FXUS66 KMTR 220014
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
514 PM PDT Tue Jul 21 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 1219 PM PDT Tue Jul 21 2026

 - Heat Advisory in effect for interior Central Coast and Bay 
   Area through 9 PM PDT

 - Breezy onshore winds return for the second half of the week

 - Temperatures will hover around normal through the week

&&

.SHORT TERM...
Issued at 1219 PM PDT Tue Jul 21 2026
(This evening through Wednesday night)

Have went ahead and issued a Heat Advisory through 9 PM this 
evening for interior areas of the Bay Area and Central Coast. 
Temperatures overnight and into this morning didn't cool off as 
much as originally expected, thanks to the mid/upper level cloud 
cover across the region. That combined with temperatures forecast 
to reach the 90s (potentially exceeding 100 deg F in the warmest 
interior spots) across the interior made for widespread Moderate 
HeatRisk. Today is forecast to be the hottest of the week! 

For tonight, expecting an increase in low level stratus to return
to the coast and expand inland into the coastal adjacent valleys.
There is a greater than 50% probability of this occuring as mid-
to-high level clouds begin to shift to the east as remnant 
moisture from Elida gets absorbed in the mean flow aloft. Cannot 
rule out coastal drizzle tonight, depending on if the shallow 
marine layer is able to redevelop. It will feel muggy once again 
tonight as humidity remains elevated.

Tomorrow will feature a significant cool down thanks to an 
increase in onshore winds and stronger marine influences. 
Temperatures across the interior will warm into the mid 70s to mid
80s with the warmest interior spots reaching into the lower 90s 
across the Central Coast. Meanwhile, cooler conditions will 
prevail near the coast with day time highs in the mid 60s to mid 
70s. 

&&

.LONG TERM...
Issued at 1219 PM PDT Tue Jul 21 2026
(Thursday through next Monday)

Not much change to the forecast beyond the short term. Still 
expecting troughing off of the Pacific Northwest coast as high 
pressure remains over the interior West through late week. This will 
generally keep conditions near seasonal averages with night/morning 
low clouds working their way inland and then retreating to the coast 
by the afternoon. As the high pressure appears to shift more toward 
the Four Corners region, we may see the marine layer compress over 
the weekend with a slight inland warming trend.

&&

.AVIATION...
(00Z TAFS)
Issued at 447 PM PDT Tue Jul 21 2026

VFR is expected to prevail for all terminals until around midnight
when we begin to feel the effects of a pattern change as the 
influence of the remnants of Elida shift north. Marine stratus is 
expected to arrive a little later than normal diurnal patterns,
and clearing Wednesday morning will shift later into the morning
hours to early afternoon.

Vicinity of SFO...Onshore flow overnight will become breezy
Wednesday afternoon with MVFR/IFR ceilings expected after 
midnight tonight and persisting into the early afternoon,
with light drizzle possible in the early morning hours.


SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR until later tonight, with MVFR/IFR
ceilings returning, possibly before midnight. Expect IFR ceilings
by sunrise with a chance of drizzle as well with a later clearing
time into early afternoon Wednesday, then VFR through the
remainder of the forecast period.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 1200 PM PDT Tue Jul 21 2026

Light northwesterly breezes are expected today, backing to become
southerly tomorrow. Hazardous conditions for small craft may 
return as early as Thursday as northwesterly breezes return and 
increase to become moderate to fresh through Saturday. Moderate 
southwesterly swell from tropical cyclone activity in the Eastern 
Pacific will bring mixed seas and potentially hazardous conditions
through the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 9 PM PDT this evening for CAZ502-504-506-508-
     510-512>518.

PZ...Small Craft Advisory from 9 PM Wednesday to 9 PM PDT Thursday 
     for Pt Pinos to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...JM
MARINE...CW

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Prepared by Boulder-Creek.com Weather at: Tue Jul 21 20:30:04 PDT 2026