, Issued at 122 PM PST Sun Dec 14 2025 (This evening through Monday)
The interaction between Tule Fog outgrowth from the east, and coastal stratus development from the west, continues to feature as the main short-term forecast issue as a shortwave trough passes over the state. The Salinas Valley has mostly cleared out, and the Monterey-Salinas region has generally cleared out, with lingering coastal stratus observed near Pacific Grove and the immediate coast between Point Lobos and Point Sur. The coastal plain of Santa Cruz County and the San Juan Bautista-Hollister valley region remain socked in, the former extending up the coast of San Mateo County, and the latter connected to the extensive inland stratus that persists across much of the Bay Area valleys. If you look closely at the satellite loop you could make out patches of clearing on the fringes -- the Cloverdale area in extreme northern Sonoma County, Lake Berryessa in northeastern Napa County, parts of Livermore, western sections of Alameda County, and the southwest corner of San Francisco. Overall, there is much more stratus coverage today than we saw this time yesterday. As a result, confidence in the clearing of the North Bay valleys, the northern and eastern sections of Contra Costa County, and even southeastern San Mateo Peninsula and the Santa Clara Valley has decreased. For the moment, the high temperatures today are similar to those from the overnight forecast update, with highs in the lower to middle 50s in the Bay Area valleys, into the middle to upper 40s in eastern Marin County and northern and eastern Contra Costa County, the upper 50s to lower 60s along the Pacific coast, and the middle 60s to the lower 70s in the Salinas Valley. There's a chance that the temperatures could still undershoot the official forecast this afternoon, which comes into play if the clearing out process continues to lag the model projections.
On Monday, conditions are expected to be broadly similar to today's with a similar evolution of the stratus deck, as ridging forms on the backside of the shortwave trough. This ridge is remarkably positively tilted, such that the flow pattern off the California coast is quite zonal. This is a clue to the forthcoming pattern change, and so are the high clouds that are expected to flow over the region, thus increasing the uncertainty over the forecast. Will the high clouds bring breezier flow aloft that could help us scour out the Tule Fog, or will they inhibit solar heating on Monday afternoon and keep the stratus around through the day? For now, have leaned towards another day of slower clearing, and have tamped Monday's lows cooler than the deterministic NBM output gives.
..issued at 122 PM PST Sun Dec 14 2025 (Monday night through next Saturday)
More zonal flow will come to the region on Tuesday, allowing a pattern change which will gradually open the proverbial storm door and lead to wetter conditions through the balance of the 7-day outlook and beyond. The first of the systems will come through Tuesday into Wednesday, with generally beneficial rainfall across our region focused on the North Bay, where rain totals will lie around 0.5-0.75" for the Sonoma coastal ranges, the 0.3-0.5" for the Mayacamas, and 0.1-0.25" for the valleys. South of the Golden Gate, rainfall totals remain generally less than 0.1", with a few hundredths of an inch being the absolute maximum total across the Central Coast. More substantial rain is expected late on Thursday into Friday and the upcoming weekend, with the current forecast showing two distinct pulses of rain, one on Thursday and Friday and another for the upcoming weekend, each with the potential for more significant rainfall totals than the forecast for the Tuesday- Wednesday system. Initial forecasts suggest that rain totals over one inch are possible for the North Bay mountains. Beyond the upcoming weekend, uncertainty becomes high to very high, but ensemble model cluster analysis suggests good agreement in a deep upper level trough setting up in the eastern Pacific, which could support an atmospheric river setup assuming that the moisture plume sets up in the right place. The latest CPC outlooks suggest that the North Bay faces a high risk (over 60% probability) of heavy rain early next week, with the rest of the region seeing a moderate risk (40-60% probability) of heavy rain in addition to the entire Bay Area and the northern Central Coast seeing a moderate risk of strong winds in the 8-14 day period (December 22-28).
(18z TAFS) Issued at 941 AM PST Sun Dec 14 2025
Combo morning with a mix of Tule Fog and marine layer impacting all terminals in some way. Marine layer depth hovers near 2k feet per profilers. ACARS and Pireps show tops in the 1400-1600 foot range. We're also see some patchy fog, locally dense, too. Based on latest satellite trends and model guidance will keep a slow clearing trend in the 19-20Z timeframe for most terminals and 21Z for N and E Bay. Brief VFR late this afternoon before cigs and fog return early tonight.
Vicinity of SFO, Solid stratus coverage with CIG AOB 1k feet. Tops showing 1400 feet. CIGS will last through AM rush. VFR this afternoon with a switch to more onshore flow. CIGS return tonight and last well into the Monday AM rush.
SFO Bridge Approach, Same as SFO.
Monterey Bay Terminals, Slow clearing through 20-21Z. Early return this evening in the 00-01Z time.
(today through Friday) Issued at 841 AM PST Sun Dec 14 2025
High pressure over the region will maintain gentle to moderate breeze continues across the coastal waters today. Southerly flow will prevail north Pigeon Point and northerly flow will prevail south of Pigeon Point. Winds increase to moderate to fresh across the southern coastal waters Monday as the first in a series of weak systems reaches the coastal waters. Rain chances increase this week. Low seas persist through the remainder of the weekend before building to moderate to rough by mid week.
Ca, None. PZ, Small Craft Advisory from 3 PM Monday to 9 AM PST Tuesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.
