Debris Flows and Flooding in California, November 21 to 23, 2018

Name: Debris Flows and Flooding in California, November 21 to 23, 2018
Start: 2018-11-21T16:37
End: 2018-11-23T22:09
Location: California

November 21 to 23, 2018 · NWS MTR · 22 events in 9 counties and zones

A couple of storm systems moved through the region just before and on the Thanksgiving Holiday. These systems brought heavy rainfall and gusty winds resulting in minor debris flows and roadway flooding.

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 22

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.

What happened

The episode as NWS MTR wrote it up.

What forecasters said that day

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 San Francisco Bay Area, CA wrote its last area forecast discussion before the first event at Nov 21, 3:57 PM PST, 40 minutes earlier.

Area forecast discussion, Nov 21, 3:57 PM PST, 40 minutes before

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The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

18 flood, 2 debris flow, 2 strong wind. Local standard time, as filed.

Debris Flow, Monterey

When: November 21, 4:37 PM PST to 5:37 PM PST
Where: Monterey County, 1.83 mi NNW of Gorda to 1.82 mi NNW of Gorda
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 35.895, -121.460

Active slide being reported just north of Willow Creek Bridge. Hwy 1 will be closed.

Flood, Marin

When: November 22, 12:02 AM PST to 12:32 AM PST
Where: Marin County, 0.62 mi W of Carte Madera to 0.63 mi W of Carte Madera
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.920, -122.511

Roadway flooding at NB 101. Standing water across all lanes.

Flood, Santa Clara

When: November 22, 3:10 AM PST to 3:40 AM PST
Where: Santa Clara County, 1.33 mi ENE of (Sjc)san Jose Intl A to 1.34 mi ENE of (Sjc)san Jose Intl A
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.380, -121.909

Roadway flooding reported at Junction Ave.

Strong Wind, North Bay Mountains

When: November 22, 5:29 PM PST to 8:29 PM PST
Where: North Bay Mountains forecast zone
Measured: 39 kt (45 mph) measured gust
Reported by: RAWS

Atlas Peak RAWS reported gusts 45-57 mph.

Strong Wind, North Bay Mountains

When: November 22, 6:36 PM PST to 7:36 PM PST
Where: North Bay Mountains forecast zone
Measured: 48 kt (55 mph) measured gust
Reported by: RAWS

Middle Peak RAWS reported gusts 45 to 55 mph.

Flood, Alameda

When: November 22, 6:48 PM PST to 7:18 PM PST
Where: Alameda County, 1.99 mi W of Piedmont to 1.98 mi W of Piedmont
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.823, -122.266

Roadway flooding reported at 3601 telegraph ave. WB 580 on central off ramp 6 inches of standing water.

Flood, Marin

When: November 22, 7:25 PM PST to 7:55 PM PST
Where: Marin County, 0.49 mi E of Ross to 0.48 mi E of Ross
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.970, -122.521

Roadway flooding reported on off ramp of us 101N and central San Rafael.

Flood, Alameda

When: November 22, 10:17 PM PST to 10:47 PM PST
Where: Alameda County, 0.96 mi ENE of Alvarado to 0.95 mi ENE of Alvarado
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.607, -122.065

Roadway flooding reported at Nb 880 to WB marina off ramp.

Flood, Alameda

When: November 22, 10:20 PM PST to 10:50 PM PST
Where: Alameda County, 6.71 mi NNW of Ramon Vlg
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.811, -121.992

Roadway flooding reported at Nb 680 on sycamore valley off ramp.

Flood, Marin

When: November 23, 12:44 AM PST to 1:14 AM PST
Where: Marin County, 0.55 mi W of Carte Madera to 0.57 mi W of Carte Madera
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.921, -122.510

Roadway flooding reported at 53 San Clemente Drive.

Flood, San Francisco

When: November 23, 6:02 AM PST to 6:32 AM PST
Where: San Francisco County, 2.81 mi ENE of San Francisco to 2.82 mi ENE of San Francisco
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.773, -122.407

Roadway flooding reported at 455 8th Street.

