textproduct: La Crosse

KEY MESSAGES

- Warm for the rest of the week with highs running 10-15 degrees above normal, but colder air lurks on the horizon for Sunday and Monday with temperatures falling by 20-25 degrees.

- Increasing clouds this afternoon with light drizzle mainly along and south of I-90 into the evening.

- There is an increasing risk for freezing rain (40-60% chance) north of I-90 and east of the Mississippi River for Thursday night, which could make for slippery conditions for any post- holiday travel.

DISCUSSION

Issued at 225 AM CST Wed Dec 24 2025

Today/Tonight: Increasing Clouds and Drizzle

A blocking longwave ridge remains the dominant feature of note across the central CONUS this morning, though with the upstream axis amplifying, a weak vort lobe rides down the ridge and will be the driver for our sensible weather later today. As this wave approaches this morning, increasing southwesterly flow across the lower Missouri River Valley and into the local region should advect a saturated lower tropospheric airmass (noted as fog/low stratus across Kansas and central Missouri early this morning) northward and into parts of the region later today. Mid-tropospheric winds should start turning more westerly this evening as the upper level perturbation scoots on through, so the best lift and deepest saturation of >1-km in depth will not linger all that long. The greatest probabilities for drizzle will therefore be along and south of I-90, mainly in northeast Iowa and southwest Wisconsin. Impacts should be minimal with temperatures well above freezing in a warm air advection regime.

The low level moisture looks to hang up mainly along and south of I-90 and west of the Mississippi River tonight, which could set the stage for dense fog development. The exact coverage and thickness of the fog is less certain given that weak negative theta-e advection will be ongoing through the boundary layer, which may limit the areal extent of the fog or erode it over time.

Thursday Night - Friday Morning: Wintry Mix Potential

The next notable chance of precipitation poses a challenge to the forecast with regards to the extent of freezing rain/drizzle Thursday night into Friday morning. Downstream surface high pressure will still be departing as 290K isentropic ascent and theta-e advection increase through the evening hours on Thursday. Light rain (maybe more of a heavy drizzle?) is likely for most locales at some point in the evening/overnight, so the freezing rain threat hinges heavily on temperature trends through the day and evening tomorrow. Some early looks at the longer range CAMs are mirroring the general consensus of the global models with placing the greatest risk for light ice accretion along and northeast of the I-94 corridor where easterly flow will be most established and temperatures struggle to reach freezing during the day. Lower probabilities for a brief bout of freezing rain (<10%) extend as far southwest and La Crosse and Rochester, but the impacts in these areas should be mitigated by steady temperatures around freezing that warm after midnight.

While overall QPF amounts are light given the disjointed nature of the system, any freezing precipitation that falls during this overnight period could quickly lead to travel impacts, especially along I-94.

Friday - Saturday: Warm!

With the overall pattern amplifying through the end of the week and the flow turning more to the southwest, Friday and Saturday feature our warmest temperatures of the period with many locales cracking the 40-45 degree mark. In fact, about 10-20% of the NBM ensemble members have areas along the same latitude as Dubuque closing in on 50 degrees on Friday, spreading as far north as I-90 for Saturday.

Sunday - Monday: Winter Temperatures Return

A sharp longwave trough finally cuts through the ridge late Saturday and a strong cold front races through the region Saturday night into Sunday morning, sending temperatures tumbling into the single digits for lows by Monday morning.

Whether we see any precipitation with this cold frontal passage is a lower confidence aspect of this forecast dependent on how quickly the attendant surface cyclone can mature. Trends over the last 24 hours have shown an increase in the probabilities (now up to 20-40%) for light snow in the post-frontal airmass during the day on Sunday.

Moderating temperatures do arrive by Tuesday and Wednesday, but to what extent temperatures rebound is quite uncertain given how the region will reside along the transition zone between a temperate and polar airmass on the downstream flank of a sharper ridge. In fact, the NBM has a nearly 40 degree spread in the high temperature forecast by midweek!

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 543 AM CST Wed Dec 24 2025

Increasing low level moisture this afternoon ushers in MVFR ceilings into northeast Iowa and southeast Minnesota, traversing the Mississippi River Valley into Wisconsin by the early evening. Further ceiling reductions expected primarily west of the Mississippi River Valley into the nighttime hours with visibility restrictions also possible (BR/DZ). Current lower confidence keeps visibility restriction out of KRST TAF site. Persistent aviation impacts expected primarily west of the Mississippi River Valley through Friday.

Rain and freezing rain impacts possible Thursday night with a rain-snow mix possible primarily north of Interstate 94 Saturday into Sunday morning.

ARX WATCHES/WARNINGS/ADVISORIES

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