An upper level system with a strong cold front moved through the Bay Area at the turn of the month with precipitation beginning late the evening of the 28th. This system brought widespread rainfall causing localized roadway flooding, strong winds, lightning, and small hail.
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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.
An upper level system with a strong cold front moved through the Bay Area at the turn of the month with precipitation beginning late the evening of the 28th. This system brought widespread rainfall causing localized roadway flooding, strong winds, lightning, and small hail. Gusts in the mountains reached 60 mph and hail was seen up to 1/2 an inch. The bulk of the precipitation and subsequent impacts were seen in early March.
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 Feb 28, 9:40 PM PST, 2 hours 11 minutes earlier.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
940 PM PST Wed Feb 28 2018
.SYNOPSIS...A potent frontal system remains on track to push
through the region on Thursday bringing widespread rainfall and
strong, gusty winds. Lingering showers will persist through
Saturday along with lowering snow levels. A drying trend is then
expected late in the upcoming weekend and into early next week.
&&
.DISCUSSION...as of 9:30 PM PST Wednesday...Rain associated with
a warm front began in the North Bay shortly after 00Z and has just
started along the San Francisco Bay Area coast. Thus far gages in
the North Bay have measured up to one- half inch. Rain will
spread over the SFO Bay Area tonight reaching the MRY Bay Area
after 10Z. This will be followed by the cold front which will move
into the North Bay around sunrise and the SFO Bay Area during the
morning commute hours. Rain will become locally moderate to heavy
as the front passes especially over the mountains.
As the front moves over the Santa Cruz and Santa Lucia Mountains
Thursday afternoon it will slow down as the upper low starts to
dig south along the west coast. As a result the largest rainfall
amounts will be in these areas where there will be a slightly more
prolonged rain event. Southerly winds will increase overnight
with the strongest winds in the higher elevations as well as
coastal areas from early Thursday morning through Thursday night.
Winds of 15 to 30 MPH will be possible in these areas with gusts
potentially exceeding 45 MPH. Some of the highest peaks across the
region may see gusts upwards of 60 MPH. Inland valley locations
such as the Santa Clara and Santa Cruz Valleys will also see
breezy conditions with gusts to 30 MPH possible.
Rain will turn to showers behind the front as the upper low
continues to spin off the Pacific Northwest coast and send
moisture into our district. Models indicate another organized
line of precip moving through late Thursday night and Friday
morning with additional showers continuing through Friday night.
There is a slight chance of thunderstorms for Thursday and Friday
afternoon and early evening in the cold unstable air behind the
front. While lightning wont be a huge concern... small hail and
locally heavy showers could accompany the stronger convection that
does develop. Snow levels will start out around 4000 feet on
Thursday then lower to 2500-3000 feet Friday into Saturday.
The upper low moves inland on Saturday and showers will decrease.
There is still a chance of residual showers Saturday. Saturday
night and Sunday will be dry.
Rainfall amounts with this storm will range from 0.5 to 1.5 inches
in the urban areas with the greatest in the North Bay with lesser
amounts in the inland valleys. Up to 2 to 4 inches are possible in
the North Bay Hills and the Santa Cruz Mountains...and 4 to 6
inches in the Santa Lucias. And of course there could be up to a
few inches of snow in the highest peaks.
Fro previous discussion...Drying conditions will develop late
Saturday into Sunday as the main mid/upper level trough shifts
inland. However, colder overnight temperatures will be likely late
in the weekend into early next week as skies clear and a colder
air mass remains in place. Daytime temperatures will warm slightly
and dry conditions will persist into early next week as a weak
short-wave ridge builds over the region. Forecast confidence
greatly drops off by the middle part of next week as the models
have diverged from one another. The GFS continues to bring another
chance of precipitation as early as Tuesday while the ECMWF has
dry conditions through Thursday of next week. Will continue to
focus our attention on the short-term and monitor the models in
the coming days with respect to weather conditions next week.
&&
.AVIATION...as of 3:57 PM PST Wednesday...A cold front will
result in cigs lowering to MVFR with rain spreading from north to
south through this evening. Heavier rain, increased winds are
anticipated approximately 2 hours after the onset of -SHRA. Wet
runways expected for the Thursday morning rush. Winds will
generally be out of the south to southwest, peaking tonight with
sustained speeds around 20 kt with gusts up to around 30 kt.
Vicinity of KSFO...MVFR cigs expected through tonight. VCSH then
afterward -RA begins around 05z. Visibility will lower to MVFR
around 07z with the arrival of heavier rain and winds. Winds are
forecast to back to the south southwest overnight and peak late
tonight into Thursday morning. Wet runways are expected for the
Thursday morning rush.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...MVFR cigs expected through tonight. VCSH
then -RA begins around 07z. Visibility will diminish around 10z
with the arrival of heavier rain and winds. Winds are forecast to
back to the south to southeast overnight and peak late tonight
into Thursday morning. Wet runways expected.
&&
.MARINE...as of 3:46 PM PST Wednesday...Southwesterly will
increase tonight with the arrival of a surface cold front. Locally
gusty southwest winds will accompany the frontal passage
overnight with steep fresh swell expected with the front as it
progresses southward through Thursday morning. Winds veer and
weaken slightly in the wake of the front.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...Wind Advisory...CAZ006-505>510
SCA...SF Bay from 9 PM
SCA...Mry Bay from 9 PM
SCA...Pt Arena to Pt Reyes 0-10 nm from 9 PM
SCA...Pt Reyes to Pigeon Pt 0-10 nm from 9 PM
SCA...Pigeon Pt to Pt Pinos 0-10 nm from 9 PM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 9 PM
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
&&
PUBLIC FORECAST: W Pi
AVIATION: CW/Canepa
MARINE: CW
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www.youtube.com/nwsbayareaThe national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Roadway flooding reported at 3601 Telegraph Ave.
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, February 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: 733179.