FXUS66 KMTR 192043 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 143 PM PDT Tue May 19 2026 ...New SHORT TERM, LONG TERM... .KEY MESSAGES... Updated at 138 PM PDT Tue May 19 2026 - Diurnally driven winds expected this week, with onshore winds during the afternoon and early evening. - Above normal temperatures continue through midweek with seasonal temperatures returning late week && .SHORT TERM... Issued at 138 PM PDT Tue May 19 2026 (This evening through Wednesday) Winds have eased across the region with most sites currently reporting light offshore winds under 10 mph. Breezy, onshore afternoon winds are likely along the coast and within mountain gaps/passes. Not too much change to the overall synoptic pattern, broad upper level troughing continues over the western United States with an area of ridging and surface high pressure to our west over the Pacific. The center of the upper level trough continues to progress eastward with the surface pressure gradient becoming more relaxed, allowing wind speeds to diminish overall. The marine layer continues to be mixed out thanks to high pressure offshore which is allowing warmer temperatures to spread across the region. High temperatures will be seasonably warm today and again tomorrow with interior highs in the 80s to possibly the low 90s and coastal highs in the 60s to 70s. Critically dry conditions continue across the interior with the majority of stations reporting RH values in the 10s to 20s. Not much relief from drier conditions has been observed overnight with most sites only seeing overnight humidity recoveries to around 20-30%. This same pattern is expected to continue again on Wednesday with no real relief until the marine layer redevelops late week into the weekend. Fire weather concerns thus remain elevated given the critically dry conditions across the interior. If you are participating in any outdoor activities involving sparks or flame, exercise caution and be aware that fine fuels are very flammable at this time. && .LONG TERM... Issued at 138 PM PDT Tue May 19 2026 (Wednesday night through next Monday) The general pattern remains the same through Thursday with high temperatures in the 80s to low 90s across the interior, 60s to 70s along the coast, diurnally breezy winds, and critically dry daytime conditions across the interior. A gradual pattern change will begin Thursday into Friday, becoming more noticeable over the weekend, as high pressure weakens, shifting west, and broad troughing dominates the West Coast. Winds will generally shift onshore again by Friday with a shallow marine layer redeveloping. High temperatures will generally drop into the 70s across the interior and 70s to mid 80s across the interior Central Coast while coastal highs stay in the 50s to 60s. As the marine layer redevelops, we will see improving humidity values across the interior which will reduce our overall fire weather concerns. Initially the marine layer will be around 500 ft Thursday into Friday but is expected to deepen to around 1000 ft by the weekend. Diurnally breezy afternoon/evening winds continue with breezier winds along the coast and in mountain gaps/passes. The initial NBM forecast shows temperatures warming back into the 80s by early next week. The caveat to this is that models are split between upper level ridging and upper level troughing developing over the West Coast towards the end of May. If ridging is able to develop, warmer temperatures are likely to round out the month but if troughing is able to develop then slightly cooler temperatures are more likely. In the troughing scenario, there is the possibility of some light rain but the more likely setup is a deep marine layer and coastal drizzle. && .AVIATION... (18Z TAFS) Issued at 1021 AM PDT Tue May 19 2026 VFR will prevail the remainder of today and tonight with a chance of MVFR/IFR cigs developing around sunrise Wednesday. Light and variable winds this morning become light but steady onshore this afternoon and evening. Vicinity of SFO...VFR is expected through today and tonight with a slight chance of MVFR cigs developing around sunrise Wednesday with confidence too low for mentioning in the TAF attm. SFO Bridge Approach...Similar as SFO. Monterey Bay Terminals...VFR will prevail today and tonight with a chance of MVFR/IFR cigs developing around sunrise Wednesday morning. Expect light and variable to light onshore winds through the TAF period. && .MARINE... (Today through Sunday) Issued at 914 AM PDT Tue May 19 2026 Fresh northerly breezes will continue over the northern outer zones through tomorrow with hazardous conditions through Thursday morning. Wave heights increase again on Thursday with increasing northwest swell that eases for the end of the weak into the weekend. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 AM PDT Thursday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Kennedy LONG TERM....Kennedy AVIATION...JM MARINE...JM 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