textproduct: San Francisco Bay Area

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

UPDATE

Issued at 856 AM PST Sat Feb 28 2026

The current forecast is on track with water vapor imagery indicating that our shortwave ridging has been replaced with more in the way of upper troughing. The large scale ascent associated with this feature has supported the development of showers and even a few lightning strikes across our offshore marine zones. The primary PV anomaly is anticipated to lift northward this afternoon and this translates to a mostly PoP-free forecast after 00Z Sun until 18Z Sun when our next storm system skirts eastward. We'll have another look at Sunday's PoPs with the primary forecast package as the trend has been for an increase in rain chances across the North Bay. As noted below, the probability of a tenth of an inch is only about 10% and that represents the higher end amount. These higher end amounts are more probable in the upslope regions of the North Bay and within locations that experience deeper convective elements. We'll continue to examine the thunderstorm potential, particularly given the presence of instability as manifest by the lightning activity that has been observed thus far. More information later this afternoon.

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 856 AM PST Sat Feb 28 2026

Average to long northwesterly swell will continue through the weekend before wave heights and swell periods both decrease. Rougher seas should be anticipated in and around shower or thunderstorm activity. The risk for this activity will continue through Sunday. Seas continue to abate until about mid-week. Thereafter, conditions will deteriorate as a series of stout strong systems usher in Gale Force wind gusts and steep seas over 12 feet.

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.