On January 4th to the 5th, a strong atmospheric river combined with a bomb cyclone led to widespread heavy rain, damaging wind gusts, and high surf across the Bay Area and Central Coast.
Every event with a place to put it; 6 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 MTR wrote it up.
On January 4th to the 5th, a strong atmospheric river combined with a bomb cyclone led to widespread heavy rain, damaging wind gusts, and high surf across the Bay Area and Central Coast.
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 Francisco Bay Area, CA wrote its last area forecast discussion before the first event at Jan 4, 10:27 AM PST, 53 minutes earlier.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
1027 AM PST Wed Jan 4 2023
.SYNOPSIS...Widespread flooding and damaging winds expected from
Wednesday afternoon through Thursday as a strong weather system
and atmospheric river moves through the region. Subsequent weather
systems will bring additional precipitation and periods of
stronger winds this weekend and into at least early next week.
&&
.DISCUSSION...As of 10:25 AM PST Wednesday...Water vapor imagery
continues to an impressive and powerful Pacific storm spinning
near 39 North and 135.85 West this morning. Warm front continues
to spread light rain across the region, and while it may seem
relatively benign at this time, rain will begin to intensify in
time for the afternoon commute, with periods of heavy rain
continuing through this evening, as all of the high resolution
models show an impressive NCFR moving across the region. This will
cause widespread flooding across the region, with rivers, streams,
and creeks rapidly rising in response to excessive run off.
Shallow landslides are also possible, and we will be monitoring
burn scars for debris flows.
At the current time, the bigger concern is with the winds. Wind
gusts in the mountains are already ranging between 35 to 50 mph,
with some of the favored windy spots like Mount Diablo and Rose
peak gusting well in to the 60 to 65 mph range. Some of our
exposed coastal areas are already gusting up to 40 mph too, and
the strongest winds are yet to come. These strong and gusty winds
today will topple trees, and potentially create power outages.
Models continue to show winds increase to between 60 and 70 kts
with the front itself late this afternoon and evening. Therefore,
expect wind gusts upwards of 80 mph possible in the favored higher
terrain, with gusts up to 60 mph possible in valley locations.
Now is the time to finish any storm preparations, but this window
is closing, as the winds will only continue to increase through
the day. Palmer
&&
.PREVIOUS DISCUSSION...As of 02:38 AM PST Wednesday...
BLUF - Here's a summary of major impacts expected during the next
48 hours or so:
* High Wind Warning the entire San Francisco Bay Area and Central
Coast. Damaging gusts are expected with downed trees and power
outages anticipated.
* A River Flood Warning was issued for the Russian River near
Guerneville where moderate flooding is expected on Thursday.
* High surf is expected along the coast and a High Surf Warning is
now in effect for Thursday.
* A Coastal Flood Advisory is now in effect for the North Bay coast
and the San Francisco Peninsula. Flooding of coastal parking lots,
parks, and roads is expected.
* A few strong thunderstorms are possible Wednesday night. Strong to
locally damaging wind gusts are the primary threat.
The forecast remains on track this morning with a potent storm
system beginning to approach the central California coast. Major
impacts are expected including widespread flooding and damaging
winds beginning later today and lasting into Thursday. Again, it is
worth noting that this system is different than the previous storm
to impact the region, yet impacts will still be significant.
Generally light precipitation will begin early this morning as a
warm front spreads inland from the southwest. This will result in
wet roadways for the morning commute, especially in the coastal
ranges where warm advection/upslope rainfall will be greatest. That
said, flooding concerns are unlikely through midday. However,
southerly winds will begin to increase this morning with the arrival
of the warm front with gusts of 30-50 mph. Given the already
saturated soils, the threat for downed branches and tress will
increase with increased threat for isolated to scattered power
outages. As the warm front shifts northward, there will likely be a
break in rainfall outside of the coastal rages as south to southeast
winds continue to increase. Thus, the rain-shadow effect will be
great in places such as the Santa Clara Valley and Salinas Valley
through midday. However, rain is likely to persist through much of
the day across the North Bay where the atmospheric river will be
places ahead of the main cold front. All this said, don't let your
guard down if things appear quieter than you expected this morning.
The aforementioned cold front and associated atmospheric river will
being to push southward by early afternoon across the San Francisco
Bay Area with strong southerly winds anticipated. Wind gusts ahead
of the boundary will increase to 40 to 60 mph with 60 to 80 mph
expected in the coastal hills. If these winds do materialize, the
threat for scattered to widespread power outages and property damage
will greatly increase. In addition, rainfall will increase in
coverage and intensity from this afternoon and into the evening.
Excessive rainfall over already saturated soils will result in rapid
rises on creeks, streams and rivers as well as flooding in urban
areas. Thunderstorms are also expected late this evening with heavy
downpours, small hail, lightning and gusty winds as the atmosphere
becomes increasingly unstable.
Winds will begin to diminish early Thursday morning, yet the post
frontal environment will allow for continued rain showers and even
thunderstorms through much of the day Thursday. When all said an
done, expecting 1-3" in most urban areas (lesser in rain-shadowed
locations) with 3-4" across the North Bay Valleys. Totals through
early Friday morning are expected to reach 3-6" in the coastal
ranges and inland hills with amounts potentially exceeding 8" in the
region's wettest spots of the North Bay Mountains, Santa Cruz
Mountains and Santa Lucia Range. Along with the wind and flooding
concerns, this amount of rain will also increase the risk of shallow
land slides, rock slides and mud slides across the region's
hilly/mountainous terrain.
