Flash Flooding and Debris Flows in California, January 1, 2023

Name: Flash Flooding and Debris Flows in California, January 1, 2023
Start: 2023-01-01T00:00
End: 2023-01-01T21:20
Location: California

January 1, 2023 · NWS SGX · 26 events in 9 counties and zones

A strong winter storm starting in late December 2022 carried over into January 2023, bringing heavy rain and mountain snow to southern California.

Where it happened

Every event with a place to put it; 6 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $2,000
Crop damage: None recorded
Events: 26

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS SGX wrote it up.

A strong winter storm starting in late December 2022 carried over into January 2023, bringing heavy rain and mountain snow to southern California.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS San Diego, CA wrote its last area forecast discussion before the first event at Dec 31, 9:33 PM PST, 2 hours 27 minutes earlier.

Area forecast discussion, Dec 31, 9:33 PM PST, 2 hours 27 minutes before

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

The radar

The Edwards AFB radar (KEYX), 129 km away, was scanning. The volume nearest the first event began at 08:02 UTC.

Open the radar archive at this moment

Event by event

10 flood, 5 debris flow, 3 heavy rain, 3 high wind, 2 flash flood, 2 strong wind, 1 heavy snow. Local standard time, as filed.

Heavy Snow, San Bernardino County Mountains

When: January 1, 12:00 AM PST to 6:00 PM PST
Where: San Bernardino County Mountains forecast zone
Reported by: Department of Highways
Coordinates: 34.841, -116.178 (the zone’s center; the record gives no point)

Various reports of heavy snow received from San Bernardino County Public Works, broadcast media, and trained spotters. Totals ranged from around 4 inches of snow near Arrowbear Lake to 7 inches near Big Bear Lake, and upwards of 10 inches near Running Springs.

Flood, San Diego

When: January 1, 12:00 AM PST to 1:00 AM PST
Where: San Diego County, 0.22 mi E of Oceanside to 0.3 mi NNW of Oceanside
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 33.200, -117.376

CalTrans report of flooding in the right lane on I-5 South near Oceanside.

Flood, San Diego

When: January 1, 12:00 AM PST to 1:00 AM PST
Where: San Diego County, 0.77 mi NNW of Carlsbad to 0.51 mi N of Carlsbad
Cause: Heavy Rain
Reported by: Public
Coordinates: 33.180, -117.355

Public report of flooding on SR78 West on the on-ramp to I-5 North.

Heavy Rain, San Diego

When: January 1, 12:00 AM PST to 8:00 PM PST
Where: San Diego County, 2.41 mi E of San Ysidro to 2.79 mi WNW of Rainbow
Reported by: NWS Employee
Coordinates: 32.544, -117.009

Heavy rain fell across much of San Diego County on January 1st. Per reports from NWS Employees and other trained spotters rainfall totals of 1-3 inches fell across much of the county through the evening hours on the 1st.

Heavy Rain, Orange

When: January 1, 12:00 AM PST to 8:00 AM PST
Where: Orange County, 1.5 mi NNW of Laguna Hills
Reported by: Trained Spotter
Coordinates: 33.600, -117.740

A trained spotter reported storm total rainfall of 1.4 inches through about 8 AM.

Heavy Rain, San Bernardino

When: January 1, 12:00 AM PST to 8:00 AM PST
Where: San Bernardino County, 1.34 mi WSW of Del Rosa
Reported by: Trained Spotter
Coordinates: 34.140, -117.270

A trained spotter reported 1.78 inches of heavy rain occurring at their location through about 8 AM on the 1st.

High Wind, Santa Ana Mountains and Foothills

When: January 1, 12:00 AM PST to 6:00 AM PST
Where: Santa Ana Mountains and Foothills forecast zone
Measured: 62 kt (71 mph) measured gust
Reported by: RAWS
Coordinates: 33.483, -116.847 (the zone’s center; the record gives no point)

High winds impacted the Santa Ana Mountains early on January 1st. The Fremont Canyon RAWS site recorded a peak wind gust of 71 mph.

High Wind, San Gorgonio Pass Near Banning

When: January 1, 12:00 AM PST to 12:00 PM PST
Where: San Gorgonio Pass Near Banning forecast zone
Measured: 51 kt (59 mph) measured gust
Reported by: Mesonet
Coordinates: 33.744, -115.994 (the zone’s center; the record gives no point)

High winds impacted the San Gorgonio Pass early on January 1st. The Cabazon SoCal-Edison site recorded a peak wind gust of 59 mph on the morning of January 1st.

