A disturbance rotating around an upper level low west of San Diego brought thunderstorm activity to the Bay Area on September 11. Widespread reports of lightning were received along with a few small hail reports and strong wind gusts. It has been reported that there were over 40,000 lightning strikes across the Central Coast of California during this event. Several brush fires were also ignited due to lightning strikes.

Strong Wind in SANTA CLARA VALLEY INCLUDING SAN JOSE, CALIFORNIA
From 11-SEP-17 03:32:00 to 11-SEP-17 03:37:00 (PST-8)
Magnitude: 34.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Measured wind gust of 39 mph at the Los Gatos Raws.

Lightning in SAN FRANCISCO, CALIFORNIA
From 11-SEP-17 20:30:00 to 11-SEP-17 20:32:00 (PST-8)
Location: OCEAN VIEW
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

News article from SF Gate reports that an airline worker was nearly struck by lightning at Ssan Francisco International Airport http://www.sfgate.com/news/bayarea/article/Airline-Worker-Nearly-Struck-By-Lightning-Monday-12191284.php.

Wildfire in SANTA CRUZ MOUNTAINS, CALIFORNIA
From 11-SEP-17 18:41:00 to 15-SEP-17 22:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

The Skeggs Fire was sparked by a lightning strike Monday night in the Santa Cruz Mountains. The fire peaked at 50 acres
http://www.fire.ca.gov/current_incidents/incidentdetails/Index/1826
http://www.mercurynews.com/2017/09/15/firefighters-fully-contain-skeggs-fire-near-woodside/.

Wildfire in SANTA CRUZ MOUNTAINS, CALIFORNIA
From 11-SEP-17 17:30:00 to 11-SEP-17 22:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Two fires broke out near Los Gatos due to lightning. One near Loma Prieta Ridge and the other near Twin Creeks Road
http://sanfrancisco.cbslocal.com/2017/09/11/lightning-strikes-recorded-bay-area/
http://sanfrancisco.cbslocal.com/2017/09/12/lightning-sparked-wildfire-burning-in-woodside/.

Wildfire in SANTA LUCIA MOUNTAINS AND LOS PADRES NATIONAL FOREST, CALIFORNIA
From 11-SEP-17 18:00:00 to 11-SEP-17 22:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Various lightning strikes sparked 15 fires in Monterey County that were contained on the same day http://www.mercurynews.com/2017/09/13/crews-contain-15-fires-started-by-lightning-in-monterey-county/. Timing has been estimated.

Lightning in SAN MATEO, CALIFORNIA
From 11-SEP-17 17:00:00 to 11-SEP-17 17:05:00 (PST-8)
Location: HALF MOON BAY ARPT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

News report from KRON showed lightning struck a tree in San Mateo County on Pearl Ave causing a tree to crash into and damage a home.

Lightning in SAN FRANCISCO, CALIFORNIA
From 11-SEP-17 17:36:00 to 11-SEP-17 17:41:00 (PST-8)
Location: SAN FRANCISCO
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported lightning.

Hail in SANTA CRUZ, CALIFORNIA
From 11-SEP-17 15:26:00 to 11-SEP-17 15:31:00 (PST-8)
Location: WATSONVILLE
Magnitude: 0.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Pea sized hail reported by spotter near Watsonville.

Flood in SAN FRANCISCO, CALIFORNIA
From 11-SEP-17 20:18:00 to 11-SEP-17 20:48:00 (PST-8)
Location: SAN FRANCISCO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Roadway flooding at 455 8th St.

Lightning in SAN MATEO, CALIFORNIA
From 11-SEP-17 06:49:00 to 11-SEP-17 06:54:00 (PST-8)
Location: SHARP PARK
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Lightning strike caused damage to a residence on Tablot Ave in Pacifica.

Strong Wind in SOUTHERN MONTEREY BAY AND BIG SUR COAST, CALIFORNIA
From 11-SEP-17 01:00:00 to 11-SEP-17 01:05:00 (PST-8)
Magnitude: 47.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Measured wind gust of 54 mph at Pebble Beach.

Hail in SAN MATEO, CALIFORNIA
From 11-SEP-17 17:46:00 to 11-SEP-17 17:56:00 (PST-8)
Location: DALY CITY
Magnitude: 0.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Social media post on twitter from the public reports small hail as well as lightning near San Francisco.

Lightning in SAN MATEO, CALIFORNIA
From 11-SEP-17 17:46:00 to 11-SEP-17 17:48:00 (PST-8)
Location: DALY CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Social media post on twitter from the public reports small hail as well as lightning near San Francisco.

Strong Wind in SANTA CLARA VALLEY INCLUDING SAN JOSE, CALIFORNIA
From 11-SEP-17 01:30:00 to 11-SEP-17 03:00:00 (PST-8)
Magnitude: 35.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Reports of fallen trees and down power poles between 2:30 am PDT and 400 am PDT. Estimated wind gusts 30 to 40 mph.

Strong Wind in SANTA CLARA VALLEY INCLUDING SAN JOSE, CALIFORNIA
From 11-SEP-17 02:21:00 to 11-SEP-17 02:26:00 (PST-8)
Magnitude: 36.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Wind gust measured at 41 mph at San Jose International Airport.

Strong Wind in SAN FRANCISCO PENINSULA COAST, CALIFORNIA
From 11-SEP-17 03:18:00 to 11-SEP-17 03:23:00 (PST-8)
Magnitude: 47.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Measured wind gust recorded at Spring Valley Raws of 54 mph.