Scattered thunderstorms impacted the Bay Area on April 4 and 5 as a cold core upper level low tracked over the region. After a front passed through the region, an unstable atmosphere set up over the region and contributed to convective activity.
Every event with a place to put it. 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.
Scattered thunderstorms impacted the Bay Area on April 4 and 5 as a cold core upper level low tracked over the region. After a front passed through the region, an unstable atmosphere set up over the region and contributed to convective activity. The SPC placed the region in a general mention of thunderstorms, with small hail being the main impact.
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 Apr 4, 4:03 PM PST, 1 hour 42 minutes earlier.
Area Forecast Discussion...UPDATED
National Weather Service San Francisco CA
503 PM PDT Thu Apr 4 2024
...New AVIATION...
.SYNOPSIS...
Issued at 121 AM PDT Thu Apr 4 2024
Unsettled weather will continue through Friday with isolated to
widely scattered rain showers, high elevation snow showers, and
possible thunderstorms. Temperatures then remain cool through the
weekend with warmer and drier conditions returning next week.
&&
.SHORT TERM...
(This evening through Friday)
Issued at 215 PM PDT Thu Apr 4 2024
The much talked about cold core storm system made its presence
known today. A front pushed through the Bay Area and Monterey Bay
region earlier today. The fropa brought periods of heavy rain,
embedded thunderstorms, small hail, gusty winds, and colder
temperatures. The public and spotters have reported hail from rice
to pea sizes. Snow levels lowered to approx. 1,500 feet per
reports and webcams. Accumulating snow occurred at slightly
higher elevations.
Tonight through Friday: The vertically stacked low is still on
track to move directly over SF Bay and the West Delta later this
afternoon/early this evening. It will be interesting to see what
the airmass looks like for the 00Z Oakland balloon sounding.
Therefore, instability showers will persist well into the
overnight hours. Given the unstable atmosphere the chance for
thunderstorms and/or showers with small hail will also last into
the other night hours. Quickly behind the stacked low another re-
enforcing shot of upper cold air aloft will sweep down the coast
and pivot behind the initial upper low. The secondary push will
keep widely scattered showers over the region into Friday. CAMs
show some decent activity with a few bands/clusters of convection
moving through on Friday. The overall airmass profile will not be
much different from today so the same weather concerns remain:
brief heavy rain, thunderstorms, small hail, gusty winds, and
high elevation snow showers. Specifically for snow, still looking
like the Santa Lucia Mt range will be the winners with the most
snow. (Webcams already show a winter wonderland today). Novelty
flakes will be possible again on Friday down to near 2,000 feet.
By Friday evening precip will taper off as the upper low moves
farther east. The next weather hazard will be the cold overnight
lows a skies begin to clear out. Cold air mass and clearing skies
will lead to temperatures in the 30s to mid 40. Protected
interior valleys and high elevation area may even reach the
freezing mark. Will have to re-evaluate but a Frost Advisory may
be needed.
&&
.LONG TERM...
(Friday night through next Wednesday)
Issued at 240 PM PDT Thu Apr 4 2024
A much more quiet long term as subtle ridging develop with a
gradual warming and drying trend. There is a weak upper trough
slated to passed through NorCal over the weekend, but it has been
trending drier and weaker. Official forecast still has a mention
of a showers Saturday night/Sunday.
Dry and warmer Monday through Wednesday.
&&
.AVIATION...
(00Z TAFS)
Issued at 456 PM PDT Thu Apr 4 2024
Scattered SHRA will continue this afternoon across the region with
the main aviation hazards being gusty winds above 30 knots and brief
bouts of hail (1/4" or less). The potential for TSRA continues over
the next several hours largely across North, East, and South Bay
Terminals, including SFO. Otherwise, mixed signals from guidance
results in a low to medium confidence wind forecast. MVFR cigs are
advertised at all TAFs, with a longer breadth of MVFR at SNS and
MRY.
