One of two inside sliders came into the region, providing cool and windy weather across the region.
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.
One of two inside sliders came into the region, providing cool and windy weather across the region.
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 Mar 22, 8:40 PM PST, 3 hours 20 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
940 PM PDT Mon Mar 22 2021
.SYNOPSIS...
Onshore flow will increase ahead of an incoming low pressure
system, resulting in gusty west winds over the mountains into the
deserts, cooler weather, and a slight chance of light rain
overnight into Tuesday morning. Santa Ana winds and warmer
conditions will develop Wednesday as that system moves east.
Another low pressure will bring a round of cooling, gusty west
winds, and a slight chance of light precipitation Thursday night
into Friday. Warmer and drier conditions will develop for the
weekend into early next week.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Update:
Marine layer cloudiness is increasing this evening along the San
Diego County coast and into the valleys. This trend will continue
overnight ahead of another shortwave trough moving in from the
north. Just enough moisture and lift will be present to produce
drizzle or light showers with the focus along the coastal
mountain slopes of the San Diego County mountains. Hi-res models
aren't bullish on QPF so we continue with less than a tenth of an
inch west of the mountains and up to 0.20" along the SD coastal
mountain slopes. Gusty west winds will continue to increase and
impact the desert slopes and parts of the deserts where a Wind
Advisory is in effect until 6 AM Tuesday.
Previous Discussion:
West winds ahead of an incoming low pressure system have started to
increase. At 1 PM peak gusts so far are 30-35 mph through the
mountain passes. Onshore flow will continue to increase into
tonight, resulting in more widespread gusty west winds over the
mountains, through passes, and into the deserts. Peak winds gusts
will be mostly 40-55 mph, with a few isolated gusts to 65 mph.
Late tonight into Tuesday morning there is a slight chance of light
precipitation. The places with the best chance of light
precipitation are San Diego County from the coast to the mountain
slopes. Away from San Diego County, the best chances of rain are the
inland valleys and mountains. Total rainfall accumulations are
expected to be 0.10" to locally 0.20" in the mountains. Snow levels
will fall to 5500 feet by Tuesday morning. A dusting of snow is
expected at elevations higher than 5500 feet.
Tuesday evening, winds become northerly and gusty. Gusty
north/northeast winds will continue into Wednesday with the
strongest winds below the coastal slopes of the San Bernardino
County and Santa Ana mountains. A few isolated gusts up to 70 mph
are possible on the coastal slopes of the San Bernardino mountains.
Temperatures Wednesday will remain slightly below average in
portions of the valleys, mountains, and deserts. Temperatures will
be at to slightly above average in coastal areas.
Onshore flow makes its return for the end of the work week. Another
approaching low pressure system will bring gusty west winds to the
mountains and deserts, cooler conditions, and another chance of
light precipitation west of the mountains Thursday evening into
early Friday morning. The latest ensemble guidance is showing more
members with light precipitation. The ECMWF ensemble has a wetter
solution than the GFS Ensemble. Temperatures will remain below
average for Friday, but warming is expected over the weekend into
early next week. By Sunday, the inland valleys could see highs in
the low 80s and the low deserts could see highs in the upper 80s.
&&
.AVIATION...
230430Z...Coast/Valleys...Areas of low clouds will continue to
develop this evening and cover most areas by 08Z Tue, though with
less coverage in Orange County, including KSNA/KFUL. Bases will
mostly be 2000-2500 ft MSL with tops to 5500 ft MSL with higher
terrain obscured. There is a slight chance of -SHRA 09Z-19Z Tue,
mainly in San Diego and Riverside County. Gradual clearing will
occur Tue, with mostly SCT-BKN clouds with bases 2500-3500 ft MSL
after 18Z Tue. Some stratus could redevelop Tue evening near the
coast. Vis will mostly be 6+ miles below the clouds through Tue
evening.
Mountains/Deserts...Areas of low clouds and terrain obscurations
will occur on the coastal mountain slopes 08Z-18Z Tue, mainly below
5500 ft MSL. There is a slight chance of -SHRA 09Z-19Z Tue, mailny
in San Diego and Riverside County. Areas of west winds 15-25 knots
with gusts 30-40 knots will occur from the mountain crests east into
the deserts through 01Z Wed, with some winds becoming north after
18Z Tue from San Bernardino into Riverside County with gusts 25-35
knots.
&&
.MARINE...
Northwest winds 15 to 25 kt with gusts to 30 kt are expected in the
outer waters this afternoon through Tuesday evening. A Small Craft
Advisory is in effect for the expected hazardous conditions,
especially near San Clemente Island. No additional hazardous marine
conditions are expected Wednesday through Friday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 6 AM PDT Tuesday for Apple and Lucerne
Valleys-Coachella Valley-Riverside County Mountains-San
Bernardino County Mountains-San Diego County Deserts-San
Diego County Mountains-San Gorgonio Pass Near Banning.
PZ...Small Craft Advisory until 9 PM PDT Tuesday for Waters from San
Mateo point to the Mexican Border Extending 30 to 60 nm out
including San Clemente Island.
&&
PUBLIC...Gregoria (Update)/CO (Previous Discussion)
AVIATION/MARINE...MaxwellThe national radar mosaic for the moment the first event began.
4 high wind. Local standard time, as filed.
Gusty winds occurred with this system. Thermal ASOS reported a peak gust of 60 MPH.
Gusty winds occurred with this system. Whitewater RAWS gusted to 64 MPH.
Gusty winds occurred along the coastal slopes of the San Bernardino mountains. Marshall Peak gusted to 72 MPH.
Gusty winds along the desert slopes in the Lucerne Valley. Castle Rock Road station reported a max gust of 64 MPH.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, March 2021
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: 950872, 950873, 950874, 950876.