A strong cross-country storm system is bringing the worst of every season as it sweeps across the nation, featuring howling winds and a serious fire danger in California, heavy snow in the Rockies and, by Tuesday night, a severe thunderstorm threat in the Plains. It comes on the heels of a weekend storm that also brought heavy snow to parts of the West and tornadoes in Oklahoma.
This new storm slamming the West has prompted the National Weather Service to hoist advisories for multiple hazards affecting tens of millions of people from California to Colorado.
The powerful system will drop up to two feet of snow in the central and northern Rockies, while summerlike warmth spreads out ahead of it to the East. In between, the seasons will wage war, spelling dangerous storms and possible flooding on the Plains, Tuesday into Wednesday.
Brewing the meteorological maelstrom is an active jet stream slicing across the country. It dips in the west, allowing frigid air at high altitudes to spill south from Canada.
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A cold front is slicing through California along the leading edge of the dipping jet stream, drawing bone-dry air southward and a surge of winds.
Meteorologists often refer to the pattern as an “inside slider” because the jet stream, instead of moving in directly from the Pacific Ocean, will dive farther inland and bring mostly wind instead of rain.
“It places all of coastal California in that drier environment,” said Gerry Diaz, a meteorologist with the Bay Area National Weather Service in Monterey, Calif.
Despite chilly temperatures, Diaz said there is still concern that any new ignitions could spread rapidly given the gusty winds, low humidity and ongoing drought conditions. Nearly 90 percent of California remains in extreme to exceptional drought, according to the latest U.S. Drought Monitor.
Red flag warnings for high fire danger have been posted through Tuesday for much of northern and central California. However, the strongest winds are expected Monday, when high wind advisories are in effect. Weather offices are warning of possible downed trees, power outages and difficult driving conditions.
Pacific Gas and Electric plans targeted power shut-offs for approximately 25,000 customers in 22 counties “to reduce the risk of wildfire from energized power lines.” Southern California Edison was considering cutting power to about 9,000 customers in Los Angeles and Ventura counties.
The winds will be fierce through the Central Valley, where air funnels easily between the coastal ranges and the Sierra Nevada, but will also overspread the Bay Area, Central Coast and Southern California. Widespread gusts of up to 50 mph are expected, while the highest peaks in the Bay Area could see gusts exceeding 60 mph. The Los Angeles region will also see potentially damaging winds and elevated fire weather.
The weather system is expected to impact the Windy Fire, which is burning through sequoia groves in the Sequoia National Forest. Although the 97,000-acre blaze is 88 percent contained, there could be a significant increase in fire behavior Monday, with wind-driven runs, according to an Inciweb report.
Cindy Palmer, another meteorologist at the Monterey office, said the event is a little unusual because winds would mostly blow from north to south. Such winds typically turn “offshore” and arrive from the east or northeast, blowing from land to sea.
Although several weather systems have passed through in the last few weeks with promise of significant fire season slowing rain, many locations have received little to no precipitation. This includes the Sacramento Valley and the Bay Area, which can be subject to frequent offshore winds in autumn. It also includes most of the Central Coast.
“Just walking around … it is brittle out there — it is just bone dry,” Palmer said.
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A disturbance embedded along the southward diving jet stream will cause areas of heavy snow to develop in the central and northern Rockies.
In Billings, Mont., which saw a record high of 86 degrees a week ago, up to several inches of snow is predicted through Tuesday, although rain may mix in at times.
The storm will deposit a swath of heavy snow across Wyoming as well. Casper is under a winter storm warning, with 6 to 15 inches expected as wind gusts up to 45 mph reduce visibility. The storm is expected to peak in intensity Tuesday and Tuesday night, bringing more widespread accumulations. Maximum snow amounts could reach two feet or so in the Bighorn Mountains.
Heavy snow is also anticipated in the high elevations of Utah and central and western Colorado, but just a few rain showers are expected in Denver. By Wednesday, the snow will be withdrawing into Saskatchewan, Canada.
As the storm system ejects into the Plains late Tuesday and encounters the warm, unstable air out ahead of it, a threat of severe thunderstorms will develop in western Kansas and Oklahoma, including Woodward, Okla., and Dodge City, Great Bend and Hutchinson, Kans.
The Weather Service has placed this region in an enhanced or level 3 out of 5 risk zone for severe thunderstorms, noting “a couple tornadoes” will be possible Tuesday evening and overnight. Large hail is likely with the storms, as well as flooding where storms repeatedly pass over the same areas. Nearly five inches fell from Sunday night’s storms as they passed through Kansas overnight.
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The storm system predicted to pass from the Rockies into the Plains on Tuesday marks the second in just three days, trailing a powerful disturbance that entered the Southern Plains Sunday night.
This initial system generated a dangerous line of thunderstorms that barreled across Oklahoma and northeast Texas. More than a dozen tornado reports were received across Oklahoma and the Southern Plains. The twisters mowed down trees and left behind pockets of structural damage but no casualties have been reported.
Baseball-sized hail pounded the southern suburbs of Oklahoma City, shattering windows, damaging vehicles and stripping trees of their leaves. It marked the second damaging hailstorm around Norman, Okla. in the last six months.
This same storm system caused heavy snow in the high elevations of Utah over the weekend, where more than 80 runners were rescued amid “near whiteout” conditions in an ultramarathon.
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The Washington Post’s Jason Samenow contributed to this article.