, Issued at 116 PM PST Wed Jan 21 2026 (This afternoon through Thursday)
Generally quiet with largely mild conditions this afternoon across the Bay Area and Central Coast. Fog continues to slowly erode at this hour, with predominantly mid/upper level clouds continuing to overspread the area. Our upper low continues churn and WV/RAP mesoanalysis trends indicates that it continues to make it slow trek to the south and east. This is in line with current thinking. Radar imagery this afternoon has shown a couple of brief attempts at a loosely organized bands of what is largely virga/fall streaks. While the trends haven't been encouraging, satellite imagery indicates still some mid-level cumuliform clouds/instability that may swing to the NE and give us another shot as sprinkles or very light rain after 4pm this evening and continuing through the pre-dawn hours on Thursday and this seems in alignment with latest short term guidance. As noted this morning, PoPs of 20-40% are advertised which remains along the higher end of the near/short term hi-resolution model guidance. Rain amounts at this time are anticipated to average around a few hundredths of an inch with the higher end scenario (10% chance of occuring) advertising a larger QPF footprint (light rain as far as the North Bay) and up to a tenth of an inch across the higher terrain of Central Coast.
As the main upper low continues to pivot eastward, subtle 700mb WAA may lift northward through the Central Valley and into the North Bay. While some orographic ascent cannot be ruled out along the eastern slopes of higher terrain, the dry low levels should translate to a low probability for measurable precipitation here, even though radar may look rather ominous.
Otherwise, fog, albeit limited due to the cloud cover, may continue overnight and into early Thursday morning. However, additional low level mixing thanks to the elevated wind field make keep the footprint smaller than previous nights.
.. Issued at 116 PM PST Wed Jan 21 2026 (Thursday night through next Tuesday)
Thursday evening will feature a subtle PV anomaly will ripple through the Great Basin and help sweep the initial upper low eastward. In its' wake, mid/upper level ridging is forecast. This will promote surface pressure rises across the Great Basin and tighten local MSLP gradients across the region. More importantly, the 925mb flow will increase with even coarser guidance advertising 30-40 knots out of the north through the Sacramento Valley.
The synoptic scale background/pattern recognition in tandem with the Extreme Forecast Index (EFI) would suggest an opportunity to alter messaging to advertise a noticeable uptick in winds, largely across the higher terrain of the North Bay and East Bay Hills. 2km PG&E WRF cross sections also indicate the potential for mountain wave type activity near and downwind of Mt. Saint Helena which could help enhance wind gusts. Given the highly localized nature of these phenomenon, have opted for targeted edits across the Mayacamas and higher terrain of the East Bay such that wind gusts reflect a blend of some of the higher end NBM percentiles. While fuel moistures have dried some, ERC values remain safely below critical fire weather thresholds. That said, please always be mindful that winter fuels could still promote some fire growth/smoke production.
Overall, the themes in the extended forecast have not changed much. Ridging is anticipated to resume this weekend and largely dominate the weather pattern across the region through the early to middle part of next week. Thereafter, about one-quarter of the multi-model ensemble advertises more vigorous troughing across the Pacific NW. This would dampen out the ridge such that mid/upper level flow becomes more southwesterly, potentially opening the door for a disturbance or two. While the official forecast paints broad PoPs across most areas (minus the far interior Central Coast), there still remains some model variability with some NWP "clusters" indicating little to no chance for precipitation. We'll continue to delve deeper into the model guidance with time.
(18z TAFS) Issued at 933 AM PST Wed Jan 21 2026
Fog and stratus persist over the North and East Bay valleys with mid- to high level clouds delaying the mixing out process. Have opted to go with a more persistent forecast for STS mixing out, and a later forecast for APC mixing out, although this is a low confidence forecast and it is possible STS and APC remain socked in through the day. Greater confidence in lingering fog and stratus impacts in the far interior East Bay and areas near the Delta, including CCR. The rest of the region should expect generally VFR conditions and mid- to high level cloud cover through the daytime hours. Winds remain light through the TAF period. Overnight, fog and stratus should develop across the North and East Bay valleys, with moderate confidence for development along the immediate coast. High resolution model data shows some stratus developing in the San Francisco Bay Area, but this is a low confidence forecast at this time and lingering high clouds may limit the impact of radiational cooling processes, lowering the chances for overnight stratus. Along the Central Coast, some isolated showers are possible along the Santa Lucia range overnight into Thursday morning.
Vicinity of SFO, VFR through the day. High resolution model output is attempting to place stratus across the East and South Bays, but impacts to SFO are lower confidence. Considered a SCT group at SFO to convey the uncertainty, but opted to hold off at this time as the area of greatest confidence seems tilted towards OAK and SJC. Winds remain light with offshore flow lingering through the morning until mild onshore flow develops this afternoon.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, VFR with mid- to high level clouds through the day. This evening and overnight, low stratus develops at the terminals with isolated showers possible across the Santa Lucia range, low to moderate confidence for impacts to the terminals. Winds remain light through the TAF period with drainage winds overnight and through the morning, and onshore flow in the afternoon and evening.
(today through Monday) Issued at 933 AM PST Wed Jan 21 2026
Gentle to moderate northerly breezes and moderate seas persist through Thursday. On Friday, winds will increase to a fresh northerly breeze along with building rough seas. Conditions will improve over the weekend as a light to gentle breeze settles in and seas gradually subside to slight Sunday through Monday.
Ca, None. PZ, None.
