FXUS66 KMTR 161133
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
433 AM PDT Thu Jul 16 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 126 PM PDT Wed Jul 15 2026
 
 - Elevated fire weather conditions Thursday

 - Breezy onshore winds through Friday 

&&

.SHORT TERM...
Issued at 1123 PM PDT Wed Jul 15 2026
(Tonight through Friday)

Fortunately our weather balloons have returned to service with 
the 00Z launch, so let's look at some of the data. The 850 mb 
temperature is 22.75 C, which is between the 75th and 90th 
percentile for this time of year. That explains why it's been warm
recently. The temperatures Wednesday weren't as hot as Tuesday, 
but still around 5- 10 degrees above normal. The PW has dropped to
0.65", or between the 25th and 50th percentile. So the monsoon 
moisture from last weekend is totally gone. The skies are still 
clear as the marine layer struggles to reform. Temperatures will 
be another 5-10 degrees cooler on Thursday, broadly similar to 
seasonal normal, as the 850 mb temperature drops a bit and onshore
winds increase to bring cooler marine air advection. While 
temperatures are coming down, afternoon winds will be moderate to 
strong along the coast and in the mountains again today, bringing 
another round of elevated fire weather conditions.

It's unclear if marine layer clouds will form this morning. The SFO-
SAC gradient is +4.0 mb, so the onshore flow is good, but there are 
no low clouds offshore at the moment. That means the stratus will 
have to form overhead, rather than advect in from the ocean like 
normal. I'll put it at a 25% chance for coastal stratus by sunrise, 
and even less chance of pushing inland. If the clouds do form, they 
will clear by late morning.

&&

.LONG TERM...
Issued at 1123 PM PDT Wed Jul 15 2026
(Friday night through next Wednesday)

It looks much more likely that the marine layer clouds will return 
Friday morning thanks to sustained onshore winds and a slowly 
approaching trough off the coast. The marine layer depth will likely 
grow to around 1,000 feet by then, enough for the morning stratus
to reach into the valleys a bit. In addition to the clouds, the 
marine layer will keep coastal areas much cooler than they have 
been this week, and help regulate fire weather concerns. Once we
get back into this cooler, marine layer pattern it looks like it's
here to stay for a while.

Tropical Storm Elida has formed in the Eastern Pacific. This system 
will move harmlessly into the open ocean through the weekend, but
some of the mid and upper level moisture is likely to be drawn 
into our southwesterly flow at 500 mb. This will be apparent with 
mid and/or upper level clouds arriving Sunday. Model soundings 
suggest that the atmospheric stability will prevent any 
thunderstorm chances, so this tropical moisture will most likely 
just be a good sunset maker with a couple novelty rain drops 
possible Sunday - Tuesday.

&&

.AVIATION...
(12Z TAFS)
Issued at 431 AM PDT Thu Jul 16 2026

Currently VFR at all terminals. There is a patch of stratus that has 
developed within the Monterey Bay over the last 2 hours that 
continues to expand. If this reaches the Monterey Bay terminals, it 
will clear by late morning. A shallow marine layer around 1,000 feet 
is expected tonight. As such, moderate to high confidence on IFR 
ceilings returning to coastal and bayshore terminals with confidence 
decreasing as you move inland. Diurnal winds will prevail.

Vicinity of SFO...Currently VFR with northwesterly flow. Moderate 
(60%) confidence on an IFR ceiling returning tonight. The TAF may be 
slightly pessimistic with a 09Z arrival. Reasonable best case 
scenario is the marine layer is too shallow to make it through the 
San Bruno Gap and has to go through the Golden Gate Gap. This would 
likely lead to a later arrival time or stratus remaining confined to 
the north of the terminal. There's a 25% chance for wind gusts to 
reach 35 knots this afternoon and evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently VFR with southerly flow at MRY 
and VFR with northerly flow at SNS. Patchy stratus in the Monterey 
Bay is expanding within 5 miles to the north of the terminals. If 
this is able to reach the terminals, it'll likely be IFR and clear 
by late morning. High confidence on IFR ceilings returning to the 
terminals tonight with a greater chance at MRY than SNS.

&&

.MARINE...
(Today through Tuesday)
Issued at 431 AM PDT Thu Jul 16 2026

Fresh to strong northwesterly breezes will bring widespread
hazardous conditions for small craft today. Localized gale force
gusts are expected along the coastal jet regions of Point Reyes
and Point Sur. Moderate to rough seas will prevail through Friday.
Conditions improve Saturday as seas abate and northwesterly
breezes diminish.

&&

.FIRE WEATHER...
Issued at 138 PM PDT Wed Jul 15 2026

The warm temperatures we have had the past several days and 
continued warm weather has resulted in fuels rapidly drying this 
week. Fire weather concerns will remain elevated this afternoon with 
afternoon relative humidity dropping to between 10-20% across the 
interior and higher elevations (away from the marine influences), 
gusty onshore winds, and very dry fuels. This may result in 
additional fire starts particularly across the interior and higher 
elevations. These conditions are gradually forecast to improve as 
the marine layer returns Thursday and deepens into Friday. Unsettled 
weather is possible late this weekend and into early next week with 
returning potential for dry thunderstorms and gusty, erratic winds. 
However, the focus has shift to the east more over the Sierra 
Nevada. 

RGass

&&

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

     Small Craft Advisory until 9 AM PDT Friday 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 Reyes to 
     Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 AM PDT this morning for Pt Pinos to 
     Pt Piedras Blancas 0-10 nm.

     Gale Warning from 9 AM this morning to 9 PM PDT this evening for 
     Pt Pinos to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Sarment
MARINE...Sarment

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea


  
Prepared by Boulder-Creek.com Weather at: Thu Jul 16 06:30:03 PDT 2026