Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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783 FXUS66 KMTR 310607 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1107 PM PDT Thu May 30 2024 ...New AVIATION... .SYNOPSIS... Issued at 220 PM PDT Thu May 30 2024 Weak ridging will bring a minor warming trend to the region through Friday. A trough will move into the Pacific Northwest this weekend though, which will help strengthen the onshore flow and deepen the marine layer, bringing a slight reprieve to the warmer conditions. However, high pressure will build back across the region by the middle of next week, bringing a much more pronounced warming trend to the region, especially across the inland areas. Inland areas could be upwards of 10 to 20 degrees above normal, with a moderate heat risk by Wednesday. && .UPDATE... Issued at 900 PM PDT Thu May 30 2024 The ongoing forecast remains on track with no updates anticipated this evening. && .SHORT TERM... (This evening through Friday) Issued at 220 PM PDT Thu May 30 2024 Water vapor imagery continues to show relatively zonal upper level flow across California this afternoon, with a few high clouds still moving across the far northern portion of the state. Meanwhile, patchy low clouds continue to linger along the Big Sur Coast and the Monterey Peninsula. Given the sunny skies this afternoon, temperatures are running similar or up to 5 degrees warmer than this time yesterday. This will make for pleasant afternoon and evening across the region. The low clouds will likely move back into the Monterey Bay tonight, with a clouds start to the day expected on Friday. Otherwise, the minor warming trend that we saw today will continue into the day on Friday, with most areas similar to or slightly warmer than where they peaked today. && .LONG TERM... (Friday night through next Wednesday) Issued at 220 PM PDT Thu May 30 2024 Things will begin to change on Friday night though as a series of systems take aim at the Pacific Northwest. As a result, this will bring the return of the marine layer to most areas as well as stronger onshore flow. Therefore, expect a cooling trend to develop, with inland temperatures seeing the greatest decrease. Low clouds may be hard to clear the coast each afternoon, with unseasonably cool conditions prevailing along the immediate coast. In fact, cannot rule out some late night or early morning drizzle each day this weekend. A more potent system will take aim at the Pacific Northwest and far Northern California on Sunday into Monday. While we are still not expecting any rain from this system this far south, expect quite a bit more cloud cover to spread across the region late Sunday and into Monday as well as some coastal drizzle. The primary concern for this forecast though is with the warming trend associated with the high pressure building over the West starting on Tuesday. While Tuesday will be warmer, expect significant warming to occur for Wednesday and Thursday as the ridge axis builds over the Four Corners and potentially even more westward than that. These days could be the hottest we have seen this year for our inland areas, with inland regions flirting with or even surging above 100 degrees. In fact, the probabilistic guidance is suggesting a 75% chance of inland areas reaching 95 degrees and a 40% chance of inland areas topping 100. Therefore, there is high confidence that the inland areas will be quite hot, ranging between 8 to 15 degrees warmer than normal and potentially upwards of 10 to 20 degrees above normal. CPC is even highlighting the potential for excessive heat in the Central Valley, especially for June 5th to 7th. While we may get some influence of the marine layer, believe that it will be quite shall, with inland areas seeing the greatest warm up and potential for significant heat and a moderate heat risk. As previously stated, the marine layer influence will be the biggest question for the coastal areas, with ensemble spreads for the coastal areas are upwards of 20 degrees. This high uncertainty really has to do with the placement of the ridge axis, and whether or not we can get some light offshore winds developing. Until the placement of the ridge axis becomes more clear, the uncertainty will remain high for the coastal areas. Therefore, we will continue to watch how this event develops over the next several days. CPC`s 8 to 14 day outlook also shows a better chance of above normal temperatures as well, so there is a chance that this heat turns into a minor heatwave, extending through the remainder of the work week. Palmer && .AVIATION... (06Z TAFS) Issued at 1107 PM PDT Thu May 30 2024 VFR for the majority of terminals through the TAF period, with the exception of Monterey Bay. Winds have eased for most locations, and are expected to remain light through the overnight. Onshore winds will increase in the afternoon tomorrow to become breezy. In the later night of Friday, stratus will begin to make an appearance at coastal terminals as it surges back along the coast. Vicinity of SFO...VFR through the TAF period. Models appear to be in good agreement that the SF bay should remain largely cloud free through the TAF period. Winds will increase out of the W/NW in the afternoon to become breezy once more, but ease into the nighttime. Low clouds will begin to advect inland in the late night, though model agreement appears uncertain as to whether CIGs will form. Current thoughts are that an approaching trough will help to deepen the marine layer and elevate cloud formation, allowing FEW-SCT low clouds to develop around area terminals. However, confidence is currently low in a CIG developing. This will be something to watch in further updates. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Currently IFR at KSNS where the metar is reporting OVC006. Models did not originally show CIGs forming at this hour, however thoughts are that current CIG formation is a result of micro-scale effects: sea salt whipped up into the air from stronger winds the past few days may be contributing as cloud droplet nuclei, allowing clouds to begin forming as the air cools and condenses in the night. Either way, thoughts are that IFR CIGs will prevail through the night for KSNS, and develop in the early morning for KMRY. It is not out of the question that LIFR CIGs could form, however, confidence is currently low on this so have left out of the TAF. Expect a return to VFR conditions after sunrise. && .MARINE... (Tonight through next Wednesday) Issued at 900 PM PDT Thu May 30 2024 Breezy to gusty winds will continue over the outer waters into the weekend with gale force winds expected late Friday night into Saturday. Significant wave heights offshore are currently up to 12 feet, but will begin to abate tomorrow through the remainder of the weekend. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 AM PDT Friday for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory from 3 PM Friday to 3 AM PDT Saturday for Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 3 PM PDT Friday for Pt Arena to Pt Reyes 10-60 NM. Gale Warning from 3 PM Friday to 3 AM PDT Saturday for Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory until 3 AM PDT Saturday for Pigeon Pt to Pt Pinos 10-60 NM. && $$ SHORT TERM...Palmer LONG TERM....Palmer AVIATION...AC MARINE...JM 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