While a break in precipitation is expected on Friday, additional
systems look to impact the region Saturday into Sunday, again late
Monday into Tuesday and potentially heading into the MLK Holiday
weekend. Thus, the message to convey is resiliency as this is not a
"one and done" storm. Of course, timing and details of subsequent
systems will be subject to change. Be sure to stay tuned to the
latest information in the coming days.
&&
.AVIATION...As of 9:47 AM Wednesday... For the 18Z TAFs. Predominant
VFR continues in the wake of the warm front, with local MVFR-IFR in
scattered areas of rain and mist. Southeasterly flow is gradually
increasing and terminals have started to report gusts above 30-35
knots. Any rain for the next few hours will be light and
intermittent in nature.
A cold front is expected to arrive in the area, bringing intense
rain to the area overnight. Timing of first impacts is expected in
the North Bay around 00-02z, the SF Bay Area by around 01-03z, and
the Monterey Bay area around 03-05z. Southerly flow is expected to
increase at the surface with gusts as high as 40 knots possible at
some terminals. In addition, a southerly jet aloft at 60-70kt will
create turbulent conditions and LLWS concerns. Showers will follow
as the front moves out around 08-12z; winds will gradually subside
throughout Thursday.
Vicinity of SFO... VFR conditions currently reported at the
terminal. Showery rain possible through the late afternoon.
Southeast winds and rain intensity will continue to strengthen with
the approach of the cold front around 01-02z and become gusty with
gusts expected to approach 35 knots; will monitor for potential need
for higher gust speeds. Conditions will diminish to MVFR/IFR within
the front. Gusts will continue overnight but gradually subside into
Thursday.
SFO Bridge Approach... Similar to SFO.
Monterey Bay... VFR conditions reported with a break in the rain.
Showers will be possible through the evening hours with gusty
southeast winds. The cold front arrives around 03-04z with the
strongest winds and most intense rain, and MVFR-IFR conditions.
After the front passes, showers continue and winds begin to
diminish.
&&
.MARINE...As of 02:37 AM PST Wednesday...Rapidly increasing
southeast winds this morning as a warm front approaches from the
southwest and a strong low pressure system approaches the northern
California coast. These features will bring strong gales across
the coastal waters and bays today with local storm force gusts
possible in the outer waters. A cold front will pass through later
this afternoon and tonight from the north bringing gusty erratic
winds and a slight chance of thunderstorms. Gale force gusts will
linger through Thursday morning. A hazardous westerly swell builds
in behind the storm Thursday afternoon peaking at 20 to 25 feet.
Hazardous seas will prevail through the end of the weak with a
series of large westerly swells and another storm system this
weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tday...Flood Watch...CAZ006-502>506-508>510-512>518-528>530
High Wind Warning...CAZ006-502>506-508>510-512>518-528>530
SCA...SF Bay until 9 AM
GLW...SF Bay from 9 AM
SCA...Mry Bay until 3 PM
GLW...Mry Bay from 3 PM
GLW...Pt Arena to Pt Reyes 0-10 nm
GLW...Pt Reyes to Pigeon Pt 0-10 nm
GLW...Pigeon Pt to Pt Pinos 0-10 nm
GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm
GLW...Pt Arena to Pigeon Pt 10-60 nm
GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm
&&
PUBLIC FORECAST: Palmer / RGass
AVIATION: Lorber
MARINE: Lorber
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www.youtube.com/nwsbayareaThe national radar mosaic for the moment the first event began.
4 strong wind, 3 flood, 2 high surf, 1 debris flow. Local standard time, as filed.
The underpass of California Highway 1 under US Highway 101 in Manzanita flooded.
A redwood tree fell onto a double wide mobile home on the 2800 block of Joy Road in Occidental, killing a 2-year old boy when the tree pinned him down on the couch in the home's living room. Rescue crews were called around 5:15 PM, and performed CPR on the boy, but the boy died at the scene.
The eastbound lanes of California Highway 152 in the Pacheco Pass were blocked due to a downed tree.
A mud slide blocked the entire westbound lane of California Highway 92 west of Pilarcitos Creek Road near Half Moon Bay.
Caltrain commuter rail reported that a tree fell on the overhead wires at its station in Burlingame, affecting Caltrain service in the area. The tree was not removed until 3 PM.
An eucalyptus tree fell onto an apartment building on Lynde Street in Oakland, forcing the evacuation of five families. The building was later red tagged.
Flooding was reported on all lanes of Eastbound Interstate 580 near the Lakeshore Avenue exit in Oakland.
The Capitola Wharf at the Capitola State Beach broke in half, with a section of the wharf collapsing into the ocean.
Large waves took down the back of a house in Carmel Highlands.
The right hand side, and part of the number 2 (right) lane of the connector between Southbound Interstate 880 and Northbound Interstate 280 in western San Jose, was flooded.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2023Every state in 2023This day in weather historyWarnings in California, January 2023
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: 1078488, 1078487, 1078494, 1078490, 1078493, 1080047, 1078489, 1078486, 1078491, 1078492.