An upper-level ridge built into California beginning May 27th, bringing another warming trend to interior central California. Fresno warmed to 99 degrees on the 27th, and reached 102 the next day. A weak low off Baja California spun mid-level moisture into California from the south, and the combination of heat and moisture triggered strong thunderstorms over the Southern Sierra Nevada and the Tehachapi Mountains each afternoon and evening, beginning on May 27th and continuing through the end of the month. Hail up to 1.5 inch in diameter fell near the town of Orange Cove on the evening of the 28th, and as thunderstorms over the Sierra Nevada, and over San Luis Obispo County, collapsed, outflow winds pushed across the San Joaquin Valley, triggering thunderstorms over the eastern and central Valley. Two of the storms merged into a strong system that produced gusty winds that toppled numerous trees on the Valley floor, as well as 1-inch hail near Visalia. Strong winds also triggered a gust-front tornado (gustnado) that damaged a mobile home park in Orosi.
Convection was weaker on May 29th, as thunderstorms developed earlier and several of the storms were pushed north of the region by a more southeasterly flow aloft. However, this southeast flow also carried thunderstorms from northeastern Los Angeles and northwestern San Bernardino Counties into southeastern Kern County near Rosamond, Edwards AFB, and Boron. One thunderstorm collapsed as it passed west of Edwards AFB in the early afternoon, generating outflow winds that were measured at a peak of 62 knots (71 mph).

Thunderstorm Wind in TULARE, CALIFORNIA
From 28-MAY-09 19:30:00 to 28-MAY-09 19:35:00 (PST-8)
Location: VISALIA
Magnitude: 50.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: NWS Employee

NWS Employee reported trees down and near zero visibility in blowing dust along SR 198 just east of Visalia.

Hail in MADERA, CALIFORNIA
From 28-MAY-09 16:30:00 to 28-MAY-09 16:40:00 (PST-8)
Location: ONEALS
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A spotter at Yosemite Lakes reported penny size hail.

Thunderstorm Wind in FRESNO, CALIFORNIA
From 28-MAY-09 20:22:00 to 28-MAY-09 20:32:00 (PST-8)
Location: REEDLEY
Magnitude: 50.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: County Official

Officials reported a large tree downed in Reedley due to severe thunderstorm winds.

Hail in MARIPOSA, CALIFORNIA
From 28-MAY-09 16:30:00 to 28-MAY-09 16:30:00 (PST-8)
Location: YOSEMITE VLG
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A spotter reported penny sized hail in Yosemite National Park.

Thunderstorm Wind in FRESNO, CALIFORNIA
From 28-MAY-09 20:44:00 to 28-MAY-09 20:50:00 (PST-8)
Location: HAMMOND
Magnitude: 50.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A large tree was downed due to severe thunderstorm winds at the corner of Lincoln and Orange Streets in Fresno.

Thunderstorm Wind in FRESNO, CALIFORNIA
From 28-MAY-09 20:13:00 to 28-MAY-09 20:18:00 (PST-8)
Location: ORANGE COVE
Magnitude: 50.00 EG
Property damage: 60.00K
Crop damage: 0.00K
Reported by: County Official

County officials reported a large tree downed onto a house from severe thunderstorm winds.

Thunderstorm Wind in TULARE, CALIFORNIA
From 28-MAY-09 19:00:00 to 28-MAY-09 19:10:00 (PST-8)
Location: PORTERVILLE
Magnitude: 55.00 EG
Property damage: 12.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement in Porterville reported a roof blown off a barn due to outflow winds from a severe thunderstorm.

Hail in MADERA, CALIFORNIA
From 27-MAY-09 15:45:00 to 27-MAY-09 15:45:00 (PST-8)
Location: COARSEGOLD
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Local broadcast media reported Nickel size hail near Coarsegold.

Flash Flood in MADERA, CALIFORNIA
From 27-MAY-09 15:30:00 to 27-MAY-09 15:50:00 (PST-8)
Location: COARSEGOLD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained SKYWARN spotter reported 1 inch of rain in only 45 minutes in Coarsegold. Several mudslides reported on SR 41 near Coarsegold.

