textproduct: La Crosse

KEY MESSAGES

- Low storm chances (20 to 40%) with a large hail threat will be possible this morning mostly south of I-90.

- A strong weather system impacts the area Wednesday into Thursday night with probabilities for wintry impacts increasing, especially for Thursday morning. After a period of wintry mix Wednesday into early Thursday morning, precipitation is expected to switch over to rain for most locations south of I-94 by mid morning Thursday.

- There is also quite a bit of rain with this system as rain totals range from 1 to 2 inches south of I-90 with the highest probabilities (20 to 40%) for 2+ inches in southwest Wisconsin and portions of northeast Iowa.

DISCUSSION

Issued at 337 AM CDT Tue Mar 31 2026

This Morning Storm Chances:

Storm chances continue overnight slightly farther north as the nocturnal low level jet persists. Eventually the cold frontal boundary, draped southwest to northeast from southwest through east- central Minnesota, drags east-southeast across the forecast area into the morning hours. Exact timing and overlap with diurnal heating will determine morning storm threat locally. Recent HRRR forecast model runs suggest possible storm initiation within the warm sector over the eastern half of the forecast area from western into central Wisconsin near 31.12Z. While mid level lapse rates will be steep enough to support elevated instability and strong to severe storms, slight moderation is expected through the overnight from current 8.5C/km in RAP Mesoanalysis. Therefore, large hail and damaging wind potential remains through early this morning.

Colder Today, Winter Weather Setup Wednesday:

As the cold front sags south across the forecast area through today, daytime high temperatures in the 50s expected. Southern extent of low level baroclinic boundary relative to forecast area will determine subsequent winter storm probabilities Wednesday through Thursday. Current forecasts suggest the low level baroclinic boundary and accompanying sharp trough lying across the forecast area, shifting slightly south of the forecast area tonight. Exact location will determine initial location of cyclogenesis lee of the Rockies Wednesday, accompanying precipitation types Wednesday, as well as subsequent progression and intensity of cyclogenesis through the Upper Mississippi River Valley Thursday into Friday.

Initial precipitation chances Wednesday afternoon will be tied to low level frontogenesis along the low level warm frontal boundary, strewn quasi-zonally near the forecast area. High resolution forecast soundings have just begun to peer into this forecast window, increasing winter weather signal with snow soundings for areas along and north of I-94 and freezing rain/sleet soundings for areas along the I-90 corridor. Now there has been a recent trend in the models to shift the cooler temperatures northward as the center of the low passes somewhere over our forecast area. The locations for where the models put the center of the low at differ from near the IA, WI, MN state line to areas closer to the I-35 corridor in southern MN. This shift northward follows what the soundings have shown where snow is now favored north of I-94 and a wintry mix is between I-90 and I-94.

Confidence & Winter Preciptiation Types Midweek:

Variation in preciptiation types inherently tied to surface temperatures, dependent on temperature gradient and strength of east winds north of the front solidifying the cold sector through the Upper Mississippi River Valley. Therefore, regardless of differences exact precipitation types and locations, all high resolution models show a stout warm nose providing some degree of off-surface melting. Furthermore, the high April sun angle will limit initial frozen precipitation accumulation on roadways given the above freezing soil temperatures. Therefore, daytime freezing precipitation impacts may be limited to elevated surfaces and grassy surfaces only to return overnight with lack of diurnal heating. Similar for snow accumulation, potentially limited to elevated surfaces until the overnight when low level frontogenesis expands in coverage. With the northward shift, precipitation type switches to all rain for most locations by Thursday afternoon whereas previous forecasts and model runs had wintry mix being possible into Thursday night. The track of this storm will be very important to watch as this will have implications on amounts, precipitation types, and transition of different precipitation types.

Heavy Rain Into The Weekend:

As the extratropical low lifts northeast of the Upper Mississippi River Valley through the end of the week, additional subsequent cyclogenesis through the Northern Plains returns precipitation chances across the Upper Midwest Friday and through the weekend. While current confidence for heavy rain will be the main concern through the early weekend, mixed precipitation as the low exits east will bring another threat of winter impacts. Current confidence for 1" of QPF in long term global ensembles raises concerns for river flooding on flashier rivers.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1229 AM CDT Tue Mar 31 2026

Mid and high clouds will persist across much of the area overnight. Still plenty of uncertainty on whether any showers or storms will develop north of Clayton and Grant counties overnight, so kept the TAFs dry and got rid of the MVFR ceilings on Tuesday morning.

HYDROLOGY

Issued at 142 PM CDT Mon Mar 30 2026

Rain amounts Wednesday night and Thursday could approach 2 inches in southwest Wisconsin. Should this occur, and the precipitation type remain as all rain, stream and river rises are possible on the Kickapoo river late in the week.

ARX WATCHES/WARNINGS/ADVISORIES

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