The heavy snow is expected to hammer Denver, Boulder and Fort Collins in Colorado, as well as places such as Cheyenne, Wyo., and western Nebraska, including Scottsbluff. Winter storm watches are in effect and will likely be converted to winter storm or blizzard warnings. Some locations could see their biggest snowstorm on record.
The weight of the snow, heavy and wet in some areas, may cause scattered power outages.
Subtle changes in the storm track could have important implications for exactly where the heaviest snow concentrates, but a substantial-to-historic snow event is expected over a large area, regardless.
The event is set to be as notable for its duration as its magnitude, lasting from Friday night through most of Sunday.
The features for the system were already coming together Thursday morning, when weather satellites revealed a broad upper-level trough, or a dip in the jet stream, moving ashore the Pacific Coast. Nestled within that dip was a pocket of high-altitude cold air and low pressure, as well as an eddy of counterclockwise spin.
That disturbance, which dropped hail in Sonoma County, Calif., and even spun up a cold-air funnel cloud west of Los Angeles on Wednesday, was drawing a wedge of warm, moist air north across the Plains late in the workweek. By Friday night, that strip of moisture will be forced up the mountains from the east, where it will encounter frigid air. The result? An upslope snow machine, with moderate to heavy snow falling for up to two days nonstop.
“Travel across the urban corridor and foothills may become nearly impossible late Saturday through much of Sunday,” warned the National Weather Service in Boulder, Co., where up to 30 inches of snow could fall. Between 18 and 24 inches is expected in Denver proper, with a bit less farther east along Interstate 70 near the airport.
Meteorologists are also tracking where one particular feature — a trowal — ends up, as it could enhance heavy snow potential even more. A trowal marks an occluded front, or where a cold front swinging around an area of low pressure catches up to and overtakes the more laggard warm front. It usually takes shape in the vicinity of a swift jet stream, the combination of jet energy and presence of moisture aloft leading to a hefty band of intense precipitation.
“At least initially, the trowal will be over our forecast area Saturday night,” wrote the Weather Service in Boulder. “This period is expected to have the most widespread moderate to heavy snowfall.”
Snowfall rates could be “very impressive,” the Weather Service wrote, approaching three inches per hour in some spots.
In the high terrain near and east of the continental divide, it’s not even out of the question that a few locations see 36 inches or more. Wind gusts of 35 mph are likely during the storm, with gusts to 45 possible in the system’s wake. That could loft freshly fallen snow and result in a ground blizzard with reduced visibilities.
In Fort Collins, if the Weather Service’s prediction of 24 to 30 inches verifies, it would rank among the top three biggest snowstorms on record.
Farther north, Cheyenne, Wyo., was bracing for what may end up being its single most prolific snowstorm ever recorded. Records have been kept there since 1935, and the greatest single-storm total in the books sits at 25.6 inches, set in November 1979. The Weather Service, calling the storm “VERY impactful” on Twitter, is forecasting 30 to 36 inches this time around.
“Make all the necessary preparations to protect life, property, livestock, and pets,” urged the Weather Service in Cheyenne. “Expect extended periods of whiteout conditions, low visibilities, and possible power outages.”
There’s a chance that some places could see 4 to 6 inches of liquid-water equivalent out of this system in the form of snow. With each inch of moisture translating to 8 to 12 inches of snow, the totals that stack up could be “absolutely historic,” the Weather Service wrote.
Scottsbluff, Neb., could flirt with record territory too; situated in the Sand Hills of western Nebraska, the city’s single greatest snowstorm dropped 28 inches back in 1894.
Heavy snow is no stranger to the Rockies during March. It’s often Denver’s snowiest month of the year. Chris Bianchi, a meteorologist who lived and forecast weather in Denver for several years, tweeted this storm would likely share similarities to the March 2016 snowstorm in the city, which unleashed blizzard conditions and dumped 13.1 inches.
Bob Henson, a meteorologist and journalist in Boulder, compared this storm to the “epic CO Front Range snowstorm of March 2003” that “dumped 60 to 80+ inches ... at quite a few mountain/foothill spots west of Boulder/Denver,” in a tweet.
While the snow will be highly disruptive this weekend, the precipitation is desperately needed in the region due to drought. According to the U.S. Drought Monitor, 99 percent of Colorado and 87 percent of Wyoming is experiencing at least moderate drought conditions and current snowpack is mostly below normal. The snow will help replenish the region’s water supply and could somewhat lower warm season fire risk by moistening vegetation.
In addition to snow, wind and potential blizzard conditions, the same storm system could instigate severe weather and flooding across the Plains and Mississippi Valley on Friday and over the weekend. That’s where springlike air on the system’s warm side could be forced upward by the approaching cold front, leading to waves of strong to severe thunderstorms with hail, wind and the chance of an isolated tornado.
Pockets of flooding are likely too as moisture pools along a stalled front draped parallel to Interstate 40 in Oklahoma, Arkansas and Tennessee. Areas to the north will be most prone to flooding.
CHECK OUT ALL MAPS AND RADAR