A cold front moved through the region bringing light to moderate rainfall across the Greater Bay Area along with breezy winds. Periods of heavy rain caused some minor roadway flooding.
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 MTR wrote it up.
A cold front moved through the region bringing light to moderate rainfall across the Greater Bay Area along with breezy winds. Periods of heavy rain caused some minor roadway flooding. Area peaks saw wind gusts between 40 and 60 mph with a peak gust of 69 mph.
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 Dec 21, 9:07 PM PST, 13 minutes earlier.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
907 PM PST Sat Dec 21 2019
.SYNOPSIS...Rain will spread across the area from late tonight
through mid morning on Sunday. Mostly light to moderate rain is
expected, although brief heavy rain is possible in the coastal
mountains early on Sunday. Most rain will end by midday Sunday,
but a few showers may linger into the afternoon. Cooler
temperatures are forecast behind the front tomorrow. Mostly dry
and seasonably cool weather is forecast for Monday and Tuesday,
although shower chances will persist into Monday across southern
Monterey County and San Benito County. The next opportunity for
widespread rain is Tuesday night into Christmas Day. Dry weather
appears likely late next week.
&&
.DISCUSSION...As of 9:05 PM PST Saturday...Although the incoming
frontal system has been spreading considerable mid and high cloud
cover across all of California throughout the day, the frontal
rain band remains well offshore this evening. Radar is just now
starting to pick up some weak mid-level returns off the North Bay
Coast, but it appears unlikely our area will see any rain prior to
midnight. The last NAM and HRRR agree quite well on precipitation
timing. Both models begin to spread rain into the North Bay
between 2 and 4 am. Once the front reaches our coast, it is
forecast to pick up speed and rain is expected to spread into all
other coastal areas by 5 AM and then across nearly all of our
forecast area by 7 am. Rain rates are expected to be mostly light
to moderate, but a brief period of heavy rain is possible along
the front, mainly in the coastal hills around 6-7 am according to
the lastest HRRR. Rain rates farther inland are forecast to remain
rather light and so concern for flash flooding over the Kincade
burn scar is low. Most rain is forecast to end by late morning,
but post-frontal showers may linger into the afternoon hours,
mainly across the southern portion of our area. Rainfall totals in
the coastal mountains through Sunday are forecast to range from
0.50-1.50", although the HRRR forecasts up to 2 inches in the
Santa Lucias. For most other locations, rain totals are forecast
to range from 0.25-0.75", although some of the rain-shadowed
inland valleys may only pick up a tenth of an inch or less.
Pre-frontal southerly winds have begun to increase this evening,
mainly in the hills where there have been isolated gusts up to 50
mph on the highest peaks. Gusty winds will become more widespread
in the hills overnight and also near the coast. Strongest winds
are expected late tonight into early Sunday (mainly between about
3 AM and 7 AM). Strongest winds will likely occur across the
hills of Monterey and San Bentio Counties, including the Santa
Lucias and southern Diablo Range. A Wind Advisory is in effect for
these areas starting at 10 PM this evening. Locally strong and
gusty winds are also forecast along the Monterey County coast. In
fact, the 00Z local WRF forecasts 35 to 45 knot sustained surface
winds from Pebble Beach south to Point Sur at 6 AM tomorrow
morning. The coast of Monterey County from Pebble Beach to Big Sur
has been added to the Wind Advisory. The Salinas Valley was also
added to the Wind Advisory since MOS guidance is forecasting
sustained winds of around 30 knots at the Salinas Airport late
tonight (this would likely mean gusts of at least 45 mph). Winds
are forecast to diminish quickly after the front moves through
early Sunday morning and the Wind Advisory is due to expire at 7
AM.
A cooler airmass will arrive behind the front tomorrow and high
temperatures are expected to be about 5 to 8 degrees cooler than
today. Seasonably cool temps are then expected to persist
throughout Christmas week with highs forecast to be mostly in the
50s and overnight low ranging from the mid 30s to mid 40s. The
coolest night will likely be Monday night when we can expect the
most clearing. Patchy frost may occur, especially in the North Bay
Valleys.
