FXUS66 KMTR 011916
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1216 PM PDT Wed Apr 1 2026
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 1214 PM PDT Wed Apr 1 2026
- Unsettled weather today and tonight with cool, gusty, and rainy
conditions
- Warming and drying trend kicks off Thursday with well above
normal temperatures and moderate offshore flow into the weekend
&&
.SHORT TERM...
Issued at 1214 PM PDT Wed Apr 1 2026
(This evening through Thursday)
A gale force low pressure system off the coast of the
Washington/Canada border and its attendant cold front will be our
weather maker the next 24 hours. Ahead of the cold front,
southwesterly winds will increase with gusts of 20-30 mph and up to
40 mph in the higher terrain. Isolated pre-frontal rain showers are
possible with the best chances for rain holding off until later this
afternoon, slowly spreading from north to south with the cold front.
So as far as a wet commute home goes, that will likely remain
confined to the North Bay with the slow progression of the cold
front. That means most of the rainfall south of the Golden Gate
Bridge will fall overnight. Rainfall totals on the order of 0.10"-
0.25" are expected with locally higher totals in the higher terrain
of the North Bay with the help of orographic lift and locally lower
totals in the Interior Central Coast. Even with the over performance
of yesterday's rainfall, no adverse impacts are expected with the
exception of slick roadways. It is possible that today's rainfall
over performs as well due to the recency bias of the well above
normal temperatures and dry spell that has occurred over the last
four weeks. This is actually a best case scenario for both water
storage and fire weather concerns. Similar to yesterday, the best
chances for thunderstorms will remain off to our north and east with
our region being instability limited.
&&
.LONG TERM...
Issued at 1214 PM PDT Wed Apr 1 2026
(Thursday night through next Tuesday)
The warming and drying trend will commence right behind the cold
front as surface high pressure noses in from the Eastern Pacific
Ocean. This will veer winds to become northwesterly with the
tightened surface pressure gradient yielding strong winds in exposed
areas like the higher terrain and over the waters. Very dry air will
get funneled in behind the cold front with PWAT values forecast to
be between the daily minimum (0.18 inches) and tenth percentile
(0.34 inches) for 12Z tomorrow. ECMWF and GFS ensembles are in
agreement that the SFO-WMC pressure gradient will change from
positive (onshore) to negative (offshore) tomorrow night, but that's
about where the agreement ends. The uncertainty lies in how the
aforementioned high builds into the Intermountain West and how
strong it gets. The ECMWF deterministic and ensemble continues to
offer a stronger solution than its GFS counterparts. Both models and
their means show a relative minimum occurring at 5 AM Friday with
the ECMWF ensemble mean at -9.26 mb and the GEFS ensemble mean at
-8.03 mb. 24 hours later at 5 AM Saturday, the ECMWF ensemble
mean bottoms out at -9.91 mb while the GEFS ensemble mean is well
on its way to relaxing at -5.50 mb. Nonetheless, confidence is
high that a moderate offshore flow event will transpire Thursday
night with the gradient beginning to weaken by Sunday morning and
returning to positive by Monday. This will equate to gusts of 40
to 50 mph in the North Bay Interior Mountains with gusts of 30 to
40 mph in the East Bay Hills, Eastern Santa Clara Hills, and Santa
Cruz Mountains. Well above normal temperatures are expected over
the weekend with Saturday being the warmest day of the week.
Chances for rain may return as early as Tuesday with the help of
an upper-level trough.
&&
.AVIATION...
(18Z TAFS)
Issued at 1046 AM PDT Wed Apr 1 2026
A mix bag of IFR to VFR conditions this morning! Fairly high
confidence for these conditions to persist through much of the TAF
period. Pre-frontal rain showers will persist at times throughout
the afternoon and then clear out in wake of the overnight/early
morning (Thursday) frontal passage. West-southwest winds will
increase throughout the afternoon before becoming northwesterly in
wake of the frontal passage as ceilings begin to lift and clear
out early Thursday morning.
Vicinity of SFO...MVFR to VFR conditions through early Thursday
morning with an increase in west-southwest winds head of an
approaching frontal boundary. Also, VCSH through 21Z today and
-SHRA afterwards to account for a greater probability of seeing
rain showers. Greater probability of VFR conditions to return
around or after 08Z Thursday in wake of the frontal passage.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR. Generally expecting VFR conditions
through the day with an increase in west-southwest winds this
afternoon. MVFR conditions are forecast to return early Thursday
morning around 07Z-09Z and then clearing in wake of the frontal
passage.
&&
.MARINE...
(Today through Monday)
Issued at 1046 AM PDT Wed Apr 1 2026
Moderate southwesterly breezes ahead of the cold front this
morning will increase and veer to become fresh and northwesterly
tonight. The cold front will bring light rain this afternoon into
tonight. Widespread hazardous conditions arrive Thursday and
continue into Friday with strong northerly breezes and rough seas.
Northerly breezes diminish and seas abate by this weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Friday for Pt Arena to Pt
Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Reyes to
Pigeon Pt 0-10 nm-SF Bay N of Bay Bridge.
Small Craft Advisory from 3 AM Thursday to 3 AM PDT Friday for
Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos
10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.
&&
$$
SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...RGass
MARINE...Sarment
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Prepared by Boulder-Creek.com Weather at: Wed Apr 1 12:30:03 PDT 2026
From the National Weather Service
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