FXUS66 KMTR 160629
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1129 PM PDT Wed Jul 15 2026
...New SHORT TERM, LONG TERM...
.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...
(06Z TAFS)
Issued at 949 PM PDT Wed Jul 15 2026
Clear skies across the region with VFR prevailing everywhere
except HAF. Confidence is decreasing that widespread stratus will
return tonight so have tentatively improved MRY and SNS to VFR
through tonight. Breezy winds diminish overnight before
restrengthening during the afternoon/evening. The marine layer
looks to return tomorrow evening with stratus reaching the coast
by late evening.
Vicinity of SFO...VFR through the TAF period. Guidance shows the
potential for a few low clouds to move into the SF Bay tonight but
confidence is low. Leaned more towards the HRRR which showed
significantly reduced cloud cover across the region and is more in
line with current satellite observations. Breezy NW winds decrease
overnight before restrengthening during the day.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR through tomorrow evening. Decreasing
confidence that stratus will reach MRY/SNS tonight. HRRR guidance
keeps skies clear tonight while other models continue to show
stratus reaching the region. If stratus does return tonight, it
would likely by IFR to LIFR given how compressed the marine layer
currently is. MVFR-IFR conditions return tomorrow evening as the
marine layer deepens. Winds decrease overnight before breezy W to
NW winds return during the day.
&&
.MARINE...
(Tonight through next Tuesday)
Issued at 949 PM PDT Wed Jul 15 2026
Fresh to strong NW gusts continue across the coastal waters
through Friday. 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. Seas subside and winds
diminish Saturday into next week.
&&
.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...Coastal Flood Advisory until 4 AM PDT Thursday for CAZ006-506-
508.
PZ...Small Craft Advisory from 9 AM to 9 PM PDT Thursday for Mry Bay-
SF Bay N of Bay Bridge.
Small Craft Advisory until 3 AM PDT Friday for Pigeon Pt to Pt
Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to
Pigeon Pt 0-10 nm.
Small Craft Advisory until 9 AM PDT Thursday for Pt Pinos to Pt
Piedras Blancas 0-10 nm.
Gale Warning from 9 AM to 8 PM PDT Thursday for Pt Pinos to Pt
Piedras Blancas 0-10 nm.
Small Craft Advisory until 9 AM PDT Friday for Pigeon Pt to Pt
Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.
&&
$$
SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Kennedy
MARINE...Kennedy
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Prepared by Boulder-Creek.com Weather at: Thu Jul 16 00:30:03 PDT 2026
From the National Weather Service
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