Winter storm warnings in six states: heavy snow, dangerous travel as fresh system surges east

A fast-moving December system has triggered winter storm warnings in six states within the past day, putting parts of Alaska, Colorado, Illinois, Iowa, Wisconsin, and Wyoming under the gun for heavy snow, gusty winds, and hazardous roads. Forecasters caution that bands of the heaviest snow could flip conditions from wet to whiteout in minutes, with blowing and drifting snow reducing visibility and creating slick, snow-covered highways.

Where winter storm warnings are active

Forecasters highlighted the following zones on Sunday into early Monday (local times), with details subject to local updates:

• Alaska: Panhandle and adjacent coastal ranges under warnings for 8–12 inches, locally higher in terrain-favored corridors. Wet, heavy snow will strain tree limbs; slushy, refreezing roads likely overnight.

• Colorado: High country passes and adjacent ranges facing 10–20 inches (locally more on windward slopes). Travel over major passes will be difficult to dangerous, with periods of near-zero visibility in blowing snow.

• Illinois (northern/Chicago metro fringes): A compact wave bringing bursts of snow and blowing/drifting under strong west-northwest winds; accumulations vary widely, but reduced visibility and icy patches are the main threats.

• Iowa: Central and northern swaths under warnings where a deformation band is expected to park; 4–8 inches are common, with localized 10+ inches possible and ground blizzard conditions over open country.

• Wisconsin (southwest into central): Snow sweeping west to east overnight; heaviest over southwest counties with 5–9 inches, sharp gradients toward the east. Gusts will polish surfaces into ice by daybreak.

• Wyoming: Teton, Snake River, and Gros Ventre ranges, plus adjacent valleys, in the bull’s-eye for 6–14 inches in the mountains and lighter—but still disruptive—amounts in populated basins.

Key message: Even where totals underperform, wind and timing (commute windows) can produce high-impact travel.

Timing and travel impacts

• Sunday night–Monday morning (local): Peak impacts in the Upper Midwest (IA/WI/IL) with quick-hitting squalls and drifting snow during the morning drive.

• Through Monday (mountain West): CO/WY mountain corridors see periodic whiteouts at pass level; chain controls and intermittent closures are possible.

• Alaska Panhandle: Persistent, moisture-rich bands through early Monday keep plows busy and sidewalks sloppy; hydroplaning risk where snow compacts to slush.

Aviation knock-ons are likely at hub-adjacent airports where visibility thresholds are crossed during bursts; expect de-icing delays even if totals are modest.

How this storm is behaving

Meteorologically, the setup features a compact surface low riding a strong baroclinic zone, with frontogenesis sharpening a narrow band of heavy snow from the central Plains into the Upper Mississippi Valley. On the back side, cold advection and 25–35 mph gusts are producing ground blizzard conditions over open terrain. In the West, deep moisture and orographic lift are wringing out high-ratio snow over favored slopes, while downslope breaks create sharp local gradients.

Forecast confidence and what could still change

• High confidence: Hazardous travel in warning areas, especially open rural stretches and mountain passes.

• Moderate confidence: Exact snowfall maxima along the IA/WI corridor; small track shifts can swing totals by several inches over short distances.

• Lower confidence: Band placement during the Monday AM commute around the Chicago–Rockford–southern Wisconsin arc; an hour or two shift changes which counties get the worst visibility.

Recent updates indicate additional advisories surrounding the warnings; expect expansions or cancellations as the core band wobbles.

Safety checklist for warned areas

• Delay nonessential travel during peak bursts; if you must drive, slow down and increase following distance.

• Watch for flash-freeze/black ice behind heavier bands as temperatures slip below freezing.

• Prepare for brief power issues where wet, heavy snow and wind combine; charge devices and keep flashlights ready.

• Mountain travel: Carry chains, extra warm layers, water, snacks, and a full tank. Check pass conditions before departure.

What’s next

The storm’s Midwest impacts fade late Monday as the core lifts into the Great Lakes, leaving lake-enhanced snow showers in its wake. In the West, additional shortwaves keep mountain snow chances alive into midweek, maintaining intermittent travel headaches along the highest routes. Another broader system may organize over the interior West later in the week; confidence on track and intensity is lower at this range.

Winter storm warnings are active in six states—Alaska, Colorado, Illinois, Iowa, Wisconsin, and Wyoming—with heavy snow, strong winds, and treacherous travel in the crosshairs. If you’re in a warned county, plan for fast-changing conditions and give plows room to work.