A strong, cold upper-level low developed over the north Pacific, with a deep trough and strong, embedded jet extending all the way down to southern California. The main area of precipitation passed through the area the 17th through the 19th, providing widespread moderate to heavy precipitation over and west of the mountains. Areas west of the mountains generally received between one-half of an inch, and one inch of rain, through San Diego County came in somewhat higher, with some amounts near 2 inches along the coastal slopes. According to the Lytle Creek HADS gauge, approximately 3 inches of rain fell in the Lytle Creek drainage (mostly over a three-hour period), causing a 2 to 3 foot rise in the creek at a point where the bed was 25 feet wide. This rise in flow did not leave the creek banks. There were also several other instances of rocks and mud in roadways, but no major flooding occurrences. The San Bernardino County Mountains were the big snow winners with Arrowbear coming in at 28 inches, Big Bear with 12 inches and Wrightwood with 7 to 13 inches. The San Diego County Mountains were not far behind with Cuyamaca receiving 15+ inches, Julian with 12 inches, and Palomar Mountain with 10 inches. Snow drifts in the San Bernardino and San Diego Mountains were upwards of 2 to 3 feet in some areas. Most areas between 3000 and 7000 feet received between 4 and 10 inches, which when melted and combined with rain received up to 3 to 4 inches of liquid equivalent. One location, near the Lake Arrowhead COOP station reported around 5 inches of water equivalent. The snow level was particularly low with this event, bringing as much as 3 inches of snow down to around 2500 feet. Graupel was observed in Temecula, accumulating to around an inch at 1200 feet. The upper deserts received moderate amounts of rain ranging from less than one-quarter inch to over three-quarters of an inch at Phelan. Some snow fell near the desert mountain slopes as well, with Hesperia at around 1 inch. The lower deserts fared quite well, with one-tenth to one-quarter of an inch in the Coachella Valley and one-quarter to slightly over one inch in the San Diego County deserts.
Strong, gusty winds also accompanied this system. Numerous gusts over 60 mph resulted in power outages, blowing dust and traffic signs blown down.

High Wind in APPLE AND LUCERNE VALLEYS, CALIFORNIA
From 17-MAR-12 00:00:00 to 17-MAR-12 11:00:00 (PST-8)
Magnitude: 65.00 EG
Crop damage: 0.00K
Reported by: Trained Spotter

A spotter in Lucerne Valley estimated wind gusts of 75 mph with numerous power outages in the Lucerne Valley area. A nearby mesonet station reported wind gusts of 58 and 60 mph between 0800 and 0900 PST on the 17th.
At 0730 PST, the Victorville airport reported visibility of one quarter mile due to blowing dust.
Around 0950 PST, another spotter reported sustained winds of 30 mph with gusts to 50 mph and blowing dusts causing visibility of less than 200 yards.

High Wind in COACHELLA VALLEY, CALIFORNIA
From 17-MAR-12 00:00:00 to 17-MAR-12 17:00:00 (PST-8)
Magnitude: 62.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

High winds began at the Sky Valley mesonet station between 0000 and 0044 PST and ended between 0200 and 0300 PST. During this time, a peak gust of 71 mph was recorded between 0200 and 0300 PST. High winds were again recorded between 1544 and 1744 PST with sustained winds of 42 mph and a gust to 60 mph.

High Wind in SAN DIEGO COUNTY MOUNTAINS, CALIFORNIA
From 17-MAR-12 04:00:00 to 17-MAR-12 08:00:00 (PST-8)
Magnitude: 58.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

High wind began at the Harrison Park mesonet station between 0530 and 0600 PST and ended between 1045 and 1100 PST on the 17th. During that time, a peak gust of 67 mph was measured between 0940 and 0950 PST. There were also several other gusts above 60 mph measured there that day.

Flood in SAN BERNARDINO, CALIFORNIA
From 17-MAR-12 08:00:00 to 17-MAR-12 13:00:00 (PST-8)
Location: DEVORE
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy rain of approximately 2.5 inches within 3-4 hours at Lytle Creek resulted in the creek running near bank-full. Upstream, the creek was 2-3 feet deep and 25 feet wide. The rise in the creek resulted in the partial wash-out of a dirt road leading to the Green Mountain Ranch Resort.

