Technical NOAA Weather Discussion

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