Alert archive / California / High Surf Advisories in 2021

High Surf Advisory 6, NWS San Francisco Bay Area, CA

January 16, 20216 counties in California

NWS San Francisco Bay Area, CA issued this high surf advisory at Jan 16, 2021, 7:08 PM PST for 6 counties in California. It took effect at Jan 17, 2021, 6:00 AM PST. It was in force for 36 hr.

The area

The counties it named.

The facts

Issued
Jan 16, 2021, 7:08 PM PST (03:08 UTC)
In effect from
Jan 17, 2021, 6:00 AM PST
Expired
Jan 18, 2021, 6:00 PM PST
In force
36 hr
Issued by
NWS San Francisco Bay Area, CA

Counties City and County of San Francisco, CA, Marin County, CA, Monterey County, CA, San Mateo County, CA, Santa Cruz County, CA, Sonoma County, CA

The radar

The San Francisco radar (KMUX), 53 km from the middle of the area, began a volume at 03:09 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Oakland, CA (KOAK), launched 00:00Z, 3.1 hours before the alert went out and 26 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Oakland, CA at 00:00Z on 2021-01-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Oakland, CA at 00:00Z on 2021-01-17The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 8 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1964 m above ground
0-6 km bulk shear
22 kt
0-1 km storm-relative helicity
8 m²/s²
0-3 km storm-relative helicity
45 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

643 
WHUS46 KMTR 170308
CFWMTR

Coastal Hazard Message
National Weather Service San Francisco CA
708 PM PST Sat Jan 16 2021

...A large, long period northwest swell resulting in hazardous 
conditions from coastal Sonoma County to coastal Monterey 
County...

.A large, long period northwest swell arrives on Sunday morning
and will result in hazardous conditions in the surf zone through 
Monday afternoon. Forerunners are expected to arrive at 3 to 7
feet with a period of 22 to 24 seconds, increasing the risk of
sneaker waves. Swell heights are then expected to build through
Sunday with breaking waves of 18 to 22 feet, locally higher at 
favored breakpoints, expected along west to northwest facing 
beaches. As a result, a High Surf Advisory is in effect through 
Monday afternoon for west and northwest facing beaches while a 
Beach Hazard Statement has been issued for the northern Monterey 
Bay including Santa Cruz. With warm temperatures present over a
holiday weekend, continuous vigilance is advised. Never turn your
back to the ocean.

CAZ006-505-509-530-171400-
/O.NEW.KMTR.SU.Y.0006.210117T1400Z-210118T2300Z/
San Francisco-
Coastal North Bay Including Point Reyes National Seashore-
San Francisco Peninsula Coast-
Southern Monterey Bay and Big Sur Coast-
708 PM PST Sat Jan 16 2021

...HIGH SURF ADVISORY IN EFFECT FROM 6 AM SUNDAY TO 3 PM PST
MONDAY...

* WHAT...Large breaking waves of 18 to 22 feet, locally higher at
  favored breakpoints, can be expected along west to northwest 
  facing beaches..

* WHERE...San Francisco, Coastal North Bay Including Point Reyes 
  National Seashore, San Francisco Peninsula Coast and Southern 
  Monterey Bay and Big Sur Coast.

* WHEN...From 6 AM Sunday to 3 PM PST Monday.

* IMPACTS...Dangerous swimming and surfing conditions and
  localized beach erosion. People are strongly urged to remain
  well back from the ocean as these types of events often result
  in an increase in cold water rescues and the loss of life.

* ADDITIONAL DETAILS...Unseasonably warm temperatures this 
  holiday weekend will likely attract more people to the coast. 
  Individuals should be reminded that our coastline and the cold 
  Pacific waters remain dangerous as these larger than normal 
  waves impact the coast. Extreme caution is advised when visiting
  area beaches..

