In the wake of a cold front and a cold upper trough overhead, strong northwest winds were observed across the Greater Bay Area in mid to late May. Observations showed gusts along the coast exceeding 50 mph with area peaks reaching 60 plus mph.
Every event with a place to put it; 9 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.
In the wake of a cold front and a cold upper trough overhead, strong northwest winds were observed across the Greater Bay Area in mid to late May. Observations showed gusts along the coast exceeding 50 mph with area peaks reaching 60 plus 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 May 19, 10:10 AM PST, 50 minutes earlier.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
1110 AM PDT Wed May 19 2021
.SYNOPSIS...A dry cold front on Wednesday will bring gusty
northwest winds through Thursday, along with well below normal
temperatures. Gradual warming is forecast from Friday through the
weekend.
&&
.DISCUSSION...as of 09:00 AM PDT Wednesday...Breezy to locally
gusty winds are developing along the coast and into the hills this
morning in wake of a dry frontal passage and mid/upper level low
pressure system to the north. Expecting these winds to increase
through the afternoon and remain gusty through much of the night
with even stronger winds out over the Pacific. Thus, Gale Warnings
remain in effect for much of the coastal waters with a Wind
Advisory for many coastal locations, hills, ridges and peaks with
gusts of 40 to 50 mph possible. With this said, the ongoing
forecast remains on track with no updates anticipated this
morning. For additional details, please see the previous forecast
discussion below.
&&
.PREV DISCUSSION...as of 04:05 AM PDT Wednesday...We've got an
area of high clouds moving across the southern Bay Area and
Central CA. Closer to the surface, just a few areas right now with
lower cloud decks such as the SF Peninsula and East Bay. Most of
our current temperatures are in the upper 40s to low 50s.
Additional cooling expected through sunrise, but most of our CWA
will stay in the 40s for overnight lows.
As has been advertised for the past several days, an upper trough
will move into NorCal today and impact us through Thursday. This
trough will enhance winds producing gusty conditions this
afternoon into Thursday along with ushering in a cooler airmass.
Increasing winds over the ocean will bring locally gusty
conditions to our coastal regions first (around late morning/early
afternoon). It's not until later in the afternoon and evening
that gusty winds will become more widespread inland and continue
overnight into Thursday morning. The current Wind Advisory
remains in effect from 5 pm Wed to 5 am Thurs, but keep in mind
that coastal gusts may start to develop earlier. Areas of concern
in the Wind Advisory are most of the coastline (excluding Monterey
Bay), North Bay Mountains, SF Peninsula, SF Bay Shoreline, East
Bay Hills, Santa Cruz Mountains, Santa Lucia Mountains, and San
Benito Mountains. Gusts 25-35 mph will be widespread with 40-50
mph gusts likely in favored coastal terrain and elevated areas.
Winds can bring elevated fire concerns, however, for coastal
regions, that concern is lower since recent marine air intrusions
earlier this week were able to moisten fuels. Areas farther inland
have drier fuels so folks should take extra caution to avoid any
activities that could start a spark.
Daytime highs today will trend cooler by about 4-10 degrees...the
more noticeable cooling will be inland. That leaves us with highs
today ranging around mid 50s to mid 60s near the coastline and mid
60s to mid 70s inland.
Winds will begin to lessen on Thursday, but could still be fairly
breezy for much of the day until they lighten by Thursday night.
Additional cooling on Thursday will leave inland areas struggling
to reach 70 so that much of our CWA is in the 50s and 60s.
Gentle warming trend begins on Friday into early next week...could
see more widespread upper 70s and low 80s by Monday and Tuesday!
&&
.AVIATION...As of 11:05 AM PDT Wednesday...For the 18z TAFs.
VFR with gusty W-NW winds today with LLWS concerns overnight.