High Wind in APPLE AND LUCERNE VALLEYS, CALIFORNIA
From 17-MAR-12 10:00:00 to 17-MAR-12 17:00:00 (PST-8)
Magnitude: 60.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

High winds began at the Burns Canyon RAWS between 0851 and 0951 PST and ended between 1651 and 1751 PST on the 17th. During that time, several gusts over 60 mph were recorded including a peak gust of 69 mph measured between 0951 and 1051 PST.

Heavy Rain in RIVERSIDE, CALIFORNIA
From 17-MAR-12 11:00:00 to 17-MAR-12 14:00:00 (PST-8)
Location: ANZA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Heavy rain caused mud and rocks to cover part of Highway 74 near Ribbonwood Drive in Mountain Center.

Heavy Rain in SAN DIEGO, CALIFORNIA
From 17-MAR-12 12:30:00 to 17-MAR-12 14:30:00 (PST-8)
Location: MT LAGUNA AFS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rain caused a rock slide across Sunrise Highway (S1) near mile marker 18.

Heavy Rain in SAN BERNARDINO, CALIFORNIA
From 17-MAR-12 14:00:00 to 17-MAR-12 22:00:00 (PST-8)
Location: LAKE ARROWHEAD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Several rock and mud slides on Highway 18 between Lake Gregory and Running Springs due to heavy rain throughout the afternoon and evening.

High Wind in APPLE AND LUCERNE VALLEYS, CALIFORNIA
From 17-MAR-12 23:30:00 to 18-MAR-12 04:00:00 (PST-8)
Magnitude: 62.00 MG
Property damage: 0.50K
Crop damage: 0.00K
Reported by: RAWS

High winds began at the Burns Canyon RAWS between 2351 PST on the 17th and 0051 PST on the 18th and ended between 0251 and 0351 on the 18th. During that time,  a peak gust of 71 mph measured between 2351 and 0051 PST. Several gusts over 60 mph were also recorded that night along with sustained winds between 44 and 49 mph.
At the other end of the Morongo Valley in Beaumont (Riverside County), a large traffic sign was blown into the fast lane on west-bound Highway 60 near the summit.

Winter Storm in SAN BERNARDINO COUNTY MOUNTAINS, CALIFORNIA
From 17-MAR-12 20:00:00 to 18-MAR-12 23:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall totals from late-night on the 17th through the 18th include: Arrowbear with 18 to 24 inches, Big Bear with 15 inches, Wrightwood with 7 to 13 inches, Onyx Summit with 11.5 inches, 9 to 10 inches at Forest Falls, Snow Summit and Bear Mountain ski resorts with 28 to 30 inches, and Mount Baldy/Mountain High ski resorts with 22 inches. Chains were required in all areas. Several periods of blizzard conditions and dense fog were reported as well.

Winter Storm in RIVERSIDE COUNTY MOUNTAINS, CALIFORNIA
From 18-MAR-12 12:00:00 to 18-MAR-12 23:59:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall totals for the 18th include: Pine Cove with 11 inches, Idyllwild with 10 inches and traces of snow sticking down to 1500 feet in Hemet and up to 3 inches at 2600 feet in Cherry Valley. The Palm Springs Aerial Tramway received 24 inches of snow, which closed the tram for most of the day on the 18th, reopening the morning of the 19th.
Highway 74 was closed at Highway 371 on the evening of the 18th between Pinyon Pines and Anza due to heavy snow and blizzard conditions. Chains were required between San Jacinto and the Coachella Valley and in several other mountain locations. Several traffic collisions occurred as well due to cars sliding around on the icy and snowy roads.

Heavy Snow in SAN DIEGO COUNTY MOUNTAINS, CALIFORNIA
From 18-MAR-12 12:00:00 to 19-MAR-12 09:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall totals from the Saturday 18th through the afternoon of the 19th include: Mt. Laguna with 14 inches, Cuyamaca State Park with 5+ inches (2-foot drifts), Julian with 12 inches, Warner Springs with 5 inches and Wynola with 4 inches. Strong winds caused many areas of blowing snow, blizzard conditions with very low visibility and large snow drifts. Many slide-outs and accidents occurred on area roadways including Highways 78 and 79.
Interstate 8 was closed in both directions from East Willows Road in Alpine to Ocotillo due to heavy snow, graupel and 100 foot visibility. The highway was closed around 0130 PST on the 19th and reopened at 0800 PST that morning.
The Boulevard West mesonet station reported sustained winds near 40 mph for several hours on the 18th between about 1600 and 1900 PST.