A shortwave trough brought light to moderate mountain snow to interior northern California March 5-6, which lead to chain controls and some travel delays for the period. Long wave troughing set up shortly after that with moderate to heavy snow being reported March 8-10.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS STO wrote it up.
A shortwave trough brought light to moderate mountain snow to interior northern California March 5-6, which lead to chain controls and some travel delays for the period. Long wave troughing set up shortly after that with moderate to heavy snow being reported March 8-10. Widespread travel impacts occurred including chain controls and travel delays.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Sacramento, CA wrote its last area forecast discussion before the first event at Mar 5, 2:51 PM PST, 7 hours 9 minutes earlier.
Area Forecast Discussion National Weather Service Sacramento CA 251 PM PST Fri Mar 5 2021 .SYNOPSIS... Rain and mountain snow returns tonight and early tomorrow with mountain travel delays. Unsettled weather and cooler conditions likely for at least the first half of next week. && .DISCUSSION... We are continuing to see quiet weather across our area this afternoon but that will be changing as we head into the overnight as an upper level trough approaches the region. Light showers have already pushed into the NW part of the state and these showers will continue to slowly push east into the evening with them reaching the Coastal Range mainly after 10pm/6z. Precip will continue to overspread the area during the overnight as the trough axis and associated cold front push through. The heaviest rain and snow will be between midnight/8z and 6am/14z. We do see some weak low level instability and this will likely bring some enhanced snow rates over the Sierra for a short period and we could see snow rates 1-2" /hr. Snow levels will start out around 5000 feet but will be falling to 3000-4000 feet by 4am/12z. Snow accumulation is looking to be 2-8" above 5000 feet with locally higher amounts over the Lassen Park area and a dusting of snow possible down to around 3500 feet. Rain totals are expected to be between 0.05-0.65" in the Valley with the lowest totals over the San Joaquin and 0.15-1.0" in the Foothills. We are seeing increased southerly flow ahead of the trough mainly from about Chico to Red Bluff and can expected a short period of increased winds along the front as it sweeps through the area. Things dry out by the afternoon saturday with broad southwest flow developing over the region. This will keep the weather quiet into Sunday with cooler highs falling back to near to just below average. The weather pattern will become more unsettled as we move into next week as long wave troughing sets up over the west. Ensembles have trended the long wave trough a bit further to the west which isn't great news for us in seeing rain or at least higher amounts of rain. Light showers are still expected on Monday though as a weak short wave trough embed in the long wave trough moves through. The best chances for showers will be in the later afternoon and evening with light showers continuing overnight as we see weak warm air advection develop. Not a ton of snow is expected on Monday but snow levels will be low in the 3000 to 4000 foot range. Highs will also be cooler running below average. -CJM && .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... Active pattern will unfold next week across northern California as a longwave trough axis sets up along 135 deg W. The associated upper level low located around 600 miles west of Seattle on Monday morning will gradually wobble south and parallel the West Coast through the middle of next week. During this time, multiple shortwave impulses will ripple through the cyclonic flow, and be aimed at California. This upper low will help reinforce a cool airmass with below normal temperatures and lower snow levels. Mountain travel impacts associated with snow are possible as snow levels are forecast to drop to 3,000 ft (possibly less). Will note that the National Blend of Models and Weather Prediction Center Guidance have both recently started to trend a bit drier for early next week. As always, will continue to keep a close eye on forecast trends and adjust accordingly. // Rowe && .AVIATION... General VFR conditions expected today. Winds will remain breezy this afternoon and evening, with southerly gusts between 20-25kt for the northern and central Sacramento Valley. The San Joaquin Valley winds will have a more northwesterly component and will remain lighter. Showers begin to spread in after 02z. MVFR conditions are expected at times with periods of IFR possible during heavier bouts of precipitation. && .STO WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 10 PM this evening to 10 AM PST Saturday for West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park. &&
8 winter storm, 3 winter weather. Local standard time, as filed.
CoCoRaHS observers at 5.3 ENE Shingletown and 2.5 E Shingletown reported 7 inches and 5 inches of new snow accumulation.
Caltrans reported 6 inches of new snow accumulation at Soda Springs, 3 inches Eagle Lakes, and 4 inches at Kingvale and Donner Summit.
Ski resorts across the Sierra Nevada reported between 1 and 5 inches of new snow by 8AM March 6. Sierra-at-Tahoe reported 5 inches of snow, Boreal, Sugar Bowl, and Soda Springs reported 4 inches, Squaw/Alpine reported 3 inches, and Bear Valley reported 1 inch of snow.
CoCoRaHS reported 1 inch of snow at the 3.4 NW Igo location.
Chester, Manzanita, Mineral, and Quincy COOP sites reported 8, 9, 6, and 8 inches storm total snow respectively.
Chester, Manzanita, Mineral, and Quincy COOP sites reported 8, 9, 6, and 8 inches storm total snow respectively.
Caltrans reported 2 and 3 feet of snow at Kingvale, Soda Springs, and Donner Summit, 14 inches of at Eagle Lakes, 10 inches at Snow Park along highway 108, 6 inches at Longbarn.
Ski resorts across the Sierra Nevada reported between 1 and 3 feet of storm total snow by 10AM March 11. Dodge Ridge reported 17 inches, Kirkwood 22 inches, Sugar Bowl 27 inches, Squaw Valley 25 inches, Alpine Meadows and Tahoe Donner 20 inches, Bear Valley reported 19 inches, Sierra-at-Tahoe and Soda Springs 15 inches, and 14 inches at Boreal.
The Bowman Lake, Calaveras Big Trees, Cherry Valley Dam, Downieville, Pacific House, and Strawberry Valley COOP sites respectively reported 16 inches, 11 inches, 10 inches, 6 inches, 8 inches, and 18 inches of storm total snow accumulation.
Observers from CoCoRaHS reported 14 inches of storm total snow in Nevada City and 8 inches in Grass Valley.
The Georgetown, Grass Valley, and Nevada City COOP sites reported 5 inches, 3 inches, and 9 inches of storm total snow accumulation.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, March 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 951368, 951369, 951370, 951374, 951377, 951378, 951379, 951380, 951381, 951375, 951376.