FXUS66 KMTR 060750
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1250 AM PDT Thu Aug 6 2026

...New SHORT TERM, LONG TERM, FIRE WEATHER...

.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 1248 AM PDT Thu Aug 6 2026
(Today and tonight)

Longwave upper-level ridging will drift in from the Eastern Pacific 
Ocean today, compressing the marine layer to near 1,500 feet in the 
process. Temperatures will be near to slightly above normal with the 
diurnal sea breeze. A surge of monsoonal moisture arrives today, 
increasing surface dew points and relative humidity in the process. 
Sensible weather wise, this will make it feel hotter and more 
uncomfortable than what the thermometer reads. Areas of moderate 
HeatRisk are expected in the interior with pockets of major in the 
higher terrain of Monterey and San Benito Counties. Stagnant air 
from the ridge may support haze from wildfire smoke. Elevated fire 
weather conditions continue today above the marine layer.

&&

.LONG TERM...
Issued at 1248 AM PDT Thu Aug 6 2026
(Friday through Wednesday)

Surface high pressure over the Four Corners will build and expand 
westward Friday and into the weekend. This will bring the hottest 
conditions of the week and compress the marine layer further. Areas 
of moderate HeatRisk across the interior on Friday will expand to 
become widespread on Saturday with areas of major. To put this into 
context: 850mb temperatures, 500mb heights, and PWAT values are all 
forecast to exceed the 90th percentile Saturday. No records are 
forecast with temperatures 10-15 degrees above normal for the 
hottest spots. A potential wild card in the precision and subsequent 
impacts of the forecast is the aforementioned surge of monsoonal 
moisture. Mid-to-high level clouds would limit solar insolation 
during the day and radiational cooling at night, potentially 
resulting in cooler highs and warmer lows than the official 
forecast. Even though the ridge will begin to break down and dry air 
will begin to get filtered in from the northwest, cumulative impacts 
from the heat and humidity will likely still be felt on Sunday. Near-
critical fire weather conditions are expected above the compressed 
marine layer Friday through the weekend due to hot and dry 
conditions with the diurnal sea breeze. Global ensemble clusters are 
in agreement that upper-level shortwave troughing off the West Coast 
will prevent the aforementioned ridge and subtropical high pressure 
across the Eastern Pacific Ocean from joining forces and building 
out of control across our area. Sensible weather wise, temperatures 
will moderate to near normal with onshore flow Monday through 
Wednesday. Minor coastal flooding is expected during the highest 
high tide (evening/overnight) for bayshore locations along the San 
Francisco Bay, San Pablo Bay, and Monterey Bay Saturday evening 
through Thursday morning.

&&

.AVIATION...
(06Z TAFS)
Issued at 953 PM PDT Wed Aug 5 2026

VFR prevails early tonight with only KHAF and KSNS with MVFR 
ceilings thus far. The stratus push inland isn't as dramatic as 
thought just three hours ago, but confidence remains high that it 
will eventually spread over most of our area below 1500ft by sunrise 
Thursday. With high pressure continuing to build, expect VFR 
conditions by late morning for most terminals, possibly early 
afternoon for the Monterey Bay sites as a compressed marine layer 
retreats back to the coast.

Vicinity of SFO...Stratus lingering in vicinity of the terminals but 
currently slow to make much more progress. The inland push isn't 
taking hold as quickly as though just a few hours ago, but 
confidence is high that IFR/LIFR ceilings will develop after 
midnight and persist through late morning. VFR through the 
remainder of the forecast period once stratus retreats back to the
coast.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...MVFR ceilings will become IFR/LIFR after 
midnight and continue through late morning at KSNS, possibly 
early afternoon for KMRY. Moderate to high confidence that 
IFR/LIFR ceilings return by early evening before sunset with VFR 
most of the afternoon on Thursday.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 953 PM PDT Wed Aug 5 2026

Light to gentle breezes will continue through Thursday with seas
between 2-6ft. Northwest winds begin to increase Friday into the
weekend with building seas and hazardous conditions for small
craft. A long period southwesterly swell of 15-17sec begins on
Saturday, peaks on Sunday then begins to subside by the beginning
of next week.

&&

.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...None.
PZ...None.
&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...JM
MARINE...JM

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