FXUS66 KMTR 031140
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
440 AM PDT Fri Apr 3 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1205 AM PDT Fri Apr 3 2026
- Moderate to strong offshore flow Friday
- Warm weather returns through the weekend
- Cooler weather and rain chances next week
&&
.SHORT TERM...
Issued at 1205 AM PDT Fri Apr 3 2026
(Today and tonight)
Post-frontal high pressure brought strong onshore winds Thursday.
This feature has moved inland over Oregon, and will continue towards
northern Nevada over the next 12 hours. As it does, the gradient
between the surface high and a trough along the coast of California
will strengthen. The SFO-WMC gradient was +14 mb last night, and is
dropping sharply. It's currently around -4.5 mb and will bottom
out around -10 mb later today. This gradient will support
moderate to strong offshore winds through midday Friday before the
high starts to weaken and the offshore gradient gradually relaxes
through the weekend. The strongest winds should be over the Vaca
Mountains in Napa County. Stable conditions in the lower
atmosphere will encourage mountain wave activity that will allow
strong gusts to reach the valley through the morning hours.
Outside of the burst of offshore winds, a warming trend is the
biggest story in the short term forecast. Now that the cold front
has moved well inland, the pattern is flipping back to warm and dry.
At 500 mb, a NW to SE oriented ridge will build over the next 48
hours. This upper level high will increase temperatures through
large scale subsidence and clear skies. The 850 mb temperature
averaged 2.8 C Thursday, which is between the 10th and 25th
percentile for this time of year. That metric will shoot up to
around 13-14 C by Friday afternoon, or roughly the 75th
percentile. Inland temperatures will respond by reaching the mid
to upper 70s this afternoon. The coast will get in on the warmer
temperatures as well, thanks to the offshore winds.
&&
.LONG TERM...
Issued at 1205 AM PDT Fri Apr 3 2026
(Saturday through Thursday)
We will pick up some high clouds on Saturday as an upper level plume
of moisture rides over the ridge. Otherwise the warming trend
will continue through the weekend as the 850 temperatures continue
to climb. Inland temperatures will reach the mid 80s on Saturday
and Sunday. That about 15 degrees above normal, and it's possible
we could set a daily record or two.
The return of weak onshore flow Sunday will likely bring the
immediate coast back into the low to mid 60s. There is a chance
for a southerly surge on Sunday as well. This can happen when the
large scale E-W pressure gradient becomes weakly offshore and the
afternoon sea breeze butts up against the coastal mountains. If
the atmosphere is stable, the air can't make it over the
mountains and has to either go north or south parallel to the
coast. The PGE-WRF shows a southerly surge developing Sunday
morning and reaching San Francisco by midday. Southerly surges are
hard to predict though, so it could be delayed until Monday or
not happen at all. There is much higher confidence that the more
typical marine layer will return Monday as stronger NW winds
return to the coastal waters. These onshore winds will also cool
inland areas back into the 70s Mon-Tue.
By mid-week ensemble clusters all agree the pattern will shift back
to a troughing regime. This pattern will very likely bring a cold
front across the cwa Wednesday, bringing a chance for
precipitation. The ECMWF ensemble mean is generally between 1/10
and 1/4 inch of rain, with a 90% chance it's will stay below 1".
That's firmly in the beneficial category, and there are no
significant impacts expected. After the rain chance wane Thursday,
seasonal temperatures continue through late week.
&&
.AVIATION...
(12Z TAFS)
Issued at 434 AM PDT Fri Apr 3 2026
Side note first - there continues to be a comms issue and METARS
are not making it to the normal data feeds. A fix is in the works.
Dry offshore flow and clear skies. VFR through the period. LLWS
in the forecast for KSTS and KOAK.
Vicinity of SFO...NE early then onshore push later this afternoon.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR.
&&
.MARINE...
(Today through Wednesday)
Issued at 434 AM PDT Fri Apr 3 2026
Winds continue to ease near shore, but fresh to strong breezes
persist over the outer waters through Friday morning. Both winds
and seas will abate by Friday afternoon. Light to moderate
northerly breezes prevail this weekend and into next week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Saturday for Pt Arena to Pt
Reyes 10-60 NM.
Small Craft Advisory until 9 AM PDT this morning for Pigeon Pt
to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...MM
MARINE...MM
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Prepared by Boulder-Creek.com Weather at: Fri Apr 3 06:30:02 PDT 2026
From the National Weather Service
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