Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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190 FXUS66 KMTR 210715 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1215 AM PDT Tue May 21 2024 ...New AVIATION... .SYNOPSIS... Issued at 1224 PM PDT Mon May 20 2024 Typical summer-like pattern to persist throughout the first half of the week. Temperatures are forecast to dip below seasonal averages by the upcoming weekend as an upper level trough impacts the region. && .UPDATE... Issued at 841 PM PDT Mon May 20 2024 Pleasant day around the Bay Area and Central Coast as it turned out to be one of the sunnier days out of the last week (yesterday was pretty sunny too). Despite the ample sunshine, temperatures struggled to reach seasonal values. Highs topped out in the upper 60s to lower 80s inland, but much cooler at the coast with highs in the upper 50s to 60s. As the sun set, some patchy stratus began to form around Monterey Bay, Big Sur coast and SF Peninsula coast. This patchy stratus will fill in a little more and up the Salinas Valley, but much less coverage than a few days ago. What`s the reason? Developing offshore flow and drier air. Latest large-scale pressure gradient (SFO-WMC) has finally flipped offshore. Not expecting a strong offshore push, but offshore nonetheless. Obs over the North Bay interior mts already showing NE flow with lower RH. The offshore flow will also lead to milder temperatures in the hills tonight. Breezy northwest winds will diminish in the evening. Model output shows a moderate confidence (40-65% probability) of MVFR stratus around the region early Tuesday morning, with the period of highest probability from 09-16Z. No update needed this evening. As noted below Tuesday will be the warmest day over the next few days. Warmest temperatures will be across the interior and away from any marine influence. Speaking of marine influence, the very persistent gusty NW winds has led to some impressive upwelling along the North Bay coast. Current SSTs are in the upper 40s to lower 50s. MM && .SHORT TERM... (This evening through Tuesday) Issued at 1224 PM PDT Mon May 20 2024 Weak offshore flow aloft is resulting in dry weather conditions this afternoon with minimum relative humidity values between 15-35% for inland areas and those higher up in elevation. Meanwhile, the coast continues to experience onshore flow with higher humidity. Humidity increases overnight in all but the highest elevations with lows generally in the mid-to-upper 40`s to low-to-mid 50`s. RH values will be even lower tomorrow as offshore flow aloft persists and will drive drier conditions even closer to the coast. As such, tomorrow will be the warmest day of the week with mid 80`s across the interior and 60`s to lower 70`s near the coast. People who are incredibly sensitive to heat should take precautions while outdoors and remember to drink plenty of water. && .LONG TERM... (Tuesday night through next Sunday) Issued at 1224 PM PDT Mon May 20 2024 By late week, temperatures cool to near seasonal averages across the interior but coastal locations will still be slightly cooler due to onshore flow. By this upcoming weekend, temperatures region-wide drop below average as a mid/upper level trough more directly impacts the region. This systems looks fairly dry with ensemble guidance indicating very low chances of accumulating precipitation with it Friday into Saturday morning. If any precipitation does fall it will be light and not very impactful. Guidance from the Climate Prediction Center indicates slightly below average temperatures and slightly above average precipitation through the end of the month. && .AVIATION... (06Z TAFS) Issued at 1211 AM PDT Tue May 21 2024 Generally VFR conditions for the interior through the night, with MVFR stratus persisting around Monterey Bay through the late morning hours. Vicinity of SFO... VFR through the TAF period. Light onshore winds overnight with breezy conditions developing by Tuesday afternoon. Peak gusts generally in the 20-25 kt range into early Tuesday evening. SFO Bridge Approach... Similar to SFO. Monterey Bay Terminals...Light onshore winds overnight with MVFR stratus persisting through mid to late Tuesday morning. Clearing this afternoon with modest onshore winds, with stratus returning tonight. && .MARINE... (Today through Saturday) Issued at 907 AM PDT Mon May 20 2024 Strong and gusty northwest winds persist over the coastal waters through Thursday. Expect hazardous conditions and steeper wind waves during the week. Winds look to ease later in the week. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 PM PDT Wednesday for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory until 3 AM PDT early this morning for Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory from 3 PM this afternoon to 3 PM PDT Wednesday for Pt Reyes to Pigeon Pt 0-10 nm. Gale Warning until 3 PM PDT Wednesday for Pt Arena to Pt Reyes 10-60 NM. Gale Warning until 3 AM PDT Wednesday for Pigeon Pt to Pt Pinos 10-60 NM. && $$ SHORT TERM...RGass LONG TERM....RGass AVIATION...SPM MARINE...DialH 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