FXUS66 KMTR 061724
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1024 AM PDT Thu Aug 6 2026

...New UPDATE, 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

&&

.UPDATE...
Issued at 1012 AM PDT Thu Aug 6 2026

Morning satellite looks a lot like Fogust - solid marine layer
covering all coastal waters and inland valleys. The depth this
morning per soundings and profilers is near 1800 feet. Latest
trends on satellite already show inland treat of the marine layer
back to the coast.  

No update needed in the near term as the forecast is on track. A
slight warm up is on tap for today, especially outside of the
marine layer foot print.

Highlights for afternoon forecast package:

Fine tuning heat for Friday through Sunday. Still looking like the
weekend will be the hottest days and advisories will be issued
this afternoon. 

Moonsonal moisture streams in from the south. Can
already see a few clouds over SoCal. Still not expecting a
convective threat for the Bay Area. Better forcing over the 
Sierra.

Given the hot and dry set up fire weather conditions will return
to near critical for the weekend. Each afternoon will feature an
onshore push of breezy conditions.

MM

&&

.SHORT TERM...
Issued at 1248 AM PDT Thu Aug 6 2026
(Today and tonight)

Longwave upper-level ridging will drift in from the Nevada and the
Desert SW 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...
(12Z TAFS)
Issued at 423 AM PDT Thu Aug 6 2026

Strong 500 mb high pressure continues while coastal stratus and 
patchy mist/fog /MVFR-IFR/ are moving inland on onshore winds. 
Onshore winds are supported by a 2.4 mb SFO-SAC pressure gradient.
Stratus, mist/fog will mix out to VFR by late morning and early
afternoon. Coastal stratus, mist/fog /MVFR-IFR/ return inland on 
onshore winds tonight and Friday morning.

Vicinity of SFO...Stratus /MVFR/ mixing out to VFR 17z today. 
Stratus returns 06z tonight. West to northwest wind 5 to 15 knots.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus /IFR/ until late morning then 
mixing out to MVFR-VFR. Stratus /IFR/ returns this evening and 
overnight. Mainly northwest winds 5 to 15 knots.

&&

.MARINE...
(Today through Tuesday)
Issued at 1012 AM PDT Thu Aug 6 2026

Gentle northwest winds continue to increase to strong by Saturday
morning across the outer Northern coastal waters. Wind-driven
moderate seas build to rough (9-12 feet) Saturday night in
response  to strengthening winds. A long period southwesterly
swell of 15 to  17 seconds approaches our coastline Saturday
morning and persists  through the weekend.

&&

.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...Canepa
MARINE...Navarrete

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Prepared by Boulder-Creek.com Weather at: Thu Aug 6 10:30:02 PDT 2026