Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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146 FXUS66 KMTR 101615 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 915 AM PDT Fri May 10 2024 ...New UPDATE, MARINE... .SYNOPSIS... Issued at 0105 AM PDT Fri May 10 2024 A moderate HeatRisk will exist for the warmest inland areas for today and Saturday as afternoon temperatures reach the 80s to around 90. Cooler along the coast with onshore breezes. A slight cooldown will occur by early next week. && .UPDATE... Issued at 915 AM PDT Fri May 10 2024 Stratus did approach the coast earlier this morning, but outside a patch along the Big Sur coast and one near the Golden Gate which has since largely mixed out, the coast remained clear through the night. High resolution models are indicating some chance for convective showers this afternoon for extreme southeastern Monterey County and southern San Benito County near Santa Rita Peak, which was added into the forecast. Otherwise, the forecast remains on track with no changes at this time. DialH && .SHORT TERM... (Today and tonight) Issued at 0105 AM PDT Fri May 10 2024 The large-scale pattern features high pressure aloft from the northeast Pacific through the Pacific Northwest, with a weak cutoff low over the Great Basin. Surface high pressure will remain prominent across much of the west, with weak coastal troughing along CA. 925 mb winds will maintain a north/northeast component today providing a continuation of warm/low humidity conditions for inland areas and the hills. However surface winds along the coast will develop a more onshore (west/southwest) component through the day. This will keep coastal temperatures more moderated, while still relatively mild. A very shallow marine layer under 300 feet is noted via the Fort Ord profiler this morning and this layer may deepen slightly across southern portions of the coast today. The most likely forecast outcome suggests that stratus/fog development should remain relatively limited in this pattern, but wouldn`t be surprised to see at least some patchy areas around the coast and bays this morning. Elsewhere, there remains a little bit of mid- level moisture and elevated instability such that we can`t rule of the development of a shower or two over the inland mountains of southeast Monterey and San Benito Counties. The most likely forecast outcome is probably just some cumulus development, but it`s worth noting that a few of the high resolution models and HREF ensemble members show some simulated reflectivity returns over these areas this afternoon. For now just something to watch. Otherwise today`s main forecast concern is temperatures. And our warmer inland areas will certainly be heating up. Probabilistic forecasts indicate a high (70%+) probability for high temperatures to reach 80 degrees or warmer for almost all areas, sans the coast and coastal marine-influenced valleys. Typically warmer places such as the Santa Clara Valley, southern Salinas Valley, and the North/East Bay valleys will see temperatures well into the 80s, with the warmest spots eclipsing the 90 degree mark. Locations with a 50% or greater probability for reaching 90 degrees today include the Sonoma Valley, Santa Rosa area, and portions of the East Bay bordering the Sacramento Valley. This will produce a moderate HeatRisk for these areas, with a minor risk elsewhere. There will be some overnight relief however, as temperatures tonight dip into the 50s for most areas, except for some lower 60s in the interior hills. Given the warm interior temperatures 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. && .LONG TERM... (Saturday through Thursday) Issued at 0105 AM PDT Fri May 10 2024 The upper ridge will remain prominent through Saturday, but will weaken into early week as weak troughing encompasses the Intermountain West. This will result in gradually cooling temperatures, albeit still above normal inland. A moderate HeatRisk will exist for the warmer areas on Saturday so it`s still a good idea to practice heat safety. Otherwise high temperatures this week will generally be in the 80s inland, 70s within the marine- influenced valleys, and 60s on the beaches. Upper ridging looks to re-establish across portions of the west for late week bringing another possible warmup heading into next weekend. && .AVIATION... (12Z TAFS) Issued at 426 AM PDT Fri May 10 2024 Currently VFR at all terminals. VFR through the TAF period. As the upper-level ridge weakens as it moves through the Pacific Northwest, winds will slowly be allowed to increase and return to onshore flow by this afternoon. Winds will diminish overnight. Vicinity of SFO...Currently VFR with breezy westerly flow. VFR through the TAF period. Winds will become offshore within the next few hours before slowly increasing and returning to westerly flow by this afternoon. Westerly winds will diminish into the night. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Currently VFR and calm at both terminals. MRY and SNS will experience easterly/offshore winds respectively over the next few hours before winds become breezy out of the west/northwest by this afternoon. Winds will diminish overnight. && .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...SPM LONG TERM....SPM AVIATION...Sarment 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