Issued at 1206 AM PDT Mon Apr 28 2025
More seasonal (warmer and drier) weather arrives today and persists through the work week. Another round of disturbed weather arrives next weekend with overcast skies, cooler weather, and strong winds, and a few rain drops possible.
, (Today and tonight) Issued at 1206 AM PDT Mon Apr 28 2025
A 500 mb positively tilted trough extends across Southern California anchored by a low pressure center over the Rockies. The lower pressure and residual moisture has allowed cloud cover to linger longer through the night than expected. In the last hour or so, the stars are finally starting to come out for much of the Bay Area as drier air moves in. The chance for widespread dense fog has decreased due to the lingering clouds keeping surface cooling in check. Despite this, there is still a decent chance for areas of fog during the Monday commute for areas currently under clear skies. If fog does form, it will mix out by late morning as the drying trend continues through the day. Mostly clear skies are expected this afternoon, which will be a nice change after a dreary weekend. At the same time, warmer air will filter in as a high pressure ridge moves in from the Eastern Pacific. Maximum temperatures should climb to the low to mid 70s for inland areas. Coastal areas will stay in the low 60s with some morning clouds as a 1000-foot marine layer starts to organize.
..(Tuesday through Sunday) Issued at 1206 AM PDT Mon Apr 28 2025
The overall pattern is dynamic as the current trough exits Monday, a ridge builds Tue-Wed, a short wave trough moves through Thursday before a more substantial trough moves through Saturday. This will cause the SFO-WMC gradient to swing from +7 mb to around -5 mb mid-week, and back positive by the weekend.
In the medium term the ridge will continue to build, and 850 mb temperatures are expected to climb from 3.7C on the Sunday 00Z sounding to roughly 13-15C by mid-week. That's a pretty drastic change, warming from around the 20th percentile to the 80th percentile for this time of year based on the sounding climatology. This will cause inland temperatures to climb into the upper 70s Tue-Wed, with mid 60s in the coastal marine layer. A short wave trough will move through Thursday, though the impacts will be limited mostly to increased cloud cover. Friday looks like a transition day as ridging briefly rebuilds before a more substantial long wave trough moves through Saturday. This system will bring overcast skies, cooler temperatures, and some light rain, but the biggest impact will likely be strong winds. The trough will support a fast moving cold front that will move through late Friday or early Saturday. As high pressure builds behind this front, the gradient will support strong NW winds. The NBM shows roughly an 80% chance of wind gusts exceeding 30 mph on Saturday for the majority of the area, with about a 40% chance of exceeding 40 mph along the coast and in higher terrain. The trend has been increasing, mainly driven by the ECMWF ensemble, which is quite a bit stronger and more confident than GEFS at this time.
(12z TAFS) Issued at 408 AM PDT Mon Apr 28 2025
Coastal low clouds /MVFR-IFR/ mostly continue from near Point Reyes southward, inland low clouds /MVFR-IFR/ continue mainly over the southern third of the area. A few patches of low clouds are seen over the Bay Area otherwise drying is moving in from the north. A few patches of valley fog /LIFR-IFR/ will mix out by late morning. Lower to mid level thermal ridging i.e. air mass stability will develop and strengthen during the 12z TAF cycle. Coastal stratus /MVFR-IFR/ develops moving locally inland tonight and Tuesday morning.
Vicinity of SFO, VFR except tempo MVFR 14z-16z this morning. Onshore wind 5 to 15 knots, strongest in the afternoon and early evening.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, MVFR-IFR in low clouds this morning, clouds mixing out by late morning. Coastal stratus /MVFR-IFR/ develops tonight moving locally inland overnight and Tuesday morning. Winds mainly onshore 5 to 15 knots, strongest in the afternoon and early evening.
(today through Saturday) Issued at 355 AM PDT Mon Apr 28 2025
Gusty northwest winds developing due to a high pressure system building over the offshore waters through early week, winds will also result in hazardous seas across the outer coastal waters. Mid to late this week surface high pressure will gradually weaken while an upper level trough moves in from the northwest. Another upper level trough from the northwest accompanied by a cold front will move across the coastal waters and bays late Friday.
Ca, None. PZ, Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory until 3 PM PDT Tuesday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.
