textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1242 PM PST Mon Nov 17 2025

- Scattered showers will gradually decrease through Tuesday morning before drier weather returns Tuesday afternoon.

- Next system brings more beneficial type rain late Wednesday through Thursday.

SHORT TERM

Issued at 312 AM PST Tue Nov 18 2025 (Today and tonight)

Near term weather continues to be driven by the slow moving upper level low pressure currently parked over the Central Coast. Enough lingering moisture and lift are present around the upper low to generate widely scattered showers. Interesting to watch KMUX radar imagery early Tuesday morning with shower activity pivoting counter-clockwise around the upper low with the heaviest shower activity over the coastal waters. Freezing level is hovering right around 5k so cannot rule out some wet snow flakes over the higher peaks of the Central Coast this morning. Latest CAMS keep these scattered showers through mid-morning, but primarily out of the Bay Area and mainly over the Central Coast. By this afternoon, overall drying will occur with fair weather CU behind the departing upper level. Despite some drying and sunshine, today will be seasonably cool with highs in the 50s to near 60 (40s higher peaks).

Subsidence behind the departing low pressure system and shortwave ridge overhead will lead to some clearing Tuesday night into early Wednesday. Given the recent rain and ample low level moisture some interior valley fog will be possible tonight.

LONG TERM

Issued at 415 AM PST Tue Nov 18 2025 (Wednesday through Monday)

Dry weather holds through most of Wednesday, but temperatures remain on the cool side again. Cold air and daytime heating will likely lead to fair weather CU again.

The dry weather quickly comes to an end Wednesday thanks to an active longwave pattern over the EPac. Another robust upper level jet becomes amplified over the EPac Wednesday leading to another round of cyclongensis off the West Coast. A surface low is forecast to develop in the Gulf of AK Wednesday and then deepen as it track east. The low will ultimately drag a cold front through NorCal Thursday. Additionally, the amplified upper level jet will help to cut-off another upper low off the CA Thursday into Friday. The passing front and developing upper low will bring precip back to the region. Rain is still on track to return to the N Bay Wednesday night and then progress S and E early Thursday. Showers will linger through Thursday night. While this front has some moisture, the main tap isn't overly robust despite it's origin back to near HI. PWATs are just shy of one inch. All that being said, guidance has been trending slightly drier with total rainfall Wednesday through early Friday. Still looking more beneficial than hazardous to the region. Rainfall amounts will generally be a tenth or two and up to three quarters of an inch N Bay and coastal mountains. If the upper low over produces, the end higher end of precip amounts (1 in 10 chc) would double those rainfall amounts. One low confidence portion is the exact timing of the front and its potential impact to the Thursday morning commute.

Warming and drier conditions are expected to develop Friday and over the weekend. Given another burst of rain, night and morning fog will likely be the bigger weather impacts this weekend.

AVIATION

(12Z TAFS) Issued at 428 AM PST Tue Nov 18 2025

Mix of MVFR and VFR conditions across the board. An upper level low continues to slide down the coast of California and is bringing lingering scattered showers across the Central Coast. This is keeping our cloud cover patchier with sites going from clear skies to BKN/OVC clouds for short periods of time before clearing out again. CIGs are predominantly expected to be VFR but patchy MVFR CIGs may temporarily develop through the remainder of the morning. Any MVFR CIGs that do develop are expected to be short in duration and not the prevailing weather condition. As the low moves southwards, CIGs will clear across the region with clear skies expected for the afternoon/evening hours. Guidance shows MVFR CIGs returning towards the end of the TAF period. For now, leaned towards later arrivals between 09-12Z when creating the 12Z TAFs but there were some outliers, notably MOS guidance, that favored earlier returns closer to 06Z. The upper level low continues to dictate winds across the region with offshore winds expected to shift back to west/northwest by late this morning as the low exits to our south.

Vicinity of SFO...VFR becoming MVFR tonight. Temporary MVFR CIGs may develop through the remainder of the morning as the low exits southwards but any MVFR CIGs that do develop should be short lived and will not be the prevailing weather. Shower chances have largely diminished at SFO with higher chances to the south over the marine environment off of the Central Coast. Moderate confidence in stratus returning overnight - for now placed the stratus return closer to 12Z but MOS guidance does show potential for stratus as early as 09Z. Offshore winds will gradually become westerly this afternoon and peak around 12 knots. Winds ease overnight and shift more southwesterly to southerly.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR expected through the TAF period. Temporary MVFR CIGs may develop through this afternoon as the low moves southwards but confidence is moderate that these will be temporary and will clear quickly. Radar shows a few scattered showers lingering offshore of the Central Coast with scattered, light showers drifting into the Monterey Peninsula. Kept vicinity showers in for both MRY and SNS through late this morning when shower chances start to drop off. Offshore winds will gradually shift west/northwesterly this afternoon and strengthen to around 10 knots.

MARINE

(Today through Sunday) Issued at 428 AM PST Tue Nov 18 2025

Scattered showers diminish by this afternoon. Wave heights remain elevated and winds remain fresh to strong with near gale force gusts possible across the northern waters through late Tuesday. Marine conditions briefly improve Wednesday as wave heights abate and winds diminish. A weak system will arrive late Wednesday into Thursday bringing a return of light rain and hazardous marine conditions. Locally fresh to moderate winds and significant wave heights between 10 to 15 feet are expected Thursday into the weekend.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory from 9 AM this morning to 9 PM PST this evening for Pt Arena to Pt Reyes 0-10 nm.

Small Craft Advisory until 3 AM PST Wednesday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.