The incoming frontal boundary is forecast to stall over southern
California tomorrow night and Monday morning, and then lift back
to the north a bit on Monday, possibly resulting in renewed shower
activity across southern Monterey County and San Benito County by
Monday afternoon. Otherwise, expect mostly dry conditions from
Monday into Tuesday.
A system approaching from the northwest may bring light rain into
our area by late on Christmas Eve and then more widespread and
significant rain on Christmas Day as an upper low drops to the
southeast just offshore. However, a high degree of forecast
uncertainty exists regarding the Christmas system. If the system
tracks close to the coast, as the latest GFS forecasts, then
widespread rain is likely on Christmas, especially in southern
coastal areas. But if the upper low tracks slightly farther
offshore, as is forecast by the 12Z deterministic ECMWF, then
very little rain will fall on Christmas, and many locations may
remain entirely dry. A look at the ECMWF ensemble mean suggests a
higher likelihood for wet weather on Christmas.
The models come into better agreement in the longer range, with
dry weather appearing likely starting Thursday and continuing into
at least the early part of next weekend.
&&
.AVIATION...as of 4:10 PM PST Saturday...Increasing southeast
winds have helped to clear out the fog today. VFR conditions this
afternoon but approaching warm front will bring gradually lowering
cigs. Bases lowering to near 5000 ft after 06Z in the Bay Area
with rain beginning then bases dropping into MVFR category after
10Z.
Southeast winds will reach their peak between 09Z and 15Z with
gusts to 30 kt. Already seeing winds above the surface to 30 kt
and this will increase to 35-40 kt tonight. LLWS is possible in
the SFO Bay Area tonight and in the MRY Bay Area late tonight.
Vicinity of KSFO...Cigs lowering through tonight. Bases around
5000 ft after 06Z lowering to 2500-3000 ft after 10Z. Conditions
improving after 15Z as cigs start to rise. Southeast winds to 10
kt increasing to 20 kt gusting to 30 kt after 10Z. Wind shift to
the west is expected after 12Z. LLWS possible through the night.
SFO Bridge Approach...Same as KSFO.
Monterey Bay Terminals...Warm front will be very slow to move into
the MRY Bay Area. VFR conditions through 12Z. After 12Z cigs
lowering into MVFR range with light rain. Conditions improving
after 20Z as cigs rise and rain moves away. Southerly winds will
strengthen tonight with gusts to 25-30 kt in the Salinas Valley
and gusts to 20 kt in MRY after 07Z. A wind shift to the west is
expected around 15Z.
&&
.MARINE...As of 8:29 PM PST Saturday...Gusty southerly winds will
continue into the overnight hours ahead of a frontal system.
Winds will briefly reach gale-force later tonight before turning
northwest and decreasing Sunday morning. A long period northwest
swell will arrive mid-week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...Wind Advisory...CAZ511-516>518-528-530
SCA...Pt Reyes to Pigeon Pt 0-10 nm until 9 PM
SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 9 PM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 9 PM
GLW...Pt Reyes to Pigeon Pt 0-10 nm from 9 PM
GLW...Pigeon Pt to Pt Pinos 0-10 nm from 9 PM
GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm from 9 PM
GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 9 PM
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Mry Bay
SCA...SF Bay from 12 AM
&&
PUBLIC FORECAST: Dykema
AVIATION: W Pi
MARINE: W Pi
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www.youtube.com/nwsbayareaThe national radar mosaic for the moment the first event began.
4 strong wind, 3 flood, 1 high wind. Local standard time, as filed.
Mesonet station (PG&E) on Old Coast Tower measured gusts of 45 to 60 mph with a peak gust of 69 mph.
Mesonet (PG&E) station on Coast Road measured gusts between 45 and 50 mph.
Pinnacles station measured wind gusts between 45 and 50 mph.
Mesonet station (PG&E) 6 miles north of Gonzales recorded wind gusts of 57 mph.
Calavareas Road station.
Law enforcement reporting all lanes flooded on I-580.
Slow lane and lane 1 of southbound 101 flooded with water on the roadway.
Paulson Roadway, before the bridge, is flooded.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2019Every state in 2019This day in weather historyWarnings in California, December 2019
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: 864932, 864940, 864934, 864938, 864927, 864920, 864922, 864923.