An atmospheric river (300-400 IVT) brought widespread heavy rain to Southern California on April 6th. A few showers lingered into April 7th, but it was low impact.
Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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.
The episode as NWS SGX wrote it up.
An atmospheric river (300-400 IVT) brought widespread heavy rain to Southern California on April 6th. A few showers lingered into April 7th, but it was low impact. A warm front moved through the region on April 8th and brought waves of showers from south to north, with persistent heavy snow in the San Bernardino Mountains. Following the warm front, an upper low moved into the California Bight and stalled on April 9th, bringing 3 to 5 inches of rain to Orange County and San Diego County through the 10th. Numerous flash floods and floods occurred, especially in coastal cities. The San Diego River at Fashion Valley reached 12.5 feet (minor flood stage). Many locations recorded their highest daily rainfall record: San Diego (1.98), Chula Vista (1.56), and Vista (3.18). Oceanside Harbor recorded their wettest 24-hours on record with 3.06.
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 Apr 6, 4:26 AM PST, 1 hour 19 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
526 AM PDT Mon Apr 6 2020
.SYNOPSIS...
A low pressure system off the central California coast will move
slowly southward through Tuesday, then slowly eastward and inland
across southern California and northern Baja for Wednesday and
Wednesday night. It will bring periods of heavy precipitation
today with periods of showers following for tonight through
Thursday. Beyond Thursday, the low pressure system could meander
in the vicinity of southern California into the weekend
maintaining below average temperatures with smaller chances for
mainly light precipitation.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
A closed upper level low pressure system is centered off the
northern and central California coast early this morning with a
plume of subtropical moisture with precipitable water values
exceeding one inch directed into southern California. There have
been scattered showers overnight along and west of the mountains
with the more widespread precipitation from Los Angeles County
westward.
Stronger and gusty south to southwest winds ahead of the cold
front for this morning into this afternoon will gust to around 35
mph near the coast and gust to around 50 mph near mountain ridge
tops and desert mountains slopes. Winds will gradually subside
tonight into Tuesday.
Periods of showers will continue behind the front for tonight into
Thursday along with a slight chance for thunderstorms for Tuesday
afternoon and evening and again on Wednesday.
This low pressure system could linger in vicinity of southern
California for Friday into the weekend which would maintain below
average temperatures with small chances for mainly light
precipitation.
&&
.AVIATION...
060900Z...Coast/Valleys/Mountains...BKN-OVC skies will continue with
cigs ranging from 1000-4000 feet MSL with -SHRA and reduced vis 2-
5SM through 13Z. A band of rain will slowly move through the region
after 13-04Z today through evening. This band will contain cigs 1000-
2000 feet MSL with local cigs 800 feet MSL and vis 1-5SM in +RA.
Higher terrain mostly obscured. A slight chance of TSRA afternoon
and tonight. Strong southerly wind along coast gusting 25-30 kt as
the band of rain moves through. Winds along mountain crests and
desert slopes 25-35 kts, gusts to 45 kts. After 03-4Z sct
-SHRA and cigs 2000-3000 feet MSL.
Deserts...Increasing clouds AOA 8000 feet MSL this morning. -RA
likely with clouds down to 4000 feet MSL and local vis 3-5SM in +RA
between 15-23Z high desert, 20-03Z low desert. SFC winds in high
desert gusting 25-35 kts, decreasing after 23Z.
&&
.MARINE...
Strong southerly winds ahead of a cold front today will feature
gusts to 25 kts. There is also a small chance of thunderstorms and
waterspouts this afternoon through Wednesday. A Small Craft Advisory
is in effect.
&&
.BEACHES...
Isolated thunderstorms with lightning possible this afternoon
through Wednesday.
&&
.HYDROLOGY...
A low pressure system off the northern and central California
coast will move slowly southward through Tuesday, then slowly
eastward and inland across southern California and northern Baja
for Wednesday and Wednesday night. It will bring periods of heavy
precipitation today with periods of showers following for tonight
through Thursday.
The more widespread precipitation will continue this morning along
south facing mountain slopes with the cold front and more
widespread showers moving slowly east and southward across the
areas during the afternoon into the evening. There is a slight
chance of thunderstorms with the front, mainly for coastal and
valley areas from late morning into the afternoon.
Periods of showers will continue into Thursday. There is another
chance for thunderstorms Tuesday afternoon and evening and another
chance for Wednesday morning into the afternoon.
