Technical NOAA Weather Discussion

FXUS66 KMTR 172103
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
203 PM PDT Thu Jul 17 2025

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 155 PM PDT Thu Jul 17 2025

 - Slight warming trend to seasonal temperatures Friday through
   the weekend before below normal temperatures return Monday.

 - Localized elevated fire weather threat continues across the
   higher elevations with drier conditions beginning this weekend.

 - Winds strengthen early next week.

&&

.SHORT TERM...
Issued at 155 PM PDT Thu Jul 17 2025
(This evening through Friday)

The marine layer will start to compress tonight as troughing over 
the West Coast is pushed northward over OR/WA by weak high pressure 
building in over California. Guidance shows high pressure building 
more slowly throughout the day with Friday acting as more of a 
transition day from weak/subtle troughing to weak high pressure. The 
main change to the forecast is how much temperatures will warm. 
Temperatures across the board will warm between 1 to 5 degrees on 
Friday. For the lower elevations, this pushes most sites closer to 
seasonal averages, but, most will remain at least slightly cooler 
than normal. Across the higher elevations, temperatures have been 
closer to seasonal averages so this slight warm up will push 
temperatures to seasonal to slightly above normal. What specifically 
does that mean for tomorrows high temperatures? Areas closer to the 
SF Bay Shoreline will only warm 2-3 degrees with highs in the mid to 
upper 70s while areas away from the bay shoreline will be in the 
upper 70s to 80s. Residents of interior Monterey and San Benito 
counties may feel this warm up more than residents of the Bay Area 
with highs rising from the low to mid/upper 90s. Coastal residents 
continue to benefit from the natural A/C of the marine layer with 
temperatures staying in the upper 50s to 60s. 

In terms of stratus and drizzle chances, the marine layer was around 
2000 ft as of the 12Z OAK sounding this morning. With high pressure 
building in more slowly tomorrow, another night of widespread 
stratus is expected across the Bay Area and Central Coast. There is 
some potential for coastal drizzle tonight, but, this is mainly 
limited to the coastal North Bay with chances decreasing along the 
rest of the coastline. 


&&

.LONG TERM...
Issued at 155 PM PDT Thu Jul 17 2025
(Friday night through next Wednesday)

Temperatures will be fairly similar on Saturday to those observed on 
Friday, upper 70s along the Bay Shoreline, upper 70s to 80s farther 
away from the shoreline, and 90s across the far interior East Bay 
and Central Coast regions. This will keep us with seasonal to 
slightly below normal temperatures across the majority of the Bay 
Area with only the higher elevations seeing slightly above normal 
temperatures. Temperatures will peak on Saturday for the interior 
Central Coast but peak on Sunday for the Bay Area as high pressure 
becomes more dominant across the region. This will bring 
temperatures largely into the 80s across the interior and low to mid 
90s across the interior East Bay and Central Coast. Temperatures 
cool down well overnight (50s to 60s) with only Minor HeatRisk 
forecast across interior regions through the weekend. 

Thought you'd seen the last of No Sky July? Nope. Upper level 
troughing is forecast to return across our area early next week and 
continue through the end of the forecast period. This will see 
temperatures dropping below normal again with high temperatures 
falling back into the mid 70s to low 80s across the interior. 
Temperatures across the interior Central Coast will continue to be 
seasonal to slightly above normal in the upper 80s to low 90s. The 
marine layer looks to deepen again Monday with widespread overcast
conditions likely to return again each night starting Monday. CPC
guidance indicates temperatures are likely to remain below normal
through the end of July as upper level troughing continues.Gusty 
onshore winds return to mountain gaps/passes, valleys, and along 
the coast late Sunday through Monday as the upper level trough 
approaches. EFI guidance highlights the potential for stronger 
winds in the vicinity of the East Bay Hills and eastern Napa 
County with the strongest winds expected over the Sacramento 
Valley.

Localized elevated fire weather concerns continue across the higher 
elevations and interior Central Coast. Seasonal to slightly above 
normal temperatures continue across these regions with daytime 
humidity values dropping as low as 15% Saturday and Sunday. Winds 
generally remain light and onshore, but, diurnally breezy winds 
gusting to around 30 mph are expected to develop each 
afternoon/evening in the Salinas Valley. Dry conditions will persist 
through the end of the forecast period with daytime minimum humidity 
values in the 20%-30% range as upper level troughing returns. 

&&

.AVIATION...
(18Z TAFS)
Issued at 1042 AM PDT Thu Jul 17 2025

Generally MVFR where low clouds persist this morning while inland 
areas continue to clear out. The remainder of the TAF sites will 
clear out between 18Z-20Z, with the exception of HAF where low 
ceilings may persist through much of the day. Onshore winds increase 
this afternoon before easing after sunset. High confidence for 
IFR/MVFR ceilings to return either by late this evening across the 
Monterey Bay terminals and then early Friday morning for Bay Area 
terminals. Ceilings will begin to lift around 18Z-20Z Friday for 
inland areas with another increase in onshore winds by Friday 
afternoon. 

Vicinity of SFO...MVFR currently with conditions expected to return 
to VFR between 18Z-20Z. Westerly to northwesterly winds increase 
this afternoon before easing late in the night. High confidence for 
MVFR ceilings to return by early Friday morning and will persist 
through about 18Z-20Z Friday. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...MVFR currently with clearing conditions 
between 18Z-20Z. However, moderate confidence for clearing to occur 
with low high confidence for IFR/MVFR ceilings to return this 
evening. Onshore winds will increase this afternoon before easing 
after sunset. LIFR conditions will be possible across the terminals 
early Friday morning before lifting by late morning.  

&&

.MARINE...
(Today through Tuesday)
Issued at 1042 AM PDT Thu Jul 17 2025

Expect a light to moderate westerly or northwesterly breeze 
across the majority of the coastal waters through this weekend. 
Gusty winds, potentially hazardous to small craft, develop each 
afternoon and evening through the Golden Gate and into the Delta 
as well as the favored coastal jets along Pigeon Point and Big 
Sur. Moderate seas also continue through the remainder of the
forecast period.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM Friday to 3 AM PDT Saturday for 
     Pt Pinos to Pt Piedras Blancas 0-10 nm-SF Bay N of Bay 
     Bridge.

&&

$$

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

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Prepared by Boulder-Creek.com Weather at: Thu Jul 17 14:30:03 PDT 2025
From the National Weather Service