


Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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379 FXUS66 KMTR 211724 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1024 AM PDT Wed May 21 2025 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 111 AM PDT Wed May 21 2025 Above seasonal normal temperatures and hazardous marine conditions today. Elevated fire weather conditions through Thursday. && .SHORT TERM... (Today and tonight) Issued at 111 AM PDT Wed May 21 2025 Conditions are warmer and drier than they were this time last night, but only in the higher terrain. Why? Well, last night there was a shallow marine layer that impacted coastal areas while tonight the region is clear and winds are calm, allowing for maximal radiational cooling. A low amplitude upper-level shortwave ridge will trek across the region today, bringing the warmest conditions of the week. Temperatures will be 10 degrees above normal with widespread minor HeatRisk and areas of moderate HeatRisk for the Interior Bay Area and Central Coast. Elevated fire weather conditions will continue through tomorrow for the Interior Bay Area and Central Coast as dry conditions (poor daytime relative humidity of 15-25%, overnight relative humidity recovery of 30-50% in the higher terrain) and moderate to strong onshore winds continue. The threat is primarily in the finer, flashier fuels of brush and grass as recent offshore flow and warm conditions continue to cure them. && .LONG TERM... (Thursday through Tuesday) Issued at 111 AM PDT Wed May 21 2025 The lack of a longwave pattern over the region is evident in the extended forecast. An upper-level shortwave trough will skirt the region Thursday, causing temperatures to return to seasonal normals. A second, deeper upper-level shortwave trough will dig into the region Friday, bringing the coolest conditions of the week. An upper- level longwave ridge builds into the West Saturday which will bring temperatures up to 5 degrees above normal. Global ensemble clusters show an Omega Block, the combination of two cutoff lows with one blocking high sandwiched between them, developing by Sunday. By nature, this will lead to uncertainty and low confidence in the progression of the longwave pattern into early next week as these features have very weak forcing and thus can be persistent. && .AVIATION... (18Z TAFS) Issued at 1023 AM PDT Wed May 21 2025 VFR conditions have returned all TAF sites and look to persist through the remainder of the afternoon and evening. Onshore winds will increase by late morning or early afternoon before easing into the night. There is moderate confidence for low clouds to return to the Monterey Bay terminals early Thursday morning. Elsewhere, VFR conditions are likely to persist through the TAF period. Vicinity of SFO...Onshore winds are forecast to increase this afternoon with gusts up to 30 kt. Winds are forecast to ease into the night potentially becoming variable early Thursday morning. Onshore winds will return by Thursday afternoon. VFR conditions are likely through the TAF period. SFO Bridge Approach...Weaker wind speeds, otherwise similar to SFO. Monterey Bay Terminals...Onshore winds increase this afternoon before easing after sunset. There is moderate confidence for low clouds to return early Thursday morning resulting in IFR/LIFR conditions by around 06Z - 09Z && .MARINE... (Today through Monday) Issued at 1023 AM PDT Wed May 21 2025 Hazardous marine conditions continue today as strong northwesterly breezes with near gale to gale force gusts and rough to very rough seas persist. Winds will slowly diminish and seas will slowly abate tonight with fresh northwesterly breezes with strong gusts and moderate to rough seas prevailing Thursday through Sunday. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for Mry Bay. Small Craft Advisory until 3 AM PDT Thursday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. Gale Warning until 3 PM PDT this afternoon for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Thursday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Sarment LONG TERM....Sarment AVIATION...RGass MARINE...RGass Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea