A cold inside slider moved into Southern California on New Year's Eve, bringing rain and snow to the region. San Diego County received most of the precipitation from this event.
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.
A cold inside slider moved into Southern California on New Year's Eve, bringing rain and snow to the region. San Diego County received most of the precipitation from this event. San Diego coastal areas received 0.25-0.50, valley and mountain areas received 0.50-1.0. The mountain areas of San Diego County received 1-2 inches of snow above 4000 ft. High winds were also observed during this event. Gusts of 50-60 mph were recorded in the Riverside and San Diego County Mountains.
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 30, 9:15 PM PST, 35 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
915 PM PST Sun Dec 30 2018
.SYNOPSIS...
Low clouds and higher humidity will move inland tonight as low
pressure intensifies over the Great Basin. Light showers are
forecast along and west of the San Diego and Riverside County
mountains late tonight and increase on Monday. The freezing level
will fall rapidly in the mountains, and several inches snow are
possible by evening in the San Diego County mountains. Strong, cold
offshore winds will follow Monday night through Tuesday night. Fair
and dry with a warming trend Wednesday through Friday. There is a
chance for rain next weekend.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
...New Years Eve showers expected
...Winter Weather Advisory for the San Diego County Mts
...Strong Santa Ana winds Mon night through Tue night
A Coastal Eddy is in full form this evening with south winds at 15
kt at KSAN at 8 PM. Low level moisture surged inland this evening
and dewpoints have risen 15 to 30 degrees over the past 24 hours in
the inland valleys and coastal zones. Light rain and drizzle will
develop tonight as the marine layer deepens. The precipitation will
be confined to the southern half of the area, and this includes
southern Orange, the southern half of Riverside County and all of
San Diego County. Farther north in San Bernardino County it will be
too dry.
A powerful shortwave is plowing down the west side of a long wave
trough over the West this evening. It will race south across Nevada
and the California interior Monday, and into AZ Tuesday. Showers are
likely in the strong upper dynamics, cold air aloft and low level
moisture ahead of the trough. The moist layer was around 4500 feet
deep this evening. Then moisture advection deepens the saturation
layer to 7000 feet Monday. As a result, the snow levels may rise a
few hundred feet as the Wet Bulb Zero level rises. But in the
evening the snow levels will fall quickly with the passage of the
trough axis. Winds will shift to the north and quickly usher in a
very, cold, dry airmass. Snow levels will lower quickly once this
happens. This will happen in Riverside County in the afternoon, and
then slide south across San Diego County through the evening, which
is when the snow and ice covered roads are most likley.
Rain amounts were increased slightly. Most of the precip will fall
in San Diego County where the coastal zones will see 0.01"-0.10",
and the valleys will see 0.10-0.25". The greatest amounts will be in
the foothills and mountains where 0.25"-0.50" are expected due to
orographics. Snow and ice covered roads could pose problems in the
higher roads of the San Diego and Riverside County mountains Monday
night where 1-2" of snow is possible as snow levels may fall to
between 3500-4000 feet. A Winter Weather Advisory has been issued
for the San Diego County mountains.
It will turn very cold in the wake of the trough Monday night with
frost and freeze concerns in wind sheltered valleys and lower
deserts. Tuesday night looks to be the coldest night. The High
Deserts will fall into the low to mid 20s, the inland valleys from
25-32, and the lower deserts from 30-40.
*From Previous Discussion*
As the trough over the interior drops farther south, strong NE winds
will develop late Mon night through Tuesday night. A High Wind Watch
has been issued. These winds will be surfacing on the coastal
mountain slopes and adjacent foothills, through the Santa Ana Mts
and adjacent portions of the Orange County coastal plain, and below
passes. Mountain waves and strong support aloft may drive some of
these gusts farther out into the valleys as well. Cold air advection
will counteract the downsloping winds onto the Coast, so it will
stay rather chilly on Tuesday, with gradual warming for the
remainder of the week as the winds abate and high pressure builds.
A weak but moist Pacific trough will try and move through the ridge
late next weekend. It will likely create a lot of high clouds,
glooming up the days a bit, but several global model runs have
suggested we could get a decent shot of precipitation out of it
early next week.
&&
FIRE WEATHER...As the strong NE winds develop, RH will crash into
the 10-15% range later on Tuesday, with poor overnight recovery in
the wind-prone areas. Meteorologically, critical Fire weather
conditions are likley over an extended period from late Tue morning
through Wednesday. Due to the recent rains and poor evaporation this
time of year, it was determined that conditions are likley too wet
to warrant any Fire Weather product issuance at this time.
&&
.AVIATION...
310500z...Coast/Valleys/Mountains...Mostly BKN clouds will continue
to develop overnight with variable bases 2000-3500 ft MSL and tops
gradually building to 8000 ft MSL. These clouds will continue most
of Monday with scattered showers, with greatest concentration in San
Diego County. Local vis 3-5 miles will occur in showers, with
mountain obscurations in clouds/fog/rain/snow. Most of the
precipitation will by 02Z Tue. Areas of northeast surface winds 15-
25 knots with gusts 30-40 knots will develop Monday afternoon VCNTY
KONT, KSBD, KRAL, KSNA, KBUO, increasing in speed and spreading
south into San Diego County Monday night. Mostly clear skies will
return Monday night.
Deserts...SCT clouds with bases generally above 6000 feet MSL will
develop tonight and continue through Monday. Isolated showers will
occur in the San Diego County deserts Monday.
&&
.MARINE...
No hazardous marine weather is expected through Monday. Northeast
winds 15-25 knots will develop over the coastal waters Monday night
and continue Tuesday, along with choppy seas, so a small craft
advisory will be needed then.
&&
.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 6 AM to 9 PM PST Monday for San
Diego County Mountains.
High Wind Watch from Monday evening through late Tuesday night
for Orange County Inland Areas-Riverside County Mountains-
San Bernardino County Mountains-San Bernardino and
Riverside County Valleys-The Inland Empire-San Diego County
Mountains-San Diego County Valleys-San Gorgonio Pass Near
Banning-Santa Ana Mountains and Foothills.
PZ...NONE.
&&
PUBLIC...Moede/10
FIRE WEATHER...10
AVIATION/MARINE...MaxwellThe San Diego radar (KNKX), 134 km away, was scanning. The volume nearest the first event began at 21:00 UTC.
4 high wind, 2 funnel cloud. Local standard time, as filed.
White Water RAWS reported a peak wind gust of 54 knots between 2150 and 2250 PST on December 30th.
Harrison Park ASOS reported a peak wind gust of 53 knots between 0200 and 0300 PST on December 31st.
Burns Canyon ASOS reported a peak wind gust of 52 knots between 0251 and 0351 PST on December 31st.
Volcan Mountain reported a peak wind gust of 56 knots between 0300 and 0400 PST on December 31st.
NWS employee reported a funnel cloud near University Heights around 1330 PST on December 31st.
Multiple spotter reports of a waterspout/funnel cloud in Carlsbad around 1400 PST on December 31st.
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: 798976, 798975, 798977, 798974, 798991, 798992.