A cold low pressure system developed in the Gulf of Alaska and deepened as it dropped south along the West Coast, before closing off and slowing as it moved inland over southern California on the 13th. The main front with this system brought widespread light to moderate precipitation on the 13th into the morning of the 14th. A secondary system, right behind the departing low, moved through the area the evening of the 14th through the morning of the 15th, bringing another, yet lighter, round of precipitation. Most coastal and inland locations received between 0.50 and 2 inches of rain, locally more where heavier showers trained. The coastal slopes of the San Bernardino Mountains received up to 3 inches of rain. Several road closures were in effect due to flooding and stalled vehicles, including areas in southwest San Diego County like Mission Bay and Midway. The heavy rain, along with astronomical high tides of almost 8 feet, resulted in areas of coastal flooding in Orange County near Seal and Sunset Beaches, where water was up to garages and covered all lanes of the Pacific Coast Highway on the 13th and halfway across that roadway on the 14th. The observed tide was about 3 to 6 inches higher than the predicted tide. The San Diego lifeguard water rescue team was busy retrieving several stranded motorists and one man stranded on a sandbar in the middle of the Tijuana River. Flooding also closed one road access to Fashion Valley Mall when the San Diego River reached a crest of 6.59 feet. The 1.56 inches of rain that fell at Lindbergh Field broke the previous daily record of 0.47 inches for December 13th. The snow level lowered to 4000-4500 feet late on the 13th, resulting in several inches of snow above that level. Most locations between the snow level and around 6000 feet received a trace to 4 inches of snow. Above 6000 feet, amounts were up to 10 inches, locally higher. The greatest amount reported was 17 inches at Running Springs in San Bernardino County. Most Big Bear locations received around 6 to 8 inches. In San Diego County, Cuyamaca received 4 inches of snow, while Julian received 2 inches. Most of the snow fell on the night of the 13th, with additional light amounts on the 14th-15th in the San Bernardino County mountains.

Debris Flow in SAN DIEGO, CALIFORNIA
From 13-DEC-12 09:00:00 to 13-DEC-12 10:00:00 (PST-8)
Location: POWAY
Flood cause: Heavy Rain
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Broadcast Media

An 8-ton boulder, measuring approximately 5 feet by 6 feet, was dislodged by rain-soaked ground and rolled down a hillside, through the garage of a house iin the 13000 block of Vian Road in Poway. The boulder ruptured a water line and a propane line.

Coastal Flood in ORANGE COUNTY COASTAL AREAS, CALIFORNIA
From 13-DEC-12 08:00:00 to 14-DEC-12 11:00:00 (PST-8)
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Tide levels peaked around 0815 PST on the 13th around 8.4 feet. This was about 3 to 6 inches higher than the predicted astronomical high tide at La Jolla and likely due to the approaching low pressure area (not wind) at the same time of the high tide. This, along with runoff from moderate rain showers resulted in flooding along the Pacific Coast Highway near Huntington Beach. The water was all the way across the the highway at one point and was closed at Warner Avenue near Seal and Sunset Beaches. One foot of water was in some homes on the beach side of the highway. Flooding was also observed along Marcus Avenue in Newport Harbor, as well as at the intersection of Newport Boulevard and 26th Street. Flooding occurred again the next morning of the 14th in similar locations, inundating some homes along Huntington Harbor in Sunset Beach and a couple lanes of the Pacific Coast Highway with up to a foot of water. The tide was slightly lower on the 14th around 8 feet and occurred around 0900 PST.

Heavy Snow in SAN BERNARDINO COUNTY MOUNTAINS, CALIFORNIA
From 13-DEC-12 03:00:00 to 15-DEC-12 00:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A spotter in Arrowbear Lake reported 7 to 9 inches of snow. Another spotter reported total of 17 inches in Running Springs near Snow Valley Resort for the 13-14 storm total. Most of this occurred in a 12 hour period. A few branches were reported to be snapped and a couple trees completed toppled in Running Springs by the weight of the wet snow.

Flood in SAN DIEGO, CALIFORNIA
From 13-DEC-12 06:00:00 to 13-DEC-12 12:00:00 (PST-8)
Location: OCEAN BEACH
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Media reports road closures and stalled cars at the intersection of Midway and Rosecrans. At least 5 motorists were trapped in their vehicles and had to be rescued by the lifeguard water rescue team. Roadway flooding was also reported along Sports Arena and West Mission Bay Drive, as well as northbound Interstate 5 and Garnet, where one vehicle was stuck in water. Lifeguard rescue crews retrieved a man trapped in his stalled vehicle along Ingraham just south of Sea World. CHP reported two highway ramp closures due to flooding: the I-5 northbound onramp at 28th Street and the off ramp at SR-163 and Washington. Flooding also reported on northbound I-5 at the Balboa off ramp. Several mudslides including one on south Interstate 5 at Balboa Avenue and another on Regents Road near SR 52, where mud was covering all lanes at 0500 PST.

Flood in SAN BERNARDINO, CALIFORNIA
From 13-DEC-12 09:00:00 to 13-DEC-12 10:00:00 (PST-8)
Location: MUSCOY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

CHP reported flooding along northbound I-215 at the intersection with SR 259. There was 12 inches of water in the number 3 lane as well as dirt from a nearby construction site running into the lanes. Number 3 lane was closed south of the incident at 5th Street.