A mid/upper level low moved through the region at the end of November. A cool unstable air mass allowed for the development of scattered thunderstorms across the region that produced lightning and small hail.
Every event with a place to put it; 15 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.
A mid/upper level low moved through the region at the end of November. A cool unstable air mass allowed for the development of scattered thunderstorms across the region that produced lightning and small hail. An associated surface low approached the coast during this time causing high surf and gusty winds. Some locations saw wave heights above 25 feet. This system caused roadway flooding, minor debris flows, and downed trees along with damage from gusty winds.
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 Nov 28, 4:06 AM PST, 4 hours 55 minutes earlier.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
406 AM PST Wed Nov 28 2018
.SYNOPSIS...Unsettled weather conditions are forecast to persist
through the upcoming weekend as a series of storm systems impacts
the area. The most potent of these systems will push inland late
Wednesday into Thursday with widespread moderate to locally heavy
rainfall, isolated thunderstorms and strong, gusty winds.
Lingering showers will be possible into Thursday night with a lull
in precipitation on Friday before another system moves through this
weekend.
&&
.DISCUSSION...as of 3:34 AM PST Wednesday...One storm system
down, but several more to go over the next seven days. The storm
with the greatest impact potential will be today into Thursday.
A few things are currently at play setting the stage for what
will likely be an active 24 to 36 hours. At 500mb an upper level
trough is deepening off the West Coast early today before becoming
a cut off low later today and Wednesday night. Higher up, a jet
max of 130+kt will continue to round the base of the trough and
the exit region will provide large scale ascent. This ascent can
already be seen on satellite with increased cooling cloud tops
offshore. At the surface, southerly flow will increase as
a sfc low deepens rapidly (almost 990mb) later today and
Wednesday. Flow also becomes perpendicular to the terrain
resulting in increased orographic lifting. Lastly, a stout
moisture plume of 1-1.25 inches (>200% PON) is taking aim at the
Central Coast per total precip water from satellite imagery.
So what does all of this mean for the Bay Area? Rain, some heavy
at times, gusty winds and potential for thunderstorms through
Thursday. Latest KMUX radar imagery has shown a trend of
increased radar returns off the coast heading toward the San
Mateo/Santa Cruz Coast. Additionally, farther to the north
lightning has been detect consistently over the last few hours.
Increased radar returns and lightning is likely caused by the
leading edge of the upper jet and embedded/passing shortwave
trough. Latest hi-res models (HRRR/WRF) bring a good push of
moderate to locally heavy rain to the San Mateo/Santa Cruz Coast
this morning before shifting southward to the Santa Lucias later
this morning/early this afternoon. Places to the north could still
see some showers, but the heaviest rain will be focused with the
moisture plume to the south. 2-3 inches of rain seem plausible for
the coastal mountains. WPC has much of the Santa Lucias in a
slight risk for excessive rainfall today and marginal risk for all
other areas. Given the convective activity to the north have also
added a slight chc for thunderstorms across the northern coastal
waters early today.
Once the moisture plume moves southward the Bay Area could see a
lull in precip before the next round. More widespread precip will
begin to develop as the sfc low deepens and a cold front moves
toward the region late Wednesday afternoon and Wednesday night.
Rain will initially be heaviest over the North Bay before moving
southward through the Bay Area as the cold front moves through.
Instability looks to increase (higher CAPE, increased lapse rates
and neg LI's) as well with the surface boundary leading to a
better shot for thunderstorms. Storm Prediction Center has much of
the region in a general mention for thunderstorms through 12z
Thursday.
During the day Thursday the rapidly deepening sfc low will sweep
directly though the Bay Area. The chance for thunderstorms will
continue with possible moderate to locally heavy rain at times.
As for winds, despite the deepening low models have really backed
off on the high winds. That is not to say gusty winds will not
develop, but model trends have lessened the chance for the 60 mph
winds. There is a high wind watch currently in effect for portions
of the Bay Area. Given that it is only one model run showing
weaker winds will leave the watch in place for now. The next shift
can re-evaluate if the trend of weaker winds continues.
Precipitation diminishes late Thursday night into Friday, but a
few lingering showers will remain. The weekend storm system has
been trending drier with almost an inside slider feel. None the
less, a few showers will be possible Friday and Saturday. One item
of note is the colder air associated with this system. Snow levels
will drop and any precip that does develop could be the wintry
variety above 5k feet. These type of setups are not great snow
producers for the Bay Area, more specifically the Santa Lucias. A
quick coating is possible none the less.
Unsettled weather remains heading into next week as medium range
models show another low dropping down the coast bringing rain
midweek.
&&
.AVIATION...As of 4:00 AM PST Wednesday...Enhanced frontal band
developing over Santa Cruz mtns/Monterey Bay/Big Sur region early
this morning, bringing RA, IFR-MVFR cigs and visbys there.