Flood, Alameda

When: November 23, 6:37 AM PST to 7:07 AM PST
Where: Alameda County, 2.14 mi SSE of Emeryville to 2.15 mi SSE of Emeryville
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.820, -122.270

Roadway flooding reported at 3601 Telegraph Avenue.

Flood, Santa Clara

When: November 23, 8:00 AM PST to 8:30 AM PST
Where: Santa Clara County, 1.5 mi WNW of Los Gatos to 1.5 mi ENE of Montalvo
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.239, -121.995

Roadway flooding reported at Daves Avenue and SR9.

Flood, Sonoma

When: November 23, 2:59 PM PST to 3:29 PM PST
Where: Sonoma County, 0.67 mi S of Agua Caliente to 0.66 mi S of Agua Caliente
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 38.310, -122.480

Roadway flooding reported at Sr12 and Mulford street, water flooding east side lane.

Flood, Contra Costa

When: November 23, 3:29 PM PST to 4:01 PM PST
Where: Contra Costa County, 0.49 mi SSE of Walnut Creek to 0.5 mi SSE of Walnut Creek
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.893, -122.067

Roadway flooding reported at I680 N and Olympic Blvd on ramp, 8-10 inches of water in number 2 lane.

Flood, Alameda

When: November 23, 3:53 PM PST to 4:23 PM PST
Where: Alameda County, 2.35 mi NE of Alameda Nas
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.808, -122.305

Roadway flooding reported at I880 S and 7th Street on ramp. Two vehicles currently stuck in water with a large amount of water on the on ramp.

Flood, San Mateo

When: November 23, 4:07 PM PST to 4:37 PM PST
Where: San Mateo County, 0.49 mi E of Colma to 0.5 mi E of Colma
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.680, -122.471

Roadway flooding at I 280N at Exit 47.

Flood, San Francisco

When: November 23, 4:09 PM PST to 4:39 PM PST
Where: San Francisco County, 2.52 mi NE of Ocean View to 2.51 mi NE of Ocean View
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.750, -122.403

Roadway flooding at US101 N and Cesar Chavez St west on ramp.

Flood, Santa Clara

When: November 23, 4:29 PM PST to 4:59 PM PST
Where: Santa Clara County, 1.63 mi SW of Wayne to 1.61 mi SW of Wayne
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.364, -121.901

Roadway flooding at US101 N and I880 N connector, 3 feet deep in number 3 and number 4 lanes.

Debris Flow, Alameda

When: November 23, 8:27 PM PST to 8:57 PM PST
Where: Alameda County, 1.26 mi N of Niles to 1.24 mi N of Niles
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.598, -121.947

Three mud slides blocking NB lanes of Palomares Rd and SR84.

Flood, Alameda

When: November 23, 9:19 PM PST to 9:49 PM PST
Where: Alameda County, 1.1 mi N of Fremont to 1.09 mi N of Fremont
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.546, -122.024

Roadway flooding reported at I880 S and Thornton ave off ramp.

Flood, Alameda

When: November 23, 9:39 PM PST to 10:09 PM PST
Where: Alameda County, 1.13 mi ENE of Alvarado
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 37.606, -122.061

Roadway flooding reported at 2434 Whipple Road.

What these are

Debris Flow: A fast-moving slurry of mud, rock and debris, usually on a slope soaked by heavy rain or stripped by a fire.
Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.
Strong Wind: Non-thunderstorm winds below high wind criteria that nonetheless caused damage or casualties.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in California in 2018 Every state in 2018 This day in weather history Warnings in California, November 2018

Sources

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: 788431, 788411, 788412, 788433, 788434, 788413, 788414, 788415, 788417, 788418, 788419, 788420, 788421, 788422, 788423, 788424, 788425, 788427, 788428, 788432, 788429, 788430.