FXUS66 KMTR 160839
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
139 AM PDT Mon Mar 16 2026
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 203 PM PDT Sun Mar 15 2026
- Early season, long duration heat wave brings record-breaking
temperatures and Moderate HeatRisk through the week
- Elevated potential for grass fires through the week due to
warm and dry conditions with periods of moderate offshore winds
&&
.SHORT TERM...
Issued at 1225 AM PDT Mon Mar 16 2026
(Today and tonight)
After building for the last couple days, the much anticipated
heat wave arrives in earnest today. A remarkably strong ridge of
high pressure over the far eastern Pacific is meandering towards
the coast this morning. This ridge has taken over the pattern and
will be the primary driver of the heat wave this week. The early
measurements on the strength of this ridge are coming in as
expected. The 00Z sounding found an 850 mb temperature of 17.15C.
That breaks the daily record of 16.8C. Similarly the 500 mb
height was measured at 5880m, breaking the old daily record of
5860m. As the ridge continues to build and move closer over the
next 24-36 hours, these benchmark values will only increase.
Ensembles show a high likelihood that the 850 temp will reach 20C
and the 500 mb height will reach 5900m by the 12Z sounding
Tuesday. Those would both set monthly records by a wide margin, and
are more typical of early August.
This translates to temperatures in the mid to upper 80s across
the interior, and 70s along the coast today. The marine layer is still
hanging on, but it is being compressed to 500 feet or lower under
the high pressure. This keeps the marine influence very localized
to the coast. Ocean Beach will feel a nice marine breeze, but
don't expect it to reach over the hill.
Offshore winds have become established and will be moderate at
times before the ridge moves firmly overhead Tuesday and winds
calm. Hot weather combined with dry offshore winds requires taking
a look at fire weather conditions, and for good reason. At 10:50
AM Sunday, Mt. St. Helena reported sustained 42 mph ENE winds with
7% relative humidity. We should see something similar later this
morning. That would be a slam dunk Red Flag Warning in the Summer.
The reason we are holding off is the live fuel moisture content.
Fortunately it's March. The hills are still green and will not be
receptive to burn. Live fuel moisture reaches its highest levels
in Spring due to peak growing season. Dead fuel moisture, on the
other hand, will respond more to the hot dry weather, and the
Energy Release Component is expected to set monthly records this
week. After the winds die down today, the next period of concern
is when the ridge breaks down sometime around next weekend. This
brings the potential for strong winds after all the fuel drying
has occurred. As always, be cautious with campfires or any other
potential ignition source.
&&
.LONG TERM...
Issued at 1225 AM PDT Mon Mar 16 2026
(Tuesday through Sunday)
After several days of this heat wave building, it will reach the
top of the plateau by Tuesday. Interior temperatures will reach
the low to mid 90s, with 70s and 80s along the coast. Wednesday
through Friday look nearly identical. Hot spots this week include
the southern Salinas Valley and Gabilan Range. There is a strong
possibility that Pinnacles National Park records the earliest 100
degree day of the year this week. The current record for March is
only 93. Along the coast the hot spot looks to be Santa Cruz,
where downslope winds will add adiabatic heating to battle any
marine influence. We expect low 90s there.
Numerous monthly records are expected to be broken this week.
Check out the Climate section below for those benchmarks. Overall
the big story with this heat wave is how early it is. Yes we've
seen much hotter days in the Summer and early Fall, but we are a
full 30 degrees warmer than normal this week. That's very unusual
any time of year.
Finally, when will it end? All ensemble clusters agree that the
ridge will start to weaken this weekend. That doesn't mean
temperatures will drop all the way back to normal, but we should
see a cooling trend of about 5 degrees per day from Saturday
through Monday, effectively ending the heat wave.
&&
.AVIATION...
(06Z TAFS)
Issued at 932 PM PDT Sun Mar 15 2026
Widespread VFR and moderate winds last into the night. Expect winds
to become light across the region overnight, with some slight
reductions in visibility from mist and spotty fog. Visibilities
improve in the mid to late morning. Winds increase slightly into
Monday afternoon. Winds become light again that night.
Vicinity of SFO...VFR through the TAF period. West winds are
reducing and are becoming light. Winds become light and variable
into Monday morning with some slight reductions in visibilities.
West winds build again Monday afternoon and last into late that
night before becoming light again.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR lasts into the late night. Expect light
to moderate winds through the evening that become light into the
night. Some pockets of mist look to reduce visibilities in the late
night and through the morning. Conditions improve by the late
morning and early afternoon as northwest winds build. These winds
reduce into the evening and become light and variable into that
night.
&&
.MARINE...
(Tonight through next Saturday)
Issued at 932 PM PDT Sun Mar 15 2026
Breezy to gusty northerly winds linger in the Northern outer
waters into Monday night before easing. Winds across the waters
will continue to reduce into the work week. Sea heights will stay
moderate due to a combination of wind waves and low southerly
swell.
&&
.CLIMATE...
Issued at 133 AM PDT Sun Mar 15 2026
The following are the record high temperatures at the long term
sites for March 15th, 16th, 17th, and 18th.
Location Mar 16 Mar 17 Mar 18
Santa Rosa 91 in 2004 87 in 1996 84 in 2010
San Rafael 87 in 1972 84 in 1972 80 in 1996
Kentfield 86 in 2004 87 in 1914 89 in 1914
Napa 88 in 2004 92 in 1914 87 in 1914
Richmond 84 in 1972 83 in 2004 78 in 1996
Livermore 88 in 1972 87 in 1972 86 in 2004
San Francisco 85 in 1914 85 in 1914 86 in 1914
SFO Airport 82 in 2004 82 in 2004 77 in 2004
Redwood City 84 in 2004 85 in 2004 84 in 2004
Half Moon Bay 78 in 1972 83 in 2004 75 in 1978
Oakland Museum 85 in 2004 85 in 2004 81 in 2004
San Jose 85 in 1914 88 in 1914 87 in 1914
Salinas Airport 87 in 2004 87 in 2004 84 in 1960
The following are the record high temperatures at the long term
sites for the entire month of March.
Location
Santa Rosa 91 on March 16, 2004
San Rafael 88 on March 25, 1952
Kentfield 91 on March 28, 1923
Napa 92 on March 17, 1914
Richmond 87 on March 31, 2021
Livermore 90 on March 25 and 26, 2025
San Francisco 87 on March 11, 2005
SFO Airport 85 on March 25, 1952
Redwood City 89 on March 31, 2011
Half Moon Bay 83 on March 31, 2000 and March 17, 2004
Oakland Museum 88 on March 11, 2005
San Jose 89 on March 14, 2015
Salinas Airport 92 on March 14, 2015
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 10 AM this morning to 8 PM PDT Friday for
CAZ006-502>506-508>510-512>518-528>530.
PZ...Small Craft Advisory until 3 AM PDT Tuesday for Pt Arena to Pt
Reyes 10-60 NM.
&&
$$
SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Murdock
MARINE...Murdock
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Prepared by Boulder-Creek.com Weather at: Mon Mar 16 02:30:02 PDT 2026
From the National Weather Service
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