FXUS66 KMTR 161115
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
415 AM PDT Mon Mar 16 2026

...New AVIATION, MARINE...

.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...
(12Z TAFS)
Issued at 410 AM PDT Mon Mar 16 2026

Widespread VFR through the TAF period with patches of MVFR-IFR 
visibilities possible along the immediate coast, although confidence 
is low enough to bump up visibilities at HAF and SNS. High clouds 
coming through the region should inhibit the widespread formation of 
stratus this morning. Light winds through the morning, with a pulse 
of gentle to moderate northwest flow in the afternoon and evening 
before light winds return overnight.

Vicinity of SFO... VFR through the TAF period with light winds 
through the morning. A pulse of moderate west-northwest flow arrives 
this afternoon and evening with light winds resuming overnight.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... VFR through the TAF period. A gentle to 
moderate pulse of northwest flow should arrive in the afternoon and 
evening. Otherwise, light winds prevail at the terminals.

&&

.MARINE...
(Today through Saturday)
Issued at 410 AM PDT Mon Mar 16 2026

Breezy to gusty north winds linger in the northern outer waters
through the day before easing tonight. Winds across the waters
continue to decrease through the work week. Sea heights remain
moderate due to a combination of wind waves and low southerly
swell.

&&

.CLIMATE...
Issued at 410 AM PDT Mon Mar 16 2026

The following are the record high temperatures at the long term
sites for March 16th, 17th, 18th, and 19th.

Location             Mar 16      Mar 17      Mar 18      Mar 19

Santa Rosa         91 in 2004  87 in 1996  84 in 2010  83 in 2004
San Rafael         87 in 1972  84 in 1972  80 in 1996  81 in 1964
Kentfield          86 in 2004  87 in 1914  89 in 1914  83 in 1996
Napa               88 in 2004  92 in 1914  87 in 1914  86 in 1914
Richmond           84 in 1972  83 in 2004  78 in 1996  80 in 1996
Livermore          88 in 1972  87 in 1972  86 in 2004  82 in 2015
San Francisco      85 in 1914  85 in 1914  86 in 1914  80 in 2010
SFO Airport        82 in 2004  82 in 2004  77 in 2004  78 in 2010
Redwood City       84 in 2004  85 in 2004  84 in 2004  81 in 2010
Half Moon Bay      78 in 1972  83 in 2004  75 in 1978  79 in 2010 
Oakland Museum     85 in 2004  85 in 2004  81 in 2004  81 in 1984
San Jose           85 in 1914  88 in 1914  87 in 1914  82 in 1988 
Salinas Airport    87 in 2004  87 in 2004  84 in 1960  87 in 1997

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 9 AM PDT Tuesday for Pt Arena to Pt 
     Reyes 10-60 NM.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...DialH
MARINE...DialH

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Prepared by Boulder-Creek.com Weather at: Mon Mar 16 04:30:02 PDT 2026