FXUS66 KMTR 070500
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1000 PM PDT Thu Aug 6 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1248 AM PDT Thu Aug 6 2026

 - Elevated fire weather conditions in the higher terrain Thursday

 - Warming trend through Saturday will result in moderate to major
   HeatRisk for the interior through Sunday

 - Near-critical fire weather conditions in the higher terrain
   Friday through Sunday

 - Minor coastal flooding for bayshore locations along the San Francisco
   Bay, San Pablo Bay, and Monterey Bay Saturday evening through 
   Thursday morning

&&

.SHORT TERM...
Issued at 200 PM PDT Thu Aug 6 2026
(This evening through Friday night)

Seeing a lot of similarities today to the last few days...the
marine layer foot print from this morning is dictating the
"cooler" temps and the hotter inland temps. Latest 24 hr trends
follow this foot print too showing slightly warmer temperatures 
this afternoon across the interior.

For tonight...a little bit of rinse and repeat. Marine layer
hugging the coast will once again march inland with a slight
compression, but still decent inland reach. Nocturnal drying and
active thermal belts persist above the marine layer exacerbating
the fire weather concerns.

Monsoon moisture influx is slowing creeping in from the south as
we speak. Latest guidance continues to show increasing moisture 
through Friday. Normally, focus would turn toward high based 
convection, but the large ridge and lack of trigger will like
limit convective potential. Also, the moisture seems to be rather
high (>10k ft) so impacts at the surface may be minimal.

Friday and Friday night...large upper level ridge will expand back
over the region bringing a more noticeable warm up across the
interior. For the coast, same old same old, persistent marine
layer influence keeping temperatures in check.

&&

.LONG TERM...
Issued at 230 PM PDT Thu Aug 6 2026
(Saturday through next Wednesday)

First and forecast, a Heat Advisory has been issue for Saturday
and Sunday. The warming trend will continue Saturday and then
moderate Sunday. The warmer interior temperatures in the mid 90s 
to lower 100s will push HeatRisk back into the critical levels 
(widespread Moderate to pockets of Major). Overnight lows will 
remain mild and in the 60s to mid 70s for interior and higher 
terrain locations. There are lots of outdoor events going on 
around the Bay Area this weekend. Interior locations will want to
take some safety precautions for the heat: hydrate, take breaks, 
seek shade, never leave pets/people in cars. Do expect a warm up 
at the coast too, but it's the Bay Area so pack a jacket as the 
marine layer will move inland during the evening hours.

HeatRisk concerns begin to fade on Monday as the large ridge
flattens and looks to split into two with sagging H5 over CA 
coast. The cooling trend will continue through at least Wednesday.

&&

.AVIATION...
(06Z TAFS)
Issued at 1000 PM PDT Thu Aug 6 2026

MVFR-IFR stratus is beginning to expand as it flows into the 
Petaluma Gap and starts edging into the Golden Gate. Stratus 
continues to expand across the coastal valleys through the night 
with low to moderate confidence that impacts extend into the 
interior East Bay. That may depend on exactly how deep the marine 
layer is. So far stratus has been developing later than the earlier 
forecast suggested and the TAFs have been updated to reflect later 
development times. Stratus is expected to mix out back to the 
immediate coastline Friday morning with the breezy onshore winds 
expected to resume in the afternoon. Some stratus expansion is 
possible Friday evening, but most coverage develops after the end of 
the 24-hour TAF period. 

The SJC ASOS will be offline within a window from 07-13Z due to 
maintenance at the station; the TAF is marked AMD NOT SKED as a 
result.

Vicinity of SFO... Low-end MVFR stratus comes into the terminal area 
within the next couple of hours, with lower confidence on timing as 
the high resolution models start with the terminal on the edge of 
the stratus deck. Stratus will gradually mix out through Friday 
morning followed by breezy and possibly gusty northwest winds in the 
afternoon and evening hours. Low to moderate confidence of stratus 
over the terminal Friday night with high resolution models trending 
towards pulling the stratus deck to the north.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... Low confidence in the timing of the 
stratus development at the terminals as observed stratus coverage is 
much lower than model output. Nevertheless high confidence that IFR 
stratus will build over the terminals through the night. Stratus 
will retreat to the coast late Friday morning with gentle northwest 
winds developing in the afternoon hours, diminishing in the evening 
as the stratus returns.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 1000 PM PDT Thu Aug 6 2026

Northwest gentle winds gradually increase to a fresh to strong
breeze, particularly across the outer northern waters on  Saturday
through the middle of the week. Moderate northwest seas  also
build to rough by Sunday morning continuing into the early  part
of next week. Winds and seas remain elevated through the  middle
of next week. A long period southerly swell of 15 to 17  seconds
will impact the coastal waters beginning Saturday  morning.

&&

.FIRE WEATHER...
Issued at 1248 AM PDT Thu Aug 6 2026

Elevated fire weather conditions continue Thursday with hot and dry 
conditions alongside the diurnal sea breeze. PSAs of Mid Coast to 
Mendocino, Diablo/Santa Cruz Mountains, and Central Coast Interior 
are all currently in the 97th percentile for ERC with Mid Coast to 
Mendocino and Central Coast Interior forecast to reach daily record 
values this weekend. This indicates potential for extreme burning 
conditions. Even the more marine layer influenced PSAs of Bay Marine 
and Central Coast are forecast to peak in the 80th-90th percentile. 
Building high pressure will bring near-critical fire weather 
conditions Friday through Sunday. Temperatures will be 10 to 15 
degrees above normal with a shallow marine layer in place. Poor 
minimum daytime relative humidity as low as 10% is expected in the 
afternoons with little-to-no recovery expected overnight. The one 
missing piece preventing this from being a Fire Weather Watch/Red 
Flag Warning as of now is wind, it's expected to be light. The 
exception being through gaps/passes (namely Altamont Pass, the 
Delta, and Pacheco Pass) and down the Salinas Valley. To add onto 
this, the critical conditions are not expected to overlap spatially 
(majority of a zone) or temporally (for at least 8 hours) to warrant 
a product. 

Sarment

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory from 5 PM Friday to 2 AM PDT Thursday for 
     CAZ006-506-508-529-530.

     Heat Advisory from 10 AM Saturday to 10 PM PDT Sunday for CAZ503-
     504-510-512>515-517-518.

PZ...None.
&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...DialH
MARINE...DialH

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Prepared by Boulder-Creek.com Weather at: Thu Aug 6 22:30:02 PDT 2026