A moderate strength upper level trough slid through the Great Basin, with upper level support that set up in a favorable position for mountain wave activity on the west slopes of the Southern California mountains on the 20th. An amazing 110 mph wind gust occurred in Burns Canyon with a surfacing mountain wave.
Every event with a place to put it; 5 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 moderate strength upper level trough slid through the Great Basin, with upper level support that set up in a favorable position for mountain wave activity on the west slopes of the Southern California mountains on the 20th. An amazing 110 mph wind gust occurred in Burns Canyon with a surfacing mountain wave. Major dust issues were reported in the Mojave Desert.
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 20, 1:30 PM PST, 30 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
130 PM PST Wed Dec 20 2017
.SYNOPSIS...
A cold front will move across Southern California this evening
bringing strong west winds to the mountains and deserts and a chance
of light showers along and west of the mountains. Moderate Santa Ana
winds will follow on Thursday, strongest in San Bernardino,
Riverside, and Orange Counties. It will be cold Thursday night with
areas of frost in the inland valleys and lower deserts Friday
morning. Dry with a warming trend Saturday through Monday with weak
to moderate offshore flow.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
A cold upper trough and surface cold front over central CA this
afternoon will move south across southern CA this evening. The 1 PM
satellite image showed a band of clouds from Bishop southwest toward
Pt Conception and the coastal waters. There has been rain with this
trough, but the rain totals have been light with 0.04 inches at
Santa Maria and Vandenberg Air Force Base.
Low clouds over the coastal waters will increase in coverage ahead
of the advancing cold front and spread inland this evening. BUFKIT
sounding forecasts for SAN show near saturation from the Sfc to 4500
feet between 6 pm and Midnight, and that will be our best window of
opportunity for light rain. Rain totals will be light with trace
amounts to 0.10" from the western mtn slopes to the coast, with
locally greater amounts most likely on the slopes aided by
orographics.
Winds have freshened in the mountains and deserts with gusts of 40
to 50 mph this afternoon. Big Bear Airport had a gust to 35 mph at
115 PM, with stronger gusts to 52 mph at Burns Canyon, 43 mph at
Lucerne Valley, and 36 mph at Boulevard. Blowing Dust was reported
in the High Deserts. A Wind Advisory is in effect through 10 pm
tonight in these areas.
Tonight: The west winds will shift north with the passage of the
cold front. The winds will be fairly strong as a 1034 mb high moves
into Oregon and the resultant N-S pressure gradient generates
sustained winds of 20-30 mph with gusts to 50 mph in the San
Bernardino, Riverside and Orange County mountains and passes and
into the Inland Empire. The winds will not be quite as strong in San
Diego County with this gradient pattern.
The clouds will clear from north to south tonight and a colder,
drier airmass will settle over the area. This will result in rapid
cooling and areas of frost in wind sheltered areas Thursday morning.
Thursday night will be colder with lighter winds and an even drier
airmass in place. The first Frost Advisory of the season may be
issued for the inland valleys and the Coachella Valley.
For Saturday through Tuesday the long range progs have backed off on
the strong Santa Ana wind potential that was advertised for Sunday
and Monday. The pressure pattern is now forecast to be about 10 mb
weaker. A surface high is still forecast over Idaho Sunday morning
on the 12Z GFS and ECMWF runs, but it is 1040 mb instead of 1050 mb.
This pattern will continue our relentless offshore weather pattern
Saturday through Tuesday with dry, warm weather and periods of
offshore flow, strongest on Sunday. Have raised Max temperatures a
couple degrees Sunday and Monday based on the higher heights and
downslope warming component west of the mountains that is usually
underforecast by the long range progs.
&&
.AVIATION...
202100Z...Coast and Valleys: Patchy low clouds, with bases 2300-3000
ft MSL and tops near 3500 ft MSL, will continue to increase in
coverage this afternoon, with more widespread coverage late this
afternoon as light showers move across the region. -SHRA will move
from west northwest to east southeast starting around 23Z this
afternoon and end around 09Z tonight. Clouds should clear out
overnight as offshore flow develops.