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Large breaking waves along the coast will lead to increased wave
run-up on beaches with waves topping and washing over large rocks
and jetties. Use extra caution near the surf zone as these large
waves will be capable of sweeping people into the frigid and
turbulent ocean water. Cold water shock may cause cardiac arrest,
and it also can cause an involuntary gasp reflex causing
drowning, even for a good swimmer. The surf zone will be
dangerous due to strong currents and powerful breaking waves.

&&

$$

CAZ529-171400-
/O.NEW.KMTR.BH.S.0002.210117T1400Z-210118T2300Z/
Northern Monterey Bay-
708 PM PST Sat Jan 16 2021

...BEACH HAZARDS STATEMENT IN EFFECT FROM 6 AM PST SUNDAY THROUGH
MONDAY AFTERNOON...

* WHAT...Breaking waves 12 to 15 feet possible in favored break 
  points.

* WHERE...Northern Monterey Bay.

* WHEN...From 6 AM PST Sunday through Monday afternoon.

* IMPACTS...Dangerous swimming and surfing conditions with 
  strong rip currents and sneaker waves. People are strongly 
  urged to remain well back from the ocean as these types of 
  events often result in an increase in cold water rescues and 
  the loss of life.

* ADDITIONAL DETAILS...While these waves are not as large as our 
  previous events in the most recent days, unseasonable warm 
  temperatures this holiday weekend will likely attract more 
  people to the coast. Individuals should be reminded that our 
  coastline and the cold Pacific waters remain dangerous as 
  these larger than normal waves impact the coast. Extreme 
  caution is advised when visiting area beaches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Beach Hazard Statement for sneaker waves means that conditions
are present to support a heightened risk of unsuspecting beach
goers being swept into the sea by a wave. People walking along
the beach should never turn their back to the sea.

Remain out of the water to avoid hazardous swimming conditions.
Rock jetties can be deadly in such conditions, stay off the
rocks.

&&

$$
5 follow-up statements
146 
WHUS46 KMTR 171010
CFWMTR

Coastal Hazard Message
National Weather Service San Francisco CA
210 AM PST Sun Jan 17 2021

...A large, very long period northwest swell will result in 
hazardous beach conditions along the coast...

.A large, very long period northwest swell will arrive Sunday 
morning and result in hazardous conditions along the coast through
Monday afternoon. Forerunners are expected to arrive at 3 to 7 
feet with a period of 22 to 24 seconds, increasing the risk of 
sneaker waves. Swell heights are then expected to build through 
Sunday with breaking waves of 18 to 22 feet, locally higher at 
favored breakpoints, expected along west to northwest facing 
beaches. As a result, a High Surf Advisory is in effect through 
Monday afternoon for west and northwest facing beaches while a 
Beach Hazard Statement has been issued for the northern Monterey 
Bay including Santa Cruz. With warm temperatures present over a 
holiday weekend, continuous vigilance is advised. Never turn your 
back to the ocean.

CAZ006-505-509-530-172300-
/O.CON.KMTR.SU.Y.0006.210117T1400Z-210118T2300Z/
San Francisco-
Coastal North Bay Including Point Reyes National Seashore-
San Francisco Peninsula Coast-
Southern Monterey Bay and Big Sur Coast-
210 AM PST Sun Jan 17 2021

...HIGH SURF ADVISORY REMAINS IN EFFECT FROM 6 AM THIS MORNING TO
3 PM PST MONDAY...

* WHAT...Initially on Sunday, very long period forerunners will
  increase the risk of sneaker waves and rip currents. Building
  swell will then bring large breaking waves of 18 to 22 feet, 
  locally higher at favored breakpoints, can be expected along 
  west to northwest facing beaches.

* WHERE...San Francisco, Coastal North Bay Including Point Reyes 
  National Seashore, San Francisco Peninsula Coast and Southern 
  Monterey Bay and Big Sur Coast.

* WHEN...From 6 AM Sunday to 3 PM PST Monday.

* IMPACTS...Dangerous swimming and surfing conditions and 
  localized beach erosion. People are strongly urged to remain 
  well back from the ocean as these types of events often result 
  in an increase in cold water rescues and the loss of life.

