A strong Santa Ana wind event was enhanced by a cut-off upper level low off the coast of Baja California on 19-20 January 2021. The placement of the upper level low allowed for moisture to surge into the deserts and mountains, leading to unique precipitation forecast challenges.
Every event with a place to put it; 9 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.
A strong Santa Ana wind event was enhanced by a cut-off upper level low off the coast of Baja California on 19-20 January 2021. The placement of the upper level low allowed for moisture to surge into the deserts and mountains, leading to unique precipitation forecast challenges. Very strong winds combined with dry relative humidity and extremely dry fuels on the coastal mountain slopes and valleys led to several smaller scale wildfires and wind damage.
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 Jan 14, 9:31 AM PST, 2 hours 59 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
931 AM PST Thu Jan 14 2021
.SYNOPSIS...
Dry conditions with above average temperatures will prevail through
Saturday. Periods of gusty Santa Ana winds are expected into early
next week. There is a potential for moderate to strong Santa Ana
winds Monday through Wednesday. Cooling is expected for Sunday
through Wednesday, temperatures are expected to return to seasonal
averages by the middle of the week.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
At 9 AM this morning there were local areas of breezy northeast
winds with peak gusts mainly around 35 mph. Most of the winds are
confined to below the San Gorgonio and Cajon Passes and along
portions of I-8 in San Diego County. High pressure continues to
stregthens over Southern California today resulting in a warm end
of the week. Temperatures today will be 15 to 20 degrees above
average west of the mountains and 10 to 15 degrees above average
in the deserts. Friday will be the warmest day of the week, with
more widespread temperatures closer to 20 degrees above average.
Saturday's temperatures will be similar to today's, with further
cooling expected Sunday into early next week. Temperatures should
be near to slightly below average by Tuesday or Wednesday.
Winds will continue to increase today, becoming more widespread and
peaking Friday morning. The strongest winds are expected along the
coastal slopes of the mountains of Riverside and San Bernardino
Counties, in portions of the Inland Empire below the Cajon and San
Gorgonio Passes, and along and near the coastal slopes of the Santa
Ana Mountains. Gusty northeast winds of 45-50 mph, with isolated
gusts to 55 mph are expected in typical wind prone locations. Winds
will weaken and become more isolated into Friday afternoon. More
gusty north to northeast winds will develop Saturday into Sunday.
Those winds are expected to be less widespread and weaker, with peak
gusts mostly 40 mph or less.
Monday through Wednesday, it looks like there will be another round
of Santa Ana winds. There is still uncertainty surrounding the
strength of the winds, but there is the potential they will be
moderate to strong. Right now it looks like winds would peak on
Tuesday. There is still decent spread in the ensemble solutions. The
Canadian and ECMWF ensembles both tend to favor a stronger wind
event.
Cluster analysis is showing some solutions that hint at the
potential of precipitation over Southern California into eastern
Arizona for early next week. Current forecast is close to NBM with
probability of precipitation 15% or less.
&&
.AVIATION...
141555Z...A few high clouds with unrestricted vis through tonight.
North to northeast surface winds 15-25 kt with gusts 35-45 kt will
develop this morning and continue tonight in areas from the mountain
crests southwest through the foothills and some valleys. This will
produce weak to moderate up/downdrafts over and west of the mtns,
including VCNTY KONT, KSBD, KRAL, KRIV, KBNG and KCNO.
&&
.MARINE...
No hazardous marine conditions are expected through Tuesday.
&&
.BEACHES...
Long-period swells from the WNW will continue through next Tuesday.
High surf is probable Sunday through Tuesday, primarily at beaches
in southern San Diego County. See the Beach Hazard Statement for
details.
&&
.FIRE WEATHER...
Periods of gusty Santa Ana winds and dry conditions will continue
through early next week. Gusty north to northeast winds continue to
strengthen and become widespread today. Winds will peak in strength
Friday morning before diminishing Friday afternoon. The stronger and
more widespread winds are expected along the coastal slopes of the
mountains of Riverside and San Bernardino Counties, in portions of
the Inland Empire below the Cajon and San Gorgonio Passes, and along
and near the coastal slopes of the Santa Ana Mountains. Winds will
gust to 45-50 mph with isolated gusts to 55 mph in the typically
windier locations. Another round of gusty north to northeast winds
is expected for Saturday into Saturday night, but with the stronger
gusts mostly 40 mph or less.
Daytime humidity will fall to 10 to 15 percent today for inland
areas and 8 to 12 percent Friday with poor overnight recovery.
Daytime humidity will be 10 to 15 percent for inland areas Saturday
through Monday.
Well above average high temperatures will continue through Saturday.
Cooling to seasonal average is expected for Sunday through the
middle of next week. There is the potential for a period of moderate
to strong northeast winds developing Monday, peaking Tuesday, and
possibly continuing into Wednesday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning from 4 PM this afternoon to 4 PM PST Friday for
Orange County Inland Areas-Riverside County Mountains-
Including The San Jacinto Ranger District Of The San
Bernardino National Forest-San Bernardino County Mountains-
Including The Mountain Top And Front Country Ranger
Districts Of The San Bernardino National Forest-San
Bernardino and Riverside County Valleys -The Inland Empire-
Santa Ana Mountains-Including The Trabuco Ranger District
of the Cleveland National Forest.
Beach Hazards Statement through Tuesday afternoon for Orange
County Coastal Areas-San Diego County Coastal Areas.
PZ...NONE.
&&
PUBLIC/FIRE WEATHER...CO
AVIATION/MARINE...PGThe national radar mosaic for the moment the first event began.
6 high wind, 2 wildfire, 1 heavy snow. Local standard time, as filed.
Comet fire occurred near Palomar College in San Marcos, which prompted evacuation warnings around the area. The fire burned just over 40 acres with no serious injuries.
Big Bear resort reported 3 to 5 inches new snow. Big Bear Yard 3 inches from 2 to 6 pm. Several spin outs and chain control was set up on highway 38 and 18.
Riverside County 72 fire. The vegeation fire burned 43 acres near Ave 72 and Pierce St, south of Oasis. Began during onset of Santa Ana winds.
Gusty Santa Ana winds occurred across the region with highest wind gust reported at Marshall Peak mesonet station at 86 MPH.
Gusty Santa Ana winds occurred across the region, especially below the Cajon Pass where SCE Lytle Creek Road reported a gust of 70 MPH and CSU San Bernardino station reported a wind gust of 64 MPH.
Gusty Santa Ana winds occurred across the region with highest wind gust reported at Fremont Canyon RAWS with a gust of 74 MPH.
Gusty Santa Ana winds occurred across the region with highest wind gust reported at SCE Apple Canyon site of 66 MPH.
Several reports of large trees down across roadways around Ramona, one instance where a tree fell on powerlines, and the powerlines were blocking the road. Wind gusts of 30 to 45 mph were reported at nearby sites of a similar elevation, with wind gusts of 61 to 67 mph observed on a ridge just east of these locations.
Very gusty winds occurred across the region during the event, where Sill Hill gusted to 82 mph and Black Mountain to 89 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, January 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: 938317, 938459, 936072, 937997, 937998, 938000, 938001, 938003, 938004.