Gusty northwest winds will peak through the afternoon and
evening, with gusts peaking around 25-35kt, locally stronger near
the coast and through coastal gaps and weaker inland. Thin high
clouds will occasionally arrive through the period. Most locations
will remain VFR through tonight due to gusty turbulent flow but
may see localized weak stratus development late tonight into
sunrise Thursday near coast and coastal gaps. Low level jet
driving these winds will decouple from the surface overnight and
bring a low level wind shear concern at 1500-3000 feet agl, with
winds roughly 30-40kt out of the NW. Gusty conditions resume on
Thursday.
Vicinity of KSFO...VFR. Main threat today will be gusty onshore
W-WNW winds peaking 35-45kt through the afternoon and evening
with sustained winds also remaining at or above 15-20 kt through
the period. A few clouds may develop late tonight but otherwise
mostly clear conditions expected. Relatively stronger winds at
1500-3500 feet should also be anticipated, ie up to 40-45kt
however these are below LLWS criteria at this time due to the
brisk surface winds.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR. Elevated onshore flow today with
sustained winds 10-16kt and gusts 18-25kt through the day. A few
weak cumulus clouds may develop over the surrounding terrain to
the south of KMRY and east of KSNS but these clouds should not
impact visuals. Surface winds taper off overnight but a jet aloft
will bring LLWS concerns to those arriving/departing at KMRY late
this evening through overnight. May see FEW-SCT clouds develop at
1500-2500 feet late tonight into sunrise Thursday.
&&
.MARINE...as of 10:55 AM PDT Wednesday...A tightening pressure
gradient will bring strong, gusty northwest winds across the
waters today and through the coming days. These northwest winds
will peak this afternoon and evening, with infrequent to
occasional storm force gusts are possible along the coast, with
frequent higher end gale force gusts expected across the entire
waters through at least late tomorrow. These strong winds will
generate very steep fresh seas of up 12 to 17 feet at 8 to 10
seconds that are hazardous, particularly for small craft vessels
which may struggle against the strong winds and rough seas. Mixed
seas will continue with a northwest swell and a longer period
southerly swell.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tday...Wind Advisory...CAZ006-505>509-511-512-517-518
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
SCA...Mry Bay until 3 PM
GLW...Mry Bay from 3 PM
SCA...SF Bay
&&
PUBLIC FORECAST: RGass/Bingaman
AVIATION: DRP
MARINE: DRP
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www.youtube.com/nwsbayareaThe national radar mosaic for the moment the first event began.
11 strong wind. Local standard time, as filed.
San Francisco Airport ASOS reported wind gusts between 45 and 50 mph with a peak gust of 56 mph.
Mesonet (PG&E) station on Snake Rd measured wind gusts between 45 and 55 mph with a peak gust of 57 mph.
Mesonet (PG&E) station at BFI Office reported wind gusts between 45 and 55 mph with a peak gust of 63 mph.
Mesonet (PG&E) station on Spolini Mountain.
San Francisco CWOP station measured wind gusts between 45 and 50 mph.
Big Rock RAWS measured gusts around 50 mph with a peak gust of 57 mph.
Mesonet station (PG&E) at Patterson Pass reported wind gusts between 45 and 55 mph with a peak gust of 61 mph.
San Francisco CWOP station measured gusts of 52 mph.
Strong winds in San Francisco caused a tree to snap and fall on to electrical wires blocking an intersection in Bernal Heights. Another large tree fell in Daly City as well where a car was struck at Serramonte and Callan with one minor injury https://www.nbcbayarea.com/news/local/strong-wind-gusts-topple-trees-cause-damage-along-sf-peninsula/2549950/.
Mesonet station (PG&E) on Snake Road measured wind gusts between 45 and 50 mph with a peak gust of 52 mph.
Mesonet station (PG&E) at Coast Road measured wind gusts around 45 mph with a peak gust of 49 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, May 2021
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: 955000, 954974, 955026, 954975, 954937, 954977, 955027, 954936, 955564, 955030, 955029.