* ADDITIONAL DETAILS...Unseasonably warm temperatures this 
  holiday weekend will likely attract more people to the coast. 
  Individuals should be reminded that our coastline and the cold 
  Pacific waters remain dangerous as these larger than normal 
  waves impact the coast. Extreme caution is advised when 
  visiting area beaches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Large breaking waves along the coast will lead to increased wave
run-up on beaches with waves topping and washing over large rocks
and jetties. Use extra caution near the surf zone as these large
waves will be capable of sweeping people into the frigid and
turbulent ocean water. Cold water shock may cause cardiac arrest,
and it also can cause an involuntary gasp reflex causing
drowning, even for a good swimmer. The surf zone will be
dangerous due to strong currents and powerful breaking waves.

&&

$$

CAZ529-172300-
/O.CON.KMTR.BH.S.0002.210117T1400Z-210118T2300Z/
Northern Monterey Bay-
210 AM PST Sun Jan 17 2021

...BEACH HAZARDS STATEMENT REMAINS IN EFFECT FROM 6 AM PST THIS
MORNING THROUGH MONDAY AFTERNOON...

* WHAT...An increased risk of sneaker waves Sunday morning. Then
  building swell will bring breaking waves 12 to 15 feet at 
  favored break points.

* WHERE...Northern Monterey Bay.

* WHEN...From 6 AM PST Sunday through Monday afternoon.

* IMPACTS...Dangerous swimming and surfing conditions with 
  strong rip currents and sneaker waves. People are strongly 
  urged to remain well back from the ocean as these types of 
  events often result in an increase in cold water rescues and 
  the loss of life.

* ADDITIONAL DETAILS...While these waves are not as large as our 
  previous events in the most recent days, unseasonable warm 
  temperatures this holiday weekend will likely attract more 
  people to the coast. Individuals should be reminded that our 
  coastline and the cold Pacific waters remain dangerous as 
  these larger than normal waves impact the coast. Extreme 
  caution is advised when visiting area beaches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Beach Hazard Statement for sneaker waves means that conditions
are present to support a heightened risk of unsuspecting beach
goers being swept into the sea by a wave. People walking along
the beach should never turn their back to the sea.

Remain out of the water to avoid hazardous swimming conditions.
Rock jetties can be deadly in such conditions, stay off the
rocks.

&&

$$
712 
WHUS46 KMTR 172202
CFWMTR

Coastal Hazard Message
National Weather Service San Francisco CA
202 PM PST Sun Jan 17 2021

...A large, very long period northwest swell will result in
hazardous beach conditions along the coast...

.A large, very long period northwest swell will result in 
hazardous conditions along the coast through Monday afternoon. 
Forerunners are expected at 3 to 7 feet with a period of 22 to 24
seconds, increasing the risk of sneaker waves. Swell heights are 
then expected to build into Monday with breaking waves of 18 to 
22 feet, locally higher at favored breakpoints, expected along 
west to northwest facing beaches. As a result, a High Surf 
Advisory is in effect through Monday afternoon for west and 
northwest facing beaches while a Beach Hazard Statement is in
effect for the northern Monterey Bay including Santa Cruz. With 
warm temperatures present over a holiday weekend, continuous 
vigilance is advised. Never turn your back to the ocean.

CAZ006-505-509-530-180700-
/O.CON.KMTR.SU.Y.0006.000000T0000Z-210118T2300Z/
San Francisco-
Coastal North Bay Including Point Reyes National Seashore-
San Francisco Peninsula Coast-
Southern Monterey Bay and Big Sur Coast-
202 PM PST Sun Jan 17 2021

...HIGH SURF ADVISORY REMAINS IN EFFECT UNTIL 3 PM PST MONDAY...

* WHAT...Initially, very long period forerunners will increase 
  the risk of sneaker waves and rip currents. Building swell will 
  then bring large breaking waves of 18 to 22 feet, locally higher
  at favored breakpoints, can be expected along west to northwest
  facing beaches.

