FXUS66 KMTR 171759
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1059 AM PDT Tue Mar 17 2026
...New AVIATION...
.KEY MESSAGES...
Updated at 113 AM PDT Tue Mar 17 2026
- Early season, long duration heat wave bringing record-breaking
temperatures and Moderate HeatRisk continues through at least
Friday
- Elevated potential for grass fires through the week due to warm
and dry conditions with periods of moderate offshore winds
- Gradual cooling trend begins this weekend
&&
.UPDATE...
Issued at 841 AM PDT Tue Mar 17 2026
Good radiational cooling took place across the valleys this morning
allowing temperatures to fall into the upper 40s to low 50s.
However, the higher elevations remained warm and only cooled down
into the 70s as the mid/upper level high pressure inches closer to
the coast. As such, another very warm afternoon is in store across
the Bay Area and Central Coast with a Heat Advisory in effect
through 8 PM Friday. Northwest facing coastal areas will warm into
the 80s the afternoon with upper 80s to low 90s across the interior
and the Santa Cruz area. Please see the previous discussion below on
records broken yesterday.
RGass
&&
.SHORT TERM...
Issued at 113 AM PDT Tue Mar 17 2026
(Today and tonight)
The heat wave is definitely here as a ridge settles over the western
United States. Yesterday's 00Z (5 PM PDT) balloon from OAK reported
a 500 mb height of 5911 meters, the highest reported height for the
month of March and close to the mean height for early August. The
850 mb temperature of 20.4 C was also a record high for the month of
March, more climatologically typical of the mid July to mid August
period. Five stations across the region reported daily record highs,
and Redwood City reported an all-time record high for the month of
March.
Today will feature even warmer temperatures and the chances
for more daily and potentially monthly record highs to fall, with
highs in the upper 80s to middle 90s inland amd close to the Bays,
while the Pacific coast hovers in the 70s. Lows this morning remain
in the middle 50s to lower 60s in the lower elevations, with the
thermal belts rather active as higher elevations see lows in the
middle 60s to lower 70s. With the influence of the high pressure
system right over the state, clear skies prevail and winds will
remain light through the day.
Widespread Moderate HeatRisk is expected today, corresponding to a
medium risk of heat-related illnesses for sensitive populations,
including children, the elderly, pregnant women, people with chronic
diseases, and people who live or work outside without adequate
shelter or cooling. Given the abnormally hot conditions for the
middle of March, a Heat Advisory remains in effect for the Bay Area
and Central Coast today. Follow these tips to protect yourself, your
loved ones, and your animals.
-Stay inside in an air conditioned environment between 10am and 7pm.
-Suspend unnecessary outdoor activities during the extreme heat, but
if you must be outdoors, take frequent breaks in the shade or AC
and drink cool water.
-Know the signs and symptoms of Heat Exhaustion vs. Heat Stroke!
Heat Stroke can be deadly if not treated immediately by a medical
professional. Call 911 if you suspect someone is suffering from Heat
Stroke.
-Wear a life vest, swim near a lifeguard, and check conditions
before entering the water if going to a river or ocean to cool off.
Rivers and the ocean are extremely cold, and Cold Water Shock can
turn into paralysis and drowning if you are not careful.
-Use a cool and damp towel on your body if you do not have AC and
are feeling hot. Or, take a cool shower or bath.
-Do not leave kids or pets in a parked car.
-Ensure pets and livestock have access to shade and water.
&&
.LONG TERM...
Issued at 113 AM PDT Tue Mar 17 2026
(Wednesday through Monday)
Wednesday through Friday feature similar conditions to today,
with temperatures far above the seasonal averages, widespread
Moderate HeatRisk, sunny skies, and light winds as the associated
upper level ridge crawls across California. A slight warming trend
will continue with portions of the Central Coast, including the
Ben Lomond-Boulder Creek area, the Morgan Hill-Hollister corridor,
and the southern Salinas Valley, seeing temperatures rising into
the upper 90s. A couple of favored patches will even see Major
HeatRisk, corresponding to a high level of danger for heat-related
illnesses for the general population. Notable regions for Major
HeatRisk impacts include the ridgelines of the Santa Cruz
Mountains, Carmel Valley, and the foothills of the Gabilan Range
east of Salinas. The Heat Advisory in effect for the entire
forecast region remains in place through Friday evening at the
earliest.
