406
FXUS66 KMTR 111736
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1036 AM PDT Mon Aug 11 2025

...New AVIATION, MARINE, BEACHES...

.KEY MESSAGES...
Updated at 333 AM PDT Mon Aug 11 2025

 - Moderate HeatRisk continues through Monday for portions of North,
   East, and South Bay counties and interior Monterey and San
   Benito counties.

 - Elevated fire weather concerns persist through Monday given the warm
   and dry conditions combined with breezy afternoon and evening
   winds.

 - Pattern change Tuesday, with cooler weather and coastal drizzle
   returning to the forecast.

&&

.UPDATE...
Issued at 850 AM PDT Mon Aug 11 2025

Marine layer ramped up slightly this morning. As such, better
coverage of clouds across the inland valleys, less dense fog being
reported, still some fog but in the 3-6 mile range, and less
drizzle. Southerly transport flow did allow for some upper level
smoke from the Gifford Fire to sneak into the forecast area.
Thankfully, this is mainly high level smoke. Latest smoke
guidance shows a shift in transport flow so will push some of the
smoke southward again.

No update needed.

One more day of inland heat. Details below...

Still waiting for all latest guidance to come, but will be doing a
deeper dive into Ivo moisture and potential impacts. Ivo details
from before down below...

&&

.SHORT TERM...
Issued at 333 AM PDT Mon Aug 11 2025
(Today and tonight)

The Fort Ord Profiler this morning shows the marine layer around
1400ft this morning, with the spread of the stratus looking to match
a marine layer depth of 1500ft. Stratus should take a touch longer
to erode this morning, especially for those closer to the coast.
Overall, another sunny day is expected for interior locations with
high temperatures peaking 90s, perhaps closer to the upper 90s to
near 105 for interior Contra Costa, San Benitio, and Monterey
counties. Stratus returns tonight and will seep into the valleys

&&

.LONG TERM...
Issued at 333 AM PDT Mon Aug 11 2025
(Tuesday through Sunday)

The pattern change begins on Tuesday, though be it, perhaps a bit
more minimally than previously expected. A shortwave trough
approaches the PacNW which will begin to flatten the upper level
ridge. High temperatures will be a few degrees cooler than Monday,
with the gradual decrease in temperatures continuing throughout the
week. The more substantial trough, kicks in on Wednesday which will
pave the way for upper level troughing to dominate the forecast
through the weekend. Look for cloudy, drizzly, and foggy overnights
and sunny skies for interior locations by the afternoon.

An interesting note in the forecast is that a few deterministic
models are trying to show moisture from Tropical Depression Ivo
being pulled over our coast. CAPE seems to struggle to manifest
given the troughing, but midlevel lapse rates are interesting around
7.5-8C/km. For now current thinking is perhaps we see some cumulus
clouds or perhaps some high level clouds. Thunderstorm development
looks unlikely at this time.

&&

.AVIATION...
(18Z TAFS)
Issued at 1034 AM PDT Mon Aug 11 2025

VFR conditions are returning to inland TAF sites, with the exception
of HAF where IFR/MVFR is expected through a good portion of the TAF
period. Onshore winds will increase once again this afternoon before
easing after sunset and more so into Tuesday morning. High
confidence for an early return of IFR/MVFR conditions at both the
Bay Area and Monterey Bay terminals this evening or by early Tuesday
morning. There is moderate confidence for LIFR conditions early
Tuesday morning around MRY, HAF, and STS. Expecting IFR/MVFR
(potentially IFR ceilings in the aforementioned sites) to clear out
similar to this morning between 16Z-19Z Tuesday. Onshore winds
increase once again by Tuesday afternoon.

Vicinity of SFO...VFR. High confidence for an increase in westerly-
northwesterly winds to increase this afternoon before easing
slightly into Tuesday morning. High confidence for IFR/MVFR ceilings
to develop over the Bay Area terminals late this evening and persist
through mid-morning on Tuesday. Onshore winds increase once again by
Tuesday afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. Onshore winds increase slightly this
afternoon before diminishing after sunset. There is high confidence
for IFR ceilings to return this evening, potentially lowering to
LIFR early Tuesday morning at MRY.

&&

.MARINE...
(Today through Saturday)
Issued at 1034 AM PDT Mon Aug 11 2025

Northwesterly breezes will be gentle to moderate through
Wednesday with diurnally driven afternoon sea breezes bringing
localized strong gusts through the Delta and along Point Sur.
Northwesterly breezes increase Thursday to become fresh to strong,
posing hazardous conditions for small craft. Moderate seas will
build to become rough for inner waters and outer waters Thursday.

&&

.FIRE WEATHER...
Issued at 908 AM PDT Mon Aug 11 2025

Another night with poor humidity recovery above the marine layer.
May sites in the 15-20% range. This is roughly 5-7 days of the
pattern so the hills are crispy. Thankfully, the overall fire
weather concerns the next few days will be easing as interior
heat breaks and humidity begins to creep upward. While the ERC had
been climbing and the Fuel moisture had been dropping the 7 day
forecast shows a reverse with dropping ERC and rising Fuel
moisture.

&&

.BEACHES...
Issued at 1034 AM PDT Mon Aug 11 2025

A long period southwesterly swell is impacting the coast and will
continue to do so through Tuesday evening. This will result in an
increased risk for sneaker waves and rip currents, especially along
southwest facing beaches such as Stinson, Santa Cruz Boardwalk and
Twin Lakes. Sneaker waves can unexpectedly run significantly farther
up the beach than normal, including over rocks and jetties. Rip
currents are typically more frequent and stronger in the vicinity of
jetties, inlets, and piers. Swimmers should always swim near a
lifeguard. Remember, never turn your back to the ocean!

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Tuesday evening for CAZ505-529.

PZ...Small Craft Advisory until 11 PM PDT this evening for SF Bay N
     of Bay Bridge.

     Small Craft Advisory from 1 PM to 9 PM PDT Tuesday for SF Bay N
     of Bay Bridge.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PDT
     Wednesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...RGass
MARINE...RGass
BEACHES...RGass

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