An upper low along with a second shortwave trough moved through the region the first weekend of June. A strong onshore pressure gradient brought gusty winds to much of the area.
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.
An upper low along with a second shortwave trough moved through the region the first weekend of June. A strong onshore pressure gradient brought gusty winds to much of the area. Observations showed gusts of 40 to 60 mph throughout the Bay Area and Central Coast. These winds fueled multiple grass and vegetation fires throughout the area, some of which prompted evacuations.
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 Jun 5, 1:58 AM PST, 1 hour 14 minutes earlier.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
258 AM PDT Fri Jun 5 2020
.SYNOPSIS...An unseasonably cool weather system will result in a
rapid cooling trend from Friday into the upcoming weekend. Dry
conditions and a gradual warming trend is likely next week.
&&
.DISCUSSION...as of 3:00 AM PDT Friday...High pressure nudged into
California through yesterday, bringing inland temperatures in the
90s to low 100s, with 100 at Concord and Livermore, 101 at
Gilroy, and 106 at Pinnacles National Park. High pressure is now
evacuating from the region due to arrival of a 570dm 500mb cut
off low from the southwest. This cut off low has been wavering
offshore for the last several days and now approximately 325 miles
southsouthwest of Point Conception. The low is forecast to lift
northeastward and eventually make landfall over southern
California in approximately 24 hours -- reintegrating with the
mean westerly flow as it does. A limited amount of moisture
wrapping around the north/northeastern flank of this feature may
bring light rain to drizzle to portions of the Big Sur coast today
but do not expect to see much if any accumulating rain outside of
the orographically enhanced southern facing slopes there. That
said, even orographics may be limited given the trajectory of the
moisture/energy will be more from the southeast rather than the
more favorable south to southwest.
Closer to the surface, a southerly surge is evident on overnight
satellite fog detection imagery and now extends northward through
Point Reyes National Seashore. These southerly surges are a
common occurrence at the end of heat spells across our region
this time of the year and often bring stark day over day
temperature differences, and today will be no different. 2AM
temperatures are already showing this change in air mass over the
higher terrain where sites at 1000 feet or higher are 15 to 30
degrees cooler than the same time Wednesday night. A similar
cooldown is expected during the day for extreme inland locations
where temperatures are expected to peak in the upper 70s to mid
80s this afternoon, or generally 10 to 20 degrees cooler than
yesterday. Coastal locations will be a few to several degrees
cooler given the moderating effect on temperatures of the nearby
bodies of water.
The cut off low will exit the region Friday night but will become
replaced by a much broader saggy trough centered offshore of the
Pacific Northwest for the upcoming weekend. Consequently, the
marine layer is expected to deepen under a cool, moist air mass
through at least Sunday. This will amplify the cooling trend and
extended it through the weekend causing Sunday to be the coolest
day of the week with afternoon highs in the mid 50s to mid 60s at
the coast and upper 60s to low 70s inland (or 5 to 15 degrees
below normal). Fairly breezy to gusty onshore winds are
anticipated along the coast and through coastal gaps this weekend
as a result of the strong onshore gradient, with sustained winds
10 to 20 mph and peak gusts in the range of 25 to 35mph possible
through the typical windy spots. Additionally, the weak cold
frontal boundary associated with this system may be able to wring
out some very light precipitation where orographics is able to
enhance lift, ie along the Big Sur coast, late Friday night into
early Saturday morning.
High pressure builds ashore from the eastern Pacific early next
week and will bring an uninspired warming/drying to the region
through mid week. Temperatures will rise to become a few to
locally several degrees above normal, with inland highs peaking on
Wednesday in the mid 80s to low 90s. Another sagging trough
descends into California late in the work week, bringing a
cooling/moistening trend with increased onshore flow by Friday.
GFS remains dry with this trough while the EURO shows a few stray
showers in the vicinity as the base of the trough passes late
next Friday.
