580 FXUS66 KMTR 040319 AFDMTRArea Forecast Discussion National Weather Service San Francisco CA 819 PM PDT Fri Oct 3 2025
...New UPDATE, MARINE...
.KEY MESSAGES... Updated at 814 PM PDT Fri Oct 3 2025
- Warmer and drier this weekend, with moderate offshore wind expected from Saturday - Tuesday in the higher elevations
- Next chances for rain come in the later part of next week
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.UPDATE... Issued at 814 PM PDT Fri Oct 3 2025
Showers have diminished across the region, and with no more precipitation expected through the night, KMUX radar has been placed into clear air mode. The strong northwest winds are also diminishing, with weather stations near the immediate coast reporting gusts generally around 20 to 25 mph, barring the Point Reyes PGE station where the latest reported gust was 36 mph. The current satellite image shows stratus developing along the southern coast of the San Mateo Peninsula north of Davenport and the Monterey-Salinas area. No changes to the forecast at this time.
DialH
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.SHORT TERM... Issued at 143 PM PDT Fri Oct 3 2025 (This evening through Saturday)
Isolated rain showers linger over the southern coastal waters and the Central Coast this afternoon. However, they appear to be diminishing in coverage as the main mid/upper level low pressure shifts towards Nevada. Temperatures this afternoon be cool, warming only into the lower 60s near the coast to lower 70s inland. Surface based cape will increase with daytime heating to around 100-300 J/kg and PWAT values around 0.80" this afternoon across the North Bay and interior East Bay before diminishing after sunset. Thus, rain shower chances, and a non-zero chance for isolated thunderstorm will continue across the aforementioned areas through this evening.
As the low pressure shifts further inland into the Intermountain West, northwesterly winds will increase through this evening and again on Saturday afternoon and evening. This will result in a drying trend into the upcoming week. Thus, temperatures will drop to or just below seasonal averages.
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.LONG TERM... Issued at 1208 AM PDT Fri Oct 3 2025 (Saturday night through Thursday)
While the weather will remain nice with seasonal temperatures and sunny afternoons through the weekend, the pattern will gradually evolve. As the deep trough that was responsible for our disturbed weather this week slides west of the Rocky Mountains by late Saturday, high surface pressure will build in its wake. Meanwhile, a weak thermal trough will develop over the Central Valley and get nudged to the coast by a 500 mb cut-off low over the NE Pacific. This will flip the pressure gradient and cause winds to shift from the typical NW to an offshore N or NE direction starting as early as late Saturday. The PGE-WRF ensemble SFO-WMC gradient envelope bottoms out anywhere from -4 mb to -9 mb on Monday morning. While it still looks like a moderate strength event, the forecast trend has been gradually increasing this gradient. Offshore winds in October can bring fire weather concerns, but the moderate speed and recent wet weather are mitigating factors this time. Outside of fire weather concerns, offshore winds this time of year tend to bring really nice weather to the Bay Area and Central Coast with warm temperatures and clear skies.
After the offshore winds die down, another cold front is likely late next week. GEFS IVT ensemble members all stay below 250 kg/ms with no chance of rain through Thursday, but longer range guidance hints that more substantial rain is possible by Friday. 4/50 ECMWF ensemble members show Santa Rosa receiving over 1" of rain in 24 hours, with the ensemble mean near 0.25" on an increasing trend. There is still a lot timing and intensity uncertainty with this pattern, and a few members (18, 38, 39, 48) don`t develop the coastal low pressure system at all and stay totally dry next weekend.
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.AVIATION... (00Z TAFS) Issued at 415 PM PDT Fri Oct 3 2025
VFR-MVFR except patchy valley fog /IFR-LIFR/ late tonight and Saturday morning. Mainly west to northwest winds 10 to 20 knots except light cool air drainage winds in the valleys late tonight and Saturday morning.
Vicinity of SFO...VFR except tempo MVFR 12z-16z Saturday. West wind 10 to 20 knots diminishing to 10 knots by mid evening. West wind near 10 knots Saturday.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR-MVFR. West to northwest winds 10 to 20 knots diminishing to 5 to 10 knots tonight. Light southeast winds in the valleys late tonight and Saturday morning. Winds west to northwest 10 to 15 knots Saturday afternoon and early evening.
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.MARINE... (Tonight through next Thursday) Issued at 814 PM PDT Fri Oct 3 2025
Fresh to gale force breezes are forecast, especially for the outer waters near and north of Pigeon Point tonight into the pre-dawn hours Saturday. This will translate to steep and rough seas up to 10 feet resulting in hazardous boating conditions. Winds abate after through sunrise Saturday, however, fresh to near gale-force northerly winds resume Saturday afternoon. Winds and seas ease next week.
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.MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 AM PDT Saturday for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory until 3 AM PDT Sunday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.
Gale Warning until 3 AM PDT Saturday for Pt Arena to Pt Reyes 10- 60 NM.
Small Craft Advisory from 3 AM Saturday to 3 AM PDT Sunday for Pt Arena to Pt Reyes 10-60 NM.
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SHORT TERM...RGass LONG TERM....Flynn AVIATION...Canepa MARINE...Canepa
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