Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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907 FXUS66 KMTR 171759 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1059 AM PDT Mon Jun 17 2024 ...New AVIATION, MARINE... .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. && .UPDATE... Issued at 952 AM PDT Mon Jun 17 2024 Forecast remains on track, with elevated fire weather concerns for today across our region, and especially the North Bay Interior Mountains, where a Red Flag Warning is in effect until 8pm PDT tonight for gusty north winds up to 30 MPH and min RH values as low as 10 percent. && .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... (18Z TAFS) Issued at 1058 AM PDT Mon Jun 17 2024 Currently VFR at all terminals. VFR through the TAF period for all terminals except MRY. Thanks to wildfires in the area, high pressure trapping the smoke, and northerly/northwesterly winds, smoke will likely be seen across the area, particularly at the terminals of APC, LVK, and STS, although no significant visibility reductions are to be expected. With the exception of STS, winds will become more westerly/onshore through the TAF period. Vicinity of SFO...Currently VFR with northerly flow. VFR through the TAF period. Winds will transition to become westerly this afternoon with gusts up to 30 knots to be expected. Westerly winds diminish overnight before becoming gusty again tomorrow afternoon. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Currently VFR with northwesterly flow at both terminals. Winds will be gusty out of the west/northwest through this evening before diminishing overnight. Moderate confidence on MRY getting an IFR ceiling with lower confidence on if it`ll reach SNS. && .MARINE... (Today through Saturday) Issued at 1058 AM PDT Mon Jun 17 2024 Widespread strong northerly/northwesterly breezes with near gale- force gusts will persist through Wednesday. These northerly/northwesterly breezes will diminish overall beginning Thursday with strong breezes remaining exclusive to the outer waters. Significant wave heights will build to 10-12 feet today, abate through Friday, and build back up to 10-12 feet towards the end of the period. && .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 until 8 PM PDT this evening for CAZ504. PZ...Small Craft Advisory until 9 PM PDT this evening for Mry Bay-Pt Arena to Pt Reyes 10-60 NM-SF Bay N of Bay Bridge. Small Craft Advisory from 3 PM to 9 PM PDT Tuesday for SF Bay N of Bay Bridge. Small Craft Advisory from 9 AM Tuesday to 3 AM PDT Wednesday for Mry Bay. Small Craft Advisory until 3 AM PDT Wednesday 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 Reyes to Pigeon Pt 0-10 nm. Gale Warning until 9 PM PDT this evening for Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning from 3 PM Tuesday to 3 AM PDT Wednesday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning from 9 PM this evening to 3 AM PDT Tuesday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...MM LONG TERM....MM AVIATION...Sarment MARINE...Sarment 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