FXUS66 KMTR 011145
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
445 AM PDT Tue Jul 1 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 212 AM PDT Tue Jul 1 2025

 - Isolated showers early Tuesday morning over the North Bay.
 
 - Typical marine layer stratus pattern this week.

 - 10 percent chance for dry thunderstorms in the North Bay
   Tuesday night.

 - Near normal temperatures with a cooling trend late week.

 - Breezy northwest winds Thursday afternoon and evening.

&&

.SHORT TERM...
Issued at 212 AM PDT Tue Jul 1 2025
(Today and tonight)

A little bit of weather excitement for the night shift. Radar
remains in precip mode as it continues to detect a few showers 
and thunderstorms over Yolo county. Given the current storm motion
a few of these showers/thunderstorms will enter NE Napa county. 
If they hold together they could (10-20%) reach northern Sonoma 
county early this morning. The near term forecast through roughly 
10 AM has been updated to reflect the low chance for precip. So 
why are we seeing showers/thunderstorms? An upper level low 
pressure continues to spin off the immediate coast. As such, upper
level moisture is being pulled in from the SE and wrapping around
the upper low. In fact, these pockets of upper level moisture are
roughly 110-150% percent of normal for early July. Combine the 
upper level moisture with some mid-level instability and you get 
thunderstorms. MUCAPE, steep lapse rates, modified Total Totals, 
are all being picked up by the models. 

Outside of precip chances we've flipped the calendar to No Sky
July and the satellite fog product shows it well. Ft Ord profiler
shows the marine layer depth near 1200-1500 feet with clouds 
moving into the inland valleys. It's always interesting 
meteorologically to watch thunderstorms/convection develop even 
with a stable surface layer like stratus. 

Similar to the last few days, morning stratus and fog will slowly
roll back to the coast by mid-morning. Don't expect a full
clearing today as clouds will hug the coast. Temperatures will
peak in the upper 50s to near 70 at the coast and upper 70s to mid
90s inland or close to seasonal averages for July 1.  

One thing will keep an eye on through out the day will be another
potential for showers/thunderstorm impacting the North Bay late
this afternoon and early tonight. Similar to what's happening now
could happen again. Upper level instability with some moisture 
may lead to a few showers/thunderstorms across interior North Bay 
(10-15%)

&&

.LONG TERM...
Issued at 323 AM PDT Tue Jul 1 2025 
(Wednesday through Monday)

The slow moving upper level low will gradually move inland along
the Central Coast on Wednesday before ultimately becoming an open
wave. In short, this will put an end to any precip chances around
the Bay Area and Central Coast. All in all, Wednesday will end up
being rather pleasant.

A more progressive upper level pattern develops on Thursday as an
unseasonably deep upper level trough takes aim at the PacNW and
NorCal. While the trough looks dry for us it will keep temps
cooler, marine layer deep, and winds breezy through the day. 

As for the upcoming 4th of July, the upper level trough finally
passes overhead re-enforcing cooler temperatures and persistent 
marine layer. If you're looking for clear skies that evening for 
any firework related activities you may have a hard time.

Relatively quiet weather for the upcoming weekend. Heading into
next week we'll need to monitor the possible development of 
another upper level low off the coast. As of now, ECM Ens shows 
more of a cut-off low while other Ens guidance less so.

&&

.AVIATION...
(12Z TAFS)
Issued at 445 AM PDT Tue Jul 1 2025

Stratus, fog and patchy light drizzle /IFR-LIFR/ along the 
immediate coastline will continue to move inland on onshore winds.
The SFO-SAC pressure gradient predominates at 2.8 mb and is 
forecast to reach near 4 mb in the afternoon and early evening. A
few mid level convective clouds are likely during the day and 
tonight. Stratus, fog and patchy light drizzle /IFR-LIFR/ return 
tonight and Wednesday morning.

Vicinity of SFO...Stratus is steadily increasing /MVFR-IFR/ during
the morning, with clearing to VFR forecast 17z today. Stratus
ceiling /IFR/ returns 10z early Wednesday. Light and variable wind
until 17z then northwest and increasing with afternoon gusts to 20
knots, then decreasing tonight and Wednesday morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus, fog and patchy light drizzle
/IFR-LIFR/ during the morning, conditions improving to MVFR-VFR by
late morning and early afternoon. Stratus, fog and patchy light
drizzle /IFR-LIFR/ return tonight and Wednesday morning. Mainly 
onshore winds 5 to 15 knots.

&&

.MARINE...
(Today through Sunday)
Issued at 423 AM PDT Tue Jul 1 2025

Significant wave heights will build early this morning as
northwest winds strengthen and gradually spread across the outer
waters  through the rest of the week. Winds will be strongest
across the  northernmost outer waters with winds strengthening to
gale force  by midweek. Winds and seas remain elevated across the
coastal waters through this week and into next week.

&&

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

     Small Craft Advisory from 3 PM to 9 PM PDT Wednesday for Pt 
     Reyes to Pigeon Pt 0-10 nm-SF Bay N of Bay Bridge.

     Small Craft Advisory from 9 AM to 9 PM PDT Wednesday for Pt 
     Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 3 PM PDT 
     Wednesday for Pt Arena to Pt Reyes 10-60 NM.

     Gale Warning from 3 PM to 9 PM PDT Wednesday for Pt Arena to Pt 
     Reyes 10-60 NM.

     Small Craft Advisory from 3 AM to 9 PM PDT Wednesday for Pigeon 
     Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Canepa
MARINE...Canepa

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Prepared by Boulder-Creek.com Weather at: Tue Jul 1 06:30:03 PDT 2025