An anomalously strong mid-level trough of low pressure went through Southern California and brought areas of light rain up to one quarter of an inch and some gusty winds up to 70 miles per hour in the mountains on June 28th and 29th.
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 anomalously strong mid-level trough of low pressure went through Southern California and brought areas of light rain up to one quarter of an inch and some gusty winds up to 70 miles per hour in the mountains on June 28th and 29th.
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 Jun 28, 2:07 AM PST, 1 hour 3 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
307 AM PDT Sun Jun 28 2020
.SYNOPSIS...
Windy and much cooler across Southern California today and Monday
as a low pressure trough deepens over the inter-mountain west. The
strongest winds will be over the mountains and deserts this
evening into Monday morning. Areas of light rain and drizzle will
develop from the coastal mountain slopes to the beaches this
evening through early Monday morning. Fair weather with a warming
trend from Tuesday into next weekend.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
This morning...As an extensive low pressure system deepens over
the Pacific Northwest, the marine layer is deepening and low
clouds have spread inland to the foothills. Associated strengthening
onshore flow has resulted in peak wind gusts of 55-60 mph at
Whitewater, a location known to be especially wind-prone in these
types of patterns. Most other locations are reporting wind gusts
of 30 mph or less.
As the low continues to deepen, gusty westerly winds will become
stronger and more widespread in the mtns and adjacent desert
areas. Winds will peak this evening through tonight with more
locations experiencing wind gusts of 40-50 mph and the windiest
places gusts of around 60 mph. The low will also bring much colder
air into SoCal from the north for today through Monday. Monday
will be the coldest day, with daytime high temperatures about 20
degrees below seasonal averages in many inland areas. Even at the
coast, temperatures could be as much as 5 degrees below seasonal
averages. As more low-level moisture moves in from the northwest
and the marine layer continues to deepen, light rain and drizzle
will likely develop late this evening through early Monday morning
from the coastal mtn slopes westward to the beaches. Accumulations
will be mostly small but will be enough to result in wet roads.
Confidence in these outcomes is high as numerical model guidance
remains consistent with these solutions.
Fair and warmer (more seasonal) weather gradually returns for
Tuesday through next weekend as the low weakens then gets
displaced to the northwest as high pressure builds over the
southern Great Plains and expands westward. We will return to a
more typical pattern of night and morning coastal low clouds and
fog while temperatures return to near seasonal averages by
Thursday then a few degrees above seasonal averages by Saturday.
&&
.AVIATION...
281000Z...Coast/Valleys...Widespread BKN-OVC stratus with variable
bases 1000-2200 ft MSL except local bases 500-900 ft MSL through 14Z
vcnty KNRS/KNZY/KSAN will continue early this morning. Clearing will
be slow, mostly 16Z-18Z in the valleys but with limited clearing and
areas of BKN conditions continuing through this afternoon near the
coast. Tops will be to 3000 ft MSL. Local vis 2-4 miles will occur
in the valleys through 17Z and vcnty KNRS/KNZY/KSAN through 14Z.
Stratus will be widespread tonight and extend through the valleys by
07Z Mon, and SCT -SHRA will develop after 05Z Mon. Bases will mostly
be 2000-3000 ft MSL with tops to 5000 ft MSL by Mon morning, with
Monday likely having limited clearing.
Mountains/Deserts...Gusty west winds will continue today with gusts
in windier locations 20-30 knots this morning, then 25-40 knots this
afternoon and evening from the mountain crests into the deserts. The
Coachella Valley will also have areas of winds, with gusts possible
exceeding 30 knots late this afternoon and evening. Winds will
weaken somewhat Monday morning.
&&
.MARINE...
No hazardous marine conditions are expected through Thursday.
&&
.BEACHES...
A long period south swell (17-19 seconds) will build late today
through Monday, bringing elevated surf to Orange County through
midweek. Surf of 3-5 feet, with local sets to 6 feet are expected in
Orange County Monday through Wednesday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 1 PM this afternoon to 8 AM PDT Monday for
Coachella Valley-Riverside County Mountains-San Bernardino
County Mountains-San Diego County Deserts-San Diego County
Mountains-San Gorgonio Pass Near Banning.
Wind Advisory from 1 PM this afternoon to 11 PM PDT this evening
for Apple and Lucerne Valleys.
PZ...NONE.
&&
PUBLIC...PG
AVIATION/MARINE/BEACHES...MaxwellThe national radar mosaic for the moment the first event began.
4 high wind. Local standard time, as filed.
Site SE586 reports 59 MPH wind gust.
Whitewater RAWS reports 70 MPH wind gust.
Mesonet station HF002 Laguna Launch reports wind gust of 70 MPH at 7 PM on June 28th.
Mesonet station SE585 measures a wind gust of 59 MPH.
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, June 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: 901184, 901180, 901185, 901186.