The storm isn’t at its worst yet, and the roads are already starting to close. The I-80 is already partially closed between Emigrant Gap and Alta for emergency work, and Caltrans has trucks stopped at three screening points across the summit corridor: eastbound at Applegate, westbound at Overland Trail Road in Truckee and at Mogul west of Reno. Maximum chains arre required at all three, with permit loads banned. On the other end of I-80, a high wind advisory on the Bay Bridge means campers and trailers are not recommended there either. Both ends of the road between the Bay Area and Reno are under restrictions right now, before the worst of the storm arrives.
The Winter Storm Warning runs through Monday afternoon. NWS point forecasts for Donner Pass called for 5 to 9 inches overnight, another 8 to 12 inches today (Sunday), and as much as 15 to 21 inches at higher elevations. Wind chill has dropped to -3, while crest gusts are forecast to reach 90 mph. Anyone not already in the mountains has no reason to be heading there now.
What Is Happening Right Now
The forecast called for snow levels to drop to 6,000 to 7,000 feet by yesterday evening. They got there by the afternoon instead, roughly 1,000 feet lower and several hours early. Accumulation built quickly on road segments that were getting rain Saturday morning, which is exactly the kind of fast transition that catches people mid-drive. The first of two Pacific systems came ashore Friday night and has been producing steady snowfall since. The second, which is colder and carries more moisture, arrived overnight.
I-80 is still technically open over the summit with chain controls, but there is a partial closure near Alta for emergency work and the distance between the current situation and a full shutdown is not large. In February, a similar setup closed 60 miles of I-80 from Colfax to the state line, and left hundreds of people sitting in their cars for hours. The forecast tonight is for heavier snow and stronger winds than those that triggered that closure.
What To Expect Tonight Through Monday
Today (Sunday). There is a pattern with these storms where people assume Sunday afternoon is the recovery window. It is not. Snow is continuing through the day, another 8 to 12 inches at pass level with 15 to 21 possible higher up, and wind chill is staying below zero. Road crews are still working through what fell overnight. How quickly they can reopen anything depends on whether the wind cooperates, and right now the forecast gives no reason to think it will. A full closure of I-80, if that hasn’t happened already, remains the most likely outcome before the day it out. When that happens, there is no detour across the Northern Sierra. NWS Sacramento is calling for 2 to 5 feet of total accumulation above 6,000 feet by Monday.
Monday. The snow tapers into the afternoon but compacted spring snow is heavier than midwinter powder, takes longer to plow, and refreezes overnight into a surface that can be harder to drive on than what the storm itself put down. The earliest realistic crossing window is Monday midday, more likely Tuesday morning.
The Other Highways
Highway 50 to South Lake Tahoe. Echo Summit at 7,382 feet carries the same closure risk as I-80 with fewer plowing resources. When both close at the same time, which they did in February, there is no alternative route across the central Sierra.
Highway 395 and the eastern Sierra. The highway itself gets 2 to 6 inches with gusts to 40 mph, which is manageable for a driver who is paying attention. The problem is everything west of it. Mammoth and June Mountain access roads face 6 to 12 inches on routes that are not plowed to interstate standards. Carson Pass and Highway 89 are higher, more exposed, and will close before 395 does. They are not worth planning around this weekend…