Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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899 FXUS66 KMTR 212025 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 125 PM PDT Sat Sep 21 2024 ...New SYNOPSIS, SHORT TERM, LONG TERM... .SYNOPSIS... Issued at 124 PM PDT Sat Sep 21 2024 Gradual warming continues through the rest of the weekend with temperatures near or slightly below seasonal averages. Even warmer temperatures expected Monday and Tuesday with moderate HeatRisk possible inland. && .SHORT TERM... (This evening through Sunday) Issued at 124 PM PDT Sat Sep 21 2024 Warmer temperatures are starting to make their way into the interior regions, with temperatures generally running 5 to 10 or occasionally 15 degrees above those at the same time yesterday. The stratus deck has pared back to the immediate coast, as the marine layer has gradually compressed with observations from the Fort Ord profiler showing a marine layer depth around 1500 feet today compared to nearly 2000-2200 feet this time yesterday. Overnight stratus is expected to develop into the coastal valleys although the interior East Bay and the Morgan Hill-Hollister corridor are expected to remain clear. Today`s temperatures should be warmer than yesterday`s, although the extensive stratus coverage this morning led me to bump down the high temperature forecast in the interior valleys by a few degrees. The current forecast shows high temperatures today ranging from the 80s across the inland valleys, to the 70s and low 80s near the Bayshore, and the low to mid 60s along the Pacific coast. Even warmer temperatures are forecast on Sunday, although some uncertainty continues into this period. A shortwave trough begins to develop off the coast of California through the day, interrupting the expanding upper level high over this part of the region and moderating the warming trend. As of time of writing, the inland valleys are expected to reach into the low to mid 90s on Sunday, with temperatures in the Bayshore up to the mid 70s to mid 80s and the Pacific coast rising to the mid to upper 60s. Low temperatures remain in the 50s across the lower elevations, up to the mid 60s along the thermal belts. && .LONG TERM... (Sunday night through next Friday) Issued at 124 PM PDT Sat Sep 21 2024 The upper level disturbance builds ever so slightly into the beginning of the upcoming work week, migrating further offshore through the next couple days with a potential window for the development of a closed low, before the pulse is absorbed into the polar jet mid week. The interaction between this upper level disturbance and the upper level ridge pushing into the northwestern United States will dominate our weather pattern for the next several days. In particular, the positioning of the low off the California coast will result in light offshore flow during the overnight and morning hours, although onshore flow should dominate the afternoon and evening hours. Temperatures are expected to peak on Monday and Tuesday, when moderate HeatRisk is possible in the interior regions. Highs in the inland valleys are expected to rise into the mid to upper 90s on those days. Of note, the extent of heat-related impacts is correlated to how cold it gets overnight, with significant uncertainty across the thermal belts, but also near San Francisco Bay. For example, the reasonable range of low temperatures near San Francisco International Airport is around 15 degrees. From the midweek onward, persistent upper level troughing should moderate temperatures to near the seasonal average through the end of the week. && .AVIATION... (18Z TAFS) Issued at 1119 AM PDT Sat Sep 21 2024 Stratus has cleared from most area terminals this morning, leaving behind VFR in its wake. VFR will persist through the early evening today with W/NW breezy winds at area terminals this afternoon. Stratus begins to return in the early portion of the evening for Monterey Bay tonight, but later for most other terminals. However, stratus is likely to bring IFR CIGs overnight for the majority of terminals. Late morning clearing to VFR on Sunday expected. Vicinity of SFO...VFR lasts through the early morning of Sunday, though confidence on this is only moderate. Some models indicate a return of stratus prior to midnight, though at this time, higher confidence is placed in stratus bringing MVFR CIGs beyond midnight for KSFO. Otherwise, breezy NW winds return this afternoon, but settle and become light into the late evening. SFO Bridge Approach...Clear through the day today. Low coastal clouds are likely to filter into the SF Bay overnight bringing low CIGs. Monterey Bay Terminals...IFR CIGs are expected to clear soon, with VFR lasting through the late afternoon today. Stratus will make an early return, bringing IFR CIGs once more towards the 00-02Z Sunday window. In the overnight, CIGs are expected to lower to become LIFR, with some reduction in visibility as fog develops. && .MARINE... (Today through Thursday) Issued at 1119 AM PDT Sat Sep 21 2024 Fresh to moderate northwest winds continue, with strong gusts over the far northern outer waters through Monday. Seas will be moderate, continuing to build and remain rough in the outer waters with significant wave heights up to 12 feet. Winds decrease and seas abate beginning Tuesday. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...DialH LONG TERM....DialH AVIATION...AC MARINE...AC 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