* WHERE...San Francisco, Coastal North Bay Including Point Reyes 
  National Seashore, San Francisco Peninsula Coast and Southern 
  Monterey Bay and Big Sur Coast.

* WHEN...Until 3 PM PST Monday.

* IMPACTS...Dangerous swimming and surfing conditions and 
  localized beach erosion. People are strongly urged to remain 
  well back from the ocean as these types of events often result 
  in an increase in cold water rescues and the loss of life.

* ADDITIONAL DETAILS...Unseasonably warm temperatures this 
  holiday weekend will likely attract more people to the coast. 
  Individuals should be reminded that our coastline and the cold 
  Pacific waters remain dangerous as these larger than normal 
  waves impact the coast. Extreme caution is advised when 
  visiting area beaches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Large breaking waves along the coast will lead to increased wave
run-up on beaches with waves topping and washing over large rocks
and jetties. Use extra caution near the surf zone as these large
waves will be capable of sweeping people into the frigid and
turbulent ocean water. Cold water shock may cause cardiac arrest,
and it also can cause an involuntary gasp reflex causing
drowning, even for a good swimmer. The surf zone will be
dangerous due to strong currents and powerful breaking waves.

&&

$$

CAZ529-180700-
/O.CON.KMTR.BH.S.0002.000000T0000Z-210118T2300Z/
Northern Monterey Bay-
202 PM PST Sun Jan 17 2021

...BEACH HAZARDS STATEMENT REMAINS IN EFFECT THROUGH MONDAY
AFTERNOON...

* WHAT...An increased risk of sneaker waves into Sunday night. 
  Then building swell will bring breaking waves 12 to 15 feet at 
  favored break points.

* WHERE...Northern Monterey Bay.

* WHEN...Through Monday afternoon.

* IMPACTS...Dangerous swimming and surfing conditions with 
  strong rip currents and sneaker waves. People are strongly 
  urged to remain well back from the ocean as these types of 
  events often result in an increase in cold water rescues and 
  the loss of life.

* ADDITIONAL DETAILS...While these waves are not as large as our 
  previous events in the most recent days, unseasonable warm 
  temperatures this holiday weekend will likely attract more 
  people to the coast. Individuals should be reminded that our 
  coastline and the cold Pacific waters remain dangerous as 
  these larger than normal waves impact the coast. Extreme 
  caution is advised when visiting area beaches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Beach Hazard Statement for sneaker waves means that conditions
are present to support a heightened risk of unsuspecting beach
goers being swept into the sea by a wave. People walking along
the beach should never turn their back to the sea.

Remain out of the water to avoid hazardous swimming conditions.
Rock jetties can be deadly in such conditions, stay off the
rocks.

&&

$$
170 
WHUS46 KMTR 180627
CFWMTR

Coastal Hazard Message
National Weather Service San Francisco CA
1027 PM PST Sun Jan 17 2021

...A large, very long period northwest swell will result in
hazardous beach conditions along the coast...

A large, very long period northwest swell has arrived to the
coastal waters, creating hazardous conditions along the coast 
through Monday afternoon. Large swell heights are expected to 
continue into Monday with breaking waves of 18 to 22 feet, 
locally higher at favored breakpoints, along west to northwest 
facing beaches. As a result, a High Surf Advisory is in effect 
through this afternoon for west and northwest facing beaches 
while a Beach Hazard Statement is in effect for the northern 
Monterey Bay including Santa Cruz. With warm temperatures present 
over a holiday weekend, continuous vigilance is advised. Never 
turn your back to the ocean.

CAZ006-505-509-530-181100-
/O.CON.KMTR.SU.Y.0006.000000T0000Z-210118T2300Z/
San Francisco-
Coastal North Bay Including Point Reyes National Seashore-
San Francisco Peninsula Coast-
Southern Monterey Bay and Big Sur Coast-
1027 PM PST Sun Jan 17 2021

...HIGH SURF ADVISORY REMAINS IN EFFECT UNTIL 3 PM PST MONDAY...

