An upper-level low developed off Point Conception by October 27, and slowly drifted northeast toward the central California coast. The low pulled a moist, tropical airmass, including remnants from former Tropical Storm Kiko, into the central California interior on the 29th.  A dry air flow became trapped in the area around the storm, clearing skies over the San Joaquin Valley during the late morning, allowing for extensive heating of an already unstable airmass. Then, in the late afternoon, a weather disturbance moved over the southern half of the San Joaquin Valley.
This combination of weather patterns triggered the worst severe thunderstorm outbreak over the central California interior in recent memory, with 15 Severe Thunderstorm Warnings, two Urban and Small Stream Flood Advisories, and a Flash Flood Warning issued between 4 PM and 8 PM.  Another Severe Thunderstorm Warning had been issued earlier in the day, at 1:16 PM PDT, for the Sierra foothills in Madera and Mariposa counties.  Hail up to an inch in diameter was reported, and flooding occurred in parts of the San Joaquin Valley, including sections of northwest Fresno and downtown Visalia.
Thunderstorm activity continued into the early morning hours of October 30, as a cold front moved through central California. A strong push of cold air into the region dropped the high temperature at Fresno from 80 on the 29th to 68 on the 30th. Bakersfield saw even stronger cooling, from 84 on October 29th to 63 the next day, a 21-degree cooling.
Severe thunderstorms caused several reports of downed power lines and trees, large hail, and flash flooding throughout portions of the San Joaquin Valley.

Hail in FRESNO, CALIFORNIA
From 29-OCT-07 16:22:00 to 29-OCT-07 16:25:00 (PST-8)
Location: FIREBAUGH
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported penny sized hail.

Hail in FRESNO, CALIFORNIA
From 29-OCT-07 17:08:00 to 29-OCT-07 17:12:00 (PST-8)
Location: FIGARDEN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Quarter sized hail in the northwest sector of Fresno.

Flash Flood in FRESNO, CALIFORNIA
From 29-OCT-07 16:44:00 to 29-OCT-07 19:00:00 (PST-8)
Location: KERMAN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Strong thunderstorms caused streets to flood and be closed in the Kerman area.

Thunderstorm Wind in TULARE, CALIFORNIA
From 29-OCT-07 19:00:00 to 29-OCT-07 19:08:00 (PST-8)
Location: LODGEPOLE
Magnitude: 50.00 EG
Property damage: 12.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

The Park Service reported a few trees downed.

Hail in KINGS, CALIFORNIA
From 29-OCT-07 16:41:00 to 29-OCT-07 16:45:00 (PST-8)
Location: CIMARRON
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported penny sized hail at Highway 41 near Mount Whitney Avenue.

Thunderstorm Wind in FRESNO, CALIFORNIA
From 29-OCT-07 16:55:00 to 29-OCT-07 16:59:00 (PST-8)
Location: HAMMOND
Magnitude: 50.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported trees down on the west side of Fresno.

Flash Flood in KERN, CALIFORNIA
From 29-OCT-07 18:00:00 to 29-OCT-07 21:00:00 (PST-8)
Location: CABLE
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Debris was reported on the roadway causing the road to be closed.

Flood in MARIPOSA, CALIFORNIA
From 29-OCT-07 19:30:00 to 29-OCT-07 21:30:00 (PST-8)
Location: YOSEMITE VLG
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

The Park Service reported minor flooding of road surfaces at low water crossings.

Hail in KINGS, CALIFORNIA
From 29-OCT-07 16:49:00 to 29-OCT-07 16:53:00 (PST-8)
Location: CIMARRON
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported penny sized hail at Grangeville Road and Highway 41.

Thunderstorm Wind in MERCED, CALIFORNIA
From 29-OCT-07 17:25:00 to 29-OCT-07 17:28:00 (PST-8)
Location: CREGAN
Magnitude: 55.00 EG
Property damage: 60.00K
Crop damage: 0.00K
Reported by: Newspaper

The local newspaper reported at least 8 downed trees, observed by Public Works Crews. Some powerlines were also downed.

Thunderstorm Wind in TULARE, CALIFORNIA
From 29-OCT-07 18:06:00 to 29-OCT-07 18:12:00 (PST-8)
Location: PORTERVILLE
Magnitude: 50.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Local police in Tulare reported trees and powerlines downed.

Hail in KERN, CALIFORNIA
From 29-OCT-07 15:48:00 to 29-OCT-07 15:50:00 (PST-8)
Location: KERN CITY
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

TV meteorologist reported penny sized hail.

Hail in FRESNO, CALIFORNIA
From 29-OCT-07 17:03:00 to 29-OCT-07 17:06:00 (PST-8)
Location: SELMA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

A NWS employee observed quarter sized hail at Mount Whitney and Peach Roads.

