FXUS66 KMTR 180415
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
915 PM PDT Tue Mar 17 2026

...New UPDATE, MARINE...

.KEY MESSAGES...
Updated at 149 PM 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 910 PM PDT Tue Mar 17 2026

No update to the forecast necessary this evening with this 
impressive heat wave in full swing. Numerous daily records were 
set today, however no monthly records were set. As overnight lows
continue to warm as the dome of high pressure keeps building, we
may see more monthly records fall over the coming days. Stay
hydrated, seek shad or AC during the day and check on family,
friends, and neighbors. Also, don't leave kids or pets in
vehicles, even for a short time. 

&&

.SHORT TERM...
Issued at 149 PM PDT Tue Mar 17 2026
(This evening through Wednesday)

We are well on our way to break more record high temperatures this 
afternoon with some all time monthly (March) records at risk of 
being broken (please see the CLIMATE below). This is as the center 
of the mid/upper level high pressure positions itself over the 
Central Coast today. Temperatures are forecast to reach into the 
upper 70s to mid 80s near northwest facing coastal locations and 
upper 80s to lower 90s across the interior and Santa Cruz area. 

Overnight temperatures are forecast to cool into the low to mid 50s 
across the valleys, upper 50s to low 60s elsewhere, and mid 60s to 
low 70s in the higher elevations. Where radiational cooling is most 
effective, a few upper 40s cannot be ruled out. Downtown San 
Francisco may remain the lower 60s into Wednesday morning.  

The center of the mid/upper level high will shift over the Desert 
Southwest by Wednesday and strengthens to 595 decameters (dam) with 
850 MB temperatures approaching or exceeding 20 degrees C by 
Wednesday. Thus, temperatures may be a few degrees warmer than today 
in areas. 

&&

.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...
(00Z TAFS)
Issued at 449 PM PDT Tue Mar 17 2026

No major changes to the forecast as VFR conditions prevail and a few 
high clouds pass overhead. Winds generally remain light and around 
10kt or less, with winds easing overnight. Similar conditions are 
expected for Wednesday. 

Vicinity of SFO...Winds have become onshore for nearly all Bay Area 
terminals and will remain that way through the evening, peaking 
around 10kt or so. Diurnally driven winds ease tonight, becoming 
light and variable or weak and offshore. A similar forecast is 
expected tomorrow, with winds becomes onshore mid to late afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Similar to above, no major changes to the 
forecast. Winds are onshore at roughly 5-10kt with isolated gusts up 
to 14kt for the the Monterey Bay Area terminals for a few hours. 
Winds will gradually ease and become offshore tonight with onshore 
winds returning tomorrow.&&

.MARINE...
(Tonight through next Sunday)
Issued at 449 PM PDT Tue Mar 17 2026

Moderate NW 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.

&&

.MARINE...
(Tonight through next Monday)
Issued at 910 PM PDT Tue Mar 17 2026

Moderate northwest breezes persist across the outer waters, with
gentle breezes over the inner waters. Relatively calm waters will
persist through Thursday and then begin building again on Friday
into the weekend.

&&

.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...RGass
LONG TERM....DialH
AVIATION...JM
MARINE...JM

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Prepared by Boulder-Creek.com Weather at: Wed Mar 18 00:30:03 PDT 2026