A trough brought Valley rain and mountain snow to northern California February 1st through the 3rd. Snow amounts generally ranged from 2 to 16 inches across the Sierra and southern Cascades and caused difficult travel conditions for motorists.
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 trough brought Valley rain and mountain snow to northern California February 1st through the 3rd. Snow amounts generally ranged from 2 to 16 inches across the Sierra and southern Cascades and caused difficult travel conditions for motorists.
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 Feb 1, 2:43 PM PST, 5 hours 17 minutes earlier.
Area Forecast Discussion National Weather Service Sacramento CA 243 PM PST Mon Feb 1 2021 .SYNOPSIS... A winter storm will move across NorCal late tonight into Wednesday with mountain travel impacts expected. Dry weather should return by Thursday and continue through the weekend with periods of increased north to east winds. && .DISCUSSION... Upper level trough is moving onshore this afternoon as seen on visible satellite imagery, bringing the next winter storm to impact interior NorCal. A few light showers have been occurring throughout the day in the mountains and northern Sacramento ahead of the main trough passage. The main moisture plume is currently situated just moving into the CWA with precipitation moving over the Coastal Range and into the western Valley. NAM 3k and HRRR show widespread precipitation slowly moving north to south through the area through the afternoon and evening hours. The heaviest precipitation is expected tonight through tomorrow with light showers lingering through Wednesday along the back side of the trough. Moderate to heavy mountain snow is expected tonight through tomorrow. Around 8 to 18 inches of snow is forecast over the Sierra through the storm. Models show snow remaining north of I-80 this evening, spreading to areas along and south of I-80 after midnight. Snow levels will start out around 5000 to 6000 feet today, falling to 4000 to 4500 feet by tomorrow behind the frontal passage. SREF plumes and NBM continue to suggest around 3 to 8 inches of snow down to Blue Canyon at around 5200 feet. Winter Storm Warning remains in effect from tonight through early Wednesday morning. HREF, NAM 3k, and HRRR indicate periods of moderate to heavy rain possible along the cold front as is moves through the area this evening through the overnight areas. HREF shows only small (10 to 15%) probability of rain rates over 0.5 inch an hour. Therefore, debris flow impacts over burn scars are not expected, though can't rule out localized flooding or minor slides due to areas of heavier precipitation. Post-frontal scattered Valley showers are expected to continue tomorrow. A slight chance of scattered thunderstorms is also possible in the Sacramento Valley. HREF and NAM indicating CAPE around 200-300 J/kg in the Valley, enough to potentially form a few stronger cells. Main impact with any thunderstorm would be small hail and brief heavy rain with maybe some lightning. HREF indicates rainfall rates should be below 0.5 inch in an hour, so burn scar impacts are also not expected at this time. There are slight discrepancies between GEFS and Euro ENS on the trough placement Wednesday. Euro ENS has the trough slightly farther south which would bring light showers into the Valley Wednesday. GEFS is a bit shallower which would leave shower chances mainly in the mountains. Either way, additional precipitation accumulations would be fairly light. Dry weather returns Thursday as ensembles show the trough pushes to the east and upper level ridging builds over the eastern Pacific. Gusty north to east winds are possible as the ridge builds, though they are not expected to be strong at this time. -HEC && .EXTENDED DISCUSSION (Friday THROUGH Monday)... Ensemble guidance has continued to indicate high pressure over the region will keep Northern California dry though the extended forecast period. High temperatures will generally be a smidge warmer than the seasonal averages for this time of year. The warmest locations will be in the Northern Sacramento Valley with highs reaching into the mid to upper 60s this weekend which is about 5 to 10 degrees above normal for early February. Low temperatures in the Valley will be a little cooler than normal for this time of year with temperatures expected to be in the mid 30s to low 40s. Upper foothill and mountain locations will have low temperatures that are slightly warmer than normal. Locally breezy north to east winds are also possible at times. && .AVIATION... VFR decreasing to MVFR with areas of IFR and LIFR possible with passing shower activity. Snow levels around 4500-6000 feet. Southerly surface winds generally under 15kts with gusts up to 25 possible. && .STO WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning from 7 PM this evening to 6 AM PST Wednesday for West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park. &&
4 winter storm. Local standard time, as filed.
CoCoRaHS reported located 2.5 E of Shingletown reported 1 inch of snow accumulation.
Chester reported 2 inches of storm total snow while Mineral and Manzanita reported 1 inch of snow accumulation each.
Local ski resorts reported between 6 and 16 inches of storm total snow. Squaw/Alpine Ski Resort reported 16 inches of snow, Sugar Bowl got 14 inches, Soda Springs received 13, and Donner Ski Ranch received 6 inches.
Caltrans reported 16 inches of snow at Donner Summit, 8 inches at Kingvale, and 2 inches of snow at Cabbage Patch along highway 4.
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, February 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: 945469, 945470, 945471, 945472.