Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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000
FXUS66 KMTR 280019
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
519 PM PDT Wed Mar 27 2024

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 120 PM PDT Wed Mar 27 2024

Unsettled conditions will prevail through the upcoming weekend.
Thunderstorms are most likely in the Friday afternoon through
Saturday timeframe in the post frontal environment. Then, warmer and
drier conditions are expected next week.

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 120 PM PDT Wed Mar 27 2024

Light rain is currently falling over the North Bay and will spread
southward overnight as a weak frontal boundary moves through the
region. Rainfall amounts are expected to be light amounting to 0.50-
1.00" in the coastal ranges, 0.25-0.50" in the low lands and coastal
areas, with <0.25" in the rain shadowed valleys through Thursday
morning.

Overnight lows will generally be in the low-to-mid 40s and near 50
degrees closer to the coastline. Thursday will feature cool and
mostly dry conditions, but cannot rule out lingering post frontal
rain showers especially over the northern half of the region.

&&

.LONG TERM...
(Thursday night through Tuesday)
Issued at 319 AM PDT Wed Mar 27 2024

After a brief pause in rain into Thursday evening, another
quicker-moving cold front and low pressure move into the upper
level trough pattern. The momentum of this next system will pull
the trough farther south and placing the trough axis into the Bay
Area. What does this mean? Increased moisture arriving into the
Bay Area and Central Coast compared to today`s system, and a cool-
looking momentum transfer on the forecast maps.

The overnight forecast update took some time looking at this second
system, and there still is a fair amount of variability possible.
The current trend pushes the focus of this system`s main rain band
farther south, increasing rain amounts along Big Sur, and reducing
them for the North Bay. Thunderstorm and shower chances behind the
rain band still look fairly evenly spread across the Bay Area and
Central Coast Friday night through Saturday evening, peaking around
25% during that time frame.

Rainfall totals from Thursday night through early Sunday morning
look to range from:

-0.5" to 1" for most areas
-1" to 1.25" for coastal low lands and interior North Bay
-1.25" to 2" for higher elevations along the coast
- and above 2" for the highest peaks along the coast with some
isolated areas on the Big Sur Coast reaching above 3"

Winds will be stronger with this next system, but the variability
makes it difficult to pin down which spots will be most affected,
but breezy to gusty conditions should be expected Friday afternoon
and into that night.

This will be something worth checking back in on within the next few
forecast updates.

Beyond these back-to-back systems, dry weather returns as an upper
level ridge snaps into place over the California Coast into the next
work week. This will push any oncoming rain systems North and into
the Washington and Oregon coasts.

&&

.AVIATION...
(00Z TAFS)
Issued at 518 PM PDT Wed Mar 27 2024

The first rain showers are moving through the region at this time,
bringing with them low clouds and MVFR CIGs. However, the main rain
band will come further into the evening today, beginning with the
North Bay, and slowly working its way down to the Monterey Bay by
about 10-12Z Thursday. Current breezy to gusty S/SW winds will turn
to become more westerly beyond the passage of the rain band and
associated cold front. As the rain moves through, terminals may
see slight reductions in visibility, though the main impact will
be lowered CIGs, brining MVFR conditions. After the rain band
passes, MVFR conditions will remain, though will become more
intermittent as low clouds and scattered showers continue to pass
through behind the front. By sunrise Thursday, shower activity
should cease for all terminals, with dry conditions returning for
the remainder of the day.


Vicinity of SFO...Rain and showery activity will continue through
the early morning of Thursday. At the moment, mainly scattered
showers are in the vicinity of the terminal, and winds are breezy
out of the south. It is not until after sunset tonight that the main
rain band will reach the terminal and winds turn to become more
westerly around 10 knots. Expect MVFR conditions to persist as
rain and low clouds impact the terminals through early Thursday.
Just before sunrise, rain activity is thought to diminish, and
conditions should improve to VFR as low clouds begin to filter
out.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Showers and breezy to gusty southerly winds
will impact the terminal this evening, but are thought to become
more scattered just beyond sunset. It will not be until closer to
10Z that KMRY sees more solid stratiform rain, around when winds
turn to become more westerly as the front moves through. MVFR CIGs
are expected to develop as rain moves in. Some scattered showers may
remain around sunrise and just beyond, though VFR and dry conditions
should return by the late morning of Thursday.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 518 PM PDT Wed Mar 27 2024

Winds have started to strengthen and turn SW ahead of a weak cold
front approaching the coastal zones. The approaching front has
slowed down with widespread light to moderate showers expected to
begin over the coastal waters this afternoon and evening. A
second, stronger low pressure system will reach the coastal waters
Friday, bringing moderate precipitation, gusty southerly winds,
and allow for wave heights to build. This second system will
create widespread conditions that are hazardous to small crafts.
Northwesterly swell continues with a new long period northwesterly
swell arriving early next week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT this evening for Pt Arena to
     Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-SF Bay N of
     Bay Bridge.

     Small Craft Advisory until 3 AM PDT Thursday for Mry Bay.

     Small Craft Advisory from 3 AM Thursday to 3 AM PDT Friday for
     Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory from 3 PM Thursday to 3 AM PDT Friday for
     Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras
     Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory from 9 AM Thursday to 3 AM PDT Friday for
     Pigeon Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...RGass
LONG TERM....Murdock
AVIATION...AC
MARINE...Kennedy

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