* WHAT...Large breaking waves of 18 to 22 feet, locally higher
  at favored breakpoints, can be expected along west to northwest
  facing beaches..

* WHERE...San Francisco, Coastal North Bay Including Point Reyes 
  National Seashore, San Francisco Peninsula Coast and Southern 
  Monterey Bay and Big Sur Coast.

* WHEN...Until 3 PM PST Monday.

* IMPACTS...Dangerous swimming and surfing conditions and 
  localized beach erosion. People are strongly urged to remain 
  well back from the ocean as these types of events often result 
  in an increase in cold water rescues and the loss of life.

* ADDITIONAL DETAILS...Unseasonably warm temperatures this 
  holiday weekend will likely attract more people to the coast. 
  Individuals should be reminded that our coastline and the cold 
  Pacific waters remain dangerous as these larger than normal 
  waves impact the coast. Extreme caution is advised when 
  visiting area beaches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Inexperienced swimmers should remain out of the water due to
dangerous surf conditions.

&&

$$

CAZ529-181100-
/O.CON.KMTR.BH.S.0002.000000T0000Z-210118T2300Z/
Northern Monterey Bay-
1027 PM PST Sun Jan 17 2021

...BEACH HAZARDS STATEMENT REMAINS IN EFFECT THROUGH MONDAY
AFTERNOON...

* WHAT...Building swell will bring breaking waves 12 to 15 feet 
  at favored break points..

* WHERE...Northern Monterey Bay.

* WHEN...Through 3 P.M. Monday afternoon.

* IMPACTS...Dangerous swimming and surfing conditions with 
  strong rip currents and sneaker waves. People are strongly 
  urged to remain well back from the ocean as these types of 
  events often result in an increase in cold water rescues and 
  the loss of life.

* ADDITIONAL DETAILS...While these waves are not as large as in
  our most recent events, unseasonable warm temperatures this 
  holiday weekend will likely attract more people to the coast. 
  Individuals should be reminded that our coastline and the cold 
  Pacific waters remain dangerous as these larger than normal 
  waves impact the coast. Extreme caution is advised when visiting
  area beaches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Remain out of the water to avoid hazardous swimming conditions.

&&

$$
168 
WHUS46 KMTR 181004
CFWMTR

Coastal Hazard Message
National Weather Service San Francisco CA
204 AM PST Mon Jan 18 2021

...A large, very long period northwest swell will result in
hazardous beach conditions along the coast...

A large, very long period northwest swell has arrived to the
coastal waters, creating hazardous conditions along the coast
through the day today. Large swell heights are expected with 
breaking waves of 18 to 22 feet, locally higher at favored 
breakpoints, along west to northwest facing beaches. As a result, 
a High Surf Advisory is in effect through this afternoon for west 
and northwest facing beaches while a Beach Hazard Statement is in 
effect for the northern Monterey Bay including Santa Cruz. With 
warm temperatures present over a holiday weekend, continuous 
vigilance is advised. Never turn your back to the ocean.

CAZ006-505-509-530-190200-
/O.EXT.KMTR.SU.Y.0006.000000T0000Z-210119T0200Z/
San Francisco-
Coastal North Bay Including Point Reyes National Seashore-
San Francisco Peninsula Coast-
Southern Monterey Bay and Big Sur Coast-
204 AM PST Mon Jan 18 2021

...HIGH SURF ADVISORY NOW IN EFFECT UNTIL 6 PM PST THIS EVENING...

* WHAT...Large breaking waves of 18 to 22 feet, locally higher 
  at favored breakpoints, can be expected along west to 
  northwest facing beaches.

* WHERE...San Francisco, Coastal North Bay Including Point Reyes 
  National Seashore, San Francisco Peninsula Coast and Southern 
  Monterey Bay and Big Sur Coast.

* WHEN...Until 6 PM PST this evening.

* IMPACTS...Dangerous swimming and surfing conditions and 
  localized beach erosion. People are strongly urged to remain 
  well back from the ocean as these types of events often result 
  in an increase in cold water rescues and the loss of life.

