textproduct: La Crosse

KEY MESSAGES

- Slight increase in snowfall amounts for the Winter Storm today into Monday morning with 6"+ along and north the Interstate 90 corridor from southeast Minnesota through western and central Wisconsin. Combination of strong winds near 45 mph may decrease overall amounts while exacerbating blowing snow and visibility impacts. Rapid cooling also raises freezing roadway concerns from initial rain this morning.

- Upgraded to Blizzard Warning in parts of southeast Minnesota and northeast Iowa while upgrading some of northeast Iowa and southwest Wisconsin from Winter Weather Advisory to Winter Storm Warning.

UPDATE

Issued at 1042 AM CST Sun Dec 28 2025

During the past 1 to 2 hours visibilities have been gradually improving, so the Dense Fog Advisory was cancelled early.

DISCUSSION

Issued at 400 AM CST Sun Dec 28 2025

Morning Observations:

An area of closed upper level cyclonic flow on GOES water vapor imagery loops meandering east-southeast into North Dakota is approaching an enhanced subtropical jet streak on GOES derived upper level winds from the Desert Southwest through the northern Great Lakes. Rapid cyclogenesis with their confluence through the morning hours expected along a low level baroclinic boundary extending southwest of the forecast area early this morning will leverage 90th to max percentile moisture (SPC RAOB Climatology) through the Upper Mississippi River Valley. Additional impacts expected from strong winds and rapid freeze due to the rapid deepening of the extratropical cyclone.

Precipitation Type Today:

Initial rainfall (HREF) spreads northeast through the morning hours along the enhanced low level moisture transport before the surface cold front slides from northwest to southeast near or shortly before noon, providing a switch in precipitation type to snow. While freezing rain cannot be completely ruled out, high resolution forecast soundings suggest a rapid, deep cool below the 0C isotherm due to the rapid progression of the system limiting overall expectations. A limited window lacking upper level ice introduction as surface temperatures cool would be the limited, scattered culprit should a minuscule extent of freezing precipitation occur.

Snowfall Timing & Confidence:

Initial, highest snowfall rates spread northeast from north- central Iowa through central and eastern Minnesota into west- central and central Wisconsin through the early afternoon tied to enhanced low level (850mb/700mb) frontogenesis. While HREF confidence has increased probabilities for higher amounts during the afternoon/evening (18Z-00Z) along our western peripheral counties in southeast Minnesota and west-central Wisconsin, membership depicts a bimodal distribution.

The most extreme solution seen in the ARW (28.00Z), targeting an area of 1" to 2.5" per hour snowfall rates where nodes of amplified low level (850mb/700mb) frontogenesis advect. While snowfall will be steady through the evening, another enhanced area of low level frontogenesis collocated with a thick (3000m) DGZ tonight returns higher snowfall rate potential progressing from northwest to southeast. Less of a signal in high resolution models for this at the current forecast hour as moisture is lower, however is something work keeping an eye on given nighttime driving and more intense snowfall rate potential.

Snow Amounts & Confidence:

A stronger solution to the low increased low level frontogenesis and extent of higher QPF across the forecast area, increasing snowfall totals by 1" to 2". The transient nature of the system and dependency on transient frontogenesis still leaves much to be desired in confidence with HREF members varying from 10"-13" (10:1 SLR) across the northern half of the forecast area in the NAMNest (28.00Z) and ARW (28.00Z) to 6"-9" (10:1 SLR) in the HRRR (28.00Z) and NSSL (28.00Z).

In collaboration with neighbors, have toned down snowfall amounts some from raw short term model output to temper 10"+ totals for northern half of the forecast area by throttling 20:1 SLRs given expected dendritic demolition from the high winds.

Winter Impacts & Confidence:

Confidence in widespread impacts remains high as the tightened low level height gradient increases northwest surface winds gusting near 45 mph concurrent with enhanced low level cold air advection through late morning and afternoon. While the higher initial snowfall rates will provide a blowable snowpack, amount of initial surface melting solidifying accumulations and limiting transport remains the inherent challenge. Regardless, the higher rates and wet roads combined with the plummeting temperatures persists freezing road impacts. Given the higher amounts slightly farther south, have extended the Winter Storm Warning a couple counties south in Wisconsin, upgrading the previous Winter Weather Advisory. While solidification of accumulating, potentially blowable snowpack remains a question, highest confidence for strongest winds collocated with confidence for enhanced snowfall rates, and initial freezing areas of the Winter Storm Warning in southeast Minnesota and northeast Iowa were upgraded to a Blizzard Warning as well which aligns with local Blizzard climatology.

Next Week Cold:

The upper level trough isn't going anywhere fast as we move into the new week. The GEFS and EPS keep the Upper Mississippi under its influence through at least Friday. Daytime highs mostly in the teens with Thursday continuing to trend coldest, LREF probabilities for single digit highs.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 601 AM CST Sun Dec 28 2025

While fog bank has somewhat improved early this morning, 1/4SM visibility has lingered and persisted in parts of southeast Minnesota, northeast Iowa, and southwest Wisconsin; affecting both TAF sites. Precipitation chances are progressing northeast on radar imagery, ultimately alleviating FG to RA through the morning hours.

This rain transitions to snow from west to east during the day with conditions deteriorating to LIFR as the snow intensifies and blowing snow risk increases during the late afternoon and evening. Light overnight winds switch to the north/northwest early this morning, increasing to 15-25G40kts west of the Mississippi River by midday and spreading slowly to the east during the afternoon and overnight.

The heaviest snow occurs overnight and clears Monday morning, though the risk of blowing snow will continue with winds remaining strong and only slowly decreasing through the day.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Winter Storm Warning from 3 PM this afternoon to noon CST Monday for WIZ017-029-033-034-041>044-053-054. Winter Weather Advisory from 3 PM this afternoon to noon CST Monday for WIZ055-061. Winter Storm Warning until 9 AM CST Monday for WIZ032. MN...Blizzard Warning until 9 AM CST Monday for MNZ086-087-094-095. Winter Storm Warning from 3 PM this afternoon to noon CST Monday for MNZ096. Winter Storm Warning until 9 AM CST Monday for MNZ079-088. IA...Blizzard Warning until 9 AM CST Monday for IAZ008>010-018-019- 029. Winter Storm Warning from 3 PM this afternoon to noon CST Monday for IAZ011. Winter Weather Advisory from 3 PM this afternoon to noon CST Monday for IAZ030.