An upper level trough from the northwest moved into Southern California on December 24th and 25th, bringing heavy rain, snow above 4000 ft and high winds. 50 of rain.
Every event with a place to put it; 3 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 upper level trough from the northwest moved into Southern California on December 24th and 25th, bringing heavy rain, snow above 4000 ft and high winds. Coastal areas received 0.25-0.50 of rain, valley areas received up to an inch of rain, and mountain areas up to 1.50 of rain. Winds gusted to 50-70 mph in the mountains and deserts.
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 24, 9:15 PM PST, 1 hour 35 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
915 PM PST Mon Dec 24 2018
.SYNOPSIS...
A cold winter storm will bring scattered showers, mountain snow and
gusty winds tonight and Christmas Day. This system will move east on
Tuesday night, followed by a upper trough over the west that will
bring colder than average weather through the rest of the week.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
The low clouds have been thickening over the valleys this evening.
Surface pressure gradients are increasing onshore, helping to make
that happen. Southwest to west winds have been picking up as well. At
8 PM PST...peak wind reports were 30 to 40 MPH over higher terrain.
The 00Z Miramar sounding had a weak inversion based near 1600 FT
MSL. The column was cooling, but PW remained constant at 0.62".
Only changes to the forecast this evening were except to expand the
Winter Weather Advisory to the San Diego County Mts and end it
earlier for the mts to the north. The dynamic storm system to visit
the area on Christmas day is on track.
A number of Advisories are in place. Gusty winds to 60 MPH or more
on the peaks and deserts slopes, several inches of snow in the
higher mountains above 5500 FT, and a Gale Warning for the Coastal
Waters. Winds will be gusty west of the mts as well, especially
close to the Coast. Expect gusts to around 35 MPH early in the day.
Storm total precip forecast....
I.E and Orange Co.....0.01-0.15"
Santa Ana Mts.........0.10-0.30"
San Bernardino Mts....0.20-0.70" with 1-5" of snow above 5500 FT
SD Co Coast/Valleys...0.15-0.60"
Riv and SD Co Mts.....0.35-1.50" Largest amounts in SD County with
a dusting of snow as low as 5000 Ft, and 2 to 4 inches on the
highest peaks.
Deserts...............Trace to 0.10"
A Winter Weather Advisory has been issued for the highest elevations
in the San Diego Mountains and also for the San Bernardino and
Riverside County Mountains fore several inches of snow, strong
winds, and low visibility at times.
From previous discussion...
The leading edge of the cold air is over the Pacific Northwest this
afternoon, and is associated with a deep 546 dm upper low that will
move into northern California this afternoon. This dynamically
driven cold upper low will race southward down the CA interior this
evening on strong northerly jet stream winds. So there will be a
strong tailwind for anyone flying in from the north tonight.
This is a cold system. Significantly lower height anomalies move
into SoCal Tuesday which will translate into a much colder day
tomorrow. Valley highs will be stuck in the 50s (!), with low 60s
near the coast. Mountain highs will range from 30-40 degrees. High
desert highs will be near 50, and lower desert highs from 60-65.
The cold will be accentuated by strong west winds that will kick in
with the passage of the cold front tonight. South winds ahead of the
cold front this evening will abruptly shift to the west and increase
overnight and continue through Tuesday. The storm track favors the
strongest winds over the coastal waters, all of San Diego County,
and most of the mountains. The strongest 700 mb winds peak over San
Diego County at 40-50 kts. Wind Advisories are in effect for these
areas, and Gale Warnings have been posted for the coastal waters.
The precipiation may start out as light rain/drizzle in the
coastal areas tonight as the marine layer rapidly deepens ahead
of the surface cold front. But it will transition to scattered
instability showers late tonight through Tuesday with the trough
pulling in much colder air aloft. A thunderstorm is possible Tuesday
when 500 mb temps plummet to -26C.
The rainfall forecast hasn't changed much from earlier today. The
bulk of the precipitation will fall over the San Diego County
Mountains and Foothills, primarily because of the track of the
upper low. Precip amounts will generally be greater in the southern
areas and lower to the north. Orange County coastal areas and
the Inland Empire may not see much rainfall. In contrast, strong
low and mid level westerly winds will make orographics the principal
driver of precipiation, especially on the west facing slopes of San
Diego and Riverside County mountains.