* ADDITIONAL DETAILS...Unseasonably warm temperatures this 
  holiday weekend will likely attract more people to the coast. 
  Individuals should be reminded that our coastline and the cold 
  Pacific waters remain dangerous as these larger than normal 
  waves impact the coast. Extreme caution is advised when 
  visiting area beaches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Inexperienced swimmers should remain out of the water due to
dangerous surf conditions.

&&

$$

CAZ529-190200-
/O.EXT.KMTR.BH.S.0002.000000T0000Z-210119T0200Z/
Northern Monterey Bay-
204 AM PST Mon Jan 18 2021

...BEACH HAZARDS STATEMENT NOW IN EFFECT UNTIL 6 PM THIS 
EVENING...

* WHAT...Building swell will bring breaking waves 12 to 15 feet 
  at favored break points.

* WHERE...Northern Monterey Bay.

* WHEN...Until 6 PM PST Monday evening.

* IMPACTS...Dangerous swimming and surfing conditions with 
  strong rip currents and sneaker waves. People are strongly 
  urged to remain well back from the ocean as these types of 
  events often result in an increase in cold water rescues and 
  the loss of life.

* ADDITIONAL DETAILS...While these waves are not as large as in 
  our most recent events, unseasonable warm temperatures this 
  holiday weekend will likely attract more people to the coast. 
  Individuals should be reminded that our coastline and the cold 
  Pacific waters remain dangerous as these larger than normal 
  waves impact the coast. Extreme caution is advised when 
  visiting area beaches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Remain out of the water to avoid hazardous swimming conditions.

&&

$$
013 
WHUS46 KMTR 190150
CFWMTR

Coastal Hazard Message
National Weather Service San Francisco CA
550 PM PST Mon Jan 18 2021

CAZ006-505-509-530-190300-
/O.EXP.KMTR.SU.Y.0006.000000T0000Z-210119T0200Z/
San Francisco-
Coastal North Bay Including Point Reyes National Seashore-
San Francisco Peninsula Coast-
Southern Monterey Bay and Big Sur Coast-
550 PM PST Mon Jan 18 2021

...HIGH SURF ADVISORY WILL EXPIRE AT 6 PM PST THIS EVENING...

Wave heights are slowly diminishing as the period reduces to 15 
to 17 seconds. The advisory is allowed to expire since the waves 
are subsiding; however, the ocean remains very active. Continued
vigilance and caution along the California coast is advised.

$$

CAZ529-190300-
/O.EXP.KMTR.BH.S.0002.000000T0000Z-210119T0200Z/
Northern Monterey Bay-
550 PM PST Mon Jan 18 2021

...BEACH HAZARDS STATEMENT WILL EXPIRE AT 6 PM PST THIS EVENING...

Wave heights are slowly diminishing as the period reduces to 14 
to 16 seconds. The beach hazard statement is allowed to expire 
since the waves are subsiding; however, the ocean remains very 
active. Continued vigilance and caution along the California coast
is advised.

$$

What forecasters said that day

The local office's own words before this high surf advisory went out, 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 this high surf advisory went out at Jan 16, 3:44 PM PST, 3 hours 24 minutes earlier.

Area forecast discussion, Jan 16, 3:44 PM PST, 3 hours 24 minutes before
Area Forecast Discussion
National Weather Service San Francisco Bay Area
344 PM PST Sat Jan 16 2021

.SYNOPSIS...A warming and drying trend will continue through this
weekend as high pressure builds over the state. Two back to back
low pressure systems to our east will produce breezy to gusty
offshore flow Sunday night through Tuesday evening. Cooling trend
is forecast from Wednesday through Friday.

