Discussion, UPDATED National Weather Service San Francisco CA 1032 AM PST Thu Nov 13 2025
, New UPDATE, AVIATION, MARINE,
.KEY MESSAGES, Updated at 1201 AM PST Thu Nov 13 2025
- Moderate to heavy rain and a chance for thunderstorms today.
- Strong wind gusts up to 60 mph may cause property damage, downed tree limbs, and difficult travel conditions.
- Cool and unsettled weather continues through the weekend.
Issued at 954 AM PST Thu Nov 13 2025
The short term forecast remains in good shape with some cosmetic changes to hazards over the next several hours. The High Wind Warning was cancelled earlier as the conveyor of stronger 925mb continues to shift eastward this morning. Wind gusts are anticipated to remain below 45mph across the North Bay and as a result, wind headlines have been dropped for this region. South of the Golden Gate, southwesterly wind gusts of at or above 45 mph are anticipated and may be encouraged within the heavier downpours. Still, the wind field will ease from northwest to southeast and a subsequent abatement of surface wind gusts are anticipated to shortly follow.
Large scale ascent still remains in place and we'll see shower activity persist. There does remain some instability that may support a very isolated thunderstorm threat, however, lapse rates will likely remain near moist adiabatic and as a result, upward vertical motion needed to support mixed-phase hydrometeors and thus lightning production in this main band of rain showers. That said, satellite imagery does reveal some deeper convective elements along the trailing cold front and this afternoon will present the next best opportunity for thunderstorm development, especially across the southern half of the Bay area and into the Central Coast. The KMUX VWP did sample an environment characterized by deep layer shear of 0-6km, so we'll need to keep monitor of any deeper convective elements as they'll have the ability to realize some of this shear. Organized convective modes, capable of bursts of stronger winds in addition to transient low- topped supercellular structures cannot be completely discounted.
, Issued at 1201 AM PST Thu Nov 13 2025 (Today and tonight)
A deep upper level trough and strong surface cold front are approaching the coast and will bring substantial rain and wind through the first half of the day. The system is currently stacked back, meaning the surface low is east of the upper level low. This configuration implies both divergence aloft and a strong temperature gradient. The divergence aloft is causing the surface pressure to drop very quickly. In fact, the low is in the middle of explosive cyclogenesis (aka a Bomb Cyclone). This was defined originally by Tor Bergeron in the 1950s as a drop of 24 mb over 24 hours and refined by Sanders and Gyakum in 1980 to adjust this standard for different latitudes. Using the adjustment for 40N, the requirement drops to about 18 mb over 24 hours. The Ocean Prediction Center analyzed this low as 1002 mb at 18Z, and most guidance is hovering around 980 mb by 12Z this morning. That would be a drop of 22 mb over 18 hours, easily meeting the criteria for a bomb cyclone.
As the surface low deepens and the front gets closer over the next 12 hours, the pressure gradient will cause the winds to increase to a strong to southerly breeze that will pump a ribbon of humid (1.5" PW) air to the Bay Area and Central Coast. The strongest winds will be along the coast and in the higher elevations where gusts will routinely reach 60 mph between 3 AM and 8 AM. So far the strongest gust recorded has been 63 mph gust at Cobb Ridge located at 3,225 ft in the Mayacamas of northern Sonoma County. Winds will very gradually decrease through the afternoon and evening.
We have already seen a few showers and thunderstorms, but the main show is still a few hours away. The total accumulation so far has been a few hundredths south of the Golden Gate, with up to 1/2" in the coastal North Bay Mountains. The main rain band is just now moving into KMUX radar coverage and will bring steady rain to the Bay Area commute this morning. The IVT is expected to spike around 750-1000 kg/m/s and remain above 250 for around 36 hours. According to the CW3E AR Scale, this qualifies as a strong atmospheric river. Although the sharp spike may be inflating that definition, the heavy rain will not last more than a few hours and we are not expecting widespread river flooding. Be advised, however, that there will be some roadway flooding as the heavier rain moves through. Even without standing water, the combination of the morning rush hour, wet roads, reduced visibility and strong winds will make for dangerous conditions on the roads this morning.
The thunderstorm threat is increasing. While the models did not predict much activity before midnight, mother nature had other plans. Several lightning strikes were observed across the Central Coast and East Bay around 8-10 PM. These storms have moved into the Central Valley and continue to produce some lightning. Mainly in deference to these earlier storms, we have increased the chance of thunderstorms embedded in the main rain band to around 20-30%. If more thunderstorms form they will most likely be non- severe with heavy rain and lightning strikes as the primary hazard. That being said, the hodographs are nicely curved with ample low level shear and, while the environment seems to be CAPE limited with cool surface temps and still high 500 mb temps, we can't rule out a water spout or a brief tornado.
