Building high pressure and a strengthening offshore pressure gradient brought gusty offshore winds to the hills of the Bay Area in late February. Higher elevations saw winds generally between 45 and 65 mph with the areas tallest peaks (Mt St Helena) nearly reaching 80 mph.
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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.
Building high pressure and a strengthening offshore pressure gradient brought gusty offshore winds to the hills of the Bay Area in late February. Higher elevations saw winds generally between 45 and 65 mph with the areas tallest peaks (Mt St Helena) nearly reaching 80 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 Feb 24, 4:13 PM PST, 1 hour 37 minutes earlier.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
413 PM PST Wed Feb 24 2021
.SYNOPSIS...Dry with gradual cooling trend and clear skies into
the weekend. Offshore flow will strengthen today. Winds aloft will
increase with the chance for them to mix down to the surface. Our
Wind Advisory will be in effect later this morning for the North
and East Bay hills, Santa Cruz mountains, and the East Bay
valleys. Offshore flow will persist Thursday and Friday, but at
weaker speeds. There is a chance for offshore winds to increase
again on Saturday.
&&
.DISCUSSION...as of 01:35 PM PST Wednesday...Wall to wall sunshine
blankets not just the Bay Area, but pretty much the entire state
this afternoon. Afternoon visible satellite shows a few clouds
lurking along the SoCal Coast and a few fair weather clouds over
the Sierra. Building high pressure and prevailing offshore flow is
the main reason for clear skies locally. Despite ample sunshine
latest 24 hour trends indicate many locations are actually colder
than yesterday. A colder airmass spilled in from the north.
Regardless, highs will still top out in the mid 60s to mid 70s,
which is still a few above seasonal averages.
The biggest near term weather impacts continue to be the offshore
flow/gusty winds. If it were late summer/early fall fire weather
concerns would be an issue and Red Flags would likely be in
effect. The current offshore flow has ushered in some very dry air
with RH in the 10-20% range. However, the winter rains have
helped with a green up and brought fuel moistures above critical
levels. Therefore fire weather concerns are greatly reduced.
Nonetheless, there could still be some wind impacts with some minor
tree damage and blowing around of unsecured items/temporary
structures. The offshore gradient has steadily increased since
this morning and the last observations are responding to this
increase. Winds over the higher terrain are still peaking in the
35-55 mph range and becoming more widespread. The offshore
gradient is still expected to increase through late this afternoon
into the evening hours. Winds are then expected to decrease over
the lower elevations late this evening, but still remain gusty
over the hills through Thursday morning. A Wind Advisory remains
in effect for the East Valleys through late this evening and the
N Bay Mts/East Bay Hills/Santa Cruz Mts through early Thursday.
It will remain breezy in the hills on Thursday, but not strong
enough to need a Wind Advisory. Further cooling is expected through
the weekend with continued dry conditions.
Next chance for precip returns early next week, but confidence is
pretty low at this point. The tail end of system is forecast to
move through NorCal increasing chances for light precip over the
Bay Area. Ensemble guidance and National Blend of Models show a
20-30% chance for at least 0.01". Will keep a slight chance for
showers on Monday, but north of the Golden Gate. Longer range
models are still advertising a better shot at rain around March
5/6. We'll see, stay tuned...
&&
.AVIATION...as of 4:13 PM PST Wednesday...For the 00Z TAFs. Near
high confidence VFR with offshore flow through the period. The
ACV-SFO pressure gradient is 7.5 mb, WMC-SFO is 8.0 mb. Low level
wind shear developing tonight and Thursday morning in the Bay Area
as surface winds decouple from winds aloft.
Vicinity of KSFO...VFR. Low level wind shear tonight and Thursday
morning with decoupling and decreasing surface winds. Thursday from
mid afternoon to evening wind westerly and increasing to 10 to 15
knots, possibly higher winds to 20-25 knots per recent statistical
guidance.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR. North to northwest winds 5 to 15
knots decreasing and becoming light and variable then east to
southeast tonight and Thursday morning. Low level wind shear
vicinity KSNS tonight and early Thursday morning.
&&
.MARINE...as of 4:00 PM PST Wednesday...Gusty northerly winds
continue persist through this evening. Winds will subside
slightly Thursday in most areas with the exception of the northern
outer waters where gale force gusts be possible. Winds will once
again strengthen late Thursday into Friday with gale force gusts
possible. These winds will generate steep fresh swell and bring
hazardous conditions for smaller vessels through the weekend. A
moderate northwest swell at around 13 to 15 seconds will continue
through the waters over the coming days.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...Wind Advisory...CAZ507-511-512
Wind Advisory...CAZ510
SCA...Pigeon Pt to Pt Pinos 0-10 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
GLW...Pt Arena to Pigeon Pt 10-60 nm until 9 PM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...SF Bay until 3 AM
&&
PUBLIC FORECAST: MM
AVIATION: Canepa
MARINE: Dhuyvetter
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www.youtube.com/nwsbayareaThe national radar mosaic for the moment the first event began.
8 strong wind. Local standard time, as filed.
Diablo-Blackhawk station (PG&E) measure gusts between 55 and 65 mph with a peak gust of 73 mph.
Ormsey Cutoff Trail (PG&E) station reported gusts between 45 and 60 mph with a lean gust of 67 mph.
Mt. Alison station (PG&E) reported gusts between 45 and 55 mph with a leak gust of 61 mph.
Healdsburg Hills North station (PG&E) reported wind gusts between 55 and 65 mph with a peak gust of 67 mph.
Cavedale Rd reported gusts between 45 and 55 mph with a peak gust of 57 mph.
Alcosta Boulevard station (PG&E) reported gusts of 45 mph.
Dagnino Rd reported there between 45 and 51 mph.
Contra Costa station (PG&E) reported gusts above 45 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, February 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: 945700, 945741, 945720, 945695, 945698, 945735, 945737, 945724.