FXUS66 KMTR 081217
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
517 AM PDT Fri May 8 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1123 PM PDT Thu May 7 2026

 - Warming and drying trend will continue through the early part 
   of next week

 - Temperatures are forecast to peak on Monday

 - Moderate risk for heat-related illnesses for sensitive
   populations across the interior early next week

&&

.SHORT TERM...
Issued at 1123 PM PDT Thu May 7 2026
(Tonight through Saturday)

Widespread low clouds have pushed inland from the coast, covering 
the bays and into some of the interior valleys. Expect chances for 
pockets of fog overnight, with the strongest chances in the North 
Bay. The marine layer's influence will be stronger than last night, 
that along with the blanket of lower cloud cover will keep overnight 
temperatures mild. Most areas will see lows in the 50s and upper 
40s. Only far interior valleys and higher peaks will see lows as 
cold as the mid 40s.

Friday will start on the cloudy side, and that cloud cover looks to 
linger into the late morning and even the early afternoon  for some 
areas. The duration of the cloud cover will keep coastal and 
slightly inland areas on the cooler side compared to the areas that 
stay clear. Inland cloud cover will start clearing in the mid 
morning, however areas around the bays will keep cloud cover into 
the late morning and early afternoon. Portions of the immediate 
coast looks to keep cloud cover through the day with moderate to 
breezy winds. This will keep temperatures on the coast in the lower 
60s, then the 60s and 70s for areas more inland, and into the 80s 
for areas not experiencing the morning cloud cover. A few areas in 
the far interior portions of Monterey Co look to break 90 degrees 
once again.

Friday night will see the affects of the building ridge to the north 
with a compression of the marine layer and a reduction in the 
overnight inland push of coastal stratus. This means that cloud 
cover will still be prevalent along the coast, but will struggle to 
enter the SF Bay and reach more of the inland areas. Additionally, 
the inland push of coastal stratus looks to be much later, more so 
into the night than the evening.

With a weaker marine influence, reduced cloud cover, and building 
ridge, many more of the inland areas to break into the 80s for 
Saturday. Coastal areas will stay low 60s, and the slightly inland 
areas stay in the 70s, but most areas away from the coast look to 
break 80. A few of the more inland areas look to break into the mid 
90s than previous days.

&&

.LONG TERM...
Issued at 1123 PM PDT Thu May 7 2026
(Saturday night through next Thursday)

The compression of the marine layer and building of the ridge 
continues Sunday and Monday, with Monday continuing to look like the 
hottest day of the forecast. For Monday itself: Most of the interior 
valleys look to break into the 90s with widespread 80s for all but 
the near-coastal areas seeing the 60s and 70s. 

The ridge and increasing pressure will form a thermal belt, causing 
much warmer lows on the higher peaks (60s and a few 70s) and will 
allow for those peaks to break into the 90s for Monday afternoon. 

Model trends continue to show notable cooling Tuesday, but it will 
still be on the hot side. The ridge begins to push east and a 
through deepens in the pacific leading to weak onshore winds along 
with a dissipation of the thermal belt. 

From there, models split off in the movement of said trough. Some
outputs place it in the Northwest, putting us into stronger zonal
flow. Others place it farther south into the Bay Area, leading to
drizzle and much cloudier conditions. Then there are some hits 
that the trough forms a cut off low in the middle of the Pacific, 
calling for continued weak onshore flow. Each of these scenarios 
call for a cool-down into the mid to late week, but offer fairly 
different magnitudes. Be sure to keep checking back as the 
forecast develops.

&&

.AVIATION...
(12Z TAFS)
Issued at 517 AM PDT Fri May 8 2026

Widespread stratus /LIFR-MVFR/ prevails while it's VFR far inland.
The marine layer depth varies from 1500 feet to almost 2000 feet.
Last evening's Oakland upper air sounding showed plenty of dry air
above the marine layer. The overall precipitable water had lowered
to 0.40" which is 10th percentile for the time of year. 500 mb high
pressure is present aloft, but it's also cooled to saturation beneath
the lower level temperature inversion, supporting marine layer stratus.
With less water vapor aloft above the marine layer, the atmosphere
is currently losing heat to space via radiative cooling (just like
in the desert at night) until it slows, stops and reverses with the
return of incoming solar energy. With daytime warming and mixing,
stratus will mix out back close to the coastline by late morning 
and afternoon. 

Whether stratus fully returns or only slowly returns tonight and 
Saturday morning is currently a low confidence forecast. For example
the 06z NAM shows 90%+ humidity ~ 1000 mb level and widespread
stratus tonight. However, HREF and HRRR show stratus only slowly
returning tonight. At the moment, it's difficult to find reason(s)
why the stratus won't return tonight (at least late tonight and
Saturday morning) meaning it's a near persistence forecast. 

Vicinity of SFO...Stratus /MVFR/ with onshore wind increasing to
15 to 25 knots possibly a few higher gusts in the afternoon.
Stratus mixing out to VFR by 20z today. Stratus /MVFR/ returns
by early Saturday (12z). West wind easing to less than 10 knots
tonight and shifting to light southerly Saturday morning. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus /IFR/ gradually lifting to MVFR
and mixing out to VFR by late morning or early afternoon. Stratus
/MVFR-IFR/ returns tonight and Saturday morning. West to northwest
winds 10 to 15 knots today, decreasing to 5 to 10 knots tonight and
Saturday morning.

&&

.MARINE...
(Today through Wednesday)
Issued at 418 AM PDT Fri May 8 2026

Fresh to strong northwest breezes will persist through the
weekend with steadily building rough seas. The rough seas will
begin to ease late Sunday into Monday, which is when winds begin
to decrease to moderate to fresh northerly breezes.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this 
     evening for Mry Bay.

     Small Craft Advisory from 3 PM to 9 PM PDT Saturday for Mry Bay.

     Small Craft Advisory until 9 PM PDT Sunday for Pigeon Pt to Pt 
     Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt 
     Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt 
     Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

&&

$$

SHORT TERM...Murdock
LONG TERM....Murdock
AVIATION...Canepa
MARINE...Canepa

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Prepared by Boulder-Creek.com Weather at: Fri May 8 06:30:04 PDT 2026