FXUS66 KMTR 042335
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
435 PM PDT Sun Oct 4 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1213 PM PDT Sun Oct 4 2026

 - Warm to hot conditions across the region through mid-week

 - Hazardous heat conditions expected to persist inland, never
   leave children or pets in unattended vehicles!

 - Elevated fire weather conditions persist in the interior
   through Thursday

&&

.SHORT TERM...
Issued at 1213 PM PDT Sun Oct 4 2026
(This evening through Monday night)

It's hot. A persistent ridge over the western United States keeps 
the area much above the seasonal average (15 to 25 degrees above 
seasonal average away from the immediate coast). As of 11 AM today 
temperatures across the region ranged from the 80s into the lower 
90s inland, the 70s to the lower 80s close to the Bays, and the 
middle 60s to the middle 70s for the Pacific coast. There are some 
high clouds flowing above the SF Bay Area, but they do not seem to 
be impacting the heat levels. High temperatures today and Monday 
will be rather similar in the inland valleys, ranging from the 
middle 90s to near 104. Closer to the Bays, today's highs will be in 
the middle 80s to the middle 90s while locations along the Pacific 
coast rise into the 70s. Across the higher elevations and some 
nearby valleys, especially in the East and South Bays, mild 
overnight lows in the upper 60s to middle 70s will limit the 
ability to recover overnight. For Monday, these temperatures are a 
little uncertain owing to potential impacts from a shallow marine 
layer or a marginally stronger onshore flow than the current 
forecast, but highs should remain in the 70s and 80s. If confidence 
in highs towards the higher part of that range increases, the Heat 
Advisory for our coastal regions may need to be extended.

Due to the hazardous heat levels, a Heat Advisory is in effect for 
coastal locations through 10 PM tonight, while inland and Bayshore 
areas remains under the Advisory through Wednesday. Widespread 
Moderate HeatRisk blankets the region, corresponding to a moderate 
risk of heat-related illnesses for sensitive populations, including 
children, the elderly, pregnant women, people with chronic 
illnesses, and people who work or live outdoors without access to 
adequate cooling or hydration. In addition, many of the higher 
elevations in addition to the East Bay, South Bay, and the Carmel, 
Hollister, and northern Salinas Valleys see Major HeatRisk, 
corresponding to a high risk for heat-related illnesses for anyone 
without hydration or cooling. Follow these tips to avoid heat 
exhaustion and heatstroke:

* Stay hydrated and drink plenty of fluids.
* Wear lightweight, light-colored clothing.
* Reduce time spent outdoors or stay in the shade.
* Never leave people or pets unattended in vehicles.
* Use sunscreen if going to the coast or the pool.

&&

.LONG TERM...
Issued at 1213 PM PDT Sun Oct 4 2026
(Tuesday through next Saturday)

The ridging persists for the next few days and as previously 
mentioned, the Heat Advisory extends to Wednesday night for the 
inland and Bayshore regions. Temperatures across the inland valleys 
remain in the middle 90s to near 105 through Wednesday. Along the 
Pacific, we continue to monitor how the forecast trends evolve as 
impacts from a shallow marine layer or stronger onshore flow than 
the current forecast may significantly impact the immediate coast. 

A pattern change will begin Thursday as the ridge flattens and 
troughing develops in the northeastern Pacific and moves into 
southwestern Canada and the western United States. This will start a 
cooling trend with most locations dropping out of Moderate HeatRisk 
by Friday. Ensemble model cluster analysis hints at significant 
uncertainty for the upcoming weekend and the early part of the 
upcoming week regarding the strength of the trough and how long it 
could persist. 

&&

.AVIATION...
(00Z TAFS)
Issued at 426 PM PDT Sun Oct 4 2026

VFR to continue for inland sites through the TAF period. High
level clouds will clear out overnight with clear skies expected
across the interior. Marine stratus is expected to expand but
remain confined directly along the coast due to a shallow 500
foot marine layer. Fog is likely at HAF and MRY tonight with low
to moderate confidence in fog reaching SNS. Diurnally breezy winds
continue with moderate onshore winds during the day and light,
variable winds overnight.

Vicinity of SFO...VFR. Moderate northwesterly winds will decrease
through this evening light, less than 6 knot, winds expected
overnight. Moderate west to northwest winds return during the day
tomorrow around 16 knots.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Moderate onshore winds decrease through
the evening with light, variable winds expected overnight. Fog is
likely to develop at MRY tonight as marine stratus expands along
the coastline. Moderate confidence in the timing of fog/stratus
return at MRY with some potential for stratus to arrive closer to
06-08Z. Conditions improve mid to late morning with onshore winds
increasing during the afternoon. Guidance is mixed as to if
stratus/fog will reach SNS with the GFSlamp suggesting it will.
Comparatively, the HRRR and NAM both suggest it will be too dry
for stratus to reach SNS tonight. The current TAF leans towards
SNS staying VFR overnight but fog may develop between 09 to 17Z. 

&&

.MARINE...
(Tonight through next Friday)
Issued at 426 PM PDT Sun Oct 4 2026

Gentle to moderate northwesterly breezes will persist into
midweek, allowing for slight to moderate wave heights to persist.
Seas begin to build by late in the week.

&&

.FIRE WEATHER...
Issued at 405 AM PDT Sun Oct 4 2026

Hot and dry conditions will continue through Thursday, which will
be accompanied with weak offshore flow. Poor to very poor 
overnight recovery is expected for the thermal belts, generally 
for elevations above 1000-1500 feet, leading to elevated fire 
weather conditions. The marine layer is expected to be confined to
the immediate coast and around 500 feet. If working in the 
thermal belts, Moderate to Extreme HeatRisk is forecast this week,
with temperature and HeatRisk trends improving late week. A 
pattern change is expected late in the week or over the weekend. 
Cooler weather and the potential for improved RH recovery is 
forecast or Friday. 

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 10 PM PDT this evening for CAZ006-502-505-
     509-528>530.

     Heat Advisory until 10 PM PDT Wednesday for CAZ503-504-506-508-
     510-512>518.

PZ...None.
&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Kennedy
MARINE...RGass

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Prepared by Boulder-Creek.com Weather at: Sun Oct 4 18:30:03 PDT 2026