisconsin during the afternoon hours.

- Warm week ahead with high temperatures in the 70s to around 80. More storms dot the forecast later in the week.

DISCUSSION

Issued at 500 AM CDT Sun Apr 12 2026

Storms this Morning Possibly again this Afternoon:

A weak mid-level perturbation lifting over a 50-kt LLJ ignited a cluster of showers and storms across northern Iowa shortly after midnight, which has been propagating northeastward into southeast MN as of 5am. The storms are rooted around 800 mb with collapsed inflow layer hodographs resulting in transient storm structures as a multitude of cells fight over limited instability (500-1000 J/kg). One cell in Winnebago County, IA did pulse up to produce half dollar size hail, but for the most part the line has remained sub severe and is expected to remain as such as it translates northeastward through the morning hours. The line is fairly progressive, but a quick 1/2 to 1 inch of rainfall is likely under the heavier cells.

Subsequent Afternoon/Evening Storms Today:

Trends in the latest forecast guidance are for the bulk of the afternoon storms to stay southeast of the forecast area, with lighter showers over our area to the north and west. While the explicit CAM and global QPF/composite reflectivity progs are in favor of this idea, a look at the forecast soundings shows a ribbon of 1000-1500 J/kg of SB/MLCAPE situated further to the northwest from north-central Iowa into western WI that is relatively uncapped by late afternoon. If there is any residual forcing, a stronger storm could develop along this axis--though such a scenario seems unlikely given the strong consensus in the guidance.

Storm Chances Monday:

A shortwave ridge erodes much of the low level moisture Sunday night into early Monday morning before another amplifying wave advects a subsequent low level warm, moist sector across the forecast area. Current timing advects initial band of non- severe storms across the forecast area from isentropic upglide Monday morning. Lower confidence through the afternoon/evening as the initial glance into high resolution soundings show a stout 800mb-700mb EML with 15C+ dewpoint depressions quickly following initial low level moisture transport. Given the plethora of instability (1500-3000 J/kg) due to steep mid level lapse rates advecting over the forecast area and strong winds causing increased effectively available shear, severe storm threat persists. Although, an overall slowing trend to the trough limits confidence in accompanying forcing. Primary hazards of large hail and damaging winds in current forecast regime.

Storm Chances Tuesday:

Unfortunately, confidence for Tuesday decreases further as resultant frontal location and available instability both remain in question. Long LREF hodograph plumes with some spread in accompanying temperature soundings suggest severe probabilities could continue from initially splitting supercells should the warm sector remain present and the EML shunts off to the southeast. Eventual east-southeast progression of a frontal boundary would provide sufficient forcing for linear storms through the forecast area although exact diurnal timing is the forecast crux.

Warm through the Week

The overall synoptic pattern does not vary through the week, keeping warm air in place. Highs each day through Friday should top out in the 70s to even low 80s in a few spots, a pattern more like May than April. A cold front slams down for next weekend, but temperatures should only fall back around average in its wake.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1241 PM CDT Sun Apr 12 2026

MVFR conditions improve to low-VFR this afternoon as our first round of precipitation departs to this east. Low-level winds will increase overnight as a nocturnal inversion builds in which may bring some LLWS to KLSE, however it is unclear for how long of a period this will result in and if gusts will still be ongoing. Otherwise, a weather disturbance passes us to the southeast overnight which will lower cigs, particularly east of the Mississippi River to MVFR, perhaps IFR thresholds. Will need to see if any fog manifests in portions of northeast IA and southeast MN if skies can remain clear overnight. This may result in IFR vsby reductions however, probabilities are not overly high at this juncture (~20% chance in the HREF for under 1SM at KRST). Skies likely improve to VFR towards 18z with showers and storms developing near and north of I-90 late Monday afternoon.

HYDROLOGY

Issued at 1129 PM CDT Sat Apr 11 2026

An anomalously moist airmass, record moisture values observed Saturday night at Chanhassen (SPC RAOB Climatology), lingers through start of the new week. Given overall confidence in exact daily storm location and accompanying impacts remains low, concerns for storms frequenting similar areas each day will require close monitoring for potential river flooding in large and small river basins given already slightly swollen river levels.

Current forecast confidence has maximum 24 hour QPF values nearing 2"+ where storms form. Current forecast timing unfortunately limits personal model availability.

CLIMATE

Issued at 1141 PM CDT Sat Apr 11 2026

Potential Record Warmth Monday & Tuesday (Record/Forecast):

April 13th High Temp Warm Low ----------- -------- ------- Rochester, MN 83 (2023) / 74 59 (1941) / 55 La Crosse, WI 85 (2023) / 76 63 (1941) / 59

April 14th ---------- Rochester, MN 87 (2003) / 72 56 (1976) / 55 La Crosse, WI 90 (2003) / 76 60 (1883) / 58

ARX WATCHES/WARNINGS/ADVISORIES

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