High Wind, San Diego County Mountains

When: January 1, 12:00 AM PST to 3:00 PM PST
Where: San Diego County Mountains forecast zone
Measured: 58 kt (67 mph) measured gust
Reported by: Mesonet
Coordinates: 33.028, -116.770 (the zone’s center; the record gives no point)

High winds impacted the San Diego County Mountains during the morning and afternoon hours on January 1st. The Boulevard West SDG&E site recorded a peak wind gust of 67 mph, with gusts of 50-65 mph elsewhere.

Flash Flood, San Diego

When: January 1, 12:45 AM PST
Where: San Diego County, 2.39 mi ENE of San Luis Rey to 2.37 mi ENE of San Luis Rey
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 33.240, -117.290

Flash flooding on College Avenue near SR76 reported by CalTrans. Full highway closure with disabled vehicles due to water up to 2.5 feet deep. Rainfall rates of 0.84 inch per hour occurred in the area, per observations from KCRQ ASOS.

Flood, San Diego

When: January 1, 1:00 AM PST to 2:00 AM PST
Where: San Diego County, 0.69 mi N of Oceanside to 0.49 mi NNE of Oceanside
Cause: Heavy Rain
Reported by: Public
Coordinates: 33.210, -117.380

Public report of flooding on SR76 at I-5. Water was reported to be up to 2.5 feet deep.

Flood, San Diego

When: January 1, 2:00 AM PST to 3:00 AM PST
Where: San Diego County, 1.81 mi NE of Encanto to 1.65 mi WNW of Lemon Grove
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 32.740, -117.050

Flooding reported in all lanes on SR94 West at College Ave. A vehicle was stuck and flooded out on the right shoulder.

Flood, San Diego

When: January 1, 5:30 AM PST to 6:30 AM PST
Where: San Diego County, 0.9 mi SE of Camp Elliot to 0.75 mi SE of Camp Elliot
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 32.840, -117.110

CalTrans report of flooding on the Mount Soledad Freeway near the I-15 on-ramp.

Flood, San Diego

When: January 1, 6:00 AM PST to 8:00 AM PST
Where: San Diego County, 0.29 mi W of Nestor to 0.46 mi NNW of Nestor
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 32.581, -117.085

CalTrans report of flooding on the Palm Ave off-ramp lanes on I-5 in Imperial Beach.

Flood, San Diego

When: January 1, 6:00 AM PST to 8:00 AM PST
Where: San Diego County, 0.57 mi NE of Palm City to 0.85 mi WNW of Nestor
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 32.585, -117.092

CalTrans report of flooding on the Palm Ave off-ramp lanes on I-5 near Imperial Beach.

Debris Flow, San Diego

When: January 1, 6:30 AM PST to 7:00 AM PST
Where: San Diego County, 0.1 mi SSE of Rancho Santa Fe to 0.17 mi S of Rancho Santa Fe
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 33.019, -117.199

CalTrans report of a mudslide leading to rocks and dirt blocking eastbound lanes on Via de Santa Fe near Rancho Santa Fe.

Debris Flow, San Diego

When: January 1, 7:15 AM PST to 7:45 AM PST
Where: San Diego County, 4.62 mi ENE of Ramona to 4.48 mi WSW of Witch Creek
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 33.052, -116.795

CalTrans report of a mudslide on Old Julian Highway by MM 4.5.

Strong Wind, San Diego County Coastal Areas

When: January 1, 7:30 AM PST to 8:30 AM PST
Where: San Diego County Coastal Areas forecast zone
Measured: 35 kt (40 mph) estimated gust
Property damage: $1,000
Reported by: Newspaper
Coordinates: 33.028, -116.770 (the zone’s center; the record gives no point)

Newspaper report of multiple trees down along Carlsbad Village Drive and Highland Drive due to wind gusts estimated around 40 mph. Time estimated.

