Additional heavy rain brought widespread flooding of small streams and rivers, with some flooding of main stem rivers. Wet conditions from previous storms brought saturated ground and elevated reservoirs, with flood control releases.
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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.
Additional heavy rain brought widespread flooding of small streams and rivers, with some flooding of main stem rivers. Wet conditions from previous storms brought saturated ground and elevated reservoirs, with flood control releases. Reduced releases at Oroville Dam resulted in the use of the emergency spillway for the first time in the dam's history. A portion of the emergency spillway began to show signs of failure which resulted in NWS Sacramento to issue a Flash Flood Warning for potential dam failure and the Oroville Sheriff to issue mandatory large scale evacuations. The emergency spillway was utilized because the main spillway had damage that required reduced flows through it. Several levee breaks also brought local evacuations.|There was also mountain snow many feet deep, and damaging winds, with numerous trees down on roads, vehicles, and homes. Many roads, including major highways such as Interstate 80, were shut down due to mudslides, heavy snow, flooding, washouts or avalanche suppression. Other significant impacts include numerous accidents due to slippery roads, evacuations and rescues due to flooding.
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 11, 3:27 AM PST, 5 hours 33 minutes earlier.
Area Forecast Discussion National Weather Service Sacramento CA 327 AM PST Sat Feb 11 2017 .Synopsis... Isolated light showers early this morning in the valley and western Sierra slopes. Otherwise, drier weather this weekend through early next week. Another round of wet weather arrives Wednesday into next weekend. && .Discussion ... 3 am radar shows some isolated light showers in the vicinity of Corning...Chico...over to Bucks Lake down to Lincoln and Rocklin area. The latest HRRR run indicates these showers should dissipate within the next couple of hours. Then interior NorCal will finally gets a respite from the wet weather this weekend into the first part of next week. Breezy north winds will develop this afternoon in the valley with a few gusts to 25 mph...mainly along the I-5 corridor and westward. Residents should note that even though precipitation is subsiding this weekend...many rivers and streams are running high while several dams are near capacity or overtopping. Flood concerns do not disappear when the rain ends...landslides and downed trees could also still occur in the next few days with the saturated soils. High pressure ridge over the eastern Pacific will build into the Western U.S. and keep NorCal dry through Tuesday. Localized to areas of fog will be possible during the early mornings with abundant low-level moisture under generally clear skies and light winds. Daytime highs will be in the 60s across the valley into the foothills with 40s and 50s across higher terrain. Tuesday should be the peak of this subtle warming trend with much of the valley in mid to upper 60s. JBB && .EXTENDED DISCUSSION (Wednesday THROUGH Saturday) Dry conditions will persist through Wednesday as high pressure remains over the region. The return of another wet pattern is expected beginning Wednesday night. A Pacific front moves through on Thursday bringing periods of moderate rain, gusty wind and mountain snow. Snow levels will be generally above pass levels before lowering to 5000-6000 ft Thursday night and Friday. Scattered showers possible Thursday night into Friday in the post frontal unstable airmass. There is the potential for another storm by next weekend. && .AVIATION... Areas MVFR with local IFR conditions continue until about 18Z with isold -SHRA, then clearing with VFR. Nly surface winds 15-25 kts develop thru the Central Valley by 20Z and continue until 02Z Sunday. && .STO WATCHES/WARNINGS/ADVISORIES... None. &&
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
At 08:00 on 2/11, a levee breach on McCormack-Williamson Tract occurred at Station 28+00 on the Mokelumne River. The 150 foot wide breach was located approximately mile downstream of the upstream end of McCormack-Williamson Tract.
A mass evacuation of over 180000 people located downstream of Oroville Dam was ordered for a possible flash flood, due to the projected near failure of the emergency spillway. The emergency spillway was used when the main spillway was discovered to have suffered severe erosion during releases back on and around February 7th. Releases from Lake Oroville had been increased due to rising lake levels due to inflow from heavy rains.
A presidential disaster declaration provided $274 million for emergency response costs from Feb. 7 though the end of May. The money targeted stabilizing the emergency and main spillways, as well as debris removal and work on the downed Hyatt Powerplant. A bid for long term repairs to the spillway was accepted at $275 million. Together, these total $549 million, though final costs could be much higher.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2017Every state in 2017This day in weather historyWarnings in California, February 2017
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: 682601, 682611.