Mountains and Deserts: SCT lenticular clouds today with unrestricted
VIS. Clouds and a few showers developing late this afternoon and
evening will obscure local coastal slopes. Westerly winds of 15-30
kt with gusts to 45 kt will continue over desert mountain slopes
through this evening and tapering off overnight. Winds will quickly
switch to northeasterly early Thu morning, gusting 30-45 kt below
coastal mountain slopes and through the Cajon Pass. LLWS is likely
near the mountains through the period.
&&
.MARINE...
A cold front will create gusty northwest winds around 25 kt this
evening and tonight, which will create choppy seas hazardous for
small craft. Winds turn offshore early Thursday morning with local
gusty northeast winds Thursday, but not likely hazardous. No
additional hazardous marine weather is forecast through Sunday.
&&
.FIRE WEATHER...
West winds were strong in the mountains and the high deserts at 1 pm
with gusts of 50 mph at Whitewater above the San Gorgonio Pass, 43
mph at Volcan Mountain, and 35 mph at Hesperia. These strong west
winds will continue through evening, then shift north tonight
with the passage of the cold front.
A moderately strong surface high will build over northern Nevada
tonight and support moderate to locally strong north to northeast
winds beginning tonight and continuing through Thursday afternoon.
The most critical fire weather conditions will be Thursday when
humidities will fall into the lower teens. Winds will decrease
Thursday night with lighter winds Friday.
This prevailing offshore flow pattern will persist through early
next week with surface high pressure settling over the Great Basin
Saturday through Monday. Yesterday the models were advertising a
strong Santa Ana Sunday, but they have backed off considerably, and
the outlook now is for weak to locally moderate offshore flow. It
will warm and dry with temperatures well above average in this
pattern, with periods of gusty northeast winds at times in the
mountains and foothills.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory through 10 PM PST this evening
for Coachella Valley-Riverside County Mountains-San Diego
County Deserts-San Diego County Mountains-San Gorgonio Pass
Near Banning-Apple and Lucerne Valleys-San Bernardino
County Mountains.
Fire Weather Watch from Thursday morning through Thursday
afternoon for Orange County Coastal Areas-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-San Gorgonio Pass Near
Banning-Santa Ana Mountains-Including The Trabuco Ranger
District of the Cleveland National Forest.
PZ...Small Craft Advisory from 6 PM this evening to 6 AM PST Thursday
for Waters from San Mateo point to the Mexican Border
Extending 30 to 60 nm out including San Clemente Island.
&&
PUBLIC/FIRE WEATHER...Moede
AVIATION/MARINE...JJTThe national radar mosaic for the moment the first event began.
3 high wind, 1 dust storm, 1 strong wind. Local standard time, as filed.
Strong winds gusting to 50 mph produced a dust storm down wind of Lucerne Valley Lake (dry lake bed) that reduce visibility to zero and lead to a closure of Highway 247 north of Lucerne Valley. Blowing dust also reduced visibility in Johnson Valley.
The mesonet station in Burns Canyon reported a 110 mph wind gust with sustained winds of 66 mph. Elsewhere wind gusts were much lower, in the 35-55 mph range. No damage was reported.
Strong winds surfaced in the Palm Springs area causing power outages and blowing dust/sand. The Palm Spring Aerial Tramway briefly lost power.
The Volcan Mountain mesonet station reported wind gusts over 60 mph for about 3 hours. The Harrison Park mesonet also saw a few gusts over 60. Elsewhere winds were in the 25-50 mph range.
Strong winds surfaced below the San Gorgonio Pass with areas of blowing dust. The Whitewater mesonet station reported wind gusts over 70 mph for 3 hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2017Every state in 2017This day in weather historyWarnings in California, December 2017
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: 731513, 731512, 731515, 731516, 731514.