San Francisco, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

726
FXUS66 KMTR 190459
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
959 PM PDT Sun May 18 2025

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 309 AM PDT Sun May 18 2025

Another gusty day today with NW winds 30-40 mph. Elevated fire
weather concerns for far interior areas late tonight and early
Monday with a brief burst of offshore winds. Winds begin to
diminish Monday evening with a warm and dry trend through the rest
of the week.

&&

.UPDATE...
Issued at 915 PM PDT Sun May 18 2025

The short term forecast is in fine shape this evening with mostly
clear skies, though there is a little haze along the coastal
areas. Our next round of winds are anticipated to continue
tonight, through thus far winds are a little on the lighter side.
Still, we anticipate winds to gust in the 25 to 35 mph range,
with maybe some 40 to 45 mph wind gusts for elevations above 2500
feet. Monday afternoon will feature dry conditions with winds
abating through the day. This may serve to elevate the grass/brush
fire potential again, though reduced winds should help keep
things in check.

&&

.SHORT TERM...
Issued at 139 PM PDT Sun May 18 2025
(This evening through Monday)

Key Messages
-Windy northerly flow persists into Monday
-Elevated fire weather concerns in flashier fuels

Blue bird skies blanket the region today. Temperatures are running
a few degrees warmer than yesterday thanks to building high
pressure. The longwave pattern shows the upper level trough that
brought drizzle yesterday is now sweeping through the Four Corners
and high pressure over the EPac is filling in behind it.

This evening through Monday: The aforementioned high pressure
over the EPac will continue to build at the surface and aloft. At
the surface, higher pressure builds along the OR/CA border with
lower pressure inland and southward. This orientation will enhance
the SFO-ACV (N-S) pressure gradient. As such, winds will continue
to increase. We`ve already seen a slight increase in wind speed
since this morning. Hi-res and mesoscale models continue to
advertise a coastal jet setting up just off of Point Reyes this
evening with gusts in the 40-50 kt range. This also corresponds
with the location of our Storm Warning over the coastal waters.
Fortunately, it won`t be that strong over land. However, still
expecting some gusts along the coast and higher terrain. Winds
remain breezy through Monday.

For a fire weather perspective, local WRF model continues to show
a shift of winds to N to NE over the North and East Bay at 2,500
ft. While this direction will usher in some drier air predicted RH
values do no reach critical levels. However, given the finer fuels
(like grass) there are some concerns of rapid spread if a fire
were to start.

&&

.LONG TERM...
Issued at 230 PM PDT Sun May 18 2025
(Monday night through next Saturday)

Key Messages
-Warming and Drying trend through midweek
-Moderate HeatRisk interior locations Wednesday

Winds will finally ease and the N-S pressure gradient begins to
relax Monday night into Tuesday. The warming and drying trend
will continue through at least Wednesday. Each day temperatures
will warm and additional five degrees. Minor HeatRisk will be
possible for much of the region Tuesday and Wednesday with pockets
of Moderate HeatRisk on Wednesday for far interior locations and
the city of San Jose. Those HeatRisk values translate to max
temperatures for 80s to mid 90s. Onshore flow will keep
coastal/bay shoreline areas in check with max temperatures in the
60s and 70s.

A breakdown of the ridge by Thursday will kick off a gradual
cooling trend that will last into next weekend. Simply put, a
little bit of a temperature roller coaster ride this week.

&&

.AVIATION...
(06Z TAFS)
Issued at 959 PM PDT Sun May 18 2025

The northerly ACV-SFO pressure gradient is 6.7 mb, the UKI-STS
pressure gradient is 1.9 mb. The SFO-SAC pressure gradient is 3.1
mb. A surface high pressure ridge over the eastern Pacific continues
to nudge eastward ahead of a weak surface trough over far northern
California. Surface high pressure ridging over northernmost California
continues through Monday. Dry northerly to northwesterly winds at the
surface continue tonight and Monday, except local upslope cooling and
night-time radiative cooling may result in a few patches of stratus
and/or fog /IFR/ e.g. KMRY 06z TAF Monday morning. Mixing winds, diurnal
surface warming along with a continued northerly wind direction Monday
will result in VFR. Sea spray into the air due to gusty winds over
the coastal waters will also cause areas of hazy/haze conditions near
the immediate coastline; sea salt is hygroscopic condensation nuclei
which favors stratus and fog under other usually favorable development
conditions e.g. night-time radiative cooling.

Vicinity of SFO...West wind decreasing overnight to Monday morning
to near 10 knots then increasing to 25 to 34 knots, possibly higher
gusts, Monday afternoon and evening beginning 20z and lasting through
04z Tuesday (Monday evening). A dry cool front from the northwest will
move through Monday night to early Tuesday morning which may produce
a secondary peak in west winds sometime tomorrow night/early Tuesday.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...A dry air mass on northwest winds results
in moderate to high confidence VFR for the terminals through mid
to late evening, thereafter night-time cooling and residual upsloping
winds combining may help a few areas of stratus /IFR/ ceilings to
form. Tempo IFR forecast KMRY Monday morning, otherwise sufficient
mixing Monday redevelops resulting in VFR. West to northwest winds
15 to 25 knots developing Monday afternoon and early evening.

&&

.MARINE...
(Tonight through next Saturday)
Issued at 953 PM PDT Sun May 18 2025

Gale warnings continue for the coastal waters through Monday
evening due to strong northwesterly winds. Hazardous seas will
persist through Thursday with strong northwesterly winds, gusts
near gale force and rough to very rough seas.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM to 9 PM PDT Monday for SF Bay N
     of Bay Bridge.

     Small Craft Advisory from 9 AM to 9 PM PDT Monday for Mry Bay.

     Gale Warning until 9 PM PDT Monday for Pigeon Pt to Pt Pinos 0-
     10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-
     10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras
     Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Canepa
MARINE...Canepa

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