National Weather Service - Area Forecast Discussion

FXUS66 KMTR 242042

Area Forecast Discussion
National Weather Service San Francisco Bay Area
142 PM PDT Fri Mar 24 2023

.SYNOPSIS...Cool, dry weather will prevail through the upcoming
weekend with chilly to cold overnight and early morning
temperatures. Another round of wind and rain expected early next
week with the brunt of the storm`s impacts to be on Tuesday.


...Increasing Wind and Rain Potential Early Next Week... of 01:41 PM PDT Friday...Today through Monday:
Dry weather conditions prevail over the region this afternoon with
temperatures warming into the 50s for most. Breezy and at times
gusty northwest winds will also prevail through much of the
weekend, especially during the afternoon and evening hours. The
main weather impact through the weekend will be the chilly/cold
overnight temperatures with lows dropping into the low-to-mid 30s
for most interior areas, mid-to-upper 30s for areas just inland
from the coast and upper 30s to lower 40s elsewhere. Thus, a Frost
Advisory is in effect through the weekend for most interior areas
of the San Francisco Bay Area and Central Coast. Monday morning
also looks to be another cold one, yet confidence is lower with
respect to forecast temperatures due to timing of our next weather
system set to impact the region late Monday into Tuesday. It is
also worth nothing that if winds remain breezy into the overnight
and early morning hours, temperatures may not reach their lowest
potential. Regardless, cold temperatures through the weekend will
pose a threat to unsheltered populations and/or those who remain
without power.

Monday night through Wednesday night: An upper level system will
develop over the Gulf of Alaska late in the weekend and drop
southward into early next week. This system is forecast to develop
into a closed mid/upper low off of the Pacific Northwest coast and
will drive a frontal boundary across the region early Tuesday. Ahead
of this, southerly winds will increase and deeper moisture out over
the Pacific will advect inland to produce widespread light to
moderate rainfall and stronger winds. As the main boundary pushes
through, locally heavy rainfall is expected with an increased
potential for urban and small stream flooding as well as shallow
landslides and/or rockslides. Additionally, winds are likely to be
strongest with the frontal passage with gusts greater than 45 MPH
from at least Tuesday morning through the afternoon. While exact
details are difficult to nail down this far out, do expect another
round of wind impacts including; downed tree limbs, trees or power
poles resulting in isolated to potentially scattered power outages.

Post frontal rain showers look to continue into at least Tuesday
night or Wednesday as the core of the mid/upper level system shifts
inland over northern or central California. Precipitation from
Monday night into Wednesday is forecast to range from 0.50-1.25" for
most urban areas with up to 2.00" near the coast and in the North
Bay Valleys. Meanwhile, 1.50-3.00" amounts are expected in the
coastal ranges. These values are likely to change in the coming days
as the forecast comes into better focus. This is also true for the
strength of the winds and exact timing/location of these impacts.
Stay tuned...

Thursday and beyond: Drier, yet cool conditions will persist as the
aforementioned weather system exits the region. Weak high pressure
will then develop into next week resulting in a slight warming trend
in daytime temperatures. Meanwhile, light winds and clearing sky
conditions will lead to chilly/cold mornings.

&& of 11:07 AM Friday....For the 18Z TAFs. VFR. West
to northwest winds locally gusty during the afternoon to evening.
The WRF model forecasts increasing low level northerly winds from
northwestern coastal Sonoma county to coastal Monterey county tonight
and Saturday morning. Gusty low level northerly winds also extends
back across the Bay Area and north Central Coast in the ~ 12z-18z
timeframe Saturday. Will continue to monitor subsequent model
forecasts and observations, however at this time it`s not enough
to include low level wind shear in the 18z TAFs.

Vicinity of SFO...VFR. Northerly wind gradually shifting over to
northwesterly and westerly during the afternoon, with gusts near
30 knots afternoon to evening. Wind diminishing tonight to 10
knots then increasingly gusty to 25 to 30 knots Saturday afternoon
and evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. Winds mainly northwesterly to westerly
through the afternoon and evening, at speeds up to 10 to 15 knots.
Winds diminishing tonight and becoming light, westerly wind to 10
knots Saturday afternoon and evening.

&& of 09:08 AM PDT Friday...Strong northwest winds
continue today and persist through the weekend as high pressure
settles over the eastern Pacific. Moderate period northwest swell
will move in over the weekend, which combined with strong wind,
will create hazardous seas up to 15 feet in the outer waters. A
low pressure system will develop over the eastern Pacific bringing
rain and wind to coastal waters and bays from early to mid next


     .Tngt...Frost Advisory...CAZ503-504-506
             Frost Advisory...CAZ510-512>518-528-529
             SCA...SF Bay until 3 AM
             SCA...Mry Bay until 3 AM
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm




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NWS MTR Office Area Forecast Discussion