FXUS66 KMTR 220505
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1005 PM PDT Tue Apr 21 2026

...New SHORT TERM, LONG TERM, AVIATION, MARINE...

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

 - Cool conditions Wednesday with lingering showers through the
   morning

 - 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 1004 PM PDT Tue Apr 21 2026
(Tonight through Thursday)

It was a pretty active day on Tuesday with quite a bit of lightning 
reported across the Bay Area and Central Coast, and a funnel cloud 
reported near Fremont. The chances for convection have basically 
shut down as with the lack of solar heating, and while lingering 
isolated showers are possible through the rest of the morning, not 
expecting convection to be an issue through Wednesday. Beyond the 
lingering showers, skies will be generally clearing Wednesday 
morning with mostly sunny conditions and a gentle onshore breeze 
developing by the afternoon hours. Low temperatures this morning 
range from the upper 30s to the middle 40s in the inland valleys, to 
the upper 40s and lower 50s near the coast and the Bays. High 
temperatures on Wednesday are close to the upper 50s to the middle 
60s in the lower elevations, with a slight warming gradient towards 
the inland valleys, and the upper 40s to middle 50s at the higher 
elevations. 

&&

.LONG TERM...
Issued at 1004 PM PDT Tue Apr 21 2026
(Thursday night through next Tuesday)

Temperatures will warm slightly for Thursday and Friday as a barely 
noticeable ridge sets up over the region, with highs in the lower 
elevations range from the lower 60s to lower 70s, close to or 
slightly below the seasonal averages. Into the weekend, another 
trough will come into the region and cause temperatures to dip 
again, introducing slight chances for light rain and drizzle that 
are expected to continue through the middle of next week. The latest 
CPC outlook leans towards precipitation totals above the seasonal 
averages heading into the first week of May, with the note that this 
late into the spring, the daily seasonal average rainfall at 
downtown San Francisco falls around two or three hundredths of an 
inch.

&&

.AVIATION...
(06Z TAFS)
Issued at 1004 PM PDT Tue Apr 21 2026

Mid to high level clouds are expected through the night and into 
Wednesday, with spotty and inconsistent low clouds possible. Showers 
will linger into the night, but chances will continue to decrease 
until the early morning where another wave of showers moves 
along/adjacent to the low pressure center. As these morning showers 
move through, expect multiple shifts in winds specifically around 
the SF Bay. Rain rates will lead to modest reductions in 
visibilities from this wave of rain. These showers exit into the 
afternoon as moderate westerly winds build and skies begin to clear. 
Winds weaken into Wednesday night, becoming light and variable in 
the inland areas, while sites near the ocean see more northerly 
winds.

Vicinity of SFO...Spotty, non-impactful showers are beginning to 
dissipate. Mid-level clouds linger across the area into the night 
with west winds turning more southwest as the low center arrives. 
Shower activity returns as the low center focuses over the SF Bay 
into Wednesday morning, and the winds will become shifty and 
variable. Showers exit into early afternoon as winds turn southwest, 
then west-northwest for the late afternoon. Winds will ease into 
Wednesday night and turn northwest.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Despite the unsettled weather, KMRY and 
KSNS should mainly expect VFR conditions this TAF period with a 
brief period of MVFR conditions brought on by passing rain showers. 
The rain Wednesday morning should remain light and will cause CIGs 
to lower. After the last shower passes through however, the cloud 
bases will begin to lift. The onset of the rain is an estimation, 
therefore there is a possibility it may begin slightly earlier or 
later. This will be updated as needed.

&&

.MARINE...
(Tonight through next Monday)
Issued at 1004 PM PDT Tue Apr 21 2026

Light pop-up showers are moving through the waters, but offer
little impacts. Additional showers will be possible into Wednesday
morning but these chances erode into that afternoon. As the
weather breaks on Wednesday, winds will shift to a moderate NW
breeze, before increasing to a fresh breeze on Thursday. Winds and
seas ease into the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 AM to 3 PM PDT Thursday for Pt Arena 
     to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Murdock/AN
MARINE...Murdock

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Prepared by Boulder-Creek.com Weather at: Tue Apr 21 22:30:02 PDT 2026