FXUS66 KMTR 281210
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
408 AM PST Sat Feb 28 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 229 AM PST Sat Feb 28 2026

 - Well above normal temperatures today

 - Slight chance (15-25%) for rain with embedded thunderstorms 
   possible today in the North Bay
 
 - Slight cooling trend with light rain likely in the North Bay
   Sunday

 - Above normal temperatures with offshore flow next week

&&

.SHORT TERM...
Issued at 229 AM PST Sat Feb 28 2026
(Today and Sunday)

The 00Z sounding observed an 850 mb temperature of 15.35 degrees 
Celsius which is the second highest (16.3 degrees Celsius in 1986) 
for the date and time. With a warm air mass in place, well above 
normal temperatures are expected today. Surface high pressure in the 
Intermountain West and a coastal trough off the California Coast 
will generate light offshore flow. So not only will we be warm, but 
our natural air conditioning (the sea breeze) will be turned off. To 
limit heat-related impacts, people should increase water intake, 
reduce time spent outdoors or stay in the shade when the sun is the 
strongest, and open windows at night and use fans to bring cooler 
air inside buildings. We will begin to feel the influence of an 
upper-level low in the Eastern Pacific Ocean today, as alluded to by 
the high clouds that are beginning to stream in. The first of two 
embedded shortwaves will swing through the region today, bringing 
with it a slight (15-25%) chance for rain with embedded 
thunderstorms possible. The highest probability of occurrence (still 
low) will be in the North Bay with ensemble members continuing to 
show little to no accumulation today. The second embedded shortwave 
will swing through on Sunday, bringing us another chance for rain 
and thunderstorms. Measurable rainfall (0.01 inches or greater) is 
now looking likely (60% chance) on Sunday for the North Bay - 
especially in the higher terrain. If the criteria gets bumped up to 
a wetting rain (0.10 inches or greater), the areal extent is 
significantly reduced to only the Mayacamas Mountains and Hills of 
Western Sonoma County. Thunderstorm chances will remain low (20% or 
less) through this upper-level low. The three ingredients needed for 
thunderstorm development are lift, instability, and moisture. While 
all will be present, they are not expected to overlap favorably in 
space and/or time. Sensible weather wise, Sunday will be about 10 
degrees cooler than today. For locations south of the Golden Gate 
Bridge, drizzle will be possible along the coast and in the higher 
terrain.

&&

.LONG TERM...
Issued at 229 AM PST Sat Feb 28 2026
(Monday through Friday)

The upper-level low will begin to fill as it moves through the 
region on Monday. As it does so, rain chances will be renewed yet 
again Monday morning with light rain possible for the North Bay and 
drizzle possible for coastal and higher terrain locations south of 
the Golden Gate Bridge. Upper-level shortwave ridging will begin to 
nose in from the Eastern Pacific Ocean the latter half of Monday. 
The pattern will remain progressive with an upper-level shortwave 
trough on the ridge's heels. There is uncertainty on the location 
and the evolution of this feature, and to some extent the strength. 
It can be discerned though that this pattern will be conducive for 
warm and dry conditions with offshore flow, especially Wednesday 
through Friday. Even though we are in Winter with rainfall totals 
right around normal for this time of year, it's never too soon to 
think ahead towards "fire season". One side of the fire triangle 
(fuels) is right around average for this time of year; however, 
Energy Release Components (ERC), Burning Indices (BI), and 100 hour 
dead fuel moisture are all expected to be above average by early 
next week. While fuels are still projected to remain within the 
"significant spread unlikely" range, this is still something to be 
made aware of as receptive vegetation will have the potential to 
burn, especially on any wind-and-terrain aligned starts. As always, 
exercise fire weather safety no matter the time of year. 

&&

.AVIATION...
(12Z TAFS)
Issued at 408 AM PST Sat Feb 28 2026

It's VFR at the terminals. KMUX radar shows high based showers 
and/or virga (precipitation evaporating before reaching the ground)
moving in from the west. Farther offshore, lightning strikes are 
occurring. Showers and thunderstorms are associated with an eastward 
extending 500 mb thermal trough connected to a low center ~ 800 
miles offshore. This entire feature will continue to move east- 
northeastward through today. There is a slight chance of a shower 
including an embedded thunderstorm, but will continue to monitor 
radar, satellite and observations before amending to include this in 
any of the 12z TAFs. The 500 mb trough axis and incoming convective 
potential will reach the Central Valley by late morning. With high 
to mid level cloud cover early today, then mixing winds and at least 
partial clearing by later today, it's moderate to high confidence 
VFR continues through the morning, afternoon and at least early 
evening. Recent high resolution model forecasts however show a 
surface cool front and stratus clouds /IFR/ reaching our coastline 
tonight with increasing stratus coverage Sunday morning.

Vicinity of SFO...VFR through today and tonight then it's moderate
to high confidence stratus /IFR/ arrives 11z Sunday morning, staying
IFR through 18z Sunday. Light and variable wind becoming onshore
10 knots by 23z today, onshore wind continues tonight and Sunday
morning. A cool frontal boundary accompanies the stratus intrusion
11z Sunday.

SFO Bridge Approach...Similar to SFO.  

Monterey Bay Terminals...VFR through today and tonight then it's
moderate to high confidence stratus /IFR/ arrives 06z this evening.
Southeast winds 5 knots except up to 15 knots in the Salinas Valley
through morning. Winds shifting over to onshore 10 knots in the
afternoon and decreasing to 5 knots in the evening.

&&

.MARINE...
(Today through Thursday)
Issued at 327 AM PST Sat Feb 28 2026

A weakening low pressure system over the Pacific will move across
northern California Sunday night and Monday. Low to moderate seas
continue into next week. A strengthening high pressure system over
the Pacific will result in stronger winds by mid week.

&&

.CLIMATE...
Issued at 1116 PM PST Fri Feb 27 2026

The following are the record high temperatures at the long term 
sites for Saturday, Feb 28th.

Location         Feb 28th Record High 

Santa Rosa       93 in 1923
San Rafael       78 in 2025
Kentfield        78 in 1929, 1923
Napa             81 in 1929
Richmond         77 in 1986
Livermore        82 in 2022
San Francisco    76 in 1992, 1986
SFO Airport      73 in 1959
Redwood City     77 in 2025
Half Moon Bay    74 in 1954
Oakland Museum   75 in 2025
San Jose         77 in 2025, 1926
Salinas Airport  81 in 2022

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Canepa
MARINE...Canepa

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Prepared by Boulder-Creek.com Weather at: Sat Feb 28 04:30:04 PST 2026