Thunderstorm Wind in TULARE, CALIFORNIA
From 29-OCT-07 18:49:00 to 29-OCT-07 18:54:00 (PST-8)
Location: LEMONCOVE
Magnitude: 50.00 EG
Property damage: 22.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trees and powerlines were downed causing power outages.

Hail in FRESNO, CALIFORNIA
From 29-OCT-07 16:29:00 to 29-OCT-07 16:31:00 (PST-8)
Location: FIREBAUGH
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

A newspaper journalist reported hail at least penny sized.

Hail in FRESNO, CALIFORNIA
From 29-OCT-07 17:32:00 to 29-OCT-07 17:35:00 (PST-8)
Location: HAMMOND
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

A NWS employee observed nickel sized hail in Downtown Fresno at the intersection of Manning and Mendocino Roads.

Flash Flood in MADERA, CALIFORNIA
From 29-OCT-07 17:32:00 to 29-OCT-07 19:30:00 (PST-8)
Location: GREGG
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A vehicle was stuck in flash floodwaters at Freeway 99 and Shaw Avenue. There was also a tree downed in the slow lane.

Thunderstorm Wind in MARIPOSA, CALIFORNIA
From 29-OCT-07 18:45:00 to 29-OCT-07 18:48:00 (PST-8)
Location: SOUTH FORK
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A Mesonet station reported a wind gust of 61 knots in association with a severe thunderstorm near Yosemite National Park.

Hail in FRESNO, CALIFORNIA
From 29-OCT-07 16:44:00 to 29-OCT-07 16:45:00 (PST-8)
Location: KERMAN
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

A storm chaser reported penny sized hail.

Thunderstorm Wind in FRESNO, CALIFORNIA
From 29-OCT-07 17:20:00 to 29-OCT-07 17:25:00 (PST-8)
Location: HAMMOND
Magnitude: 50.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Downed powerlines caused power outages to 16,000 customers, according to local Broadcast media in Fresno.

Flood in TULARE, CALIFORNIA
From 29-OCT-07 18:15:00 to 29-OCT-07 22:00:00 (PST-8)
Location: CINOWTHS CORNER
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Newspaper

Newspaper reports several roadways flooded in the City of Visalia, mainly in the downtown and southside areas. The time was estimated using radar data and newspaper accounts.

Hail in KERN, CALIFORNIA
From 29-OCT-07 15:45:00 to 29-OCT-07 15:47:00 (PST-8)
Location: FORD CITY
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported penny sized hail.

Hail in FRESNO, CALIFORNIA
From 29-OCT-07 16:55:00 to 29-OCT-07 16:59:00 (PST-8)
Location: HAMMOND
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Penny sized hail occurred on the west side of Fresno.

Thunderstorm Wind in FRESNO, CALIFORNIA
From 29-OCT-07 18:06:00 to 29-OCT-07 18:10:00 (PST-8)
Location: HAMMOND
Magnitude: 50.00 EG
Property damage: 8.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Local police reported a tree down at Gettysburg Avenue and Van Ness Boulevard.

Thunderstorm Wind in TULARE, CALIFORNIA
From 29-OCT-07 18:15:00 to 29-OCT-07 18:20:00 (PST-8)
Location: CINOWTHS CORNER
Magnitude: 55.00 EG
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Newspaper

Newspaper accounts of trees downed on two houses causing property damages. One house had roof and structural damage.

Thunderstorm Wind in TULARE, CALIFORNIA
From 29-OCT-07 18:25:00 to 29-OCT-07 18:30:00 (PST-8)
Location: TULARE
Magnitude: 50.00 EG
Property damage: 60.00K
Crop damage: 0.00K
Reported by: Newspaper

There were several reports of trees downed in the city of Tulare. There were also reports of trees and power lines downed in the town of Lindsay.  A tree fell on a family's automobile between Visalia and Tulare.

Flood in FRESNO, CALIFORNIA
From 29-OCT-07 17:20:00 to 29-OCT-07 21:00:00 (PST-8)
Location: FIGARDEN
Flood cause: Heavy Rain
Property damage: 500.00K
Crop damage: 0.00K
Reported by: Newspaper

Newspapers and broadcast meteorologists reported a number of roadways  flooded in Northwest Fresno.  Numerous vehicles were stranded and water rescues occurred.  Heavy rain caused a roof to collapse at an industrial plant on the northwest side of the city.  Damages were estimated at 250,000 to the roof structure alone.

Thunderstorm Wind in TULARE, CALIFORNIA
From 29-OCT-07 18:08:00 to 29-OCT-07 18:12:00 (PST-8)
Location: CINOWTHS CORNER
Magnitude: 62.00 EG
Property damage: 110.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Powerlines and trees were downed on roadways. Boats were damaged at a Lake Kaweah boat dock. It was estimated that 200 boats were affected by severe thunderstorm wind gusts as the lake boat dock was cut loose.