Snowy, Icy Mess Expected In the Northwest and Rockies This Weekend

Brian Donegan and Jon Erdman
Published: January 6,2017
Snow and ice will target the West this weekend not only in mountain locations, but also in some lower elevations. This wintry mess will then turn its sights on parts of the Midwest and Northeast later next week.
(MORE: Winter Storm Central)
Winter storm watches currently blanket much of Oregon, far southwest Washington, the Siskiyous of northern California, and parts of Idaho. This includes Oregon's highly-populated Willamette Valley, along the Interstate 5 corridor from Portland through Salem and Eugene.

Winter Weather Alerts

Cold air will linger through the weekend in the Northwest, as an atmospheric river draws in ample amounts of moisture to the region. This system will push several bands of precipitation from southwest to northeast across the area, beginning Saturday morning.
(MORE: California Will Be Pummeled By An Atmospheric River Event This Weekend)
The result will likely be a variety of winter weather, including heavy snow and some ice in the Columbia Gorge and a potential ice storm in the Willamette Valley and adjacent hills.
Let's break down the details day by day, and then get into potential snow and ice amounts.

Saturday/Saturday Night

• Precipitation will spread from northern California and southern Oregon early into the rest of Oregon, western Washington, Idaho, Nevada, Utah, and western Wyoming by late afternoon.
• In western Oregon and western Washington, that precipitation should start as snow, but then will change quickly to sleet and freezing rain.
• From the mountains of northern California into central and eastern Oregon, Idaho, northern Nevada, Utah, and western Wyoming, that precipitation should mainly be snow, however, some sleet or freezing rain may mix in, at times.

Saturday's Forecast

Sunday

• Temperatures are expected to gradually warm above the freezing mark Sunday away from the Columbia Gorge in western Oregon and western Washington, changing all precipitation to rain.
• Snow, sleet or freezing rain will continue in the parts of the Great Basin and interior Northwest, including the Columbia Gorge. 
• Some lowest elevations in the Great Basin may see precipitation change to rain.
• Snow will likely be heavy over the higher elevations of the northern Rockies, Wasatch, and high country of Colorado, but snow levels will be rising.

Sunday's Forecast

West Snow, Ice Forecast

The Willamette Valley, from Portland to Eugene, Oregon, will likely see some minor accumulating snow before the changeover to sleet and freezing rain.
However, the main concern appears to be from freezing rain and ice. Anywhere from one quarter to three quarters of an inch of ice may accumulate from Saturday evening into Sunday, before the changeover to plain rain.
(MORE: Five Reasons Why Freezing Rain Really Is The Worst)
Ice accretion of this magnitude can lead to downed trees and power lines, and travel will become treacherous as untreated roadways become very slippery.
Otherwise, the heaviest snow will fall in the Sierra (snow levels will be quite high), Siskiyous, and the higher elevations of Idaho, western Wyoming and Utah.
Significant accumulations of snow, possibly mixed with sleet or ice, will also occur in lower elevations of the Great Basin, including the Snake River Valley of Idaho, eastern Oregon and eastern Washington.

Snowfall Forecast

This follows on the heels of Winter Storm Helena, which brought over 4 feet of snow to parts of the mountain West.

Next Week Outlook

Starting late Sunday night, the wintry mess begins to spread into parts of the Midwest, then Northeast. Here is our latest timeline.

• Monday: Snow continues in the Cascades, Sierra and Rockies with lowering snow levels; Light snow spreads into the northern Plains and Upper Midwest and Great Lakes, possibly becoming heavier Monday night. Some sleet/ice is possible on the southern edge of that Plains/Midwest precip area.
• Tuesday: Low pressure wraps up in the Great Lakes with snow and wind in the northern Great Lakes and a wintry mix of sleet, ice or snow pushing into the interior Northeast and eastern Great Lakes. Mainly rain along/near I-95 Boston-Washington corridor.
• Wednesday: Cold front sweeps through the Northeast, changing any lingering ice in northern New England to snow before ending.

(MAPS: 7-Day Rain/Snow U.S. Forecast)

The general setup for snow to spread into the Midwest and Northeast into the upcoming week.

Be sure to check back frequently to weather.com for the latest updates on this upcoming system.

MORE: Winter Storm Helena Photos (January 2017)