Vicinity of SFO...The next batch of SHRA continues to advance
eastward across the SF Peninsula as of this writing. Instability
still supports inclusion of TSRA, though confidence in frequent
lightning isn't overly high. Gusty/erratic winds with gusts above 30
knots and MVFR/IFR cigs/visibility associated with SHRA/TSRA are
within the realm of possibility along with a threat for 1/4"
diameter hail. Some guidance does suggest a brief N to NNE wind
shift between 04Z-09Z associated with SHRA/TSRA, and we'll monitor
trends and update accordingly. Otherwise, a period of MVFR cigs
is forecast through the pre-dawn hours on Friday. W to WNW winds
will ramp up through the day on Friday, with forecast peak wind
gusts near 30 knots. There's another shot at convection (SHRA),
mostly across the East Bay. For now, Friday afternoon and onward
will feature a precip-free TAF with wind gusts gradually subsiding
after 00Z Saturday.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...The potential for TSRA is a bit lower
here and at this time, the dominant weather type will be SHRA,
mostly this evening. MVFR stratus is most likely (> 60% chance)
here just prior to midnight local time with VFR returning just
prior to midday. Wind gusts to near 20 knots will subside after
nightfall with wind gusts increasing to around 25 knots by Friday
afternoon.
&&
.MARINE...
(Today through Tuesday)
Issued at 1051 AM PDT Thu Apr 4 2024
An anomalously cold low pressure system will bring rain, gusty
winds with gale force gusts possible at times, and rough seas to
the coastal waters through Friday. There is a 40% chance for
thunderstorms through Friday morning. Because temperatures are
going to be so cold, these thunderstorms in addition to lightning,
locally heavy rainfall, and locally gusty winds, will be capable
of producing copious amounts of small hail.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT this evening for SF Bay N of
Bay Bridge.
Small Craft Advisory until 9 PM PDT Friday for Mry Bay-Pigeon Pt
to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt Pinos
to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Gale Warning until 3 AM PDT Friday for Pt Arena to Pt Reyes 10-
60 NM.
Gale Warning until 9 PM PDT this evening for Pigeon Pt to Pt
Pinos 10-60 NM.
&&
SHORT TERM...MM
LONG TERM....MM
AVIATION...Bain
MARINE...Sarment
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www.youtube.com/nwsbayareaPreliminary Local Storm Report
National Weather Service San Francisco CA
414 PM PDT Thu Apr 4 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0410 PM Hail 1 S Sausalito 37.85N 122.49W
04/04/2024 E0.25 Inch Marin CA Trained Spotter
Storm spotter reported pea size hail at 4:10
PM on Wolfback Ridge Road in southern Marin
County.
&&
RKPreliminary Local Storm Report
National Weather Service San Francisco CA
429 PM PDT Thu Apr 4 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0429 PM Hail Morgan Hill 37.13N 121.64W
03/30/2024 E0.25 Inch Santa Clara CA Broadcast Media
Delayed LSR from 3/30/24 - report of pea
sized hail and heavy rain from Morgan Hill,
CA from a member of the broadcast media.
&&
RKPreliminary Local Storm Report
National Weather Service San Francisco CA
431 PM PDT Thu Apr 4 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0624 PM Hail Belmont 37.52N 122.30W
03/30/2024 E0.25 Inch San Mateo CA Broadcast Media
Delayed LSR report from 3/30/24 - a member
of broadcast media reported pea sized hail
at 6:24PM in Belmont, CA.
&&
RKPreliminary Local Storm Report
National Weather Service San Francisco CA
435 PM PDT Thu Apr 4 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0536 PM Hail Belmont 37.52N 122.30W
03/30/2024 E0.25 Inch San Mateo CA Public
Delayed LSR report for 3/30/24 - pea sized
hail reported by members of the public at
5:36PM in Belmont, CA.
&&
RKPreliminary Local Storm Report
National Weather Service San Francisco CA
442 PM PDT Thu Apr 4 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0454 PM Hail 7 NW Morgan Hill 37.21N 121.72W
03/30/2024 E0.25 Inch Santa Clara CA Broadcast Media
Delayed LSR report rom 3/30/24 - pea sized
hail reported by a member of the broadcast
media near Highway 101 and Bailey Avenue. A
severe thunderstorm warning was issued at
4:15PM for this region.
&&
RKThe San Francisco radar (KMUX), 17 km away, was scanning. The volume nearest the first event began at 01:43 UTC.
3 thunderstorm wind, 1 flood. Local standard time, as filed.
A large pine tree was blown down near Soquel.
Roadway flooding was reported at Westbound California Highway 4 and Westbound Interstate 80.
Powerlines were downed along Boulevard Way near Walnut Creek.
Tree down in roadway along Danville Boulevard near Walnut Creek. Time estimated via radar.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2024Every state in 2024This day in weather historyWarnings in California, April 2024
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: 1164961, 1164960, 1164962, 1164963.