Through Thursday for Orange, southwestern San Bernardino, and
western Riverside Counties, rainfall is expected to range from 1.5
to 2 inches near the coast to 4 to 6 inches on south facing
mountains slopes with locally greater amounts to around 8 inches.
In high desert areas, 1 to 2 inches of rainfall is expected with
0.75 to 1.5 inches in the Coachella Valley.
For San Diego County, rainfall is expected to range from around 2
inches near the coast to 3 to 5 inches in the mountains with
around one half to one inch in the deserts. Local amounts to
around 6 inches are possible on southwest facing mountain slopes.
Snow levels near the 5500 to 6000 feet today, will lower to 4500
to 5000 feet for tonight through Wednesday, gradually rising to
5000 to 5500 feet Wednesday night, and 6000 to 6500 feet Thursday.
Through Wednesday evening in the mountains of San Bernardino and
Riverside Counties, total snow accumulations could range from 6
to 10 inches between 5,000 and 6,000 feet, 10 to 20 inches between
6,000 and 7,000 feet, and from 20 to 36 inches above 7,000 feet
with local amounts up to 48 inches on the highest peaks. The San
Diego County mountains could receive 3 to 6 inches above 5000
feet, mainly Tuesday night and Wednesday.
Urban and small stream flooding will be a possible for most areas
below the snow level. The greater potential for flash flooding
would be on Tuesday into Tuesday evening and again Wednesday with
thunderstorms or bands of showers training across the same areas.
There could also be flooding of low water crossings along the San
Diego River through Mission Valley. The Whitewater River could
flood low water crossings in the Coachella Valley.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Storm Warning until 5 AM PDT Thursday for Riverside
County Mountains-San Bernardino County Mountains.
PZ...Small Craft Advisory until 6 PM PDT this evening for Coastal
Waters from San Mateo Point to the Mexican Border and out
to 30 nm-Waters from San Mateo point to the Mexican Border
Extending 30 to 60 nm out including San Clemente Island.
&&
PUBLIC/HYDROLOGY...17
AVIATION/MARINE/BEACHES...MMThe Santa Ana Mts radar (KSOX), 36 km away, was scanning. The volume nearest the first event began at 13:43 UTC.
17 flood, 8 flash flood, 7 debris flow, 3 heavy rain, 2 strong wind, 2 heavy snow. Local standard time, as filed.
Orange County Register reported a swift water rescue in Coyote Creek channel near Buena Park. Person was yelling for help and the fire department was called. 3 feet of moving water was reporting in the canal near 4600 Minorca avenue.
Lytle Creek reported 3 inches of rain in 6 hours between 0600 and 1200 PST on April 6th.
Swift water rescue occurred in Seal Beach, near Westminister Blvd in a drainage canal.
Orange County Register photo of large tree that crush a truck. Combination of winds and heavy rainfall appear to cause the tree to topple over.
Widespread urban flooding reported throughout Costa Mesa with water on roadways and some fast moving shallow water.
Flooding in lanes 3 and 4 on Hwy 55 near Yorba Linda.
Heavy rainfall rates over 0.70 per hour caused 8 inches of swift moving water to flood Lakeview Ave, just north of Miraloma Ave.
Near 1 inch of rain in 20 minutes in San Juan Capistrano.
In Silverado Canyon, 0.88 of rain was reported in 1 hour from 2 gages.
Rock slide at Highway 18 and Highway 138 near Crestline. Rocks were covering both sides of the road.
Large rocks in lane on Highway 38.
Westbound lanes of Highway 60 in Moreno Valley heavily flooded.
Reports of heavy snow throughout the San Bernardino Mountains starting the evening of April 6th and continuing through April 10th. In Arrowbear, 37 inches of snow was reported. Mountain High received 34 inches. Snow Valley received 30 inches. Snow Summit (Bear Mountain) received 28 inches. Green Valley Lake received 33 inches. Barton Flats received 29 inches.
A few inches of snow fell in the San Diego County mountains between April 6th and 10th. Palomar Mountain received 6.5 inches of snow. Mount Laguna received 4 inches of snow.
Up to 12 inches of standing water was reported on Aero Drive in Kearny Mesa.
Indian Canyon Drive temporarily closed at the Whitewater Wash due to flooding (1-5 inches of water over the road) caused from rain runoff down the mountains.
