FXUS66 KMTR 201548
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
848 AM PDT Fri Mar 20 2026
...New UPDATE, MARINE...
.KEY MESSAGES...
Updated at 333 AM PDT Fri Mar 20 2026
- The last day of the long-duration, record- breaking
temperatures, and Moderate HeatRisk.
- Elevated potential for grass fires today, but fire concerns
begin to east into the weekend.
- Gradual cooling trend begins this weekend and lasts through the
next work week.
&&
.UPDATE...
Issued at 844 AM PDT Fri Mar 20 2026
A clear morning across the region, with the clear skies continuing
throughout the day. This morning's 12Z (5 AM PDT) sounding at OAK
set another 850 mb temperature record at 23.4 C, a maximum
temperature record that is not reached again until the middle of
May. It follows that today is another day of extreme heat across
the region with a lot of daily temperature records, and possibly
some monthly records, under threat. For more details on the
expected conditions today, and the cooling trend this weekend, see
the previous discussion.
DialH
&&
.SHORT TERM...
Issued at 333 AM PDT Fri Mar 20 2026
(Today and tonight)
Another warm morning followed by a hot day. Overnight lows plateaued
in the mid 50s to mid 60s for the lower elevations, while some of
the higher elevations remain in the 70s and a few along the Big Sur
Coast remain in the 80s. The warm start will allow another day of
widespread 80 to 90 degree high temperatures for all but the
immediate coast. A very compressed marine layer will affect those
coastal areas, but its influence will not make it very far inland.
Today will offer some of the warmest temperatures of the week as air
aloft (850 mb temperatures) continue to cook. Some areas may be
slightly cooler than previous days by a degree or two as the ridge
of high pressure weakens slightly into the afternoon.
The weakening of the high pressure and the influence of a trough to
our north will allow for improved cooling into the night and pull us
out of heat advisory criteria into the weekend. As such, it doesn't
look like the current Heat Advisory will need to be extended into
the weekend. But we'll still be far from average high
temperatures.
&&
.LONG TERM...
Issued at 333 AM PDT Fri Mar 20 2026
(Saturday through Thursday)
Saturday will be the first day of notable relief from the week-long
heat event. Most of the region will see the upper 70s to mid 80s
for highs; which is an improvement from previous days, but is
still 10 to 15 degrees above average. The immediate coast looks to
fall back into the lower 60s, which is around average and will
benefit from a slight expansion of the marine layer that will move
slightly more inland in the next few days.
Temperatures overall will continue to slowly cool going into the
next work week as the jet stream sees a modest zonal flow develop
with some very slight ridging to the south. This will allow for weak
onshore flow and an expanding marine layer. Models are hinting at a
weak southerly surge of marine stratus and fog moving up the Big Sur
coast early Sunday, which could result in much cooler coastal
temperatures in Monterey County, especially if it makes it all the
way to Monterey Bay. Longer term models also entertain the
possibility of coastal drizzle along the tail end of a cold front in
the mid week, but these chances look unimpactful.
The extended model outlooks continue to offer a building trough at
the end of the month, which could push a deteriorating low pressure
down the coast from the Pacific Northwest. This could result in good
chances for light, scattered rain, but this is way to far out to
speak on this with too much confidence. It's still worth keeping an
eye on as the forecast continues to develop.
&&
.AVIATION...
(12Z TAFS)
Issued at 423 AM PDT Fri Mar 20 2026
Pressure gradients ACV-SFO 5.1 mb, WMC-SFO 6.8 mb, UKI-STS 2.0 mb
and SAC-SFO 0.4 mb favor offshore (dry) winds across the forecast
area. The shallow layer of fog and low stratus over the waters
yesterday morning steadily eroded under diurnal mixing. Current
satellite is clear of fog and low stratus so far, though it could
radiate and cool to saturation for a patch or two of fog through
daybreak. Forecast is VFR. Recent HREF however does show fog and
low stratus advancing to the coastline tonight and Saturday
morning.
Vicinity of SFO...VFR. Light and variable wind becoming westerly
15 knots in the afternoon, decreasing to 10 knots late tonight.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR. Southeasterly winds 5 to 15 knots
through morning, winds shifting to onshore 10 to 12 knots in the
afternoon and early evening. Fog and low stratus /IFR/ advancing
toward the terminals tonight and Saturday morning.
&&
.MARINE...
(Today through Wednesday)
Issued at 844 AM PDT Fri Mar 20 2026
Lingering high pressure will maintain northerly flow over the
coastal waters today. Northwesterly winds will increase this
weekend as a cold front sweeps through. Gales will develop across
the northern waters Saturday into early Sunday. Hazardous seas
will develop due to strengthening winds.
&&
.CLIMATE...
Issued at 1021 PM PDT Thu Mar 19 2026
The following are the record high temperatures at the long term
sites for March 20th.
Location Mar 20
Santa Rosa 84 in 2004
San Rafael 82 in 1960
Kentfield 82 in 2001
Napa 86 in 2004
Richmond 81 in 2004
Livermore 87 in 1915
San Francisco 78 in 2004
SFO Airport 78 in 2004
Redwood City 82 in 2004
Half Moon Bay 75 in 2010
Oakland Museum 78 in 2001
San Jose 78 in 2004
Salinas Airport 80 in 1934
The following are the record high temperatures at the long term
sites for the entire month of March.
Location
Santa Rosa 92 March 19, 2026
San Rafael 89 March 19, 2026
Kentfield 91 March 28, 1923
Napa 92 March 17, 1914
Richmond 88 March 18, 2026
Livermore 90 March 25 and 26, 2025
San Francisco 87 March 11, 2005
SFO Airport 85 March 25, 1952, March 17, 2026, March 19, 2026
Redwood City 93 March 17, 2026
Half Moon Bay 83 March 31, 2000 and March 17, 2004
Oakland Museum 89 March 17, 2026
San Jose 89 March 14, 2015
Salinas Airport 93 March 18, 2026
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 8 PM PDT this evening for CAZ006-502>506-
508>510-512>518-528>530.
PZ...Small Craft Advisory from 3 PM this afternoon to 3 PM PDT
Saturday for Pt Arena to Pt Reyes 0-10 nm.
Gale Warning from 3 PM to 9 PM PDT Saturday for Pt Arena to Pt
Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory from 3 AM to 9 PM PDT Saturday for Pt Reyes
to Pigeon Pt 0-10 nm.
Small Craft Advisory from 3 PM to 9 PM PDT Saturday for Pigeon
Pt to Pt Pinos 0-10 nm.
Small Craft Advisory from 9 AM to 9 PM PDT Saturday for Pt Pinos
to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory until 3 PM PDT Saturday for Pt Arena to Pt
Reyes 10-60 NM.
Small Craft Advisory from 3 PM this afternoon to 9 PM PDT
Saturday for Pigeon Pt to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...Murdock
LONG TERM....Murdock
AVIATION...Canepa
MARINE...MM
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Prepared by Boulder-Creek.com Weather at: Fri Mar 20 10:30:02 PDT 2026
From the National Weather Service
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