textproduct: La Crosse

KEY MESSAGES

- Fog continues this morning, primarily west of the Mississippi where visibilities are 1/4 mile or less in spots. The fog will begin to lift after daybreak this morning.

- Rain chances return Thursday (20 to 40%), mostly impacting portions of northeast Iowa and southwestern Wisconsin however amounts remain below 0.2".

- Rain very likely (95%) for Friday morning and thunderstorms - perhaps severe - for Friday evening. There is a 35 to 85% chance (highest in NE IA and SW WI) for at least 1" of rain to fall Friday into Saturday.

UPDATE

Issued at 520 AM CST Wed Mar 4 2026

Areas of dense fog have developed across the region resulting in 1/4 mile visibilities across portions of southeast MN and northeast IA. As a result, have the Dense Fog Advisory continuing through 10am across these areas. Currently, calm winds, clear skies and a present nocturnal inversion will aid in maintaining ongoing fog until sunrise where diurnal mixing processes will allow fog to disperse by mid-morning. Based on the current HREF probabilities for 1/4 mile or lower, confidence is high (70-90%) for continued 1/4 mile visibilities west of the Mississippi River towards daybreak but with much lower probabilities (20-40%) east of the Mississippi River which is being verified with current observations. As a result, likely will not need to expand the Dense Fog Advisory further east. With some locations in southeast MN and northeast IA seeing ongoing dense fog with below freezing temperatures, some slick spots may develop on elevated surfaces.

DISCUSSION

Issued at 1214 AM CST Wed Mar 4 2026

Fog overnight

Clear skies and light winds have led to potential for fog overnight with concerns for dense (at or under 1/4 of a mile) fog focusing on locations west of the Mississippi, particularly locations with snowpack. Have issued a Dense Fog Advisory for areas with snow pack and farther west toward south central MN and north central IA, where observations at multiple locations are at a 1/4 or less as of 10 PM.

Low potential for rain Thursday in northeast Iowa and southwest Wisconsin

Wednesday in to Thursday, wave currently over Colorado moves just to our south as it treks toward southern Ontario. With surface ridging present in the southeast CONUS, southerly moist fetch at the surface and 850mb should bring enough northward for widespread precip to develop across the OH Valley with the northwestern edge of the precip shield potentially grazing NE IA and SW WI. 04.00z HREF and 04.01z NBM continue to maintain a 20-40% chance for precip so have continued to maintain this in the forecast. Should rain occur, amounts will be low with 04.00z HREF max values up to only 0.2".

Rain very likely Friday morning, potential for severe storms evening, uncertain nighttime into Saturday

Strong upper wave currently heading for the Pacific Northwest looks to break over the Four Corners Friday and barrels toward Lake Superior. With surface ridging still firmly in place in the SE CONUS, continue southerly moist advection across the central CONUS will set the stage for widespread rain with virtually all guidance depicting this occurring Friday morning in the Driftless region with additional rain likely during the evening into Saturday. 04.12z mean PWAT values climb to around 1" before the rain arrives, just below model climatology maximums for this time of year. 04.01z NBM probabilities generally depict a 35 to 85% chance for 1" of rain across Friday and Saturday with chances toward the high end of that range in NE IA and SW WI. Given potential for frozen ground - 6 to 17 inches of frost depth were observed Monday and Tuesday - additional runoff could lead to rises on creeks and streams. However, afternoon highs in the 40s and 50s Wednesday and Thursday may help thaw things before the rain arrives.

Aside from rises on rivers, other potential hazard looks to be severe thunderstorms. With strong winds expected aloft, focus will be on where sufficient instability is present for thunderstorms to develop and potentially tap into said seasonably strong shear. In shorter terms, much depends on how far north the warm front advances and guidance continues to differ quite a bit on this. Illustrative are the 04.00z operational runs of the GFS and NAM which bring the warm sector to encompass most of the CWA and just Fayette/Clayton/Grant counties, respectively. CSU-ML probabilities based on the GEFS suggest some chance across virtually the whole CWA while 03.12z ECENS joint MUCAPE-shear probability values sufficient for organized convection are around 15% in Taylor County increasing to near 60% in our south. Will need to closely monitor this period as, given deep shear values upwards of 50 knots and seasonably cold temps aloft, severe hail seems plausible should the warm front reach our CWA and thunderstorms develop.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 520 AM CST Wed Mar 4 2026

LIFR conditions are expected to start the TAF period at KRST and areas west of the Mississippi River with ongoing areas of dense fog in the region. As a result, expecting 1/4 mile visibilities at times to remain at KRST until after daybreak as diurnal mixing processes begin to allow the fog to lift. Meanwhile, LIFR/IFR fog seems unlikely at this point at KLSE with the recent HREF having low probabilities (20-40%) for IFR vsbys or lower. In any case, expecting fog to lift by mid-morning leaving VFR conditions for the remainder of the day. Cigs will increase overnight with MVFR cigs likely (50-70%) at KRST after 06z.

ARX WATCHES/WARNINGS/ADVISORIES

WI...None. MN...Dense Fog Advisory until 10 AM CST this morning for MNZ079- 086>088-094>096. IA...Dense Fog Advisory until 10 AM CST this morning for IAZ008>011- 018-019-029-030.