FXUS66 KMTR 180723
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1223 AM PDT Sat Apr 18 2026

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

.KEY MESSAGES...
Updated at 1134 PM PDT Fri Apr 17 2026

 - Seasonably warm temperatures expected through the weekend

 - Cooler temperatures with minor flooding possible in the North
   Bay Monday, mostly beneficial rain for the remainder of our
   area 

 - Increasing chance of thunderstorms Tuesday
&&

.SHORT TERM...
Issued at 1223 AM PDT Sat Apr 18 2026
(Today and tonight)

A progressive upper level ridge axis will shift east across our area 
this morning, while temperatures inland climb into the upper 70s to 
low 80s. Locations most likely to reach or exceed 80 will be in the 
interior valleys of the South Bay and Central Coast where there will 
be plenty of sunshine and light winds. Coastal locations will be 
only slightly warmer than Friday with weak onshore flow during the 
day out ahead of the developing offshore disturbance. Even with the 
ridge exiting to the east, overnight lows into Sunday will be more 
mild than we've seen the last few nights with increasing mid/high 
level cloud cover insulating some of todays heat.

&&

.LONG TERM...
Issued at 1223 AM PDT Sat Apr 18 2026
(Sunday through Friday)

Sunday will be a nice transition day as the pattern changes for the 
first half of next week. Overall, consensus is improving but the 
timing of the first ejecting wave of the developing upper low is 
still in question. What we do know is that deep onshore flow will at 
least bring a return of stratus along our entire Pacific Coast 
Sunday night. Our official forecast has slight chance PoPs over the 
North Bay late Sunday evening but any rainfall initially would be
measured in the hundredths. By sunrise Monday morning we may see 
more impactful rain over the North Bay coastal ranges then shift 
into the interior valleys. The slow moving system with notable 
longitudinal orientation out ahead initially will see areas of 
showers training over the North Bay. The WPC does have much of 
Sonoma County in a Day 4 Excessive Rain Outlook on Monday. The 
second wave approaches the coast overnight Monday into Tuesday as 
the associated trough becomes negatively tilted providing added 
lift and increasing baroclinic instability by late morning/early 
afternoon for any showers/storms moving onshore. The system will 
be slow to move onshore initially, but once inland it will eject 
east quickly. Attm, the pattern indicates another disturbance 
splitting off the back side with an inside slider trajectory for 
the second half of next week.

&&

.AVIATION...
(06Z TAFS)
Issued at 953 PM PDT Fri Apr 17 2026

Breezy onshore winds are diminishing across much of the region with 
only relatively breezy conditions continuing at SFO. Winds remain on 
track to continue diminishing overnight and become variable. LAMP 
guidance continues to indicate stratus is possible at HAF but 
confidence remains low. If stratus were to develop at HAF it would 
likely be short lived between 12Z-18Z. Elsewhere, VFR conditions 
prevail through the remainder of the TAF period. Stratus looks to 
return shortly after 06Z Sunday.

Vicinity of SFO...VFR. Breezy onshore winds continue to diminish 
tonight before becoming variable through tomorrow morning. Winds 
restrengthen during the afternoon/evening with winds around 15 knots 
expected. Some potential for stratus to return towards the end of 
the TAF period but confidence is currently lower.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. Light, variable winds continue 
overnight with breezy onshore winds redeveloping during the 
afternoon/evening. Winds peak between 10 to 13 knots.&&

.MARINE...
(Tonight through next Thursday)
Issued at 953 PM PDT Fri Apr 17 2026

Fresh north to northwest winds will continue to diminish through
Saturday with moderate winds expected Saturday afternoon into
Sunday. Winds shift southerly Sunday ahead of an incoming low
pressure system and cold front. Winds are expected to strengthen
ahead of cold frontal passage Monday into Tuesday with localized
strong gusts expected. Moderate seas, rain, and a slight chance of
thunderstorms Monday and Tuesday.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 953 PM PDT Fri Apr 17 2026

Fresh north to northwest winds will continue to diminish through
Saturday with moderate winds expected Saturday afternoon into
Sunday. Winds shift southerly Sunday ahead of an incoming low
pressure system and cold front. Winds are expected to strengthen
ahead of cold frontal passage Monday into Tuesday with localized
strong gusts expected. Moderate seas, rain, and a slight chance of
thunderstorms Monday and Tuesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Kennedy
MARINE...Kennedy

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Prepared by Boulder-Creek.com Weather at: Sat Apr 18 04:30:02 PDT 2026