Technical NOAA Weather Discussion

FXUS66 KMTR 232116
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
216 PM PDT Thu Apr 23 2026

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 1201 AM PDT Thu Apr 23 2026

 - Seasonal temperatures and dry conditions return today

 - Potential for rain/drizzle and slightly cooler temperatures 
   this weekend into early next week

 - Warming trend begins early to mid next week

&&

.SHORT TERM...
Issued at 126 PM PDT Thu Apr 23 2026
(This evening through Friday)

Radar is finally quiet this afternoon after a period of somewhat
active weather. Visible satellite shows mostly clear skies around
the region with a few pop up CU hugging the hills. Increased
insolation this afternoon has led to a warmer temperatures across
the board.

Stepping back and looking at the longwave pattern over EPAC and
CONUS reveals an interesting pattern. The EPAC is highly 
amplified with a solid ridge extending into E AK and W BC with a 
low off the CA coast with a rex block vibe. Farther east two 
pronounced upper lows spin, one north of MT and the other east of
Nova Scotia with a ridge smacked in between with an omega block 
vibe. In other words a little bit of a traffic jam in the upper 
atmosphere. That being said, we do see some minor movement on the 
small scale and closer to home. A weak embedded shortwave/fuzzy 
upper low off the CA coast is slowly moving eastward. As this 
feature moves eastward high clouds will increase over the region 
tonight and Friday. The higher clouds may limit fog production 
tonight, but some low stratus will be possible. Interestingly, 
some of the CAMs resolve some forecast 1KM radar reflectivity
tonight. Forecast is dry for Friday morning, but a few echoes may
appear on radar. Increased cloud cover will also lead to cooler 
temperatures on Friday with highs dropping below seasonal averages
again. 


&&

.LONG TERM...
Issued at 126 PM PDT Thu Apr 23 2026
(Friday night through next Wednesday)

A trend that emerged a few days ago is still on track for the
upcoming weekend, "wetter" and cooler. Broad troughiness remains
over region with re-enforcing upper lows. Another upper low is on
track to move over the region Friday night into Saturday and
subsequent vort maxes Saturday into Sunday. These features 
combined with the northern fringes of sub-tropical moisture 
pulses will lead to some drizzle/light rain showers Friday night 
through Sunday morning. Not expecting much in the way of 
accumulation, trace to a few hundredths. Areas most favored will 
be coastal mts with enhanced low level lift. Temperatures for the
upcoming weekend will be below seasonal averages with highs in 
the upper 50s and 60s.

By early next week 500mb heights begin to rebound with warming
850mb temps kicking off a gradual warming and drying trend. No
precip in the forecast Monday through Wednesday.

&&

.AVIATION...
(18Z TAFS)
Issued at 1141 AM PDT Thu Apr 23 2026

Quiet weather with some fair weather cumulus clouds popping up over 
the region and high clouds passing overhead. VFR conditions will 
prevail through the evening and perhaps early overnight hours for 
most sites. Guidance suggests that a mix of stratus and fog will 
return at some point, but there are some caveats. High clouds could 
disrupt fog and stratus formation, in addition to winds. Trended 
towards KAPC and KSTS seeing another night of reduced ceilings and 
visibility, with KHAF likely joining them. The models are bit 
divided on the expanse of the stratus and fog, thus I opted to hint 
at lowering cigs for KSJC and KLVK. Medium to high confidence in the 
forecast. 

Vicinity of SFO...Onshore flow is expected to return this afternoon, 
and increase to around 15kt around 0Z. This will last into the late 
evening hours with winds falling below 10kt near or after 7Z. Quite 
a few models indicate MVFR ceilings moving into the Bay, with much 
of the Bay seeing MVFR cigs increase between 11-14Z and continuing 
until at least 17-18Z. Opted to go with a slightly more optimistic 
forecast with cigs clearing between the 17-21Z. Medium confidence in 
the forecast. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR conditions prevail for the majority of 
the region for the afternoon with high clouds streaming overhead and 
cumulus popping up over the mountains. Much like the discussion 
above, stratus and any associated fog may be dependent on the high 
clouds and winds. Guidance shows Monterey Bay with ceilings around 
035-050 for heights, though a few bring KMRY closer to MVFR status. 
Expect this to occur just before or around sunrise, before mixing 
out by mid to late morning.

&&

.MARINE...
(Today through Tuesday)
Issued at 924 AM PDT Thu Apr 23 2026

Moderate north breezes this morning will develop into a northwest
breeze this afternoon. Choppy seas at times today will begin to
subside Friday and continue into the weekend. Light rain and
drizzle return to this weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT this evening 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 until 9 AM PDT Friday for Pt Arena to Pt 
     Reyes 10-60 NM.

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

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...KR
MARINE...KR

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Prepared by Boulder-Creek.com Weather at: Thu Apr 23 14:30:03 PDT 2026
From the National Weather Service