Many weather hazards continue this holiday weekend. Ongoing flooding is widespread in California as the “atmospheric river” storm track begins to wind down. Heavy mountain snow continues for Northern California and Sierra Nevada Mountain Ranges. Snow advisories extend inland to the Rocky Mountains. Dense fog in the Midwest and Northern Gulf States, typical of unseasonably mild air. An ice storm rages in Western Pennsylvania and Winter Storm Warning for the northern Mid-Atlantic region today for heavy snow.

The negative phase North Atlantic oscillation forecast continues and inevitably drives colder changes in the East U.S. Helping to increase East U.S. cold risk is a southern and sustained shift of snow cover across the Northeast States.

The Climate Impact Company month 1-4 climate outlook for South America valid for January through April is updated. The constructed analog forecast is based primarily on lingering La Nina climate through Q1/2026 coupled with unusually warm SSTA off the West Coast. A trend toward El Nino could initiate as early as April.

As a precursor to the developing “atmospheric river” pattern, widespread high wind covers the Northwest U.S. to North-central States for WED/THU. Highest wind is downslope the Northern Continental Divide into the northwest Great Plains and across mountain areas of the Northwest States. Mountain areas will observe blizzard conditions already in effect for the Washington Cascades.