FXUS66 KMTR 302111 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 211 PM PDT Sat Sep 30 2023 ...New SYNOPSIS, SHORT TERM, LONG TERM... .SYNOPSIS... Issued at 120 PM PDT Sat Sep 30 2023 Lingering afternoon showers in the North Bay after a cold front passed through the Bay Area this morning. Warming trend with dry weather next week. && .SHORT TERM... (This evening through Sunday) Issued at 120 PM PDT Sat Sep 30 2023 The cold front passed through the Bay Area and central coast early this morning, bringing scattered light to moderate rain showers, particularly south of San Francisco. Most populated areas recorded less than 0.1", which 0.25" or more in some coastal mountains of Santa Cruz and Monterey Counties. While the surface front has passed, the supporting upper level low is still bringing instability to the North Bay. Scattered showers are observed on radar moving north to south across Napa and Sonoma Counties, and will soon reach Marin. These showers look quite robust, though they haven't produced any lightning. Cloud tops are not deep enough into the freezing layer to generate the conditions necessary for thunderstorms, but some strikes are possible as the afternoon progresses. Shower activity is expected to decrease this evening as daytime heating subsides. Sunday is expected to be calmer, drier, and warmer, with no threat of rain. && .LONG TERM... (Sunday night through next Friday) Issued at 120 PM PDT Sat Sep 30 2023 By Sunday night the upper-levl low will be over the Great Basin, well east of our area. This will support moderate NNE wind, which will keep the forecast dry and initiate a warming trend through the week. As the low pressure continues to march East, high pressure will encroach from the Pacific. The gradient between these two systems will support moderate NNE flow Sun afternoon. By Mon, the Bay Area will enter the high pressure portion of an omega block in the jet stream. This pattern will slow down approaching weather systems and should keep the forecast dry through the week. The big story is a warming trend through Fri. Despite temperatures being well below average today, coastal locations will see daytime highs in the 70s (roughly 5 degrees above normal), while some inland locations end up in the 90s (roughly 10 degrees above normal) from Wed-Fri. Early October is typically one of the warmest periods of the year, so anything above normal will be noticeable. The longer nights and drier airmass will allow for good nighttime cooling so no heat products are expected. This general pattern should last through the weekend. The pattern will dry the fuels and increase fire weather concerns as we head into the historical peak month for fire weather concerns for the Bay Area. && .AVIATION... (18Z TAFS) Issued at 1120 AM PDT Sat Sep 30 2023 The frontal zone responsible for earlier rainfall has pushed east of the terminals. However unsettled conditions, MVFR clouds, and a few light showers will persist. At least partial clearing and a return to VFR is expected for the northern terminals this afternoon, with a ceiling likely sticking around the Monterey Bay terminals all day. At least patchy BR/FG is expected overnight into Sunday morning with boundary layer saturation, especially for the Central Coast. All areas return to VFR by ~16-19Z on Sunday. Vicinity of SFO...Can't rule out a rogue/brief light shower this afternoon but confidence/coverage is too low for inclusion in the TAFs. Any impacts would be minimal. Otherwise look for breezy onshore winds and a transition to VFR ~21-22Z. Expect FEW-SCT lower cloud group to return overnight but confidence in a ceiling developing at the terminals is not explicitly advertised in the TAFs. Gusty onshore winds this afternoon, diminishing overnight. VFR tomorrow with gusty onshore winds returning during the afternoon. SFO Bridge Approach... Similar to SFO. Monterey Bay Terminals...Currently seeing MVFR conditions at both terminals with winds primarily out of the W-NW at about 10 knots. Winds have been gusty at times today and that will continue through this afternoon. MVFR ceilings are expected to linger all day while higher frontal clouds begin to clear from north to south. Despite the cold frontal passage, low level humidities are expected to remain high, facilitating an environment for IFR ceilings for both terminals in the early morning hours. With this may bring some reduced visibilities, but the confidence right now is low. && .MARINE... Issued at 842 AM PDT Sat Sep 30 2023 Coastal Buoys are reporting fresh to strong NW winds throughout the area with near gale force gusts north of Point Reyes. Moderate to rough seas are on a building trend through the day. Sunday will be a transition day as high pressure becomes the dominant feature through the week. Winds will decrease and seas abate beginning Sun with more favorable conditions expected through the week. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 AM PDT Sunday for PZZ540-545-575. Small Craft Advisory until 3 PM PDT this afternoon for PZZ560. Gale Warning until 3 PM PDT Sunday for PZZ570. && $$ SHORT TERM...Flynn LONG TERM....Flynn AVIATION...SPM MARINE...Flynn Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea