Published: May 12,2017
Snow will blanket much of the mountain West into next week and add to a still-impressive mid-May snowpack from a winter that was the wettest on record for some areas.
(MORE: Winter Storm Central)
Although we're barely more than a month from the summer solstice, a major shift in the weather pattern will turn the West much colder in the week ahead.
(FORECAST: 4 Things to Know About the Pattern Change Ahead)
The first of several sharp southward plunges of the jet stream swept into the Northwest Friday and was expected to drop snow levels in the Cascades as low as 4,000 feet during the weekend.
Current Radar, Satellte, Temperatures, Conditions
While most low-elevation locations will likely remain too warm for snow – it is mid-May, after all – some high-mountain valleys and plateaus are likely to pick up measurable snow by later next week.
Higher elevations of the northern Rockies of Idaho, southern Montana, Wyoming, and Utah may see heavy snow accumulations – possibly a foot or more in a few areas.
Plowable snow accumulations are also expected in the Cascades and Sierra, as well as the mountains of northeast Nevada and Colorado's high country.
Snowfall Potential Through Next Thursday
Piling on the SnowpackDespite recent warmth, there is still plenty of snow left to melt in the mountain West.
Basin-wide estimated snow water content as a percent of average on May 12, 2017. Areas shaded in dark blue were at least 150 percent of average snow water content.The Natural Resources Conservation Service's SNOTEL network estimated water content in the snowpack on Friday was an incredible 641 percent of average in parts California's Sierra and over 150 percent of the average for the date in parts of Wyoming, Idaho, Utah, northern New Mexico, western Nevada, Oregon and southern Washington.
In fact, a half-dozen locations from the Sierra to Wyoming have a record-high snow water content for this time of year in 30 to 40 years of records, according to the SNOTEL network.
Several locations in Wyoming have had a record wet October-through-April in 2016-17. As a result, spring flood potential is either moderate or high in river basins that charge with snowmelt in western Wyoming, according to the National Weather Service.
In Utah, releases from Deer Creek Dam were expected to trigger flooding on the Provo River.
Mandatory evacuations were expanded Thursday for additional homes in Hailey, Idaho, due to flooding of the Big Wood River, which was expected to remain in flood stage for a prolonged period due to the remaining snowpack. According to the NWS, this flooding could persist for several weeks.
While some roads in Yosemite National Park have been cleared, the snow-clearing effort of higher paved roads continues in other national parks. So this fresh snow won't just add to the snowpack – it'll also worsen snowmelt flooding in the weeks ahead.
Jonathan Erdman is a senior meteorologist at weather.com and has been an incurable weather geek since a tornado narrowly missed his childhood home in Wisconsin at age 7. Follow him on Facebook and Twitter.
MORE: 50 States' Biggest Snow Days
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.