FXUS66 KMTR 102029 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 129 PM PDT Fri May 10 2024 ...New SYNOPSIS, SHORT TERM, LONG TERM... .SYNOPSIS... Issued at 125 PM PDT Fri May 10 2024 Warm temperatures continue inland through Saturday with highs from the upper 80s to lower 90s. Cooling has begun at the coast and spreads inland over the weekend into Monday with seasonal to warm temperatures through the next week. && .SHORT TERM... (This evening through Saturday) Issued at 125 PM PDT Fri May 10 2024 A larger scale ridge is starting to weaken as it comes into the Pacific Northwest, diminishing the offshore flow that contributed to the warm coastal temperatures the last two days. Satellite imagery shows stratus decks along the Big Sur coast, flowing into Monterey Bay and the coast of the San Mateo Peninsula. While this definitely looks like a southerly surge, observed coastal winds are more westerly than southerly, helping to cool off the coastal regions as the breezes develop through the day. Downtown San Francisco, which hit a high of 81 yesterday, is forecast to top out at 76 today. Elsewhere, the Pacific coast should expect highs around the low to mid 60s while the Bayshore could see highs reach the low 80s today. Further cooling is expected on Saturday with the coast seeing highs around 60 and the Bayshore seeing highs in the mid to upper 70s. Without the moderating impact of the onshore sea breeze, and with the ridge axis moving into the state, interior regions remain warm. The highs today will range from the upper 80s to lower 90s across the interior valleys with similar highs expected to continue into tomorrow. A Minor HeatRisk throughout the inland area, and a Moderate HeatRisk for the interior North Bay, East Bay, and South Bay will continue into Saturday; this means that a low to moderate risk of heat-related illnesses continues for vulnerable populations. The higher elevations should see highs in the 70s with a few degrees of cooling on Saturday. Low temperatures throughout the region on Saturday morning will hover in the low to mid 50s in the lower elevations, and the upper 50s to low 60s in the mountains. Given the continuing warm temperatures inland, here's a reminder of some heat safety tips: * Stay hydrated and drink plenty of fluids. * Wear lightweight, light-colored clothing. * Reduce time spent outdoors or stay in the shade. * Never leave people or pets unattended in vehicles. * Use sunscreen if going to the coast or the pool. Satellite imagery is also showing some pop-up clouds over the area near San Bruno Mountain. The HREF and NAM are suggesting some chance of showers over the extreme south of San Bruno County and southeast of Monterey County through the afternoon. The HRRR isn't showing any rainfall developing in the area. The forecast shows a slight chance of showers in the area, which was carried forward from overnight. If showers do develop, any rainfall totals will be very light with around a few hundredths of an inch at most. && .LONG TERM... (Saturday night through next Thursday) Issued at 125 PM PDT Fri May 10 2024 The weakening ridge will allow for a cooling and moistening trend to start for the interior regions and continue in the coastal regions on Sunday into Monday, with slight fluctuations in the temperature expected through the upcoming work week. Coastal locations will rise to the low to mid 60s through the end of the next week, with the inland valleys hovering around the low to mid 80s for the most part, perhaps up to the upper 80s in the warmest spots. Tuesday, in particular, should see an uptick in the temperatures as a second ridge comes into the Pacific Northwest, combining with a weak upper level low tracking into southern California to bring some northeasterly flow to the region. Atmospheric moisture does begin to develop through the region towards the middle and end of next week, although the highest chances for precipitation appear to lie near the Sierras. Ensemble clusters are hinting at a possible trough coming through the western United States around the end of next week or the upcoming weekend. The CPC's 8-14 day outlook suggests that temperature and precipitation for the period between the 18th and the 24th will be around the seasonal averages. && .AVIATION... (18Z TAFS) Issued at 1106 AM PDT Fri May 10 2024 VFR all terminals through early tonight. Compare to the previous few days winds are much lighter and less impactful for terminals this morning. Weather impacts through the taf period will be ongoing stratus moving up the Central and San Francisco Peninsula Coast. Highest confidence for cigs impacting the region Saturday morning will be MRY Bay terminals. Latest trends and guidance suggests stratus clouds may filter into SF Bay, but not make it to SFO or OAK. Vicinity of SFO...VFR. Light NE early before switching NW this afternoon. Will be watching the surge up the coast closely, but latest thinking is to keep solid cigs out of SFO. Did include a FEW group for a few hours early Saturday. Could even see a SCT group, but conf for cigs is less than 20%. SFO Bridge Approach...Less likely for any cigs impacting the approach. Monterey Bay Terminals...VRF through early tonight. As surge moves into MRY Bay cig chances increase through early tonight. Impacts with IFR/MVFR cigs will first impact KSNS 10-12Z and then KMRY. Moderate confidence (40-50%) of reduced vis for KSNS Saturday AM. Shallow nature of cigs will lead to early clearing. && .MARINE... (Today through Wednesday) Issued at 915 AM PDT Fri May 10 2024 A weak surface trough along the coast will maintain light to moderate winds over the waters through Saturday. Looking forward to next week, surface high pressure over the Eastern Pacific Ocean will build and move east, keeping things dry and strengthening northwesterly winds to a fresh breeze status. Significant wave heights will also begin building at the start of next week. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ SHORT TERM...DialH LONG TERM....DialH AVIATION...MM MARINE...MM 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