textproduct: La Crosse

KEY MESSAGES

- Light snow is possible (20-60%) tonight into Saturday morning, most probable along and north of I-90. Some patchy light freezing rain ahead of any snowfall is possible (10-20%).

- Another period of light snow is possible (10-40%) Sunday night into Monday.

- Quick transitions between above and below normal temperatures this weekend with a warming trend through the new week.

DISCUSSION

Issued at 203 PM CST Fri Dec 19 2025

This Afternoon Into Saturday

A 700hPa shortwave trough and warm air advection overspreads the region from the west throughout the afternoon, supporting some mid-level cloud cover. Can't completely rule out some flurries with this wave and push of warm air given these forcings coincide with a saturated DGZ, although dry air below 8000ft will largely inhibit any precipitation reaching the surface.

Moving into tonight, the surface mid-latitude cyclone currently located over southern Saskatchewan will shift eastward into the Upper Midwest, supported by a 500hPa shortwave trough evident on water vapor imagery. The cold front associated with these synoptic features moves southeast through the region late tonight through Saturday morning with strong frontogenesis depicted throughout the column which will support greater potential for snowfall (20-60%). Probabilities are highest north of I-90 as deeper saturation is expected for these areas. For areas south of I-90, dry air in the sub-cloud layer again leads to uncertainty in precipitation potential. A fairly deep dry layer is present in HREF/RAP/HRRR soundings, generally between the surface and 10,000ft. However, strong forcing throughout the atmosphere given the approaching cold front may be able to overcome the lack of saturation. Given the uncertainties, 10-20% probabilities of precipitation are present.

Ahead of the cold front, warm air advection in the 850-70hPa layer results in a fairly stout warm nose developing per HREF/RAP/HRRR soundings. This warm nose could result in some light freezing rain with the initial onset of precipitation before a transition to snow occurs. However, the aforementioned dry air leads to uncertainty whether any precipitation will be observed at the surface. If the dry layer is able to be overcome, a light glaze of ice is possible which would result in some slick spots Saturday morning.

Sunday Night Into Monday

Another quick hitting shortwave at 850hPa traverses the Upper Midwest Sunday night into Monday in the wake of an area of high pressure. Southerly flow will usher warm air into the region, supporting precipitation development primarily along and north of I-90. Precipitation type is expected to be primarily snow, but some rain could mix in with southward extent as warm air increases temperatures to near freezing. Amounts are expected to be light.

Temperatures Through Next Week

With the various quick hitting waves this weekend, fairly rapid temperature fluctuations are expected as highs Saturday reach into the 30s, but drop into the 20s for Sunday.

A more consistent warming trend is expected through the new week as ridging will become the dominant pattern over the United States. High temperatures climb into the upper 30s to low 40s by Tuesday, with some locations south of I-90 possibly reaching 50F for Christmas Day (20-50%).

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1147 AM CST Fri Dec 19 2025

Predominantly VFR conditions expected through the TAF period. Mid level clouds, around 10kft, continue to move into the area and will stay into Saturday morning. Winds are currently shifting to the south and later this afternoon and into the evening will gust up to 25 to 30 mph, especially west of the Mississippi River. Winds then shift back to the northwest as a cold front sweeps through the region Saturday morning. Sustained winds of 15 to 20 mph and gusts of 25 to 35 mph expected, especially along and north of I-90. Wind shear may be a problem across much of the area as light south winds at the surface combine with 35 to 45kt winds at 2kft. As a result, have gone ahead and put wind shear in the TAF for the evening and early overnight periods at KLSE and KRST. Lastly, there is a low to medium chance (20 to 50%) of snow Saturday, better chance for areas north of I-94. Have gone ahead and introduced a prob30 for KLSE for this potential.

ARX WATCHES/WARNINGS/ADVISORIES

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