Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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661 FXUS66 KMTR 061610 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 910 AM PDT Thu Jun 6 2024 ...New UPDATE... .SYNOPSIS... Issued at 215 AM PDT Thu Jun 6 2024 Hot inland otherwise expecting the beginning of a cooling trend today mainly on the coastline then cooling reaches further inland Friday through Sunday. Another potential hot period mid next week. && .UPDATE... Issued at 905 AM PDT Thu Jun 6 2024 Forecast looks on track today, overall running about 5-10 degrees cooler than 24 hours ago. Still warm today with minor to moderate Heat Risk for most. Some haze currently being observed may act to keep temps a bit cooler than expected for areas more near the coast. Still looking like we`ll shave off another 3-5 degrees for tomorrow. && .SHORT TERM... (Today and tonight) Issued at 259 AM PDT Thu Jun 6 2024 There are markedly different temperatures across the Bay Area and north Central Coast depending on your location this morning. For example there`s as much as 36F degree difference in temperatures from 83F on Mt Tam (within the lower level temperature inversion - a result of large scale sinking motion with the high pressure system) vs mid 50s to upper 40s near sea level (due to a chilly maritime influence) in Marin county at 2 am. Similarly it`s in the lower 80s elsewhere along the ridgetops of the Bay Area, however again it`s generally cooler with light breezes closer to sea level nearest the bay and especially along the coastline. Surface winds are settling in to a new regime in response to newly developing adjustments in surface pressure gradients. Northerly and southerly directed winds will join with the onshore wind and begin to steepen today, this will bring about cooling from sea level up through about 2500 feet today, best chances of this along the immediate coast. At the moment, will let the Heat Advisory continue as is, but we are closing in on the time when we can think about reducing some of its coverage, possibly more so during the day shift and/or evening shift. On the mid shift we`ll continue to closely monitor the development of coastal stratus and fog and marine layer depth. Seeing the northerly pressure gradient gradually reducing is a good sign, which will help give more equal weight to the onshore gradient and wind today, the NAM forecasts the SFO-SAC gradient to near 4 mb this afternoon. Sea surface temps in our coastal waters vary from a few upper 40s to lower 50s, nice and chilly which helps provide good potential for a sea breeze. HREF output shows more coastal stratus and fog tonight. && .LONG TERM... (Friday through Wednesday) Issued at 259 AM PDT Thu Jun 6 2024 A cooling trend continues into the weekend, onshore breezes will extend farther inland. Daytime highs on the coastline cooler than typical for this time in June, inland daytime highs will also cool back to near typical in June. Weak upper level troughing moves across the forecast area over the weekend then the global models forecast increasing high pressure redeveloping over northern California early to mid next week. && .AVIATION... (12Z TAFS) Issued at 438 AM PDT Thu Jun 6 2024 Sky condition is VFR mixed with MVFR surface visibility in haze along the coastline. Microphysics satellite imagery shows stratus and fog slowly moving northward along the Big Sur Coast connected to an extensive pool of stratus and fog from Point Conception and areas to the southeast through southwest. Also, a few patches of coastal stratus and fog are forming around the Monterey Bay and in the Bay Area near the Golden Gate and in the North Bay. In our forecast area the marine layer depth varies from a few hundred feet along the coast of the North Bay to 1,000 feet along the north Central Coast. Bodega Bay and Fort Ord profilers and Wednesday evening`s Oakland upper sounding show the marine layer temperature inversion is still strong. The ACV-SFO pressure gradient (northerly wind) is diminishing to 4.6 mb, the SBA-SFO and SMX-SFO pressure gradients (southerly wind) are 2.1 mb and 1.7 mb respectively, while the SFO-SAC pressure gradient is onshore at 2.2 mb. As of current, the meso-scale model output are under-forecasting the aforementioned southerly pressure gradient(s) by at least 50%. With the newly developed combined northerly and (under-forecasted) southerly wind potential coupled to the onshore wind, am expecting at least what the meso-scale models show for cooling at 1000 mb (~300 feet) and at 925 mb (~2500 feet), therefore the lower level temperature inversion should weaken somewhat today below the 850 mb level (~5000 feet). Bottom line, this and current nocturnal radiative cooling provides coastal stratus and fog /VLIFR-IFR/ a foothold for additional development through daybreak, then mixing out temporarily during the day with the usual vertical mixing then redeveloping tonight and Friday morning. Vicinity of SFO...VFR. West wind 10 to 15 knots through this morning, increasing to 18 to 25 knots in the afternoon and evening. West wind decreasing tonight and early Friday morning to near 10 knots. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...LIFR-IFR developing early this morning, stratus and fog mixing out 16z-17z to VFR during the day. West to northwest winds in the afternoon, possibly shifting to southwest at KMRY depending how strong the southerly wind reversal is during the day. KSNS surface wind northwesterly and becoming gusty in the afternoon. Stratus /MVFR-IFR/ forecast this evening and likely to continue tonight and Friday morning. && .MARINE... (Tonight through next Tuesday) Issued at 220 AM PDT Thu Jun 6 2024 Expect breezy northerly winds to persist through the day before gradually easing into Friday. These winds along with rough seas will lead to hazardous conditions for small craft. A moderate period Northwest swell will continue impact the coastal waters but will diminish Friday through Saturday before waves build again towards the end of the period. && .BEACHES... Issued at 222 AM PDT Thu Jun 6 2024 A Beach Hazards Statement is in effect through Thursday evening. Forecast remains on track. Moderate period swell is entering the coastal waters at 14-17 seconds with heights varying 7-11 feet. The would generate breaking waves of 8-15 feet with locally higher waves at favored break points. Sneaker waves can run over 100 ft up a dry beach, pulling people in the water from rocks, jetties, and beaches. Inexperienced swimmers should stay out of the water. Observe the ocean for 20 minutes before relaxing on the beach. The hot weather inland will lead to more people visiting the beach this week. Know where lifeguards are, obey their instructions, and never turn your back on the ocean! && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement through this evening for CAZ006-505-509- 530. Heat Advisory until midnight PDT tonight for CAZ503-504-506-510- 512>516-518. PZ...Small Craft Advisory until 3 AM PDT Friday for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt to Pt Pinos 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 3 PM PDT Friday for Pt Arena to Pt Reyes 10-60 NM. && $$ UPDATE...Behringer SHORT TERM...Canepa LONG TERM....Canepa AVIATION...Canepa MARINE...Murdock 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