&&
.AVIATION...As of 10:29 PM PDT Thursday...for 06Z TAFs. The Fort
Ord Profiler shows the marine layer at around 2,000 ft becoming
more shallow towards the Bay Area where the Bodega Bay Profiler
has it just under 1,000 ft AGL. Satellite imagery shows the
southerly surge of stratus has moved into the Monterey Bay Region
and down the Salinas Valley. Low clouds will continue to move
northward overnight. MVFR/IFR conditions expected for coastal
sites overnight and tomorrow morning. Most areas will see VFR
conditions return late tomorrow morning or early tomorrow
afternoon. Light winds overnight and early tomorrow morning
before onshore winds increase in the afternoon to around 15 kt
with locally higher gusts expected.
Vicinity of KSFO...VFR conditions through the evening before low
clouds are expected to reach the Bay Area later tonight and
persist through mid to late tomorrow morning. MVFR/IFR cigs
overnight and tomorrow morning. Lighter winds overnight to then
increase again tomorrow afternoon with gusts of about 20 to 25 kt.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...Low clouds have moved in earlier than
anticipated this evening. Satellite imagery shows the Monterey
Bay, Peninsula, and Salinas Valley now covered in low clouds.
Observations show cigs at around 500 to 1,200 ft AGL. MVFR/IFR
cigs to prevail overnight with patchy reduced vis early in the
morning possible. Guidance as well as the local WRF continue to
show low clouds persisting all day tomorrow over the Peninsula,
though cigs are expected to raise some late tomorrow morning.
Light winds overnight turning onshore around 15 kt by tomorrow
afternoon.
&
.MARINE...as of 02:34 AM PDT Friday...Winds out of the northwest
will prevail over the coastal waters, with strongest winds are
anticipated over the northern waters north of Point Reyes. These
winds will generate steep fresh swell resulting in hazardous seas
conditions for small crafts. Mixed seas will continue with a
shorter period northwest swell and a longer period southwest
swell.
A long period southwest swell will likely generate an increase in
rip current activity as well as potentially strong shore break at
steep beaches through tomorrow.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tday...SCA...Pt Arena to Pigeon Pt 10-60 nm until 3 PM
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm until 3 AM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM
SCA...Pt Reyes to Pigeon Pt 0-10 nm from 9 AM
SCA...SF Bay
&&
PUBLIC FORECAST: DRP
AVIATION: AS
MARINE: DK
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www.youtube.com/nwsbayareaThe national radar mosaic for the moment the first event began.
6 strong wind, 6 wildfire. Local standard time, as filed.
Altamont RAWS station reported gusts between 40 and 61 mph.
Wind-driven grass fire reported in the San Francisco neighborhood of Potrero Hill. Evacuations were issued, the fire was contained with no structures damaged https://sanfrancisco.cbslocal.com/2020/06/05/grass-fire-in-san-franciscos-potrero-hill-forces-evacuations/.
Big Rock RAWS station reported wind gusts between 40 and 60 mph.
Las Trampas RAWS station measured gusts between 40 and 50 mph.
The Lakeville Fire broke out Friday afternoon near Petaluma in Sonoma County. Exact end time uncertain https://www.mercurynews.com/2020/06/06/map-seven-fires-amid-high-winds-in-the-bay-area/.
The Gulch Fire broke out on Saturday afternoon about a mile from where the Lakeville Fire began near Petaluma https://www.mercurynews.com/2020/06/06/map-seven-fires-amid-high-winds-in-the-bay-area/. Timing approximated.
The Willow Fire broke out in Contra Costa County late Saturday afternoon. Like the other wildfires that day, this one was aided in spread by gusty winds https://www.mercurynews.com/2020/06/06/map-seven-fires-amid-high-winds-in-the-bay-area/. Exact end time uncertain.
The Bitterwater Fire broke out on Sunday afternoon near King City https://www.fire.ca.gov/incidents/2020/6/7/bitterwater-fire/.
San Francisco Airport ASOS reported wind gusts between 40 and 45 mph.
The Bradley Fire broke out just north of Bradley in Monterey County on Monday afternoon https://www.fire.ca.gov/incidents/2020/6/8/bradley-fire/. Although winds had begun to die down at this point, breezy conditions still fueled the spread of the fire.
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, June 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: 892090, 891973, 892087, 891975, 891981, 891982, 891990, 891992, 891994, 891996, 892086, 891998.