&&

.DISCUSSION...as of 02:05 PM PST Saturday...Pinch. Yes, it is
January. About the only way we can tell right now is due to a
highly active North Pacific that has produced some of the most
consistent swell/surf for our area in recent memory. Otherwise a
stout upper ridge is dominating the Bay Area and Monterey Bay
region, bringing unseasonably warm and dry conditions. Today there
has been a weak offshore component to the winds up a few thousand
feet. This has really toyed with our area microclimates to the
point that we have seen some serious nano climates. A RAWS site
down toward Big Sur popped to 90 today, where two ridges away it
was only in the mid 70s. This is the power of wind on air in
action.

While the offshore flow has only played with the temperatures
today, Sunday evening will bring a wholesale shift in what wind
can do. The upper ridge that has been dominate for the last
several days will be pushed on by upper low pressure as it dives
from the north over California. This will setup a tightening
pressure gradient across the Bay Area and Monterey Bay regions.
Current model forecast are indicating a strong SFO-WMC gradient on
the order of 13 to 17 mb, which is a significant offshore wind set
up. EC ENS mean standardized anomalies are showing 2 to 3 standard
deviations. In short, this is a solid offshore event taking shape.
While we have seen strong offshore wind events in the past, the
piece that makes this one stand out is the spatial coverage.
Typically in our "offshore season", October, we see set ups favor
an area such as North Bay. This time around we're looking 925mb
winds in the 40 to 55 kt range from North Bay through Monterey
County. This is a widespread event.

Two pieces to cover. 1) The wind itself. Sustained winds are
forecast to be in the 5 to 20 mph range though populated areas,
with the exact value being location dependent. Sustained winds in
the hills and mountains are forecast to be in the 15 to 30 mph
range. However, in events like this, it's the gusts that really
do the damage. Occasional gusts in valley populated locations
could be in the 20 to 45 mph range, again depending upon location.
While in the hills and mountains, expect to see maximum gusts
reach 45 to 60 mph range with the possibility of an isolated site
or two trying to jump into the 70+ arena. Winds are dangerous in
general due to fall and blowing trees and debris, but a mid-dry-
winter wind event like this can be especially concerning for life
and property safety. Branches are dry and brittle in many areas
which means they are prone to break and fall, while trees may
simply topple in some of the stronger gusts. Please know your
risk. Take care of anything you need to take of before the wind
hits Sunday evening. Wind statistically is the second leading
cause of death due to weather in our area. Too many people have
lost their lives to falling trees. 2) While we have seen a little
rain this winter, it hasn't been a lot and most areas are running
about 30% of average on the water year thus far. The rain we have
had has helped the larger trees (fuels) to get some moisture in
them. However, the fine fuels such as grasses and bushes moisten
up quickly and dry out quickly. With the dry warm weather that
has been occurring the last few days has shown itself in the fine
fuels. Many areas have brown grasses and bone dry shrubs. With the
wind set up locking in, fire becomes a concern, mainly in the
grasses. Think of it like an early fire season set up. We have dry
grasses, gusty winds coming, and plummeting relative humidities.
Since the larger fuels still have moisture, we are not thinking of
a red flag warning at this point, but will be watching closely
each shift to analyze incoming data. In short, fire concerns
exist. Be fire smart, don't be that spark.

Looking down the road of the week, models continue to hold on to a
slight pattern shift toward the end of the week with a slight
chance of rain on Friday. Don't get your hopes up though, the QPF
doesn't look that great. Either way, it'd be good to have a cool
down and at least a chance of a few drops of rain.

&&

.AVIATION...as of 03:42 PM PST Saturday...For the 00Z TAFs. There
is a patch of stratus off the coast providing intermittent low
clouds on the Monterey Peninsula, but otherwise VFR across the
Bay Area and the Central Coast. Low chance for low clouds and fog
overnight as winds become offshore and conditions dry out. Winds
aloft are expected to increase late tonight and early tomorrow
morning with LLWS of about 25-30 kt into Sunday afternoon. After
a brief lull in winds aloft expect winds to increase again
tomorrow night and into the next couple of days during bursts of
offshore winds.

