textproduct: La Crosse

KEY MESSAGES

- Remaining cooler than normal through much of the week with daytime highs and overnight lows a few degrees below normal.

- Initial storm chances Monday night through Tuesday with low confidence for strong storms or heavy rain locally.

- More widespread (60%-80%) heavy rain and storm chances Wednesday. Local storm strength and accompanying severe threat depends on exact storm track as highest confidence remains well south of the local forecast area. Current low confidence (15%-30%) mainly for southern and western counties locally.

DISCUSSION

Issued at 109 AM CDT Mon Jun 15 2026

Remaining Cool Through Much Of The Week:

Re-intensification of the synoptic mid level cyclone over Hudson Bay from unification of a retrograding extratropical cyclone over eastern Canada on GOES WV imagery causes a cooler than normal forecast over the Upper Mississippi River Valley through much of the week. While ECMWF Extreme Forecast Index (-0.5) and the accompanying Shift of Tails doesn't paint any widespread cold over the Upper Mississippi River Valley, deterministic and ensemble long term model solutions suggest 10th to 25th (SPC RAOB Climatology @ MPX) 850mb temperatures for much of the period, outside of temporary transient warm air advection during passing extratropical cyclones Monday night and Wednesday. Current forecast confidence for daytime highs in the mid 70s through the work week, potentially increasing into the weekend, with overnight lows in the mid 50s.

Precipitation & Storm Chances Monday Night/Tues:

Initial precipitation chances Monday night accompany passage of initial appendage of mid level vorticity advection Monday night through Tuesday from northwest to southeast. While current model confidence (50-70%) has increased over previous runs for location of surface low traversing over the local forecast area, overnight diurnal timing limits local instability and therefore local storm threat.

Given the synoptic forcing, have increased precipitation chances slightly from the NBM using high resolution models. Although, local confidence in heavy rain remains low as phasing of the upper level wave will cause the limited leftover moisture to fall slightly farther south, subsequently tapping into increased moisture south of the forecast area. Precipitation chances exit east of the forecast area by Tuesday evening.

Wednesday Storm Chances, Limited Severe Storm Confidence:

An appendage of the synoptic mid level cyclone over Hudson Bay causes an area of mid level confluence and subsequent intensification in a widespread ribbon of positive mid level vorticity advection from the Canadian West Coast. Subsequent near zonal cyclogenesis of a Rocky Mountain Low on Wednesday is expected near or over the forecast area, abdicating overall confidence for instability within the warm sector well south of the forecast area. Depending on diurnal timing of cyclogenesis in relation to the forecast area, a window of strong to severe storms could be possible within the tightening warm sector being drawn north before the low occludes. Machine learning severe hazard models show a small hump of increased, albeit relatively low (15%-30%), probabilities grazing southern half of the forecast area primarily. Although, inter-model difference in northern and eastern extent of this node of spatially- relative higher probabilities varies, highest and increasing most in recent FengWU (14.00Z). Therefore, will be important to remain cognizant of potential in coming forecasts as pattern becomes less ambiguous.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1219 AM CDT Mon Jun 15 2026

VFR conditions expected for the next 24 hours at the terminals. Winds overnight will be light at less than 10 kts out of a general westerly direction. Winds are expected to pick up some by mid to late morning but sustained speeds should stay less than 15 kts with confidence in gusts too low to include with this package.

ARX WATCHES/WARNINGS/ADVISORIES

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