FXUS66 KMTR 151134
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
434 AM PDT Sun Mar 15 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 133 AM PDT Sun Mar 15 2026
- Minor HeatRisk today with temperatures above seasonal averages
- 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 133 AM PDT Sun Mar 15 2026
(Today and tonight)
Satellite imagery is showing a band of stratus setting up at the
immediate coastal region from Half Moon Bay down through Point Sur,
with a finger of clouds extending from the Monterey Peninsula into
the Salinas area. Model output is suggesting that some cloud
development is possible along the San Francisco Bay shoreline
overnight, but otherwise the region remains generally clear through
sunrise with low temperatures across the region remaining in the
middle 40s to middle 50s.
Today will mark the start of a major heat wave that will challenge
or set all time records for the month of March -- more about that in
the long term discussion -- as an anomalously strong ridge develops
in the eastern Pacific and crawls into the state. It will certainly
feel quite a bit warmer across the region as temperatures around 5
to 15 degrees warmer than those seen yesterday are expected, with
highs in the 80s forecast across the inland valleys, the middle 70s
to lower 80s near the Bays, and the middle 60s to middle 70s at the
Pacific coast. Also note that the shallow marine layer that kept the
immediate coastline cooler yesterday will further compress or even
erode away as the ridge takes hold, allowing for substantially
warmer conditions at the coastal regions. Winds will generally be
light to gentle with a northerly component to the large scale flow.
Widespread Minor HeatRisk is expected today, corresponding to a low
risk of heat-related illnesses for the most sensitive populations,
including children, the elderly, pregnant women, those with chronic
illnesses, and people working or living outdoors without adequate
shelter or cooling. Remember to stay hydrated and allow time to rest
in the shade during outdoor activities, and never leave children or
pets unattended in the car!
&&
.LONG TERM...
Issued at 133 AM PDT Sun Mar 15 2026
(Monday through Saturday)
The ridge continues to trek across the state through the early part
of the work week and will strengthen a little bit as the ridge axis
begins to enter the Desert Southwest during the middle of the work
week, where it will stall out for a couple of days. Model output is
showing a possibility for 500 mb heights at OAK to exceed 5900
meters, which would set an all time record 500 mb height... for the
entire month of March. As noted by the previous forecaster, the
Wednesday to Friday timeframe is when we expect the warmest
conditions to occur, when highs in the interior valleys reach the
upper 80s to the upper 90s and the coastal regions range from the
lower 70s to the middle 80s. We are even starting to see some areas
of the Gabilan Range reaching triple-digit high temperatures for the
Wednesday through Friday timeframe, and NBM probabilistic guidance
continues to show low probabilities (around 10%) for triple digit
highs in portions of the northern Salinas Valley, the foothills of
the Berkeley-San Leandro Hills, and the interior East Bay valleys.
Low temperatures during this period will range from the middle 50s
to middle 60s across the lower elevations, to the upper 60s and
lower 70s in the higher elevations.
This will be our first major heat wave of the year, where
temperatures that feel more like late summer heat extend pretty much
through the work week. Widespread Moderate HeatRisk is expected from
Monday through Friday, with a moderate risk of heat-related
illnesses for sensitive populations, while patches of Major
HeatRisk, corresponding to a high risk of heat-related illnesses for
the general population, are possible within the higher elevations of
the Santa Cruz Mountains, the foothills of the Gabilan Range near
Pinnacles National Park, to the east of Salinas, and the mountains
surrounding Carmel Valley. To re-emphasize points made by the
previous forecaster: Given the long duration of this heat event,
susceptibility to heat related illnesses will increase throughout
the week. If you are going to be outside for prolonged periods of
time make sure you are drinking plenty of water and allowing time to
rest in the shade. Never leave people or pets unattended in the car.
If possible, avoid going outside during the peak afternoon heat
(approx. 10AM - 4/5PM). A Heat Advisory will go into effect on
Monday across the Bay Area and Central Coast, which will extend
through Friday at the earliest with some potential for expansion
into the following weekend.
In addition, the unseasonably warm heat will help dry the fine fuels
across the region, elevating the potential for grass fires through
the week. Offshore winds will remain light to moderate, which will
help mitigate the growth of any fires that take hold. Anyone who is
engaging in outdoor activities (including camping, hiking, and
offroading) should exercise caution when using fires and open
flames.
As for the longer term, ensemble model cluster analysis does show
the ridge flattening as it starts to make its way into the southern
Great Plains towards the upcoming weekend and beyond. The current
forecast does show a cooling trend for the upcoming weekend, as
"extraordinarily hot" becomes merely "pretty hot", but how fast that
cooling trend takes hold will depend on how soon the ridge moves
eastwards and how fast it flattens.
&&
.AVIATION...
(12Z TAFS)
Issued at 426 AM PDT Sun Mar 15 2026
Spotty LIFR CIGs and VIS, mainly impacting HAF, MRY, and SNS,
although APC has also been reporting some mist and fog at times
this morning any time the wind dies. With a compressed marine
layer across the Bay Area, there is very little chance for these
impacts to reach SFO, OAK, or SJC, which should enjoy VFR
conditions through the day. Otherwise winds will remain gentle to
moderate and diurnally driven with offshore winds in the morning
and stronger onshore winds in the afternoon.
Vicinity of SFO...No notable weather impacts expected today. There
is a slight chance for mist Monday morning.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...For some reason the stratus has pulled
off on MRY, but continues to fill the Salinas Valley. SNS is
reporting 1/4 mi visibility in dense fog. It's unclear if the
ceilings and fog will push back to MRY this morning. The current
satellite trend doesn't show any forward progress, but with the
cloud bank so close to the terminal I decided to include a tempo
line to indicate the possibility. VFR conditions will prevail from
late morning through the day after the marine layer stratus mixes
out.
&&
.MARINE...
(Today through Friday)
Issued at 426 AM PDT Sun Mar 15 2026
A fresh to strong NW breeze will continue across the outer waters
before the wind speed gradually decreases to a moderate breeze
Monday and continues through mid 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 15 Mar 16 Mar 17 Mar 18
Santa Rosa 88 in 2004 91 in 2004 87 in 1996 84 in 2010
San Rafael 83 in 1972 87 in 1972 84 in 1972 80 in 1996
Kentfield 85 in 2004 86 in 2004 87 in 1914 89 in 1914
Napa 86 in 2004 88 in 2004 92 in 1914 87 in 1914
Richmond 85 in 2004 84 in 1972 83 in 2004 78 in 1996
Livermore 83 in 1972 88 in 1972 87 in 1972 86 in 2004
San Francisco 82 in 2004 85 in 1914 85 in 1914 86 in 1914
SFO Airport 81 in 2004 82 in 2004 82 in 2004 77 in 2004
Redwood City 84 in 2004 84 in 2004 85 in 2004 84 in 2004
Half Moon Bay 74 in 1974 78 in 1972 83 in 2004 75 in 1978
Oakland Museum 85 in 2004 85 in 2004 85 in 2004 81 in 2004
San Jose 82 in 2004 85 in 1914 88 in 1914 87 in 1914
Salinas Airport 83 in 1972 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 Monday 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.
Small Craft Advisory until 9 AM PDT this morning for Pigeon Pt
to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Flynn
MARINE...Flynn
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Prepared by Boulder-Creek.com Weather at: Sun Mar 15 08:30:02 PDT 2026
From the National Weather Service
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