For the upcoming weekend, the ridge begins to break down as it
crawls eastwards across the Desert Southwest. This will give us a
gradual cooling trend, but will also promote an strengthening
pressure gradient, leading to stronger winds and an elevated risk
for grass fires across the region. The extreme heat of the last few
days will dry out a lot of fine fuels across the region, and pulses
of offshore flow are possible Friday into the weekend, especially in
the South Bay and Central Coast. There are a couple of mitigating
factors. The first is that live fuels remain rather moist as the
peak growing season continues. The second is that the larger scale
pattern is for winds to remain onshore, especially in the North Bay.
As for the temperatures, they will gradually cool around 5-10
degrees per day starting on Saturday, and by the early part of next
week, temperatures might only be slightly higher than the seasonal
averages.
&&
.AVIATION...
(18Z TAFS)
Issued at 1059 AM PDT Tue Mar 17 2026
A few high clouds are passing over the region, with VFR conditions
prevailing. Expect quiet weather and generally light winds to
continue through the forecast period.
Vicinity of SFO...Winds will become onshore by this afternoon and
should get up to 10kt before becoming light and variable or weakly
offshore later this evening. VFR conditions will prevail.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Quiet weather continues with winds being a
bit variable around the Monterey Bay. For KSNS and around KMRY,
winds remain offshore this morning but will become onshore by the
afternoon. The forecast will be on repeat for tonight, with offshore
flow returning and onshore flow again by tomorrow afternoon. &&
.MARINE...
(Today through Sunday)
Issued at 859 AM PDT Tue Mar 17 2026
Moderate NNW to N breezes will prevail offshore, with gentle
breezes within 10NM. Seas are moderate from a combination of wind
waves and a low southerly swell. Similar conditions will persist
through Thursday before winds increase to a strong NNW breeze with
rough seas from Friday through Sunday.
&&
.CLIMATE...
Issued at 113 AM PDT Tue Mar 17 2026
The following are the record high temperatures at the long term
sites for March 17th, 18th, 19th, and 20th.
Location Mar 17 Mar 18 Mar 19 Mar 20
Santa Rosa 87 in 1996 84 in 2010 83 in 2004 84 in 2004
San Rafael 84 in 1972 80 in 1996 81 in 1964 82 in 1960
Kentfield 87 in 1914 89 in 1914 83 in 1996 82 in 2001
Napa 92 in 1914 87 in 1914 86 in 1914 86 in 2004
Richmond 83 in 2004 78 in 1996 80 in 1996 81 in 2004
Livermore 87 in 1972 86 in 2004 82 in 2015 87 in 1915
San Francisco 85 in 1914 86 in 1914 80 in 2010 78 in 2004
SFO Airport 82 in 2004 77 in 2004 78 in 2010 78 in 2004
Redwood City 85 in 2004 84 in 2004 81 in 2010 82 in 2004
Half Moon Bay 83 in 2004 75 in 1978 79 in 2010 75 in 2010
Oakland Museum 85 in 2004 81 in 2004 81 in 1984 78 in 2001
San Jose 88 in 1914 87 in 1914 82 in 1988 78 in 2004
Salinas Airport 87 in 2004 84 in 1960 87 in 1997 80 in 1934
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 90 on March 16, 2026
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 until 8 PM PDT Friday for CAZ006-502>506-508>510-
512>518-528>530.
PZ...None.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...KR
MARINE...KR
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Prepared by Boulder-Creek.com Weather at: Tue Mar 17 12:30:03 PDT 2026
From the National Weather Service
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