, Issued at 1152 AM PDT Tue Mar 31 2026 (This afternoon through Thursday morning)
It only took 29 days, but it's finally raining. A stationary front is offering an area of convergence for its tropical moisture tap. Rain shower activity will continue to drift south through the day as surface high pressure tries to nose in from the Eastern Pacific Ocean. A gale force low in the Gulf of Alaska will put a stop to that as it heads to the Washington/Canada border. The attendant cold front will bring us a winter-like feel with below normal temperatures, gusty conditions, and rain. Southwesterly winds will increase ahead of the cold front with northwesterly winds developing in the post-frontal environment. Widespread gusts of 20-30 mph can be expected with gusts up to 40 mph in the highest terrain. Rainfall totals are expected to be in the 0.10"-0.25" range with locally higher totals in the higher terrain of the North Bay and locally lower totals in the Interior Central Coast. Slick roadways can be expected due to the dry spell that has allowed oil to accumulate.
..issued at 1152 AM PDT Tue Mar 31 2026 (Thursday night through next Monday)
The pattern will quickly change Thursday afternoon as upper-level shortwave ridging noses in from the Eastern Pacific Ocean. The short wavelength of the aforementioned trough and ridge will tighten the pressure gradient. Strong northerly winds will result, primarily affecting exposed areas like the higher terrain and marine environment. The SFO-WMC pressure gradient is expected to become negative Thursday night as the wavelength moves inland, resulting in offshore flow. At 5 AM Friday, the ECMWF Ensemble mean is forecasting the gradient to be -9.81 mb while the GEFS mean is forecasting the gradient to be -7.76 mb. The 2 mb discrepancy is due to the ECMWF Ensemble showing a stronger high and stronger low closer together than weaker features farther apart in the GEFS. This uncertainty is propagated through Friday and Saturday with the ECMWF Ensemble bottoming out at -10.96 mb at 5 AM Saturday while the GEFS is well on its relaxing trend at -5.24 mb. Nonetheless, a moderate offshore flow event can be expected Thursday night through the weekend with a 35 knot 925 millibar jet streak across the North Bay. This will translate to gusts of 40 to 50 mph in the higher terrain, namely the North Bay Interior Mountains, East Bay Hills, and Eastern Santa Clara Hills. The ridge will also send temperatures soaring back to well above normal.
(18z TAFS) Issued at 1104 AM PDT Tue Mar 31 2026
Mostly VFR across the region with ceilings between 5k-15k feet. Winds are light and variable this morning but will become west- southwest this afternoon with rain showers tapering off. Winds ease overnight becoming light and variable as rain showers return early Wednesday morning. The greatest potential for rain showers will be over the North Bay and Bay Area terminals through 18Z Wednesday, shifting southward later in the afternoon/evening. Along with the rain, ceilings lower to sub-VFR with the greatest potential for IFR across the North Bay.
Vicinity of SFO, VFR. West-southwest winds increase this afternoon and early evening before easing overnight and into Wednesday morning. This is when we expect MVFR conditions to return to the region by around 12Z Wednesday. In addition, VCSH has been added to the TAFs around 12Z Wednesday with -SHRA returning by 18Z when we may see lower end MVFR ceilings at times of heavier rain showers.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, VFR. Lingering rain showers will persist through about 21Z that may produce MVFR ceilings. Otherwise, expecting west-southwest winds at KMRY with the potential for northwesterly winds at KSNS this afternoon. Winds ease overnight with MVFR ceilings returning late this evening and likely to persist into Wednesday morning. Rain should stay to the north of the Monterey Bay Terminals, depending on timing of our next frontal system forecast to move through.
(today through Sunday) Issued at 1104 AM PDT Tue Mar 31 2026
Gentle southwesterly breezes today will increase to become moderate to fresh tomorrow ahead of the cold front. Fresh to strong northwesterly breezes will develop in the post-frontal environment Wednesday night into Thursday morning. Strong northerly breezes will develop Thursday afternoon and persist into Friday. Moderate seas will build to become rough Thursday into Friday. Widespread hazardous conditions are expected Thursday and Friday. Conditions improve by the weekend.
Ca, None. PZ, None.
