Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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530 FXUS66 KMTR 011644 AAA AFDMTR Area Forecast Discussion...UPDATED National Weather Service San Francisco CA 944 AM PDT Wed May 1 2024 ...New UPDATE... .SYNOPSIS... Issued at 125 AM PDT Wed May 1 2024 High pressure brings quiet weather and slowly warming temperatures this week. Breezy onshore winds will keep temperatures along the coast cooler however. Wet, unsettled conditions returning Friday night and Saturday, much cooler inland Saturday. Unseasonably cool daytime highs continuing into early next week then gradually warming by the middle of the week. && .UPDATE... Issued at 938 AM PDT Wed May 1 2024 The short term forecast is in good shape with just a couple of minor tweaks the the wind grids. Northerly breezes between 15 and 20 mph with gusts to 30 to 35 mph are forecast (higher over the marine zones) with our local WRF appearing to handle some of the subtleties associated with the complex terrain/shorelines. Otherwise, it should be a pleasant day with mostly sunny skies (a few high clouds may stream in later in the day). We`ll continue to warm through the week, with a pattern change (cooler and windier) shaping up for the weekend. More details later this afternoon. && .SHORT TERM... (Today and tonight) Issued at 133 AM PDT Wed May 1 2024 Today`s weather will be similar to Tuesday`s weather, dry conditions prevailing with high pressure over the offshore waters to far northern California. Gusty northwest winds continuing over the coastal waters. Forecast highs today 60s near the coast and bays to the 70s-80 inland. && .LONG TERM... (Thursday through Tuesday) Issued at 133 AM PDT Wed May 1 2024 Dry Thursday and Friday, increasing clouds Friday night with rain developing over the North Bay, rain spreading southeastward across much of the rest of the forecast area Saturday. It`ll turn noticeably cooler especially inland Saturday with daytime highs Saturday 10F to 18F cooler inland compared to Friday`s forecast highs. In the last 12-24 hours global and mesoscale models are more in line focusing on the arrival of a cold core low pressure system from the Bering Sea/Aleutian Islands arriving in northern California Friday night and Saturday. The southeastward trajectory takes it across cooler than normal sea surface temperatures (negative phase PDO) at least somewhat minimizing maritime thermal modification along the way and for maintenance/development it`ll travel through a long wave trough on the West Coast. The low will brush by and tap higher levels of water vapor extending far north of Hawaii, however the low is forecast to move through our forecast area retaining a strong mid-latitude influence. Recent precipitable water values on the GFS have been 1.00" to 1.10" for Saturday, not far from the max moving average on Oakland upper air sounding climatology in early May. Model forecast rainfall amounts vary from 0.25" to 0.70" North Bay, 0.15"-0.25" low elevations to 0.40" hills/mountains elsewhere across the Bay Area to around 0.10" interior north Central Coast to 0.33" Big Sur Coast. Wet and cooler weather Saturday, gusty northwest winds over the coast temporarily subsiding with the passage of a surface cold front/trough. Dry weather returns Sunday. The surface pressure pattern looks favorable for gusty northwest winds redeveloping over the coastal waters beginning next Tuesday. Daytime highs gradually warming by the middle of next week. && .AVIATION... (12Z TAFS) Issued at 426 AM PDT Wed May 1 2024 Generally VFR through the TAF period with patchy stratus in the higher elevations. LLWS concerns continue for the rest of the morning throughout the region as light surface winds have decoupled from strong northerly winds aloft. Northerly winds build through the afternoon, generally gusting through 20-25 knots, with LLWS concerns returning as the surface winds diminish in the evening. Vicinity of SFO... VFR through the TAF period. Light onshore surface flow tonight with strong northerly flow aloft causing LLWS. Northwest winds build through the afternoon gusting to 20-25 knots, before diminishing through the evening. SFO Bridge Approach... Similar to SFO. Monterey Bay Terminals... Patches of stratus intermittently impacting MRY through the rest of the morning. Otherwise VFR through the TAF period. Directional LLWS continues this morning as light drainage flow meets northerly winds aloft. Northwest winds develop later today with gusts up to 20-25 knots, diminishing again in the evening with directional LLWS resuming at MRY. && .MARINE... (Today through Sunday) Issued at 938 AM PDT Wed May 1 2024 Breezy and gusty winds continue throughout Friday, with gale force gusts of 40 to 45 knots possible in the outer waters. Strong winds will result in hazardous seas and steep wind waves with significant wave heights reaching 10 to 14 feet in the outer waters. Conditions gradually improve over the weekend and into next week as winds begin to ease. Rain chances begin early Saturday as a trough descends over the region. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 9 AM to 9 PM PDT Thursday for SF Bay N of Bay Bridge. Small Craft Advisory until 9 PM PDT this evening for Mry Bay. Small Craft Advisory from 9 AM Thursday to 3 AM PDT Friday for Mry Bay. Gale Warning until 3 PM PDT this afternoon for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory until 3 AM PDT Friday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. Gale Warning until 3 AM PDT Thursday for Pt Arena to Pt Reyes 10- 60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning until 9 AM PDT Thursday for Pigeon Pt to Pt Pinos 10-60 NM. && $$ UPDATE...Bain SHORT TERM...Canepa LONG TERM....Canepa AVIATION...DialH MARINE...RGass 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