FXUS66 KMTR 230103
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
603 PM PDT Wed Apr 22 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1004 PM PDT Tue Apr 21 2026

 - Cool conditions Wednesday with lingering showers through the
   day

 - Seasonal temperatures and dry conditions arrive Thursday

 - Monitoring potential rain and drizzle this weekend into the
   early part of next week

&&

.SHORT TERM...
Issued at 129 PM PDT Wed Apr 22 2026
(This afternoon through Thursday)

While not as active as 24 hours ago we still have KMUX is precip 
mode. Current radar loop this afternoon still shows widely 
scattered showers around the Bay Area and Central Coast. 
Afternoon visible satellite shows popcorn city with an extensive 
CU field blanketing the region. Why the showers? The main storm
system from yesterday has exited to the east. On the back side of
this system are trialing embedded vort maxes/shortwaves. Those
features in conjunction with lingering moisture, daytime heating,
and weak instability has led to the showers. That being said, not
enough lift or vertically developed storms to generate 
thunderstorms. 

This evening and tonight, once the sun sets expect shower activity
to quickly diminish and CU field thin. One potential impact
tonight will be some developing low stratus and fog. Clearing
skies and decreasing winds will allow for some fog development 
over the inland valleys.

Thursday: Dry, warmer, and more sunshine due to weak upper level
ridging. Max temps will be in the 60s to mid 70s, which is closer
to seasonal averages.

&&

.LONG TERM...
Issued at 129 PM PDT Wed Apr 22 2026
(Thursday night through next Tuesday)

A few days ago the longer term forecast didn't look to interesting
from a weather impact standpoint, but a trend has emerged over the
last 24-36 hrs showing active weather will continue. First and
foremost it will not be as dynamic as the system that we just
had. However, a previously dry-ish weekend is now trending
"wetter". What's the trend? Subtle ridging aloft is now looking
more trough-y with an upper low over the region. The longwave
pattern keeps kicking the upper low from yesterday eastward. In 
its wake subtle ridging is now being replaced by another upstream
trough. It now appears enough jet dynamics aloft emerge to shift 
the broad upper trough to a more pronounced upper low late 
Thursday into Friday. Heights begin to fall by Friday lowering 
temps and ushering in more clouds. By Saturday morning an upper 
low develops off the Central Coast. As such, light drizzle/light 
rain will return. This set up will persist through early Sunday 
with drizzle/light rain. Not expecting much accumulation, just 
some wet ground, clouds, and cooler temps. Another upper low 
develop early next week bring additional rain chances on Tuesday 
into Wednesday. Again, not a big storm, just additional moisture. 

&&

.AVIATION...
(00Z TAFS)
Issued at 601 PM PDT Wed Apr 22 2026

Residual light rain is making its way out of a few TAF sites this 
afternoon. As a result, some sites will see low cloud bases (4500 to 
8000 ft) in the earlier portion of the TAF period, but they are 
expected to lift through the evening. VFR conditions are forecast as 
the drying trend continues. Winds will be light throughout the night 
and will increase by tomorrow afternoon with some locations 
experiencing embedded gusts. Model guidance is hinting at the 
potential for valley fog in the early morning hours for STS & SJC, 
however confidence is currently too low to include in the TAF. We 
will continue to monitor this and update as needed.

Vicinity of SFO...Westerly winds will dominate this TAF period at 
moderate speeds. The winds should become light overnight before 
picking up again tomorrow afternoon. VFR conditions will persist for 
the remainder of the day and night. There is some potential for low-
level cloud decks tomorrow night around 05Z, though it does not seem 
impactful at this time.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Moderate west winds last into the late 
evening before winds reduce and become light and variable. Low 
clouds look to form on the mountain tops in the area overnight, but 
don't look to affect the TAF sites. Those clouds erode into the 
early morning with moderate west to northwest winds affecting the 
region into the late morning. 

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 601 PM PDT Wed Apr 22 2026

Isolated light showers linger across waters this afternoon and
will continue to diminish into the early evening. A moderate
north breeze will develop this tonight, then increase on Thursday
to a fresh northwest breeze. Wind and seas will begin to
gradually subside on Friday, continuing into the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM to 9 PM PDT Thursday for Pigeon 
     Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt 
     Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-
     10 nm.

     Small Craft Advisory from 3 AM Thursday to 3 PM PDT Friday for 
     Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory from 3 PM Thursday to 3 AM PDT Friday for 
     Pigeon Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Navarrete/Murdock
MARINE...KR

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Prepared by Boulder-Creek.com Weather at: Wed Apr 22 20:30:02 PDT 2026