An upper-level trough deepened down the California coast and swung through southern California on the 11th, into the early morning of the 12th. This system brought gusty winds and moderate to locally heavy precipitation to areas over and west of the mountains, as well as a few hundredths of an inch of rain to the upper and lower deserts. Precipitation for most areas west of the mountains ranged from one-tenth to one-half on an inch of rain, though Orange County received more rain overall than San Diego and Riverside Counties. Mountain locations received between one-quarter and three-quarters of an inch of rain. Above 6000 feet, a trace to 2 inches of snow was observed in the San Bernardino Mountains. A  couple thunderstorms with damaging winds also occurred near Hemet in Riverside County.
A deeper upper low developed right behind the last and closed off before diving inland over southern California on the 13th. Instability ahead of the cold front set off several waterspouts and thunderstorms during the afternoon of the 13th. Lightning strikes and wind resulted in roof damage as well as downed power lines trees. The thunderstorms, along with the main area of stratiform rain, brought heavy rainfall amounts over and west of the mountains. Coastal locations received generally between one-third and three-quarters of an inch, locally up to an inch where the heavier thunderstorms passed. Several hundred cloud to ground lightning strikes were observed on the Coastal areas. The valleys of San Diego County and the Inland Empire received between one-third of an inch to 1.5 inches in heavier thunderstorms and along the coastal mountain slopes. Some urban flooding was observed, including a stranded motorist in standing water near Ontario and another truck pulled out of a flooded riverbed near San Bernardino. Some lower mountain locations in San Diego County received up to 2 inches of rainfall. Moderately low snow levels near 4000 feet dropped heavy snow in the mountains as well, especially in the higher elevations of San Bernardino and Riverside Counties. San Diego County received 1 to 5 inches between 4000 and 5000 feet and up to 10 inches near Mt. Laguna. Riverside County was similar with 6 to 10 inches of snow above 5500 feet. San Bernardino County was the big snow winner with several locations reporting 10 to 14 inches above 6000 feet and a max of 16 inches of snow at Arrowbear Lake.

High Wind in COACHELLA VALLEY, CALIFORNIA
From 10-APR-12 21:30:00 to 11-APR-12 00:30:00 (PST-8)
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

High winds began at the Whitewater RAWS between 2150 and 2250 PST on the 10th and ended around 0050 PST on the 11th. During that time, sustained winds of 35-40 mph occurred with a peak gust of 64 mph between 2250 and 2350 PST on the 10th.
The Sky Valley mesonet station also recorded sustained winds of 42-46 mph with a peak gust of 63 mph between 2144 and 2344 PST on the 10th.

High Wind in APPLE AND LUCERNE VALLEYS, CALIFORNIA
From 13-APR-12 11:00:00 to 13-APR-12 15:30:00 (PST-8)
Magnitude: 72.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

High winds began at the Burns Canyon RAWS between 1051 and 1151 PST and ended between 1541 and1351 PST on the 13th. During that time, sustained winds were between 31 and 53 mph and gusts were consistently above 60 mph. A peak gust of 83 mph was measured between 1251 and 1351 PST with a secondary peak gust of 77 mph measured during the following hour.

Lightning in SAN DIEGO, CALIFORNIA
From 13-APR-12 14:15:00 to 13-APR-12 14:45:00 (PST-8)
Location: SAN DIEGO
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Broadcast Media

NBC San Diego reported a lightning strike to the Unified Port of San Diego building, resulting in part of the roof getting peeled back. The strike also took out power to the building, but no injuries were reported.

Flood in SAN BERNARDINO, CALIFORNIA
From 13-APR-12 14:30:00 to 13-APR-12 15:30:00 (PST-8)
Location: COLTON ARPT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A 30-foot section of Slover Boulevard was covered with 5 inches of water due to heavy rain from a passing thunderstorm.

Heavy Snow in SAN BERNARDINO COUNTY MOUNTAINS, CALIFORNIA
From 13-APR-12 15:00:00 to 14-APR-12 12:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy snowfall totals for the 13th-14th include 16 inches at Arrowbear Lake, 14 inches at Snow Summit, Onyx Summit and Forest Falls, and 10 inches at Wrightwood and Big Bear City.

Heavy Snow in RIVERSIDE COUNTY MOUNTAINS, CALIFORNIA
From 13-APR-12 15:00:00 to 14-APR-12 12:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy snowfall totals for the 13th-14th include 12 inches at Mt. San Jacinto, 10 inches  in Idyllwild and 6 inches in Pine Cove.

Thunderstorm Wind in ORANGE, CALIFORNIA
From 13-APR-12 12:45:00 to 13-APR-12 13:30:00 (PST-8)
Location: YORBA LINDA
Magnitude: 59.00 EG
Property damage: 4.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A spotter 4 miles ESE of Yorba Linda reported trees down, bark peeled off trees and post office drop boxed flipped near Weir Canyon and the 91 freeway.
High winds were reported at the Fremont Canyon RAWS between 1251 and 1351 PST on the 13th with a peak gust of 63 mph.
The area was surveyed for possible tornado damage but only evidence of straight line wind was observed.

Thunderstorm Wind in RIVERSIDE, CALIFORNIA
From 11-APR-12 12:00:00 to 11-APR-12 14:00:00 (PST-8)
Location: HEMET
Magnitude: 56.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winds from a thunderstorm in the Hemet area ripped off a 30-foot section of a mobile home carport awning and damaged part of the roof near the intersection of Gilbert and Chambers Streets. A piece of the awning landed roughly 150 yards away at Diamond Valley Middle School. A tree at the school was also damaged. Based on spotter reports and a survey of the area along with radar data, it was determined to be a possible gustnado with estimated gusts to 65 mph. Small debris was
found near McSweeny Elementary School. The extent of damage is unknown, but time was based on another report of a thunderstorm in the area.