FXUS66 KMTR 160958
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
258 AM PDT Fri Oct 16 2026
...New MARINE...
.KEY MESSAGES...
Updated at 1201 AM PDT Fri Oct 16 2026
- Above normal temperatures continue into Saturday before
cooler, below normal weather returns Sunday into next week
- Critical to near critical fire weather conditions continue
across the higher elevations of the Bay Area and Central Coast
due to very dry conditions and offshore flow through Saturday
- Pattern change expected early to mid next week with periods of
breezy onshore winds and light, accumulating rain
&&
.SHORT TERM...
Issued at 1201 AM PDT Fri Oct 16 2026
(Today and tonight)
A Red Flag Warning remains in effect through 11 AM Friday for the
North Bay Interior Mountains due to moderate offshore winds and
critically dry conditions overnight. Minimal to no overnight
humidity recovery is expected with humidity values between 15 to 25%
expected. Winds across the North Bay Interior Mountains have picked
up across the highest peaks and will spread into the remainder of
the NB Interior Mountains tonight. Offshore gusts are expected to
peak between 20 to 30 mph with stronger gusts possible across the
highest ridgelines. Gusts between 40 to 60 mph have been observed
across the highest peaks (3500+ ft) in northern Sonoma and Napa
counties. As offshore winds pick up across the rest of the NB
Interior Mountains, humidity values will drop with rapid fire spread
possible should a fire start. Winds are expected to decrease by late
morning with the Red Flag Warning set to expire at 11 AM. Although
the winds will have decreased, very dry conditions (RH 10-20%) will
persist through the rest of the day with poor overnight recoveries
expected Friday into Saturday. As such, near critical fire weather
conditions will continue across the higher elevations of the Bay
Area and Central Coast through Saturday. If you are participating in
any activity involving flames outdoors, be very careful and do not
allow sparks/embers to escape. Listen to all guidance from local
officials.
Upper level ridging continues with widespread above normal
temperatures and Moderate HeatRisk peaking today. Minimal relief is
expected along the coast due to upper level ridging mixing out the
marine layer. Interior highs peak in the upper 80s to low 90s with
coastal highs in the 70s to low 80s. Portions of the Santa Cruz
Mountains and the southern Santa Clara Valley may reach the upper
90s. Expect hot conditions and patchy Moderate HeatRisk to continue
into Saturday although a few degrees cooler than on Friday. If
you're not a fan of hot weather, you're in luck as a pattern change
is expected Sunday into next week (see Long Term discussion).
&&
.LONG TERM...
Issued at 1201 AM PDT Fri Oct 16 2026
(Saturday through Thursday)
Temperatures return to more seasonal temperatures by Sunday as upper
level ridging is replaced by broad troughing. High temperatures cool
into the 70s to low 80s across the interior while the coast drops
back into the 50s to 60s thanks to the return of the marine layer.
Upper level troughing impacts become more pronounced over the course
of the next week as a deep upper level low becomes cut-off from the
jet stream and lingers along the Central/Southern California
coastline through late next week. At the same time, a surface low
pressure system originating from the Gulf of Alaska will move
southwards along the California coast next week. This system will
bring a much cooler airmass into the region and see a return of fall
temperatures in the 60s to 70s and morning lows in the 40s to low
50s. Recent guidance has trended towards the low staying offshore
rather than moving onshore next week. The current forecast shows the
highest rain totals along the Santa Lucia Range and Santa Cruz
Mountains where totals are between a quarter to half an inch. For
the lower elevations expect up to a tenth of an inch across the Bay
Area and up to a quarter of an inch across the Central Coast.
Periods of gusty onshore winds are likely along the coast, the
higher elevations, and across mountain gaps/passes next week. Winds
don't look to be widespread enough to necessitate a Wind Advisory
but favored windy locations (Altamont Pass) will definitely be
gusty. Another item to watch is the potential for thunderstorms with
this system. NBM guidance has consistently maintained a low chance
(<15%) of thunderstorms across the region. In favor of thunderstorms
is the fact that this is a cold core low which is bringing in cooler
air and may be more favorable for ice crystal development/eventual
lightning development. Anti-thunderstorm development is the new more
offshore track of the low which keeps the best MUCAPE and CAPE
values offshore. This may be a setup where we see some sort of
convective activity over the marine environment but it doesn't make
it onto land (if the current track holds).
Bottom line: expect a pattern change to occur next week with below
normal temperatures, potential for light rain, breezy to gusty
onshore winds, and a low potential for thunderstorms.
&&
.AVIATION...
(06Z TAFS)
Issued at 950 PM PDT Thu Oct 15 2026
Not much change from previous TAF package...VFR through the
forecast period due to offshore flow and dry air. Biggest
challenge aviation wise will be dialing the winds. At points winds
will be relatively light and variable. Offshore flow will
strongest over the N and E Bays. Didn't include in the TAF for
STS/OAK, but marginal (20-30% chc) of LLWS. LLWS most likely from
08-15Z.
One new item for the 06Z will be monitoring winds for KHAF early
tomorrow. In these offshore flow set ups winds can sometimes
align for the E to NE and increase as they surface toward the
ocean.
Vicinity of SFO...VFR. Offshore push for the Friday AM rush.
Onshore heading into the Friday afternoon rush.
SFO Bridge Approach...VFR.
Monterey Bay Terminals...VFR.
&&
.MARINE...
(Today through Wednesday)
Issued at 258 AM PDT Fri Oct 16 2026
Gentle to moderate northerly breezes will prevail over the
coastal waters today and become moderate to fresh on Saturday.
These winds hold into the early portion of the week. The
increasing winds will bring a fresh swell and steeper wind waves.
&&
.FIRE WEATHER...
Issued at 132 PM PDT Thu Oct 15 2026
A Red Flag Warning was issued for the North Bay Interior
Mountains that goes into effect at 10PM tonight and runs through
11AM Friday morning. This is due to moderate offshore winds very
dry with very poor overnight humidity recoveries only reaching 15
to 25 percent. Rapid fire spread is possible given the
combination of gusty northerly winds and very dry overnight
conditions.
Elsewhere in the Bay Area, elevated to near critical fire weather
conditions continue for the higher elevations late tonight
through Friday morning. Dry conditions, poor overnight RH
recovery, combined with the breezy winds, warmer weather, and
available fuels leads to the elevated to near critical fire
weather conditions.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning until 11 AM PDT this morning for CAZ504.
PZ...None.
&&
$$
SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...MM
MARINE...KR
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Prepared by Boulder-Creek.com Weather at: Fri Oct 16 04:30:03 PDT 2026
From the National Weather Service
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