A cold front moved through the Bay Area in early November bringing gusty northwest winds across the region. Wind gusts between 40 and 50 mph were observed with a 58 mph gust at Mt Tamalpais overnight as well as a 43 mph gust at the San Francisco Airport.
Every event with a place to put it; 5 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 Bay Area in early November bringing gusty northwest winds across the region. Wind gusts between 40 and 50 mph were observed with a 58 mph gust at Mt Tamalpais overnight as well as a 43 mph gust at the San Francisco Airport.
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 5, 9:55 PM PST, 4 hours 5 minutes earlier.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
955 PM PST Thu Nov 5 2020
.SYNOPSIS...Temperatures turn sharply cooler on Friday as a cold
front sweeps through the region. This system will bring breezy
onshore winds, much cooler temperatures and the chance for
isolated to scattered rain showers through Saturday morning. While
Saturday looks to be mostly dry, another round of rain showers
will be possible on Sunday along the continued cool weather. Dry,
yet below average temperatures will persist through next week.
Overnight lows will be the coldest of the year with widespread 30s
for the interior valleys.
&&
.DISCUSSION...as of 08:53 PM PST Thursday...Impressive to look at
the max temperatures across the Bay Area and Central Coast from
today. Weak offshore flow and ample sunshine early in the day
allowed for temperatures to soar into the 80s across much of the
interior with a few coastal spots even in the 80s. Two official
climate sites, Kentfield and SFO Airport, both hit 80 degrees
breaking their records. There were a handful of other non-
official sties that broke records for their period of record.
Simply put, temperatures were 10-20 degrees above normal for early
November. Interesting to watch temperature trends late afternoon
along the coast as high clouds filled in overhead and more
importantly the seabreeze kicked in. Some sites dropped almost 15
degrees in a hour as the seabreeze pushed through.
No update this evening as the current forecast remains on track
with a major pattern shifting bearing down on CA. In short - a
significant drop in temperatures, first real chance of precip
since tropical moisture mid-August, first chance for high
elevation snow, and lastly widespread 30s across the interior
valleys. For all the details see below.
Here are a few extra tidbits to watch over the next few days. The
airmass change from today through tomorrow continues to look
impressive. The KOAK 00Z sounding 850mb temp from this evening
was 18.5C...tomorrow's 850mb temp is projected to be about 1-2C.
The cold airmass looks unstable, especially over the coastal
waters, with a chance for thunderstorms Friday afternoon and
Friday night. SPC Day 2 outlook still has much of the coast and
coastal waters in a general mention for thunderstorms. In this
scenario, experience says convective showers seems likely with
small hail, but may not see any lightning.
&&
.PREV DISCUSSION...as of 01:17 PM PST Thursday...
A significant pattern change will occur on Friday as a mid/upper
level trough quickly drops out of the Gulf of Alaska and drives a
cold front across the region. A few light rain showers will be
possible along the frontal boundary, yet widespread rain appears
unlikely at this time. As cold air advects southward through Friday,
afternoon temperatures will struggle to warm into the lower 60s with
50s common in some locations and especially in the region's higher
elevations. Breezy northwest winds will develop in wake of the
frontal passage with 10-20 mph and gusts of 25-35 mph likely,
especially along the coast and in the hills. A few spots may
occasionally gust up to 50 mph in the wind prone areas. Post frontal
showers are then forecast from midday Friday into early Saturday
morning as the core of the mid/upper level low slowly moves
overhead. The exact track of the low will likely determine where
scattered showers will develop. Some models keep the best chances
for precipitation over the Pacific while others favor locations
from San Francisco southward across the Central Coast. Given the
cold air aloft, instability will also increase enough to produce
the potential for isolated thunderstorms, yet mainly offshore.
Rainfall amounts will generally range from 0.10" to 0.25" for the
aforementioned areas while much of the North Bay will pick up less
than 0.10". Given the showery nature of this precipitation, not
expecting everyone to pick up beneficial rainfall. As mentioned
earlier this morning: "Any temporary structures/tents and other
outdoor items should be secured today. In addition, fire weakened
and any diseased/drought stressed trees may be impacted by this
first strong cold frontal passage of the season."
Chances for precipitation diminish during the day Saturday as the
mid/upper level low shifts a bit inland. However, isolated showers
cannot be ruled out near the coast and out over the Pacific. Cool,
breezy conditions will persist into Saturday and the remainder of
the weekend for that matter as the colder air settles over the
region. This will help keep overnight temperatures from falling too
much, generally in the 40s for most while a few of the coldest
interior locations drop into the upper 30s. A second short-wave will
drop down the backside of the trough and bring a reinforcing chance
of rain showers and cold air advection on Sunday. Again, rainfall
amounts will vary depending on where the heavier showers develop.