Flood, San Diego

When: January 1, 8:30 AM PST to 10:30 AM PST
Where: San Diego County, 0.72 mi ESE of Overlook to 1.72 mi SE of Overlook
Cause: Heavy Rain
Reported by: NWS Storm Survey
Coordinates: 32.767, -117.188

Per an NWS Storm Survey, levels on the San Diego River at Fashion Valley reached up to 10.2 feet. Fashion Valley Road had 1 foot of flowing water and was closed. Avenida Del Rio had 2 feet of flowing water and was closed. The entire lower parking structure at the Fashion Valley Mall was filled with 1 to 2 feet of water. Mission Center Road was closed but did not have flowing water. Riverwalk Golf Driving Range was filled with water. San Diego Mission Road had minor water flow debris at crossing, but was open.

Strong Wind, San Diego County Coastal Areas

When: January 1, 9:30 AM PST to 10:30 AM PST
Where: San Diego County Coastal Areas forecast zone
Measured: 35 kt (40 mph) estimated gust
Property damage: $1,000
Reported by: Newspaper
Coordinates: 33.028, -116.770 (the zone’s center; the record gives no point)

Newspaper reported a palm tree fell and crushed a parked Toyota Tundra due to strong winds estimated about 40 mph. The truck was parked in the 900 block of 8th street in Coronado. Time estimated.

Flash Flood, Riverside

When: January 1, 3:15 PM PST to 5:15 PM PST
Where: Riverside County, 2.95 mi ESE of Valle Vista to 3.14 mi E of Valle Vista
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 33.740, -116.850

Rainfall rates of 0.5 to 0.8 inches per hour were observed in this area between 4 and 5 PM. Total rainfall of 1.30 inches occurred just west of Cranston Station near Valle Vista at Blackburn Road and State Highway 74. Flooding occurred at this location around 2:30 PM as well.

Debris Flow, San Diego

When: January 1, 5:30 PM PST to 6:00 PM PST
Where: San Diego County, 2.57 mi SE of Santa Ysabel to 2.66 mi SE of Santa Ysabel
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 33.095, -116.647

CalTrans report of a 4' X 5' boulder on Highway 78 by Wynola Road.

Flood, San Diego

When: January 1, 6:00 PM PST to 8:00 PM PST
Where: San Diego County, 0.94 mi SSE of Valley Center to 1.31 mi SSW of Valley Center
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 33.207, -117.024

Report received from CalTrans. Woods Valley Road near Valley Center was flooded in both lanes due to rainwater runoff and poor drainage.

Flood, San Diego

When: January 1, 6:00 PM PST to 8:00 PM PST
Where: San Diego County, 0.69 mi S of Valley Center to 1.23 mi SSW of Valley Center
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 33.210, -117.030

CalTrans report - Woods Valley Road near Valley Center was flooded in both lanes due to rainwater runoff and poor drainage.

Debris Flow, Riverside

When: January 1, 8:40 PM PST to 9:15 PM PST
Where: Riverside County, 0.14 mi E of Cabazon to 0.22 mi E of Cabazon
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 33.920, -116.778

CalTrans report of rocks and debris in roadway on Seminole Drive at Main Street in Cabazon.

Debris Flow, Riverside

When: January 1, 8:50 PM PST to 9:20 PM PST
Where: Riverside County, 4.39 mi WSW of Lakeland Vlg to 4.59 mi WSW of Lakeland Vlg
Cause: Heavy Rain
Reported by: Department of Highways
Coordinates: 33.614, -117.424

CalTrans report of basketball-sized boulders on Ortega Highway near the Ortega Oaks Candy Store.

What these are

Heavy Snow: Snowfall reaching the local warning threshold without the other hazards of a winter storm.
Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.
Heavy Rain: Rainfall totals unusual for the place and season that did not produce a flood.
High Wind: Sustained non-thunderstorm winds of 40 mph or more for an hour, or gusts of 58 mph or more.
Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.
Debris Flow: A fast-moving slurry of mud, rock and debris, usually on a slope soaked by heavy rain or stripped by a fire.
Strong Wind: Non-thunderstorm winds below high wind criteria that nonetheless caused damage or casualties.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in California in 2023 Every state in 2023 This day in weather history Warnings in California, January 2023

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-30. Each event’s entry at NCEI: 1075208, 1075225, 1075226, 1075233, 1075236, 1075238, 1075239, 1075240, 1075241, 1075209, 1075227, 1075228, 1075229, 1075220, 1075230, 1075200, 1075201, 1075215, 1075231, 1075214, 1075224, 1075204, 1075221, 1075232, 1075211, 1075212.