FXUS66 KMTR 070857
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
157 AM PDT Tue Jul 7 2026
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 1238 PM PDT Mon Jul 6 2026
- Seasonably cool temperatures through today before a warming
trend arrives for the second half of the week
- Marine layer stratus develops each evening and overnight
before retreating to the coast each morning and afternoon
- Long period southwest swell causes an increased risk of
sneaker waves and strong rip currents today through Friday
&&
.SHORT TERM...
Issued at 157 AM PDT Tue Jul 7 2026
(Today and tonight)
Satellite and surface observations show a well established and
widespread marine layer stratus pattern. Onshore winds prevail
due to a 3.1 mb SFO-SAC onshore pressure gradient. Sea surface
temperatures in the coastal waters vary from the 50s to lower 60s
(approx 1F to 4F above July normals). A clear night above the
stratus will allow for radiative cooling to space furthering
stratus development to daybreak. A radiative and gentle upsloping
cooling feedback loop may produce patchy light drizzle during the
overnight to predawn hours. A stable weather pattern continues
with 500 mb heights slightly above normal (near 587 decameters) at
~ 75th percentile for early July. Stratus will mix out inland
with patchy stratus lingering along the immediate coastline today
under diurnal surface warming. Daytime highs are forecast to
reach the 60s at the coast and around the SF Bay Shoreline to the
70s/80s inland to the 90s far inland. Stratus redevelops and moves
back inland tonight. Lows tonight are forecast to reach the 50s most
places to the lower to mid 60s at higher elevations near the marine
layer temperature inversion.
&&
.LONG TERM...
Issued at 157 AM PDT Tue Jul 7 2026
(Wednesday through Monday)
CA is currently on the western side of a high pressure system
centered over CO/NM/AZ and northern Mexico. Over the next 24-48
hours the high center will retrograde to just west of southern CA
where it'll become stationary during mid-week then is forecast to
advance northeastward late in the week and weekend. Daytime highs
will warm through mid-late week including a few areas getting
above 100F in the southern interior Thursday and Friday.
With approx 6 longwave troughs in the northern hemisphere, a
strong meridional temperature gradient and an ongoing negative
Pacific Decadal Oscillation this combination will place a longwave
trough over the eastern Pacific and as mentioned nudge the high
northeastward. The temporary westward motion of the aforementioned
high then its northeastward motion away from CA may transport
increasing 700-500 mb layer humidity and instability on southerly
winds close to and possibly over our forecast area over the
weekend and early next week. Recent global model guidance has
hinted at showery qpf and it's too soon to say if lightning will
be in the mix. We can have a marine layer while separate from this
high up in the atmosphere an elevated layer of humidity and
instability can move over the top of the marine air. Trying to
detect if there is a recent EPS/GEFS ensemble model trend in the
500 mb synoptic pattern: It does look like the 500 mb high is
shifting slightly northeast in recent trends, a sign of strength
in the westerlies and this may help mitigate the warm up prior to
any instability arriving. It's difficult to say with any certainty,
the door to higher humidity coupled to instability may still reach
here. Stay tuned to further updates.
&&
.AVIATION...
(06Z TAFS)
Issued at 940 PM PDT Mon Jul 6 2026
The stratus came in a little faster than last night with ceilings
a couple hundred feet lower. The TAFs have been adjusted to
account for this trend, as well as delaying the clearing time for
many terminals given the deeper cloud layer than expected. This is
also a good set up for some coastal drizzle, and patchy fog is
also possible from 12-16Z or so.
Vicinity of SFO...The clouds actually made it over the mountains
rather than swirling around the Bay. This indicates a higher cloud
top and overall deeper cloud layer than last night. With stronger
onshore wind developing over the next 24 hours, there is actually
a chance that the ceilings don't clear at all this TAF period. I
still show 6 hours of VFR conditions surrounding 00Z, but the
window is closing with the latest trends. Winds will remain out of
the standard WNW direction, but will gust to near 30 knots in the
afternoon.
SFO Bridge Approach...The approach was the last part of the Bay to
fill in, but will soon be firmly ensconced in the stratus.
Monterey Bay Terminals...With the deeper marine layer, it's very
unlikely MRY will clear for more than a few hours tomorrow
afternoon. SNS should still get a break, however.
&&
.MARINE...
(Tonight through next Sunday)
Issued at 940 PM PDT Mon Jul 6 2026
NW winds will increase to a strong breeze Tuesday and persist into
the weekend. Wind waves will build to rough by Wednesday, while a
long period low SW swell moves through this week.
&&
.BEACHES...
Issued at 1238 PM PDT Mon Jul 6 2026
A Beach Hazards Statement remains in effect for Pacific coast
beaches from Tuesday morning through Friday afternoon. Long period
southwesterly swell will create an increased risk of sneaker
waves and strong rip currents, as well as breaking waves up to 10
feet. This will be especially true for south and southwest facing
beaches with moderate to steep slopes along the North Bay, San
Francisco Peninsula, and Santa Cruz coasts. Sneaker waves can
sweep across the shoreline without warning, pulling people into
the sea from rocks, jetties and beaches. Dangerous swimming and
surfing conditions and localized beach erosion can be expected.
Stay off of jetties, piers, rocks, and other waterside
infrastructure. Remain out of the water to avoid hazardous surf
and NEVER turn your back on the ocean. Monitor local weather, surf
and tide forecasts at www.weather.gov/mtr.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from 5 AM PDT Tuesday through Friday
afternoon for CAZ006-505-509-529-530.
PZ...Small Craft Advisory from 9 AM Tuesday to 9 PM PDT Wednesday for
Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm.
Small Craft Advisory from 9 AM Tuesday to 3 AM PDT Thursday for
Pt Arena to Pt Reyes 0-10 nm.
Small Craft Advisory from 3 PM Tuesday to 3 AM PDT Thursday for
Pigeon Pt to Pt Pinos 10-60 NM-Pt Reyes to Pigeon Pt 0-10
nm.
Small Craft Advisory until 3 AM PDT Thursday for Pt Arena to Pt
Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.
&&
$$
SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...Flynn
MARINE...Flynn
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Prepared by Boulder-Creek.com Weather at: Tue Jul 7 04:30:04 PDT 2026
From the National Weather Service
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