FXUS66 KMTR 201119
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
419 AM PDT Sun Sep 20 2026

...New AVIATION, MARINE, FIRE WEATHER...

.KEY MESSAGES...
Updated at 925 PM PDT Sat Sep 19 2026

 - Brief cooling Sunday through Monday

 - More substantial warming trend Tuesday through Thursday

&&

.SHORT TERM...
Issued at 925 PM PDT Sat Sep 19 2026
(Tonight through Monday night)

Residual polar jet stream winds will merge with the subtropical jet
stream at the base of a weak 500 mb low currently ~ 500 miles west
of Monterey and move the low eastward across our forecast area 
later Sunday through Monday. Cool onshore breezes will help keep 
temperatures below normal. Daytime highs Sunday will be cooler 
than typical for Sep 20th with highs in the 60s coastside/bayside 
to the 70s and 80s inland. Highs Monday will be about the same as 
on Sunday. A few patches of late night and morning light drizzle 
may form in the cooled air near surface to aloft.

&&

.LONG TERM...
Issued at 925 PM PDT Sat Sep 19 2026
(Tuesday through next Saturday)

500 mb low amplitude ridging will develop Tuesday into early
Thursday. This will bring a warming trend here during these three
days, which will help push daytime highs up to the 90s/100 inland
Wed-Thu (cooler at the coastline and bays). The pattern across 
the North Pacific to the western CONUS is progressive, which lowers
confidence a little in the timing of 500 mb ridging residence time
and this may influence the duration of warm/hot weather currently
forecast for mid next week. Stay tuned to the latest updates.

&&

.AVIATION...
(12Z TAFS)
Issued at 416 AM PDT Sun Sep 20 2026

Currently LIFR-MVFR with high clouds streaming in. IFR-MVFR ceilings 
will prevail through late-morning before stratus retreats to the 
coast. Confidence is decreasing in any fog development this morning. 
Moderate to high confidence in IFR-MVFR ceilings returning to all 
terminals tonight. Drizzle will be possible in the mornings. Diurnal 
winds will prevail.

Vicinity of SFO...Currently MVFR with westerly flow. High confidence 
in a ceiling on the cusp of IFR/MVFR prevailing through late-
morning. High (80%) confidence in an MVFR ceiling returning 
tonight. Diurnal winds will prevail. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently IFR with westerly flow at MRY and 
IFR with southwesterly flow at SNS. IFR will prevail through the 
morning with stratus retreating to the coast during the afternoon. 
The close proximity may keep MRY sub-VFR through the TAF period with 
an early return slated tonight. Diurnal winds will prevail.

&&

.MARINE...
(Today through Friday)
Issued at 416 AM PDT Sun Sep 20 2026

Fresh to strong northerly breezes will create hazardous conditions
for small craft across most of the coastal waters through Monday
morning. Moderate to fresh northerly breezes will prevail Tuesday
through Thursday with locally strong breezes across the northern
outer waters. Slight to moderate seas will prevail through Monday,
building to become moderate to rough Tuesday through Thursday.

&&

.FIRE WEATHER...
Issued at 416 AM PDT Sun Sep 20 2026

Near to slightly below normal temperatures, diurnal winds, a deep 
marine layer, and a chance for drizzle are on tap for Sunday and 
Monday. Warming and drying trend kicks off Tuesday with temperatures 
up to 15 degrees above normal by Thursday. Areas of moderate 
HeatRisk are expected as a result Wednesday and Thursday. The marine 
layer will compress below 1,000 feet during this warm-up with 
nocturnal drying expected above it. Diurnal winds will prevail; 
however, they will be weaker than the preceding days.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 AM PDT this morning for Pt Arena to 
     Pt Reyes 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this 
     evening for Pigeon Pt to Pt Pinos 0-10 nm.

     Small Craft Advisory until 3 AM PDT Monday for Pigeon Pt to Pt 
     Pinos 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 AM PDT Monday for Pt Arena to Pt 
     Reyes 10-60 NM.

&&

$$

SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...Sarment
MARINE...Sarment

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Prepared by Boulder-Creek.com Weather at: Sun Sep 20 04:30:04 PDT 2026