Vicinity of KSFO...VFR. Winds are still onshore and breezy, but
will subside over the next several hours. Stratus lingers along
the coast, but with winds expected to be light and offshore,
conditions should remain VFR through the night. LLWS is in the
TAF as winds allow become 25-30kt early Sunday morning. Winds will
increase and be breezy once again Sunday afternoon.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Stratus clouds approximately 400 ft AGL
off the coast have become annoying as they spilled over the KMRY
terminal briefly and shows moving toward the Salinas Valley.
Winds over the ocean are northwesterly, so there is still a chance
for the low clouds to push back over the terminals in the next
couple of hours, but is not expected through the night. VFR with
light winds is forecast. Winds will once again be breezy Sunday
afternoon.

&&

.BEACHES...as of 09:26 AM PST Saturday...A moderate, long period
northwest swell will impact the coastline through this evening
resulting in hazardous conditions in the surf zone. Breaking waves
of 15 to 17 feet (locally up to 20 feet at favored breakpoints)
can be expected along west to northwest facing beaches.

While these waves are not as large as our previous events in the
most recent days, unseasonable warm temperatures this holiday
weekend will likely attract more people to the coast. Individuals
should be reminded that our coastline and the cold Pacific waters
remain dangerous as these larger than normal waves impact the
coast. Extreme caution is advised when visiting area beaches.

Additionally, a second very long period and larger west to
northwest swell will arrive on Sunday. Additional hazard products
will likely be needed once the current ones expire.

&&

.CLIMATE...Record Type: Highs (Old Record Temp/Year)

                    Jan 16th    Jan 17th    Jan 18th

Santa Rosa          74/1991     71/1991     74/1976
Kentfield           70/2009     71/1994     70/2014
Napa                76/1920     72/1920     76/1920
Richmond            74/2014     73/2009     71/2018
Livermore           75/1920     70/1986     74/1919
San Francisco       72/2014     73/1991     70/1920
SFO                 73/2014     70/1991     68/1948
Redwood City        74/2014     77/1948     74/2009
Half Moon Bay       76/2014*    75/2009     72/2009
Oakland Downtown    78/2014*    74/2014     73/2014
San Jose            73/2014     76/1920     74/1920
Gilroy              76/2014     77/2014     80/2014*
Santa Cruz          84/2014     83/2014     83/1920
Salinas Airport     84/2014     86/2014*    81/1994
King City           85/1976     86/2014*    83/2009

*Monthly Records

&&

.MARINE...as of 02:03 PM PST Saturday...Northwest winds will
gradually increase into tonight while a moderate to large west
swell persists over the waters into the evening. Isolated gusts
near gale force will be possible this afternoon and evening along
the coast north of Point Reyes and south of Point Sur. The
combination of swell and breezy winds will result in hazardous
seas conditions, particularly for smaller vessels. Winds will
shift more northerly tomorrow to tomorrow night and increase as
offshore winds pick up over land. These stronger winds will then
continue into early next week with gale force conditions likely. A
second larger long period northwest swell will arrive late
tomorrow.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...High Surf Advisory...CAZ006-505-509-530
             SCA...Mry Bay until 9 PM
             SCA...Pt Reyes to Pigeon Pt 0-10 nm until 9 PM
             SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm

&&

PUBLIC FORECAST: BFG
AVIATION: DK
MARINE: AS

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The office that day

Everything else NWS San Francisco Bay Area, CA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jan 16, 7:08 PM PSTBeach Hazards StatementMTRSanta Cruz47 hr
Jan 17, 2:18 AM PSTGale WarningMTR60 hr
Jan 17, 2:18 AM PSTSmall Craft AdvisoryMTR43 hr
Jan 17, 12:25 PM PSTFire Weather WatchMTRMonterey, San Benito21 hr
Jan 17, 1:39 PM PSTHigh Wind WarningMTRMonterey, San Mateo, Santa Clara, Santa Cruz44 hr
Jan 17, 2:13 PM PSTGale WatchMTR12 hr

Nearby

High Surf Advisories in California, 2021Every high surf advisory in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.