textproduct: La Crosse

This forecast discussion was created in the public domain by the National Weather Service. It can be found in its original form here.

KEY MESSAGES

- A breezy period for the next several days with daytime gusts of 25-35 mph, possibly reaching into the 40-45 mph range (40% chances) Tuesday in southeast Minnesota and northeast Iowa. Periodic light rain shower chances through mid-week as well, with better chances north of I-90.

- The latest forecast has lower temperatures - with highs only in the 45-52F range for Tue-Thu and frost/freeze possible late week for many. Tuesday will have brisk winds and the coldest temperatures...a raw day.

DISCUSSION

Issued at 317 AM CDT Sun Oct 19 2025

Sunny and Breezy Today

GOES water vapor imagery at 08Z is showing a strong shortwave trough ripping north through northwest IN, with surface pressure falls and cyclogenesis occurring over IN/MI. Radar is showing a light band of very light rain showers moving through associated with mid-level frontogenesis. Clearing skies are now about one county east of I-35. As pressures fall with the MI low pressure, the surface pressure gradient will support gusty winds of 25-30 mph for a period early this morning, with another ramp up in the afternoon as mixing depth increases. Mixing to about 5kft should allow for gusts to 30 mph for much of the area, although slightly higher chances exist in WI. These wind gusts will decrease after 3 pm as winds aloft diminish.

Breezy with Rain Chances To Begin The Week

GOES water vapor is showing an amplified ridge trough pattern upstream of the area with ridge building today. Another deep trough is approaching the WA coast with some lightning seen at 06Z, indicative of some good lift in this system. Tonight, strong southerly warm advection begins in the low-levels in response to the strong trough moving into the Pac NW and falling heights in the Northern Plains. This will bring southerly wind gusts to about 30 mph, especially in the morning hours Monday when the low-level jet is still 30-40 kts and the mixing depth is growing to tap into it at 2kft.

With todays system and moisture stream shunted well east of the area, this next weather system will have much less available moisture initially - precipitable water near 0.70 inches in the southerly inflow - closer to normal for mid-October. Much of the warm advection will go into warming Monday and lift will not overcome the drier inflow air until later in the day when stronger forcing comes in. The 925mb low will track from SD to between DLH and INL by Monday evening, bringing the initial cold front through the area. Forcing is strong with moderate QVector convergence aloft by late Monday. There may be a bit of MUCAPE, enough to help initiate showers (< 200 J/Kg) as well. Rain chances have increased, with 50% chances north of I-90 closer to the low track, however again will be light amounts less than 0.10". These rain chances may need to be brought further south and increased in future forecasts based on the forcing suggested and 18.12Z Grand Ensemble guidance which suggest higher rain chances than the NBM.

Tuesday Looking Windy, Showery, and Cool

Probably the most noticeable weather day of the week will be Tuesday under the influence of cold advection in northwest winds and possibly showers for much of the area. With broad, occluding low pressure over the northern Great Lakes, the area is set up for northwest winds in a moderate pressure gradient and deformation / trowal precipitation across the area...the question is where. The 19.00Z NAM isentropic 290K surface suggests moisture from the mid-atlantic and Ohio valley will run around the low into Canada and south again through Wisconsin while gently lifting. The 18.12Z LREF suggests ~20% probabilities for a couple tenths of an inch of rain Tuesday in northwest/central WI. There is a scenario packet of ensemble members that suggest the deformation band could be further southwest into southeast MN, so still some adjustment possible.

Maybe the bigger story is the moderately strong wind field across much of MN/IA Tuesday with deeper mixing southwest of the rain shower band. A strong gradient in probabilities exists along the Miss river (increasing westward) for gusts 35+ mph Tuesday afternoon...40% at La Crosse, increasing to 70% on I-35 per the 18.12 and 18.18Z ECMWF ensembles. The mean wind gust for La Crosse and Rochester are around 35 mph and 42 mph, respectively. Have used a blend of NBM and NBM 90th percentile for the wind and wind gust forecasts based on ensemble guidance and probabilities. Seems northeast IA and southeast MN are edging closer to Wind Advisory criteria (45 mph). Temperatures will only rise 4-5 degrees on Tuesday it appears, with highs in the 45-50F range and wind chills 38-45F.

Frost/Freeze Chances Late Week

The rain showers and winds slowly decrease Tuesday night and Wednesday as the low over the Great Lakes moves east and weakens. This will set up the possibility of a late week frost or freeze with probabilities of 20-60% (higher values to the north) for 33F or less Thursday and Friday mornings at this time /per 18.12Z Grand Ensemble/.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1215 AM CDT Sun Oct 19 2025

Light rain showers quickly progressing east at 19.06Z TAF issuance could provide transient MVFR visibilities at smaller airports locally in western Wisconsin.

Increased northwest winds through Sunday will be main impact with widespread gusts 25+ knots.

Decoupling boundary layer winds result in potential LLWS primarily west of the Mississippi River Valley Sunday night. Current confidence for surface winds decreasing during longer forecast hour leaves mention out of either TAF site at this time but will be important detail to monitor.

ARX WATCHES/WARNINGS/ADVISORIES

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


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