Precipitable Water values peak at 0.65-0.75" Tuesday, which isn't
all that high, but this cold, dynamic system will wring out showers
just about anywhere. It's looking more likely that San Diego County
will be the focus for the highest amounts, with 1.00-1.50" quite
possible in areas with the strongest orographic potential.
The trough moves inland Tuesday night and will be followed by cold,
dry northerly flow that will put a chill in the air through weeks
end. A strong shortwave races down the CA interior Thursday and
Friday that will bring a reinforcing shot of cold, dry air into
SoCal. High temperatures will be 5 to 10 degrees below average, and
nights will be very cold. The first Frost and Freeze products for
the coastal and valley areas appear likely during this time.
&&
.AVIATION...
250400Z...Coast/Valleys...BKN-OVC cigs with bases 1,000-1,500 FT
will return 25/05Z. VIS oscillating between 3-6 mi in BR/HZ,
occasionally below 1 mi, mainly before 25/12Z and during showers. -
SHRA starting after 25/08Z and ending in the afternoon. These will
be more widespread in SD County, so restricting to VCSH elsewhere. W
winds will be strong at times after 25/09Z with SFC gusts up to 25
kts possible.
Mountains...Skies becoming BKN-OVC after 25/08Z. Areas of -SHRA/-
SHSN early morning into the afternoon. Expect strong W winds gusting
40-50 kts along ridgetops into the afternoon, with STG UDDFS likely
over/east of the mountains. VIS of 2-3 mi, locally below, will be
possible on obscured slopes and during showers.
Deserts...SCT-BKN clouds with bases 3-5k FT after 15Z, with some
VCSH possible Tue morning into the afternoon. Mostly unrestricted
VIS, with SFC winds gusting up to 20 kts and STG UDDFTS possible
over desert slopes.
&&
.MARINE...
Strong WNW winds 20-30 kt with gusts to 35 kts, combined seas of 10-
13 ft, and steep waves late tonight into Tuesday. A Gale Warning is
in effect 10 PM this evening through 10 PM Tuesday. Conditions
improve Wednesday, but gusty winds will return Thursday.
&&
.BEACHES...
A fresh WNW swell of 10-13 ft/8-12 sec from 290 degrees on Tuesday
will generate elevated surf of 4-7 ft, diminishing Wednesday. A
Beach Hazards Statement is in effect from 8 AM through 10 PM Tuesday.
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Weather Advisory from 8 AM to 6 PM PST Tuesday for San
Diego County Mountains.
Wind Advisory until noon PST Tuesday for San Diego County
Deserts-San Diego County Mountains-San Gorgonio Pass Near
Banning.
Winter Weather Advisory from 2 AM to 2 PM PST Tuesday for
Riverside County Mountains-San Bernardino County Mountains.
Beach Hazards Statement from 6 AM PST Tuesday through Tuesday
evening for Orange County Coastal Areas-San Diego County
Coastal Areas.
Wind Advisory from 4 AM to 4 PM PST Tuesday for Orange County
Coastal Areas-San Diego County Coastal Areas-San Diego
County Valleys.
PZ...Gale Warning from 10 PM this evening to 10 PM PST Tuesday 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...10/Moede
AVIATION/MARINE/BEACHES...RodriguezThe national radar mosaic for the moment the first event began.
3 high wind, 1 flood. Local standard time, as filed.
White Water RAWS recorded a peak wind gust of 50 knots between 2250 and 2350 on December 24th.
Burns Canyon recorded a peak wind gust of 61 knots between 0251 and 0351 PST on December 25th.
Volcan Mountain recorded a peak wind gust of 55 knots between 0840 and 0940 PST on December 25th.
Quarry Road in Spring Valley closed around 1030 PST on December 25th due to flooding.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2018Every state in 2018This day in weather historyWarnings in California, December 2018
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: 798900, 798896, 798898, 798903.