..issued at 1201 AM PST Thu Nov 13 2025 (Friday through Wednesday)
While the main show is today, unsettled weather will continue through the majority of the forecast period. The low discussed above will gradually become vertically stacked by Friday while getting cut-off from the jet stream. This will cause the system to transition from purely baroclinic to partially barotropic as it parks somewhere near the Channel Islands through Saturday. All the while the continued southerly flow will support periods of lighter rain showers, particularly along the Central Coast. The system will catch the next bus out of town on Sunday as the jet stream dips back down and kicks the system quickly to the NE. The trough axis will slide over the coast on Monday bringing a period of more moderate and widespread rain, followed by strong northerly winds and colder temperatures. Tuesday looks dry and cool before a third trough approaches the coast late Wednesday and may bring even more rain to the Bay Area and Central Coast. The uncertainty really balloons past Tuesday tough, so don't give up all hope for nicer weather next week.
(18z TAFS) Issued at 954 AM PST Thu Nov 13 2025
Poor flying conditions continue for a majority of the terminals today due to rain, winds, and ceilings. Outside of +SHRA, cigs are anticipated to remain MVFR with periods of VFR. Gusty outflow winds in excess of 20-30 knots are forecast, though this threat will gradually ease through the afternoon. There's a risk for isolated TSRA, most likely across the Monterey Bay Terminals. Tonight, the forecast is uncertain, but the general trend is anticipated to be MVFR to IFR ceilings and potentially visibility. The greatest potential for visibility below 2-3SM resides across KSTS and KAPC.
Vicinity of SFO, An impactful day will continue at SFO with periods of SHRA for at least a few more hours, with VCSH through at least 00Z. Reductions in visibility, down to 2SM or less, and brief bursts of stronger winds to 30 knots should be anticipated with +SHRA. Wind gusts have subsided through the morning and I anticipate that gusts may fall below 20 knots by 20Z. While the wind direction will remain southerly, the diminished gusts may allow for a return to the west plan. Confidence in the exact wind direction is low to medium. Rain showers may return during the overnight hours and into Friday morning and we'll refine that in future TAFs, but at a minimum, we're unlikely to see wind gusts exceed 30-35 knots outside of SHRA. Currently anticipating VFR in the extended portion of the TAF, but scattered cloud decks below FL040 are forecast and this may impact approach operations.
SFO Bridge Approach, Clouds below FL040 are probable when West Plan operations continue.
Monterey Bay Terminals, Intermittent SHRA is anticipated through the afternoon. The instability/fuel for TSRA is greatest across these terminals, but low confidence precludes the mention of TS at this time. Gusty/erratic outflow winds in excess of 25-35 knots and visibility down to or below 2SM should be anticipated with any SHRA or TSRA. MVFR stratus is forecast after 00Z, however, with low to medium confidence and refinements probable to the TAFs.
(today through Tuesday) Issued at 954 AM PST Thu Nov 13 2025
Widespread hazardous marine conditions continue this morning, conditions gradually diminishing from north to south later in the morning and afternoon. Gales force winds, heavy rain and a slight chance of thunderstorms will accompany a strong cold front as it moves eastward. Winds will then continue to steadily decrease tonight. Moderate to rough seas will build to become rough for the inner waters and very rough for the outer waters today through Friday. Seas abate to become moderate by Saturday.
Issued at 124 AM PST Thu Nov 13 2025
A Beach Hazards Statement is in effect from this afternoon through Friday evening. Long period westerly swell will result in an increased risk for sneaker waves and rip currents. Breaking waves of 13 to 18 feet with the highest waves up to 23 feet in favored locations are expected. Sneaker waves can unexpectedly run significantly farther up the beach than normal, including over rocks and jetties. Rip currents are typically more frequent and stronger in the vicinity of jetties, inlets, and piers.
Ca, Wind Advisory until noon PST today for CAZ006-509.
Beach Hazards Statement from 3 PM PST this afternoon through Friday evening for CAZ006-505-509-529-530.
Wind Advisory until 4 PM PST this afternoon for CAZ508-510- 512>518-528>530.
PZ, Gale Warning until 3 PM PST this afternoon for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm-SF Bay N of Bay Bridge.
Small Craft Advisory until 3 PM PST this afternoon for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm.
