'Large And Dangerous' Avalanches Possible In The West Amid Strong Pacific Storm

A strong Pacific storm that will affect the West Coast Tuesday has triggered Avalanche Warnings in some parts of the region, as rainfall combined with snow and strong winds have been forecasted to increase the risk of avalanches in affected areas.

"Increasingly stormy weather to impact the West Coast through Tuesday," the National Weather Service (NWS) said in its Short Range Public Discussion report published Monday.

The office added that there is also a potential threat "for widely scattered instances of flash flooding" at lower elevations in parts of the western U.S. through Wednesday morning.

In California, moderate to heavy rainfall is expected through Tuesday, the NWS in Sacramento tweeted. Small streams and creeks are expected to rise, which could then lead to urban flooding.

The heaviest rain of more than 4 inches is expected from Monday night through Tuesday afternoon.

In Utah, officials at the NWS in Salt Lake City said residents should expect winter weather to return to the state this week. The first system will start Tuesday, bringing rain showers across most valleys throughout Tuesday.

Over in Washington, mountain snow and lower-elevation rain is expected Tuesday, with some areas possibly seeing up to 3 inches of rainfall.

The NWS in Portland has forecasted heavy rain and strong winds in Oregon through Tuesday. Some areas such as Santiam Pass could see up to 6 inches of rain, while Mount St. Helens could get up to 10 inches of rain.

In Nevada, officials warned of a high probability of avalanche danger in portions of Inyo and Mono County as well as in the Central Sierra Mountains and the Greater Lake Tahoe Area.

For Colorado, officials at the NWS in Grand Junction noted that moderate snowfall is expected Tuesday and could transition to heavier snow by Wednesday.

Officials at the NWS in Boulder also noted that avalanche danger could possibly go high by Wednesday afternoon. "Large and dangerous avalanches will be easy to trigger once the new snow accumulates. Avalanches will run naturally," the office said.

In Montana, officials at the NWS in Great Falls said some areas will see up to 12 inches of snow Tuesday as a mix of snowfall and rain hits the state.

In Idaho, Old Faithful and Island Park are expected to see up to 12 inches of snow accumulations, while Galena could see up to 24 inches of snowfall totals.

Avalanche Warnings

Colorado – effective through 8 a.m. Thursday

• Park Range, Elkhead Mountains, Ruby Range, Flat Top Mountains, West Elk Mountains, Grand Mesa, San Juan Mountains, San Miguel Mountains, Rico Mountains, La Plata Mountains, Needle Mountains, Grenadier Range, Sawatch Mountains and Elk Mountains south of divide

Montana – effective through 7 p.m. Tuesday:

• Rattlesnake, Bitterroot, southern Swan Mountains and southern Missions
• Whitefish Range, John F. Stevens Canyon, Flathead Range, Maria Pass area and Apgar Range

Idaho – effective through 6 a.m. Tuesday:

• Kootenay, Cabinet, St. Regis Basin in Lookout Pass Zone
• Silver Valley

High Wind Warnings

Idaho – effective through 8 p.m. Tuesday:

• Owyhee Mountains (wind gusts of up to 70 miles per hour possible)

Nevada – effective through 10 a.m. Tuesday:

• Lassen-Eastern Plumas-Eastern Sierra
• Greater Lake Tahoe Area (wind gusts of up to 130 miles per hour possible)
• Mono County (wind gusts near 100 miles per hour possible)
• Greater Reno-Carson City-Minden Area
• Northern Washoe County
• Mineral and Southern Lyon

California – effective through 10 a.m. Tuesday:

• Coastal Del Norte, Southwestern Humboldt, Del Norte Interior, Northern and Southern Humboldt Interior
• North and Central Sacramento Valley
• Motherlode

Oregon – effective through 7 p.m. Tuesday:

• North and Central Oregon Coast
• South Washington Coast
• Coast Range of Northwest Oregon and Central Coast Range of Western Oregon
• Willapa Hills
• South Central Oregon Coast and Curry County Coast (wind gusts of up to 75 mph possible)
• Central Siskiyou County
• Central and Southern Oregon Cascades

Montana – effective through 11 p.m. Tuesday:

• Madison River Valley
• Eastern Glacier National Park (wind gusts of up to 80 miles per hour possible)

Flood Watches

Oregon – effective through Tuesday evening:

• Gold beach, Harbor, Ophir, Brookings and Pistol River
• Trask, Netarts, Willapa, Lees Camp, Ocean Park, Vernonia, Summit, Naselle, Raymond, Pacific City, Cathlamet, Ryderwood, Cape Disappointment, Long Beach, Cannon Beach, Jewell Astoria and Tillamook

California – effective through Tuesday afternoon:

• San Francisco, Scotts Valle, Santa Cruz, Live Oak, Day Valley, Watsonville, Pacifica and Boulder Creek
• Marina, Monterey and Seaside
• South Santa Rosa, San Rafael, Angwin, Woodacre, Petaluma, Tamalpais-Homestead, Lagunitas-Forest Knolls, Napa, Sausalito, Rohnert Park and Novato

Washington – effective through Wednesday morning:

• Marysville, Freeland, Lacey, Silverdale, Shelton, Tumwater, Aberdeen, Langley, Anacortes, Sequim, Sedro-Woolley, Evertt, Edmonds, Chehalis, Mount Vernon, Lynnwood, Seattle, Port Townsend, Fords Prairie and Olympia