textproduct: La Crosse

KEY MESSAGES

- Scattered thunderstorms more favored (30-50% chance) for the July 4th afternoon. Locally heavy rain would be the main concern.

- Aside from a low (20%) chance for storms on Sunday, the first part of next week is shaping up to be dry.

- Seasonably cool temperatures expected for the holiday weekend with a slow warming trend through midweek as highs return to the mid to upper 80s.

DISCUSSION

Issued at 1125 PM CDT Fri Jul 3 2026

Independence Day: Scattered Storms in the Afternoon and Evening

A convective outflow from earlier lake breeze thunderstorms in northwest Wisconsin has kept clusters of storms ongoing along and north of I-94 in western Wisconsin this evening. While confidence is low in the exact longevity of these storms, they should steadily decay through the early morning hours as the lower boundary layer stabilizes with continued nocturnal cooling.

An MCS developing on the nose of an albeit weak low-level jet across southern Iowa late tonight with some of the latest HRRR runs showing some token showers or stratiform precipitation spreading towards northeast Iowa, but fading as the MCS weakens just after sunrise. The main concern will be the impacts from the attendant cloud shield--whether it slows daytime heating and the resultant storm development or creates a differential heating boundary that could ignite storms later in the morning.

However, confidence is highest (30-50%) that scattered storms will develop ahead of a 700-500-mb shortwave and weak surface low during peak heating. Forcing with these storms is expected to be weak and concentrated closest to what constitutes as the surface low (more of a wind shift) with compact/complex hodographs limiting storm strength and longevity. However, storms may continue to redevelop along incipient cold pools and leading to effective cell clusters. Given the weaker steering flow and ample moisture still present in the lower troposphere, storms will be capable of producing a quick 1-2" of rain in very localized corridors with some explicit, higher end solutions even showing close to 3 inches of rain. Again, these higher end rain amounts will be VERY localized--the 04.00Z HRRR shows nearly dry conditions within a few miles of these higher splotches. This should limit flooding risks to locales with poor drainage, such as urban areas.

As is to be expected in such a setup, there is very poor intra- and inter-model variability in the placement of the surface low and where/when this rain falls. If the surface low is slower to arrive in the evening as some of the latest HRRR runs suggest, the risk for showers and storms may persist for much of the night closest to the low centroid.

Sunday: A Few Storms?

Cyclonic flow lingers in the wake of our departing trough for the afternoon on Sunday with forecast profiles showing an uncapped boundary layer by midday. THe forcing will be weak and heights on the rise, but there is enough of a QPF footprint with both the global and convective allowing ensembles to add in lower PoPs for mainly the afternoon hours.

Next Week: Dry Start and Slightly Warmer, Active Midweek

Amplifying ridging to the west coupled with high pressure building over the Great Lakes should ensure at least one quiet and dry day for Monday with weak southerly flow helping to nudge temperatures closer to normal. Confidence in the forecast begins to degrade for Tuesday and Wednesday as a pattern takes on a more zonal flow and repeated rounds of perturbations ripple on through. The first round of storms are progged to occur from central MN into northern WI Tuesday afternoon, and the behavior of these storms will play directly into Wednesday's storm risk, some of which could be severe. However, this looks to clear out by Thursday with drier conditions for the end of the week.

High temperatures beyond Monday become increasingly uncertain owing to convective influences, but a slow warming trend is expected through Wednesday to around or slightly above seasonal norms.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 554 AM CDT Sat Jul 4 2026

The fog will burn off by 04.14z. Until this occurs, expect IFR/MVFR visibilities and ceilings.

A couple of troughs will move through the area through tonight. The first will move east across Iowa this morning. This will bring scattered showers to Fayette, Clayton, and Grant counties. Another shortwave trough will move east through Minnesota and Wisconsin tonight. This system will impact the TAF sites. These systems will provide periodic chances for showers and storms. Overall VFR conditions are expected. However, there may be brief periods of IFR/MVFR ceilings and visibilities in thunderstorms.

Overnight tonight, the combination of light winds and a moist boundary layer, may result in some more fog on Sunday morning.

ARX WATCHES/WARNINGS/ADVISORIES

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