textproduct: La Crosse

KEY MESSAGES

- Extended Cold Weather Advisory in Clark & Taylor Counties of Central Wisconsin where apparent temperatures remain near and below -25F through Tuesday morning.

- Widespread dangerous cold returns Thursday with -25F to -40F wind chills possible Thursday night through Sunday morning.

- Snowfall Tuesday night & Wednesday afternoon/evening. Higher accumulations expected Tuesday night with a band of 2" to 4". Lower confidence for 1"+ Wednesday afternoon/evening.

DISCUSSION

Issued at 224 PM CST Mon Jan 19 2026

Tuesday Snowfall:

As the polar synoptic low churns over Hudson Bay on mid level GOES water vapor imagery, open appendages swinging southeast provide local precipitation chances Tuesday night and Wednesday. Surface cyclogenesis along a low level baroclinic baroclinic boundary within a phasing low-mid level trough advects the deepening low across the Upper Mississippi River overnight Tuesday into Wednesday.

Initial precipitation chances increase Tuesday evening along our west from isentropic upglide and increasing moisture within low level return flow as the low starts to phase upon reaching the Missouri River Valley. Further phasing into the nighttime hours increases northwest to southeast oriented low level frontogenesis across the southern half of the forecast area. Current confidence in timing and phasing of the low allows PWATs to recover from 10th percentile (0.1") to near 75th percentile (0.3") according to HREF mean. The ample moisture combined with isothermal high resolution soundings grazing the DGZ could provide increased hourly snowfall rates. Current confidence keeps rates 0.5" to 1" per hour as isothermal soundings are a couple of degrees warmer than the DGZ as the wave progresses. This keeps overall confidence for 2" to 4" of accumulations from northeast Iowa into southwest Wisconsin but again, should low level temperatures cool a couple of degrees in future high resolution soundings, amounts will require increasing.

Lighter Snowfall Wednesday Afternoon-Evening:

A short reprieve in snowfall through Wednesday morning ceases Wednesday afternoon as synoptic positive vorticity advection within an additional open wave progresses east through the Upper Mississippi River Valley. Accompanying low level frontogenesis potentially driving additional 1"+ snow accumulations within a strengthening frontal boundary requires further investigation in coming forecasts as previous ample moisture is carved away. LREF confidence for snowfall is 70-100% for the western half of the forecast area Wednesday afternoon decreases to 70% in the EPS (19.12Z), 50% in the GEPS (19.12Z), and 0-40% in the GEFS (19.12Z)for the eastern half of the forecast area Wednesday night. While this is an increase over previous forecasts, this remains the lowest confidence part of the forecast as lingering impacts could impact the Wednesday evening commute. Deterministic GFS soundings suggest rapid eradication of all/any moisture, sustaining the driest forecast. Unfortunately the glorious NBM appears to be buying into the GFS solution with a lower PoP forecast.

As the synoptic mid level low finally shifts east through Thursday, flurry chances will persist. Current LREF (18.00Z) confidence for 0.1" of snow in 6 hours is 30%-50% outside of the GEFS (18.00Z) at <10%. Unfortunately, restrictions regarding increasing PoPs away from NBM (1%-3%) at the longer forecast hour but there will likely be some limited impacts to plan around.

Cold Later In The Week:

Clearing skies have allowed surface temperatures to slightly rebound a few degrees above & below zero for apparent temperatures to warm above -25F. Classic cold spots in central Wisconsin are holding on to the coldest temperatures locally, therefore extended the Cold Weather Advisory through Tuesday morning in these spots in collaboration with neighboring forecast offices.

Return flow through Tuesday associated with increasing precipitation chances keeps dangerous cold at bay through midweek. The cold returns on Thursday as the 850mb -20C isotherm, present locally earlier today, advects south through the afternoon/evening, quicker and earlier than previous LREF forecasts. ECMWF (19.00Z) extreme forecast index of -0.8 to -0.95 from Saturday through Sunday Night suggests "very unusual" cold is likely. An accompanying >0 shift of tails covers the forecast area, suggesting a few members solutions for 99th percentile cold temperatures compared to Model climate for this time of year.

The slightly earlier solution in the most recent LREF (19.12Z) (aligning with EPS dProg/dT) also provides an earlier exit to the coldest temperatures through Sunday. Besides 40-50% probabilities in the most recent GEFS (19.12Z) and EPS (19.12Z) for negative surface temperatures lingering over the northern half of the forecast area through Sunday, the GEPS (19.12Z) remains the overall problem outlier with a widespread 80-100% nightly probabilities through day 7.

Resultant NBM 25th to 75th 2m temperature spread is 10-15 degrees from Thursday afternoon through day 7. While current confidence would mean collaborating these dangerously impactful temperatures, fealty to the NBM keeps forecasting at bay.

Regardless, removing the GEPS from the LREF, accompanying probabilities for Advisory criteria reaches 100% Thursday night through Friday morning, 80-100% Friday night into Saturday morning, and 30-60% Saturday night and Sunday morning (EPS/GEFS). Probabilities for warning criteria (<-35F) are highest (80-100%) north of the IA/MN border Friday morning while decreasing to 40-80% north of Interstate 94 in the EPS for Saturday morning and 30-40% in the GEFS. Therefore, headlines will be required come Thursday night. Diurnal heating availability Friday will be future headline difficulty as LREF temperature probabilities fluctuate.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 528 PM CST Mon Jan 19 2026

A shortwave trough will move southwest and south of the area tonight. This system will bring with it some mid- and high clouds to the TAFs. Another system will approach the area on Tuesday afternoon. This will bring some snow to the area on Tuesday night.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Cold Weather Advisory until 10 AM CST Tuesday for WIZ017-029. MN...None. IA...None.