Sky conditions will clear early next week along with diminishing
winds. This will bring some of the coldest overnight/morning
temperatures to the region so far this fall. Most valley locations
will cool into the low/mid 30s with the potential for widespread
frost. Frost products for early next week may be needed as we head
into the upcoming weekend. People without shelter and those with
sensitive crops, plans, or pet will need to monitor this closely.
Next week looks likely to be dry with temperatures below seasonal
averages as troughing persists over much of the West Coast.
Precipitation chances through the week will likely remain to our
north and over the northern Sierra. Looking out a bit farther, the
models are hinting at another wet system arriving sometime the
weekend of the 14th of November.
&&
.AVIATION...As of 9:55 PM PST Thursday...For the 06z TAFs. The
marine layer is compressed to within a few hundred feet of sea
level, but will undergo a rapid deepening and mix out completely
as a sharp cold front arrives tonight and Friday morning. A
period of low level wind shear will develop over the North Bay and
along the immediate coast with frontal passage. At present the
prefrontal air mass is a little drier since morning based on the
evening Oakland sounding with a precipitable water (pw) value at
0.58", but the pw is forecast to near 1" tonight with frontal
passage. Moisture convergence and lift along the frontal boundary
will result in ceiling development and showers tonight, and in the
post frontal deep layer cold and unstable air on Friday expect
showers, some heavy with a slight chance of thunderstorms. Expect
a significant lowering of freezing levels with snow showers at
lower altitudes. Small hail also very likely with any thunderstorm
development Friday.
Vicinity of KSFO...VFR-MVFR, west to northwest wind 10 to 15 knots
increasing and becoming gusty tonight and Friday with gusts near
30 knots. A few patches of fog observed along the San Mateo coast
this evening, fog could briefly develop in vicinity of KSFO later
tonight until a quick mix out of the marine layer temperature
inversion takes place early to mid Friday morning under strong
cold air advection. Low confidence dry runways through the period.
May have a few showers or sprinkles late tonight and Friday morning
with cold frontal passage; 00z high resolution models show best
chances for moderate to heavy showers arriving Friday afternoon
and evening. May have an isolated thunderstorm in the afternoon or
evening, not in 06z TAF, but will monitor radar and satellite and
add as needed.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR-MVFR, west to northwest winds near 5
knots shifting to southwest prior to frontal passage Friday morning.
A few fog patches could develop prior to frontal passage tonight
and early Friday morning. Expect a quick mix out of the marine
layer temperature inversion Friday morning and/or afternoon under
strong cold air advection. May have a few showers or sprinkles
late tonight and Friday morning prior to cold frontal passage; 00z
high resolution models show best chances for moderate to heavy
showers arriving Friday afternoon and night.
&&
.MARINE...as of 9:46 PM PST Thursday...It'll turn much colder
with northwest winds strengthening after a low pressure system
sweeps a cold front southeastward over the coastal waters and bays
tonight and Friday morning. Post frontal deep layer cold and
unstable air originally from northern Siberia will result in
scattered showers, some heavy and a slight chance of thunderstorms.
Strong and gusty northwest winds will produce fresh steep wind
waves coupled with a moderate period northwest swell Friday into
Saturday.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...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 Arena to Pigeon Pt 10-60 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 12 AM
GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm from 12 AM
SCA...Mry Bay from 12 AM
&&
PUBLIC FORECAST: MM/RGass
AVIATION/MARINE: Canepa
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www.youtube.com/nwsbayareaThe national radar mosaic for the moment the first event began.
12 strong wind. Local standard time, as filed.
Mesonet station (PG&E) at Snake Road measured wind gusts between 35 and 40 mph.
Altamont RAWS station reported gusts between 45 and 50 mph with a peak gust of 54 mph.
San Francisco ASOS reported gusts in excess of 40 mph.
Big Rock RAWS station reported gusts.
Middle Peak RAWS station near Mt. Tamalpais reported gusts between 45 and 55 mph with a peak gust of 58 mph.
Mesonet station near Mt. Tam reported gusts between 45 and 50 mph.
Hawkeye RAWS station reported gusts between 45 and 50 mph.
Mesonet station (PG&E) on Coast Road.
Santa Rosa RAWS station reported wind gusts of 35 mph.
Atlas Peak RAWS station reported gusts.
Mesonet station (PG&E) at Old Coast Tower reported gusts of 40 mph.
Big Rock RAWS station reported gusts.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2020Every state in 2020This day in weather historyWarnings in California, November 2020
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: 924383, 924391, 924388, 924385, 924390, 924389, 924392, 924396, 924384, 924387, 924393, 924386.