First Bout of Widespread Mountain Snow Invades Western US

By Alex Sosnowski, AccuWeather.com Senior Meteorologist

November 3,2015; 10:16PM,EST

 

 

Soaking rain and accumulating snow will continue to accompany a sweep of dramatically cooler air over a large part of the West this week.
While cold air and snow will be an early boost for ski resorts and rainfall could be just the start of drought recovery in some communities, the winterlike conditions are creating travel problems.

First Significant Snow of the Season Falls in California's Sierra County

Temperatures will plunge 15-30 degrees Fahrenheit over much of the interior West as the leading edge of the cool air arrives.
Preceding the arrival of the chilly air will be gusty winds that can kick up dust from the Four Corners to the high plains of eastern Wyoming. The dust can cause sudden low visibility.

Winds can be strong enough to knock down power lines in some communities.
In many areas, the chilly air outbreak will deliver the lowest temperatures since last spring.
The list of cities that will experience their chilliest air in months includes Los Angeles and Sacramento, California; Phoenix and Flagstaff, Arizona; Las Vegas; Salt Lake City; Portland and Pendleton, Oregon; Seattle and Spokane, Washington; Boise and Pocatello, Idaho; Missoula and Great Falls, Montana; Jackson, Wyoming; and Aspen, Colorado.
The weather pattern will bring the coldest nights and the chilliest days since April in many locations.
Nighttime temperatures will dip well down into the teens and 20s in the mountains and deserts from Montana and Idaho to northern Arizona.
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On the coldest days, temperatures will be held to the 30s in the mountains and in some of the northern high desert areas of the Great Basin.
Along with the outbreak will be areas of snow.
According to AccuWeather Senior Meteorologist Brian Wimer, snow will be mostly confined to the higher elevations of the Wasatch Range and Rockies during the middle days of the week.

"Enough snow can fall over the higher passes to make roads slushy and snow-covered. Up to a foot of snow is forecast over the highest elevations," Wimer said. "However, enough snow can reach the valley floors in northern Nevada and Utah and in the lower elevations in Montana to blanket non-paved surfaces."
Where it snows hard, even at lower elevations, roads can become slushy and slippery.
At low and intermediate elevations the snow will be clinging in nature. The wet snow can bring down tree limbs and power lines.
The snow will tend to melt as it falls on the pavement along much of I-80 in Nevada through the middle of the week.
Farther east, road surfaces can get slippery over the higher terrain along I-15 in Utah, Idaho and Montana, I-70 in Colorado and I-80 in Utah and western Wyoming during the middle days of the week.
Motorists should be alert for areas of black ice over the mountains and colder valleys at night, even where rain fell during the day.
The air is not likely to get cold enough for snow to fall on Cajon and Tejon passes in Southern California and in the Denver metro area.
Rain showers will change to snow showers over northern Arizona, including along portions of I-40. Motorists should be on guard for slushy conditions.
The mountains of northern New Mexico, which received some snow late last week, could get a bit more snow late this week.
According to AccuWeather Senior Meteorologist Ken Clark, "While the snow will be significant in the Sierra Nevada, it will be a drop in the bucket compared to what is needed."
The high country of the Sierra Nevada receives an average of 300 to 500 inches of snow per year according to the Central Sierra Snow Laboratory.
Snowfall in recent years has been much less than average and above-average temperatures have greatly reduced the existing snowpack. Sierra Nevada snowpack was determined to be the lowest in 500 years on April 1, 2015.
Approximately 30 percent of California's water supply originates from the Sierra Nevada snowpack.
Enough snow to cover a three-story building or more will have to fall on the Sierra Nevada and Cascades this winter to have a significant impact on the drought.
"At least the storm this week is a small step in the right direction," Clark said.
In addition to the snow, locally drenching rain will fall on some communities. The bulk of the rain will fall along the west and southwest facing slopes of the mountains, where a general 1-3 inches is in store.

Drying and clearing will progress from west to east later in the week and into the weekend over much of the region.