Thunderstorm Wind in TULARE, CALIFORNIA
From 28-MAY-09 19:37:00 to 28-MAY-09 19:42:00 (PST-8)
Location: OROSI
Magnitude: 50.00 EG
Property damage: 1.50M
Crop damage: 0.00K
Reported by: NWS Storm Survey

NWS officials toured damage around the town of Orosi in Tulare County. Extensive wind damage from thunderstorm outflow in the town was evident. Several homes exhibited minor roof damage. Fences and trees were damaged or downed. Property damages were estimated. NWS concluded that a gust front tornado, commonly called a gustnado, occurred in this location, based on damage pattern as well as patterns indicated in tall dry grass and tree trunks and tops, and eyewitness accounts. Gust front tornadoes can occur in the outflow of a severe thunderstorm and are not considered to be true tornadoes. Winds were estimated at 60 mph.

Hail in MADERA, CALIFORNIA
From 27-MAY-09 15:40:00 to 27-MAY-09 15:40:00 (PST-8)
Location: COARSEGOLD
Magnitude: 1.50 
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained SKYWARN weather spotter reported numerous windshields broken in the Coarsegold area and along SR 41 near the Chukchansi Report.

Thunderstorm Wind in TULARE, CALIFORNIA
From 28-MAY-09 20:05:00 to 28-MAY-09 20:05:00 (PST-8)
Location: GOSHEN
Magnitude: 50.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A three foot diameter tree was downed by severe thunderstorm winds.

Thunderstorm Wind in KINGS, CALIFORNIA
From 28-MAY-09 20:15:00 to 28-MAY-09 20:20:00 (PST-8)
Location: HANFORD
Magnitude: 55.00 EG
Property damage: 7.00K
Crop damage: 0.00K
Reported by: NWS Employee

NWS Employee reported 2 large trees downed in Hidden Valley Park in Hanford.

Thunderstorm Wind in KINGS, CALIFORNIA
From 28-MAY-09 20:40:00 to 28-MAY-09 20:50:00 (PST-8)
Location: ROSSI
Magnitude: 50.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: NWS Employee

NWS Employee reported several power poles knocked down by high thunderstorm winds on the west side of Lemoore.

Thunderstorm Wind in KINGS, CALIFORNIA
From 28-MAY-09 20:25:00 to 28-MAY-09 20:30:00 (PST-8)
Location: SHORT ACRES
Magnitude: 55.00 EG
Property damage: 12.00K
Crop damage: 0.00K
Reported by: Public

The public reported three tree trunks sheared. One tree fell on a canopy. The other two trees were sheared about 5 feet above the ground.

Hail in TULARE, CALIFORNIA
From 28-MAY-09 19:45:00 to 28-MAY-09 19:50:00 (PST-8)
Location: CINOWTHS CORNER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported quarter sized hail on the west side of Visalia.

Hail in TULARE, CALIFORNIA
From 28-MAY-09 19:40:00 to 28-MAY-09 19:50:00 (PST-8)
Location: LINNELL
Magnitude: 1.50 
Property damage: 125.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained NWS spotter reported ping pong ball sized hail (1.5 inches in diameter) 6 miles east of Orange Cove. The large hail caused broken windows, roof damage, dented metal and damaged windshields on cars.

Thunderstorm Wind in FRESNO, CALIFORNIA
From 28-MAY-09 20:55:00 to 28-MAY-09 21:00:00 (PST-8)
Location: RIVERDALE
Magnitude: 50.00 EG
Property damage: 2.50K
Crop damage: 0.00K
Reported by: County Official

County government reported a large tree downed in Riverdale.

Thunderstorm Wind in FRESNO, CALIFORNIA
From 28-MAY-09 20:45:00 to 28-MAY-09 20:50:00 (PST-8)
Location: SANGER
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency Management reported a large tree downed in the town of Sanger.

Thunderstorm Wind in KERN, CALIFORNIA
From 29-MAY-09 12:45:00 to 29-MAY-09 12:50:00 (PST-8)
Location: RUNNINGTON
Magnitude: 62.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

Outflow winds from a severe thunderstorm. Report relayed by NASA employees.