Technical NOAA Weather Discussion

FXUS66 KMTR 072314
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
414 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...
(00Z TAFS)
Issued at 413 PM PDT Tue Apr 7 2026

VFR across the region through the evening hours, with gentle to 
moderate onshore pattern wind flow continuing through the afternoon 
before diminishing through the evening. Stratus should return to the 
region overnight, 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 the moderate onshore flow resuming in the 
afternoon.

Vicinity of SFO... Moderate westerly winds persist into the evening 
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.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... Gentle to moderate northwest winds 
continue through the evening hours, with light winds overnight. MVFR-
IFR stratus will develop through the late evening hours, with 
impacts continuing through Wednesday morning. Breezy northwest winds 
resume in the afternoon, with the best confidence for stratus 
return Wednesday night after the end of the TAF period.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 413 PM PDT Tue Apr 7 2026

A gentle to moderate NW breeze and slight to moderate seas will
prevail through the evening. Winds will remain moderate while
gradually shifting to a SW direction from Wednesday through
Thursday ahead of a low pressure system. This system will will
bring disturbed weather with possible thunderstorms on Friday and
Saturday. 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...Flynn

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Prepared by Boulder-Creek.com Weather at: Tue Apr 7 16:30:02 PDT 2026
From the National Weather Service