A moisture plume with a weak atmospheric river arrived on December 5th and brought rain to the region. On December 6th, a strong closed upper level low pressure brought an unstable air mass into Southern California with showers and thunderstorms, especially Orange and San Diego Counties. Rainfall of 1 inch per hour amounts occurred in Costa Mesa and downtown San Diego as well as adjacent cities. The main storm system on December 6th brought widespread rain to the entire region. All mountains and the coast and valleys areas received 1-3 inches and some spots receiving over 4 of rainfall over higher terrain. The most significant mud and debris flows occurred at recent Holy burn scar areas, and many reports of flash flooding across the region. Another strong cold front brought widespread rain on Christmas Day though the impacts were minimal. Snow fell as low as 4000 feet with mountains receiving 1 to 4 inches of snow including the San Diego mountains. Burns Canyon in the high deserts of San Bernardino County had a wind gust to 70 mph.

Flash Flood in ORANGE, CALIFORNIA
From 06-DEC-18 10:00:00 to 06-DEC-18 13:00:00 (PST-8)
Location: (SNA)SANTA ANA CO AR
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported flash flooding along Highway 55 at Paularino Ave. in Costa Mesa. Reported that approximately 1 ft of water was along the right side of the road.

Heavy Rain in ORANGE, CALIFORNIA
From 06-DEC-18 10:00:00 to 06-DEC-18 13:00:00 (PST-8)
Location: (SNA)SANTA ANA CO AR
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

John Wayne Airport reported 2.56 inches of rainfall in about 2 hours on December 6th. This is a 1 in 100 year return interval. Cars in nearby Costa Mesa were seen completely submerged completely or stalled in deep water up to the windows.

Flash Flood in ORANGE, CALIFORNIA
From 06-DEC-18 10:00:00 to 06-DEC-18 13:00:00 (PST-8)
Location: ANAHEIM
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported flash flooding on Orangethorpe Avenue at Raymond Street in Anaheim.

Flood in SAN DIEGO, CALIFORNIA
From 05-DEC-18 23:00:00 to 06-DEC-18 03:00:00 (PST-8)
Location: SORRENTO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Broadcast media reported flooding in Sorrento Valley caused road closure on Carmel Valley Road.

Flash Flood in ORANGE, CALIFORNIA
From 06-DEC-18 14:00:00 to 06-DEC-18 17:00:00 (PST-8)
Location: ESPERANZA
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Newspaper

Victor Valley News Group reported that Del Gado Road between Anacapa Road and Palmdale Road was closed due to flash flooding. Three vehicles were stranded but no injuries were reported.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 06-DEC-18 17:51:00 to 06-DEC-18 18:50:00 (PST-8)
Location: (SAN)SAN DIEGO INTL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

San Diego International Airport reported 0.84 of rainfall betweem 1751 and 1851 PST on December 6th.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 06-DEC-18 15:03:00 to 06-DEC-18 15:33:00 (PST-8)
Location: OCEANSIDE ARPT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Oceanside Airport reported 0.50 of rainfall in 20 minutes between 1503 and 1533 PST on December 6th. This is a 1 in 20 year return interval.

Flood in SAN DIEGO, CALIFORNIA
From 06-DEC-18 17:00:00 to 06-DEC-18 22:00:00 (PST-8)
Location: HILLCREST
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

The San Diego River at Fashion Valley went from 5 ft to 12 ft (minor flood stage) between 1700 and 2200 PST on December 6th. Avenida del Rio and Fashion Valley Road were both flooded out December 6th and 7th.

Debris Flow in RIVERSIDE, CALIFORNIA
From 06-DEC-18 12:00:00 to 06-DEC-18 17:00:00 (PST-8)
Location: DURANT
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

Mud and debris flowed right next to Rice Canyon Elementary School on December 6th due to heavy rain in the burn scar area.

Debris Flow in RIVERSIDE, CALIFORNIA
From 06-DEC-18 12:00:00 to 06-DEC-18 17:00:00 (PST-8)
Location: DURANT
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

Mud, water and debris impacted Grand Ave near Lakeshore Drive in Lake Elsinore due to heavy rain in the Holy fire burn area around 1400 PST on December 6th. Some areas of Grand Ave. reported mud 1 to 3 feet deep covering streets and yards.

Debris Flow in RIVERSIDE, CALIFORNIA
From 06-DEC-18 12:00:00 to 06-DEC-18 17:00:00 (PST-8)
Location: DURANT
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

Mud and debris in the road on Grand Ave. near Via Lakistas in Lake Elsinore due to heavy rain.

Debris Flow in RIVERSIDE, CALIFORNIA
From 06-DEC-18 12:00:00 to 06-DEC-18 17:00:00 (PST-8)
Location: ARCILLA
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

Mud and debris forced the closure of Temescal Canyon Road on December 6th due to heavy rain.

Heavy Rain in RIVERSIDE, CALIFORNIA
From 06-DEC-18 14:00:00 to 06-DEC-18 16:00:00 (PST-8)
Location: DURANT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Notable heavy rainfall rates at the Holy Fire burn scar. Coldwater Canyon received 0.35 of rainfall in 30 minutes. McVicker Canyon received 0.35 in 15 minutes. USGS 30-minute burn scar rainfall thresholds were exceeded in 60 canyons, and the 1-hour thresholds were exceeded in 5 canyons.

Flash Flood in RIVERSIDE, CALIFORNIA
From 06-DEC-18 12:00:00 to 06-DEC-18 17:00:00 (PST-8)
Location: DURANT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Pacific Coast Highway (Route 1) was closed between 3rd and 9th street in South Laguna Beach due to flash flooding.

Flash Flood in SAN DIEGO, CALIFORNIA
From 06-DEC-18 17:00:00 to 06-DEC-18 22:00:00 (PST-8)
Location: CORONADO
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Broadcast media reported that the Alpha Project Bridge Shelter in East Village San Diego closed for a week due to flooding from the heavy rain.

Funnel Cloud in SAN DIEGO, CALIFORNIA
From 06-DEC-18 15:00:00 to 06-DEC-18 17:00:00 (PST-8)
Location: ESCONDIDO
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Broadcast media reported a funnel cloud in Escondido around 1500 PST on December 6th.

Flash Flood in SAN DIEGO, CALIFORNIA
From 06-DEC-18 17:00:00 to 06-DEC-18 19:00:00 (PST-8)
Location: (SAN)SAN DIEGO INTL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Flash flooding was observed throughout downtown San Diego as a result of the heavy rain. Eight cars were seen floating on Laurel and Pacific Street in downtown requiring rescues with two cars having occupants.

Flash Flood in ORANGE, CALIFORNIA
From 06-DEC-18 16:00:00 to 06-DEC-18 19:00:00 (PST-8)
Location: SAN CLEMENTE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A foot of water was reported in downtown Oceanside with multiple cars stalled. Oceanside reported 2.5 of rainfall in 2 hours.

Flood in SAN DIEGO, CALIFORNIA
From 06-DEC-18 16:00:00 to 07-DEC-18 00:00:00 (PST-8)
Location: CARLSBAD
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: County Official

Heavy rain resulted in flooding near the Shoppes at Carlsbad. Five businesses reported flooding damage. A roof collapsed at a childcare center in the shopping center.