Winter Storms Threaten to Disrupt Travel in the Northwest

A frosty weekend is expected in the Pacific Northwest, where holiday travel could be disrupted by winter storms that have covered the mountains with snow, forecasters said.

The National Weather Service said single-digit temperatures could follow the storms in Oregon and Washington, as officials called on residents to heed warnings about dangerous road conditions and to prepare for the cold.

Heavy snow was likely in the western mountain ranges, including the Sierra Nevada mountain range and Cascades, according to the Weather Prediction Center of the National Weather Service.

“Travel will be treacherous” and at times “impossible,” from the Sierras to the central Rockies this weekend because of whiteout conditions and drifting snow, the agency warned.

Marc Chenard, a meteorologist at the National Weather Service, said the amounts of snow expected in some of the mountain areas, particularly the Sierra Nevadas in California, were extreme.

Snowfall was being measured in feet in the mountains, while the estimates for coastal areas in the West were in inches.

Forecasters said there could be two to five inches of snow in Portland, Ore., this weekend and two to seven inches in Seattle. Mr. Chenard said it was not unheard-of for there to be snow in Seattle. In 12 of the past 15 years, the city has had at least an inch of snow, he said.

The Pacific Northwest was also bracing for an unusual cold snap.

The Weather Service said temperatures in Washington and Oregon could drop to single digits on Sunday and the cold spell could last into early next week. The agency advised that the most vulnerable populations, including homeless people and those without access to heating, would be especially at risk.

Kate Brown, the governor of Oregon, on Thursday declared a state of emergency to last through Jan. 3 because of the forecast.

“Our state has experienced a number of climate-related emergencies this year, and with another coming, I urge all Oregonians to make a plan with your family now and be prepared,” she said.

The Emergency Management Division of the Washington State Military Department advised people to prepare for the storms by limiting their time outdoors, staying off the roads and dressing warmly.

The cold weather contrasted with conditions in much of the United States, where record-breaking high temperatures were recorded at the end of the week and were expected to continue through the weekend.

“There will be more record highs than there will be record lows,” Mr. Chenard said.

In the Southern Plains and mid-Atlantic, temperatures on Christmas Day were expected to be 25 to 35 degrees above normal. In Oklahoma and Texas, the weather was in the 90s.

In Wichita Falls, Texas, near the state’s border with Oklahoma, the temperature on Friday reached 91 degrees, breaking the previous December record of 88 degrees set in 1954.