textproduct: La Crosse

KEY MESSAGES

- Precipitation chances increase through Friday from west to east with local confidence decreasing in higher rainfall amounts (1-2"+) and stronger storms (<5%).

- Seasonable temperatures and mostly dry conditions are expected Sunday through early next week.

DISCUSSION

Issued at 1243 AM CDT Thu Jul 30 2026

Incoming Heavy Rainfall Overnight & Through Friday:

The area of higher pressure and accompanying anticyclonic flow will slowly exit east/southeast through the end of the work week as a deepening mid/upper level perturbation ushers in heavy rainfall potential across the Upper Midwest overnight Thursday through Friday. The responsible upper level jet streak seen on GOES18 derived wind loops exhibits slight troughing will strengthen as it circumnavigates the ridge periphery. Resultant easterly advection of a very moist, with a daily maximum PWAT of 1.63" observed at International Falls, MN 30.00Z RAOB to 90th percentile at Omaha, NE (SPC Climatology), traverses through the Upper Mississippi River Valley. Accompanying LREF (EPS/GEFS) 100% probabilities for 1.5" to 2" PWATs bifurcate and graze the local forecast area, respectively, through Friday night.

Heavy Rainfall Impacts:

Similar to previous forecasts, main differences between LREF members (EPS/GEFS) surround location and strength of the deepening extratropical cyclone. A slightly more northern solution between EPS members results in higher member consensus for heavier precipitation amounts compared to the GEFS. Current forecast confidence for 1" to 2" of rainfall through Friday but should the more northern, deeper solution come to fruition higher amounts will need to be accounted for in the forecast.

Timing:

While confidence is high for initial precipitation to reach the local forecast area overnight into Friday morning, exit behavior and subsequent duration remains additional forecast detail to remain cognizant of. The stronger EPS solution suggests lingering low level frontogenetical bands within the deformation zone perpetuating precipitation through Saturday. Current LREF cluster analysis confidence keeps PoPs abated through Saturday afternoon although additional scrutiny may need to be spent on Saturday as forecast hour nears should heavy rainfall impacts persist.

Severe Storm Potential:

While overall severe storm potential appears low (<5%), relatively close proximity to the surface low amplifies low level vorticity maxima raising some concern and questions surrounding tornado potential should surface stretching occur.

Sunday - Tuesday: Seasonable Temperatures and Mostly Dry

Behind the late week showers and storms, synoptic scale ridging builds across the central United States and remains in place through early next week with seasonable temperatures expected in response. Stability associated with this ridge looks to keep showers/storms at bay through at least Tuesday when ensemble guidance suggests a shortwave at 500hPa shifts eastward across the United States/Canada border, forcing a weak surface boundary through the Upper Midwest. Precipitation is possible late Tuesday along this boundary, though variations amongst the various ensemble suites keeps probabilities on the lower end for the time being, sitting around 30-40% in the 29.12z LREF.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 602 AM CDT Thu Jul 30 2026

Valley fog within the Wisconsin/Kickapoo River valleys and other Mississippi River tributaries dissipates over the next few hours. Once the valley fog dissipates, VFR conditions will prevail through the afternoon with increasing high cloud coverage. Southerly winds are expected generally around 10KT or less, but some stronger winds towards 15KT are possible west of the Mississippi River. Showers and storms move into the region from the west towards the end of the TAF period bringing periods of heavy rainfall and MVFR/IFR ceilings and visibilities.

ARX WATCHES/WARNINGS/ADVISORIES

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