Gusty winds (estimated 40 mph) prevented the Coast Guard from towing in a 25-foot distressed boat to shore in Encinitas.
Turner Road was closed due to flooding.
Mudslide under a home spilled onto Black Mountain Road in Rancho Penasquitos, closing part of the road and causing stress to owner's house and property.
Around 6 AM, firefighters were dispatched to Harmony Grove Road, where 4 people, 3 dogs and 1 cat were trapped in the swiftly flowing Escondido Creek. Everyone was rescued and accounted for.
Media reported and had video of water above vehicle tires and streets flooded. Flood prone area but they received 1.8 inches of rain in 24 hours on saturated grounds.
NWS Employee reports flooding at W San Marcos Blvd at Discovery Street.
A car sized boulder was reported on a road in Bonsall. This area had received 3 inches of rain in the past 12 hours and still heavy rainfall occurring at the time.
Interstate 8 landslide and debris on highway caused closure.
The Buena Vista Creek left its banks and flooded an entire golf driving range and 3 lanes of highway 78 eastbound. At 2 pm, despite efforts to pump water away, Caltrans and CHP closed all 3 lanes of westbound Highway 78. A sig alert was issued around 930 am. The highway was not fully reopen until 10 pm Friday.
Riverleaf Inn in Mission Valley was surrounded by flood waters as the San Diego River reached minor flood stage. 80 persons were displaced from the hotel as it was uninhabitable.
Water rising and flooding on Sandia Creek into the Santa Margarita River. 1-2 feet of water reported flowing over Sandia Creek Drive via SDCFCD webcam.
San Luis Rey River and tributaries caused flooding across Cole Grade Road, where the road was closed from the low water crossing to Route 76.
Flash flooding and boulders reported on roads in Valley Center. Area received 4 inches of rain in about 12 hours.
In addition to the 6 am to 11 am closures on Fashion Valley road and Avenida Del Rio further west on the San Diego River when it was exceeding 9.5 feet, from 1130 am to 2 pm, San Diego river rises to 12 feet as heavy rain showers continued. Upstream closures by police expanded to Qualcomm Way, Mission Center Road, along Camino De La Reina at the Highway 163 underpass, Camino Del Este crossing, as well as Ward road (Mission San Diego station) and Grantville trolly station (barricades set up) and north to the San Diego Mission road crossing gate closure - river reached a peak of 12.5 feet at 6 pm. Between noon and 2 pm swift water rescues were observed along the river east of Mission Center road. Storm survey conducted during this period.
Flooding on I-5 northbound offramp to Garnet/Grand Streets causing the ramp to temporarily close.
San Diego Fire and lifeguards rescued 2 people that drove their Jeep into a drainage ditch on Chollas Creek. Both people were rescued. The creek was within its banks.
Southbound on-ramp for Route 125 from Paradise Valley Rd closed due to flooding.
Several boulders completely blocking southbound lane and partially blocking northbound lane. Area has seen just over an inch of rain over 6 hours.
City of Oceanside had significant damage to the wastewater treatment plant. Estimated up to 2 millions gallons spilled as the plant was inundated by the flash flooding of Buena Vista Creek.
Swift water rescue of a pregnant women and pets near or in Otay River. Rescue occurred in dark and may have been homeless camp. Heavy rainfall had ended but river was running fast and swift at bank full levels.
Encinitas Police Department is reporting 12 incidents of flooding and flash flooding in Encinitas. Several people have been evacuated from homes in the Encinitas Blvd/Quail Gardens Road area. Twenty persons evacuated from a nursing home. Debris flow also in flooded area up to window of structure at Sunshine Gardens Apartments.
A debris flow occurred on El Camino Real at Tennis Club Drive in Encinitas. The entire road was covered in mud and debris.
Flash flooding and debris on Encinitaas Blvd at Quail Gardens Road. Power lines fell into the water and were hazardous.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2020Every state in 2020This day in weather historyWarnings in California, April 2020
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 2026-09-24. Each event’s entry at NCEI: 889488, 889498, 889515, 890761, 889489, 889490, 890736, 889492, 889495, 889499, 889500, 889501, 889509, 889626, 889510, 887618, 889511, 889514, 887869, 889628, 887885, 889630, 890748, 890751, 887886, 889631, 890728, 890733, 890745, 890726, 887870, 889633, 887873, 887877, 890775, 890730, 886661, 889634, 889635.