Showers are possible this morn over KSFO/KSJC/KLVK before the band
moves farther southward. A brief lull will then be anticipated
through the late morning through early afternoon before the
arrival of yet another storm system later tonight. Expect periods
of RA/+RA with gusty winds, reduced visbys, and lowered ceilings
as next storm system arrives.
Vicinity of KSFO...IFR to MVFR cigs, with VCSH/-SHRA thru the
early morning. MVFR cigs prevail thru midday, then increasing
winds and gusts with lowering ceilings arrive ahead of next storm
system by 06Z THU. Periods of moderate to heavy rain possible
overnight into sunrise Thursday.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...Enhanced precip band will move over KWVI
KMRY and KSNS into sunrise WED, bringing IFR to MVFR conditions
and brief mod to heavy rain. Conditions improve somewhat during
the afternoon after precip band moves southward towards Big
Sur/SLO/SoCal. Conditions deteriorate once again tonight in
anticipation of arrival of next storm system into early Thursday
morning. Strongest winds with 2nd system in the Salinas Valley.
&&
.MARINE...as of 03:57 AM PST Wednesday...A storm system is moving
through the waters early this morning and will exit the waters
later today. Southerly winds will increase tonight ahead of a
different storm system approaching the region. Gusty post frontal
northwest winds are then forecast for later Thursday into Friday.
Gale force gusts are possible in the post frontal environment
later Thursday. A moderate to large longer period westerly swell
train will peak today and tonight.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tday...High Surf Advisory...Entire Coastline
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Pigeon Pt to Pt Pinos 0-10 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
SCA...Rough Bar Advisory for SF Bar
&&
PUBLIC FORECAST: MM
AVIATION: DRP
MARINE: DRP
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www.youtube.com/nwsbayareaThe San Francisco radar (KMUX), 27 km away, was scanning. The volume nearest the first event began at 05:24 UTC.
13 strong wind, 10 flood, 5 high surf, 3 high wind, 2 debris flow, 2 hail, 1 heavy rain. Local standard time, as filed.
Thirty foot monster waves reported at Mavericks Wednesday morning.
SB 17 at Sugarloaf Rd 6 inches accumulating into number 2 lane.
Mesonet station, 5 SSW Middletown.
Half Moon Bay Airport reported wind gusts 45 mph.
Water on all lanes.
Two feet of water across the road.
Mesonet station, 2 miles W Mill Valley.
Los Gatos RAWS measured 45-51 mph gusts.
Market and Church St flooded intersection.
Gusts of 45 mph recorded at KSFO.
Heavy rain causes a section of the roof at a West Oakland warehouse to cave in overnight. Timing of event is uncertain https://sanfrancisco.cbslocal.com/2018/11/29/potent-storm-brings-heavy-rain-pounding-surf-high-winds-and-flooding/.
Large tree fell on pickup truck.
Middle Peak RAWS station reported gusts.
Atlas Peak RAWS reported wind gusts between 45 and 61 mph.
The Alameda was closed overnight as heavy rain flooded the railway crossing beneath the Stockton Bridge. A water rescue was called in as a vehicle with one occupant was stranded in knee deep water https://sanfrancisco.cbslocal.com/2018/11/29/potent-storm-brings-heavy-rain-pounding-surf-high-winds-and-flooding/.
Rockslide entire sb lane.
Flooding at Hwy1 and Hwy 68.
BB sized hail reported at the NWS office.
SB 280 at Woodside 3-4 lane, major flooding low spot in roadway. DOT unable to drain, placed cones and signs.
Golden Gate Dr in Napa area.
Dime-sized hail reported on the San Francisco Peninsula https://sanfrancisco.cbslocal.com/2018/11/29/potent-storm-brings-heavy-rain-pounding-surf-high-winds-and-flooding/.
Gust of 45 mph reported at Point Reyes.
Los Gatos RAWS measured 50-54 mph gusts.
Gusts of 48 mph at Los Vaqueros RAWS.
Tree down in Oakland on McArthur Blvd.
Trees and power lines down in Ben Lomond.
West Monterey Bay buoy reported waves of over 20 ft.
Tree fell on minivan on Empire Grade. One person minor injuries.
Flooding on SB I-680 at Koopman Rd.
Buoy at Point Reyes reported waves of over 20 ft.
Buoy at Point Reyes reported 22 ft waves.
West Monterey Bay Buoy reported 22 ft waves.
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, November 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: 788885, 788888, 788889, 788900, 788871, 788872, 788873, 788890, 788949, 788874, 788951, 788891, 788868, 788875, 788892, 788898, 788899, 788870, 788893, 788877, 788866, 788878, 788882, 788867, 788897, 788950, 788901, 788902, 788894, 788895, 788955, 788896, 788883, 788953, 788952, 788954.