FXUS66 KMTR 032342
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
442 PM PDT Mon Aug 3 2026

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

.KEY MESSAGES...
Updated at 1155 PM PDT Sun Aug 2 2026

 - Moderate HeatRisk in the interior through Tuesday, becoming 
   patchy midweek

 - Near critical fire weather threat across the interior North and East
   Bays, and the Diablo and Santa Lucia ranges through Monday 
   with elevated fire weather threat through the week

 - Widespread Moderate HeatRisk looks to return for the end of 
   the work week. 

&&

.SHORT TERM...
Issued at 1255 PM PDT Mon Aug 3 2026
(This evening through Tuesday night)

Nearterm:The southerly surge continues to inch its way northward
along the coast and finally made it past Pt Reyes. The surge has
really taken a bit out of temperatures along the immediate coast
this afternoon. 24 hr trends show many locations along the
coastline are running cooler than Sunday, which isn't surprising
with nearby clouds. On the flip side, head inland and away from
the surge influence and temps are soaring into the 90s and lower
100s. As such, Heat Adv remains in effect through this evening for
Interior North Mts and Interior East/South Bays.

Tonight through Tuesday night:
The surge will become less of a surge and more just onshore with
more stratus. Moderate marine layer stratus coverage for inland
areas tonight. This stratus will bring some relief and better RH,
but above the shall layer will remain mild and dry. 

Interesting set up for Tuesday as the upper level pattern shows a
slight rebound of the ridge, but lower surface levels keep the
southerly/onshore flow. Pretty hard to bet again stratus and
cooler SST along the coast. As such, temperatures for Tuesday will
be within a few degrees of Monday, but on the cooler side. Just
enough to knock down HeatRisk values to Moderate with little to no
Major.

Tuesday night will see even more stratus coverage with a slight 
deepening. 

One final concern for the short term will be smoke/haze. Ample
fire activity across OR/WA will push some smoke over the coastal
waters. Longer range RRFS actually brings some smoke/haze to the
coastal waters late Tuesday into Wednesday.

&&

.LONG TERM...
Issued at 1255 PM PDT Mon Aug 3 2026
(Wednesday through next Sunday)

Rinse and repeat for the long term, but in the other direction
with a gradual warming and drying trend.

Upper level high pressure that briefly flattened will rebuild 
over the West Coast beginning late Wednesday lasting through at 
least Friday. While there is a slight reprieve in temps mid-week 
inland heat and increasing HeatRisk return Thursday and more so 
Friday. In fact, some of the guidance suggest an airmass 
approaching 30C at 850mb. 30C is a pretty toasty airmass, which 
would easily yield max temps over 100 across the interior. Would 
also expect mild overnight lows in the hills. If this trend 
continues we may need another Heat Advisory. 

&&

.AVIATION...
(00Z TAFS)
Issued at 420 PM PDT Mon Aug 3 2026

VFR conditions will prevail through much of the overnight except
for the Monterey Bay terminals, where stratus is expected to
begin to move in after sunset. The marine layer continues to
struggle but may begin to rebound slightly tonight, along with a
more impactful KSFO-KWMC pressure gradient. Outside of the
Monterey Bay terminals, the MVFR/IFR ceilings are expected to
return closer to the pre-dawn hours and clear by late morning.

Vicinity of SFO...VFR through much of the overnight with MVFR/IFR
ceilings expected to return in the pre-dawn hours and lift by late
morning. Breezy onshore flow will develop by late afternoon and
persist through the evening hours.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR until after sunset when IFR/LIFR
ceilings are expected to spread over the peninsula into the
Salinas Valley. VFR conditions should return by early afternoon, a
little sooner at KSNS with steady, occasionally breezy onshore
flow Tuesday afternoon. 

&&

.MARINE...
(Tonight through next Saturday)
Issued at 420 PM PDT Mon Aug 3 2026

Northwest moderate to fresh breezes prevail into the evening with
occasional strong gusts across the far northern outer waters. By
tomorrow, winds become light to gentle (5-10 kt) with some degree
of  variability in the wind direction, generally from the
southwest.  Widespread moderate northwest winds around 15 kt
settle in towards  the end of the week. West-northwest seas
continue to subside to  moderate and remain around 4-8 feet
through the work week.

&&

.FIRE WEATHER...
Issued at 420 PM PDT Mon Aug 3 2026

Near critical fire weather conditions continue through this
evening, with elevated fire weather conditions persisting through
the middle of the week, and potentially a return of near critical
conditions later in the week. Temperatures remain around 10 to 15
degrees above normal across the interior (except for Wednesday,
with near normal temperatures) through early next week with highs
in the upper 80s to 90s. No major changes to the forecasted dry 
conditions. Daytime humidity retention remains poor across the 
interior (20-30%) with humidity values dropping into the 10s 
across the interior Central Coast, East Bay Hills/Valleys, and the
higher elevations. Portions of the interior Central Coast may see
daytime humidity values drop into the single digits Tuesday, then
again towards the end of the week into the weekend. Overnight RH 
recovery remains poor at locations above 2,000 feet with values 
between 25 to 40% expected with some favored locations struggling 
to reach even 25%. This will be particularly true across the 
Mayacamas, highest peaks of the East Bay Hills, the Diablo Range, 
the Santa Cruz Mountains, the Santa Lucia and Gabilan Ranges. 
Nocturnal drying (rapid decrease in RH through the pre- dawn 
hours) may also transpire which will increase the burn period or 
time in which fire behavior may remain active. Energy Release 
Component (ERC) values are projected to climb above the the 
percentile across the interior Central Coast, Mid Coast to 
Mendocino (North Bay), and Diablo- Santa Cruz (Diablo Mountains 
and Santa Cruz Mountains) zones by the middle of the week. 
Diurnally breezy onshore winds are expected along the coast, 
mountain gaps and passes, and along the ridgelines each 
afternoon/evening. With near critically dry conditions and above 
normal temperatures expected, individuals across these areas are 
advised to avoid activities that may spark a fire. Fire crews are 
urged to exercise extra caution when executing any prescribed 
burns, especially where fuels, topography, and weather align. 

&&


.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 10 PM PDT this evening for CAZ504-510-
     513>515.

PZ...Small Craft Advisory until 9 PM PDT this evening for Pt Arena to 
     Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...JM
MARINE...Navarrete

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Prepared by Boulder-Creek.com Weather at: Mon Aug 3 20:30:02 PDT 2026