Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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234 FXUS66 KMTR 171000 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 300 AM PDT Mon Jun 17 2024 ...New SYNOPSIS, SHORT TERM, LONG TERM, MARINE, FIRE WEATHER... .SYNOPSIS... Issued at 158 AM PDT Mon Jun 17 2024 Red Flag Warning remains in effect for the North Bay Interior Mountains from 11 AM to 8 PM Monday. Dry and breezy conditions continue into Monday night. Better onshore flow and moisture return by midweek. Another warming trend on the way for the upcoming weekend. && .SHORT TERM... Issued at 158 AM PDT Mon Jun 17 2024 (Today and tonight) Short term weather impacts will be mainly Fire Weather focused. For specific details see the Fire Weather Section below. Simply put, dry northerly winds and lack of marine layer continue to bring elevated fire weather concerns to the region. The longwave pattern currently shows an upper low dropping into the Great Basin. The associated upper level trough will sweep through NorCal early Monday. The passing upper trough will do two things: shift winds and usher in dry air. Northwesterly flow currently being observed will shift more northerly to northeasterly early Monday morning. This will be most pronounced above 1,000 feet, especially over the interior North mts and East Bay hills. The shifting winds will usher in much drier air. RH values could be as much as 10-20% lower than yesterday. As for temperatures, still looking at seasonably cool temperatures across most of the region again this afternoon - or similar to what what see on Sunday. For tonight: Breezy to gusty offshore flow will persist overnight with a shallow marine layer if one forms at all. Expect mild and dry conditions most area, especially in the hills. Given the ongoing wildfire in the North Bay smoke/haze was added to the forecast for portions of the North and East Bay. For smoke impacts and spare the air information check out information being provided by the Bay Area Air Quality Management District (BAAQMD). && .LONG TERM... Issued at 300 AM PDT Mon Jun 17 2024 (Tuesday through Sunday) Tuesday through Thursday: The upper level low exits the Great Basin and moves further east into the Plains. For the West Coast general troughing at 500 mb remains. For the most part that translates to minor day to day changes with sensible weather. Onshore flow does return, which helped to reestablish night/morning marine layer clouds. Friday into next weekend:The broad trough will fade and ultimately be replaced by upper level ridging. As a result, a notable warming and drying trend will develop, especially over the interior. Long range forecast continues to advertise interior temperatures in the 90s to lower 100s with elevated HeatRisk values. Stay tuned... && .AVIATION... (06Z TAFS) Issued at 1055 PM PDT Sun Jun 16 2024 VFR through the TAF period. Strong and gusty winds linger along the immediate coast and at SFO into the mid morning, with more inland areas seeing light to moderate. Winds aloft are still strong and will stay so into the early morning, particularly over the North Bay causing concerns for LLWS at STS. Winds aloft and at the surface weaken in the mid morning. Expect winds to increase again into the afternoon, with strong winds over the ocean and at SFO. Elevated winds last into the late night before reducing. A fire in the North Bay will cause some reduction to visibility around STS and potentially APC. Vicinity of SFO...VFR through the TAF period. Winds stay gusty through the mid morning before reducing and staying more moderate. Another round of gusty winds starts building in the afternoon with peak gusts expected to be around 28 kts. These stronger gusts last into the late night, before winds reduce and become moderate again. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR through the TAF period. Light to moderate winds last into Monday afternoon before more breezy westerly winds arrive. Winds at the terminals reduce into the evening, but looks to stay moderate. && .MARINE... (Today through Saturday) Issued at 158 AM PDT Mon Jun 17 2024 Widespread gale force gusts continue before diminishing gradually into Sunday night. By early Monday, gale force gusts will have weakened to strong to near gale force with widespread conditions dangerous to small crafts persisting through mid-week. Significant wave heights will peak between 12 to 14 feet Sunday into Monday before gradually diminishing to 8 to 11 feet by mid- week. Hazardous conditions will persist through the late work week with strong gusts expected to continue over the majority of the coastal waters. && .FIRE WEATHER... Issued at 245 AM PDT Mon Jun 17 2024 ...Red Flag Warning remains in effect interior North Bay Mts Monday... ...Elevated Fire Weather Conditions Through Monday night... *Breezy to gusty northerly winds, especially higher terrain *Lowering relative humidity values day and night Point Wildfire (near Lake Sonoma): Latest heat trends on GOES satellite and webcams show less heat, but that doesn`t mean the fire is "out" or contained. For fire specific updates follow CalFire for the latest. Weather wise, winds near the fire remain NW with gusts in the 10-20 mph range. Despite the breezy conditions, RH values have crept upward to moderate, which is good. Transport flow continues to show smoke impacts SE of Lake Sonoma stretching into the East Bay. This is also being reflected at the surface with AQ sensors showing poor AQ. For more AQ info check BAAQMD. Overall fire weather concerns: No change with ongoing Red Flag for interior North Bay for later today. The northerly shift in winds are still on track with gusts in the 25-40 mph. Winds will be strongest over the higher terrain of the North and East Bay. While winds increase RH values will begin to plummet. Hi-res guidance continues to advertise RH values dropping into the upper single digits to lower teens this afternoon. The greatest impact will be over the North Bay Interior Mts - hence the Red Flag. Elsewhere, conditions will be marginal for Red Flag, but still elevated nonetheless. Winds remain breezy offshore for Monday night into Tuesday keeping elevated fire weather concerns in play. Better relief arrive Tuesday into Wednesday with increased onshore flow. Longer range forecast will need some watching as hot and dry conditions return to the district. MM && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Red Flag Warning from 11 AM this morning to 8 PM PDT this evening for CAZ504. PZ...Small Craft Advisory until 3 AM PDT early this morning for Mry Bay-SF Bay N of Bay Bridge. Gale Warning until 3 AM PDT early this morning for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. && $$ SHORT TERM...MM LONG TERM....MM AVIATION...SO MARINE...SO 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