Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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944 FXUS66 KMTR 221756 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1056 AM PDT Sun Sep 22 2024 ...New AVIATION... .SYNOPSIS... Issued at 337 AM PDT Sun Sep 22 2024 Temperatures will continue to warm this afternoon, with highs in the low 90s inland across the North Bay, East Bay and higher elevations above the marine layer extending south into Monterey County and San Benito County. The heat builds further Monday and Tuesday, with areas of moderate HeatRisk possible for inland locations not under the influence of the marine layer. && .UPDATE... Issued at 853 AM PDT Sun Sep 22 2024 Extensive stratus coverage has developed across the valleys this morning, beginning to mix out along the very fringes of the stratus deck. The 24-hour temperature trends show temperatures across the region running near or slightly above those seen this time yesterday. Still expecting a warming trend to continue today and Monday, but possibly not as dramatic as the current forecast shows. Will evaluate the trends throughout the rest of the morning, taking a closer look at the short-term temperature forecast with the afternoon forecast package. DialH && .SHORT TERM... (Today and tonight) Issued at 337 AM PDT Sun Sep 22 2024 Low level ridging below a slow developing upper level weakness in the H50 height fields will result in warmer temperatures today and then climb even higher tomorrow to start the work week with moderate HeatRisk possible for inland locations away from the marine layer. Deterministic guidance has consistently advertised the weakly forced upper level disturbance, though the exact location and evolution over the next couple days has been difficult to pin down. It has likely limited the impacts of the heat somewhat over the next few days, but highs on Monday will still be in the mid 90s to near 100 inland across the North, South and East Bay, also farther south into Monterey County above the marine layer and San Benito County. && .LONG TERM... (Monday through Saturday) Issued at 337 AM PDT Sun Sep 22 2024 The potential for moderate HeatRisk will extend into Tuesday under a stagnant airmass between a developing upper low offshore to our west and building ridge over the Intermountain West. By Wednesday, the offshore upper low merges with a strengthening trough over the Pacific Northwest. The upper troughing to our north will spread cooler temperatures aloft over our region, resulting in lower surface temperatures closer to normal for this time of year for Wednesday and beyond, while another upper level disturbance develops offshore of SOCAL and remains quasi-stationary into next weekend. && .AVIATION... (18Z TAFS) Issued at 1042 AM PDT Sun Sep 22 2024 Tricky forecast earlier this morning with amendments and adjustments to many TAFS. The reason? A compressing marine layer through sunrise allowing for expansion of the marine layer, but also patchy fog/reduced visibility. As of the 18Z TAF package issuance, vis satellite shows rapid thinning of stratus layer yielding VFR all terminals by 18Z or shortly thereafter. VFR this afternoon/this evening with low stratus hugging the coastline. Do expect the lurking stratus to move inland again tonight. However, building high pressure will leading to further compression. Extent of stratus will not be as much as this morning. Additionally, NE flow begins to develop late night just above the marine layer. Earlier clearing of stratus for Monday AM rush. Vicinity of SFO...Clearing over terminal by 1815Z. Stratus lingering SE and E of runways. Onshore flow developing later this afternoon. IFR to LIFR late tonight. Earlier clearing tomorrow. SFO Bridge Approach...Stratus layer clearing from the edges...therefore some stratus will linger longer over the approach than SFO. Monterey Bay Terminals...VFR this afternoon. CIGS return early this evening. && .MARINE... (Today through Friday) Issued at 853 AM PDT Sun Sep 22 2024 High pressure over the Eastern Pacific and low pressure over California will lead to breezy northwesterly flow over the coastal waters through at least Monday. Winds will be strongest over outer waters north of Point Reyes. The locally stronger winds will result in a steeper fresh swell. Northwesterly breezes decreasing and seas abating Tuesday. Seas rebuilding to become rough in the outer waters towards the end of the forecast period. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 9 AM PDT Monday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...JM LONG TERM....JM AVIATION...MM 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