FXUS66 KMTR 080458
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
958 PM PDT Tue Apr 7 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1038 AM PDT Tue Apr 7 2026
- Marine layer clouds in the morning with clear skies in the
afternoon Tue - Wed
- Unsettled weather with widespread light to moderate rain
Friday through Saturday
- Thunderstorms possible Friday and Saturday
&&
.SHORT TERM...
Issued at 1038 AM PDT Tue Apr 7 2026
(This afternoon through Wednesday)
The weather is mostly quiet in the short term. The marine layer
deepened to 2,200 feet according to the 12Z sounding. That was
enough to bring stratus to the coast and bay adjacent valleys.
Those clouds are now clearing, and the cooler humid air will
retreat back to the immediate coast this afternoon. Temperatures
today will climb into the 70s across the interior, while the coast
is stuck in the low to mid 60s. A building short wave ridge will
cause a subtle pattern shift through Wednesday. The most obvious
impact will be some compression of the marine layer under the
higher pressure. This will cause less extensive stratus coverage
Wednesday morning compared to what we saw this morning. Otherwise
conditions will be very similar to today with a gentle NW breeze,
comfortable temperatures, and mostly clear skies in the afternoon.
&&
.LONG TERM...
Issued at 1038 AM PDT Tue Apr 7 2026
(Wednesday night through next Monday)
The pattern starts to change on Thursday. A mature, vertically
stacked, cut-off low pressure system over the Eastern Pacific
will slowly drift East towards the coast through the day. The
first indications of this system will be increasing high clouds
and a wind shift from NW to SW. The North Bay may get some light
prefrontal rain in the afternoon or evening, and it's possible
that an outer rain band could bring a lightning strike or two, but
for most it will be a nice day. As the low continues to drift
towards the coast, rain will become more widespread Friday morning
and continue, off- and- on, through the day. The biggest question
of the forecast is thunderstorm chances. Cut-off lows making
landfall have surprised us in the past, so it's certainly worth a
deep investigation as we get closer to the event. Since there is
no obvious steering mechanism, it's hard to pin down what path
these cut-off lows will take. That's important as the maximum
lift, wind shear, and vorticity will all line up right near the
low pressure center. The timing also plays a role, with maximum
instability during the warmest temperatures in the afternoon.
The thunderstorm chances are revitalized Friday as a reinforcing
trough digs down from the Gulf of Alaska. Whether we get storms
or not remains in question, but an associated cold front will more
than likely bring additional rain to the region. Right now the
afternoon looks like the wettest period, but that could still
change. All told we expect to get somewhere between 0.25-0.75"
across the valleys, and up to 1.5" in the coastal mountains. From
a rainfall perspective, that puts this event firmly in the
beneficial category, with no flooding impacts expected. The only
caveat is if thunderstorms or strong showers do develop, the
storm motion will likely be relatively slow, so any associated
downpours could cause localized flooding, especially in urban
areas. A drying trend will probably start on Sunday, but the
ensemble clusters disagree on the pattern next week. There's
currently a 60% chance for a warm dry ridge, and a 40% chance for
a cool, wet trough.
&&
.AVIATION...
(06Z TAFS)
Issued at 957 PM PDT Tue Apr 7 2026
Gentle to moderate onshore pattern wind flow will continue to
diminish through the evening hours. MVFR stratus is developing at
the immediate coast and should eventually cover the coastal regions
and parts of the East Bay near OAK, but a compressed marine layer
should allow for less inland development than last night,
particularly in the North Bay interior valleys. Stratus should
retreat to the immediate coast on Wednesday morning with moderate
onshore flow resuming in the afternoon. Expecting more stratus
coverage to develop Wednesday night as an incoming system promotes
the growth of the marine layer.
Vicinity of SFO... Moderate westerly winds continue for a couple
more hours with winds becoming light overnight. Moderate confidence
that the terminal remains VFR overnight, although some low scattered
clouds could intrude into the terminal area. Confidence for stratus
impacts is slightly higher at OAK. Any stratus that develops in the
vicinity will dissipate through Wednesday morning, with the west-
northwest winds returning in the afternoon, with a moderate
confidence for stratus returning in the evening hours into Thursday
morning.
SFO Bridge Approach... Similar to SFO.
Monterey Bay Terminals... Light winds overnight through Wednesday
morning. MVFR-IFR stratus has developed in patches near MRY and will
expand across the terminals through the night, with impacts
continuing through Wednesday morning. Breezy northwest winds resume
in the afternoon, with MVFR-IFR stratus returning late Wednesday
evening.
&&
.MARINE...
(Tonight through next Monday)
Issued at 957 PM PDT Tue Apr 7 2026
A gentle to moderate northwest breeze and slight to moderate seas
prevail through the night. Winds will remain moderate while
gradually shifting to the southwest from Wednesday through
Thursday ahead of a low pressure system. This system will will
bring disturbed weather with possible thunderstorms on Friday
through Sunday. Winds will increase to a strong NW breeze by
Sunday as subtropical high pressure builds over the Eastern
Pacific.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Wednesday for Pt Pinos to Pt
Piedras Blancas 0-10 nm.
&&
$$
SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...DialH
MARINE...DialH
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Prepared by Boulder-Creek.com Weather at: Tue Apr 7 22:30:02 PDT 2026
From the National Weather Service
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