489 FXUS66 KMTR 272048 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 148 PM PDT Sun Apr 27 2025 ...New SYNOPSIS, SHORT TERM, LONG TERM... .SYNOPSIS... Issued at 144 PM PDT Sun Apr 27 2025 Shower chances are diminishing across the Bay Area and Central Coast through the remainder of today. Drier, warmer conditions are expected Monday through late next week when unsettled weather returns again. && .SHORT TERM... (This evening through Monday) Issued at 144 PM PDT Sun Apr 27 2025 Light showers persist across the southern half of the Bay Area and Central Coast through early this afternoon. Showers overperformed along the Central Coast in part due to orographic lifting and in part due to a lingering moist air mass. Enough moisture lingered in the wake of yesterday`s low pressure system that light rain showers were able to continue across the Bay Area and Central Coast today. The 12Z (5AM) sounding observed a PWAT value of 0.84 inches at OAK this morning with the daily 12Z mean PWAT value being only 0.78 inches. While only slightly higher than the mean, this was still more than enough moisture to support continued light rain development this morning. Shower chances decrease this afternoon as our moist air mass continues to progress eastward with the upper level trough and a drier air mass arrives. Notably we will see drier air advected into the mid and upper levels of the atmosphere with mid and high level cloud cover expected to dissipate tonight. Surface conditions, however, look to remain slightly more moist with drier surface air staying offshore. Moist conditions in the lower levels and light winds overnight will result in a high likelihood of fog development tonight along the coast and across the interior valleys. Fog and low clouds will likely linger into the early morning commute tomorrow so for those early morning commuters remember to slow down if you encounter fog and watch for sudden changes in visibility. High temperatures across the interior will be in the low to mid 60s while high temperatures along the coast will largely be in the 50s today. Tired of below seasonal temperatures? The pattern is set to change beginning Monday with temperatures warming, becoming more seasonal, into the upper 60s to low 70s across the interior and upper 50s to 60s along the coast. Some potential for light offshore winds on Monday as the trough deepens, becoming more positively tilted over the Four Corners region. This will result in developing upper level ridging taking a slightly positive tilt over the West Coast on Monday before switching to zonal (horizontal) flow Monday into Tuesday. This will shift our surface winds to be out of a more N to NE direction (offshore) but winds should remain light due to persisting high pressure at the surface. Locally breezy conditions may develop across the higher elevations with gusts up to 25 mph possible. && .LONG TERM... (Monday night through next Saturday) Issued at 144 PM PDT Sun Apr 27 2025 Surface high pressure and upper level ridging will generally persist through late next week. Temperatures will continue to warm Tuesday/Wednesday with seasonal highs in the mid to upper 70s across the interior and 60s along the coast. Temperatures will start to trend downwards on Thursday, with highs dropping by 2 to 4 degrees, before continuing to trend downwards Friday into Saturday as our next system arrives. High temperatures Friday and Saturday will drop into the 60s across the interior and upper 50s to low 60s along the coast. Both the Euro and GFS show a weak cut-off upper level low dropping into Central/Southern CA in the Wednesday-Thursday timeframe which will bring decently moist PWATs back to the Bay Area and Central Coast. Ensembles do not show much in the way of rain from this weak upper level low, despite the increased moisture, with drizzle along the coast and a return of low level clouds the most likely result. Interestingly, the GFS shows this weak cut-off low merging with a deeper upper level trough that is set to arrive Friday into next weekend. This system does look to bring light rain (similar in totals to this weekend`s system) and breezy to locally gusty winds across the region Saturday into Sunday. The more impactful component of next weekend`s system is likely to be the breezy to gusty winds with initial ensemble guidance suggesting gusts around 40 mph may be possible across the region. There does appear to be some low level support, with a strong 850 mb jet setting up along coastal portions of our CWA Saturday into Sunday and a strong 500 mb jet just offshore. We will get a better idea about both peak winds and rainfall totals associated with this system as we get closer to next weekend, so stay tuned! && .AVIATION... (18Z TAFS) Issued at 1103 AM PDT Sun Apr 27 2025 Impacts of upper low moving to our east is still impacting the terminals and airspace with extensive low clouds over the region this morning with bases roughly 1500-2500 feet. Radar showing lingering showers from Santa Clara Valley southward through Monterey county with KMRY the most likely to hold onto lingering showers or drizzle through early afternoon. Expect gradual clearing and lifting of cloud bases after 21z this afternoon with light nw winds. Enough lingering moisture and cyclonic flow for low clouds to stay in place overnight with higher confidence for skies clearing with VFR conditions beyond 18z Monday. Vicinity of SFO...Improving conditions after 21z with cigs mixing and lifting before returning overnight through Monday morning. Higher confidence for clearing skies and a return of VFR after 18z Monday. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Lingering showers and drizzle through early afternoon. High confidence for MVFR cigs to return overnight through Monday morning with VFR conditions likely after 18z Monday. && .MARINE... (Today through Friday) Issued at 904 AM PDT Sun Apr 27 2025 Northwest winds will be gusty 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. From mid to late week surface high pressure will gradually weaken while an upper level trough will move in from the northwest. By late week another upper level trough from the northwest will approach the coastal waters and bays. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 9 PM PDT this evening for Mry Bay. Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory from 3 PM to 9 PM PDT Monday for Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt to Pt Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 9 PM PDT Monday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Kennedy LONG TERM....Kennedy AVIATION...RW MARINE...RW Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea