Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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343 FXUS66 KMTR 140603 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1103 PM PDT Thu Jun 13 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 247 AM PDT Thu Jun 13 2024 Quiet through the rest of the week with slight warm up on Friday across the interior. Near normal temperatures by the weekend. Increasing confidence for high wind potential and increased fire danger Sunday into early next week. && .UPDATE... Issued at 802 PM PDT Thu Jun 13 2024 The forecast remains on track this evening. Some patchy fog overnight can be expected from the South Bay southward into the Santa Cruz coastal region. An upper level system moving onshore across the Pacific Northwest this weekend will bring drier air and gusty winds, elevating fire weather concerns across our region for the weekend into the beginning of next week. Any activities that could spark a wildfire should be discouraged. && .SHORT TERM... (This evening through Friday) Issued at 207 PM PDT Thu Jun 13 2024 Zonal flow has caused some rinse and repeat for weather conditions today, compared to yesterday. Most of the clouds have eroded back to the coast while areas in Monterey Bay and Salinas, still remain pretty socked in with some low clouds and is anticipated to remain so for the rest of the day. Overnight temperatures will also be similar to last night but a few areas in the North Bay will see 1-3 degrees warmer with minimum temperatures in the 50s, while the remaining of the region will see upper 40s to mid 50s. As a weak ridge moves over the region tomorrow, expect max temperatures to become warmer compared to today with inland areas seeing mid 80s to low 90s. Coastline remains pretty consistent with low 60s. && .LONG TERM... (Friday night through next Wednesday) Issued at 207 PM PDT Thu Jun 13 2024 As we move into the weekend, a deep low pressure system pattern dips down into our area bringing some cooler temperatures and some increased winds. Max temperatures inland will reach up to mid to high 80s Saturday, with temperatures beginning to dropping a few degrees every day with Sunday and Monday seeing temperatures in the low 80s and 70s. The coast will remain in the high 50 to 60s through the weekend into the first half of next week. Overnight lows generally will be in the 50s through most of the area. Winds will also increase as the trough deepens into our area causing some gusty winds throughout our region, with the highest possible winds speeds between 30-40 mph occuring over the waters, coastal area, valleys and inland coastal gaps. Although we will have some moisture recovery overnight through the weekend, there is some fire concerns Sunday into Monday, as there have been recent drying of fine fuels and grasses. We are expecting overall onshore winds associated with this low pressure system, but depending on the magnitude and positioning of the trough, offshore winds are not completely off the table. This will dry fuels out even further. With the ensemble members showing some differences in the magnitude of the trough, we are able to explore a best case and worse case scenario for elevated fire concerns. The best case, is represented by the European and GFS ensembles where it supports a deepening of the trough, which will bring some moist air, cooler temperatures, and stronger onshore winds, which will alleviate some fire concerns. The worst case scenario would be if the trough becomes weak or a short wave ridging develops. This will bring the possibility of offshore winds, drier conditions, and warmer temperatures, which will increase some fire weather concerns. Therefore, we will continue to monitor the trough as it gets closer to our region to update our forecast, as well as our messaging. As we move into the middle of the week, long-range models show a possible ridging or weakening of the trough that will bring possible warmer temperatures. Stay tuned! && .AVIATION... (06Z TAFS) Issued at 1102 PM PDT Thu Jun 13 2024 MVFR-IFR stratus is developing along the immediate coast and into the East Bay north of OAK and across the Central Coast valleys. Stratus coverage tonight is expected to expand slightly into the northern SF Bay and patches of the Napa Valley. Lingering breezy onshore winds will diminish through the rest of the night. Stratus will clear out through Friday morning, with intensely breezy west winds developing on Friday afternoon. Wind gusts are expected to approach 20-30 knots at the terminals in the afternoon, with strong gusts continuing through the evening. Model output indicates that surface sustained winds will begin to diminish as the nocturnal boundary layer decouples, but strong winds aloft will introduce the risk of LLWS overnight. Model output shows signals of LLWS along the coast, but magnitudes are not strong enough to include in the TAFs at this time. Vicinity of SFO... Westerly winds expected to diminish through the night, with a moderate confidence for MVFR-IFR stratus to flow over the terminal. OAK is just on the edge of the stratus deck, but has consistently reported MVFR cigs which is reflected in their TAF forecast. VFR conditions return Friday morning with strong west- northwest winds developing Friday afternoon. Current forecast calls for gusts around 30 knots extending late into the evening as winds funnel through the San Bruno Gap, only coming down as the TAF period ends. LLWS concerns develop on Friday evening but the magnitude is marginal and confidence is low. SFO Bridge Approach... Lower confidence for stratus impacts along the approach path. Otherwise similar to SFO. Monterey Bay Terminals... IFR-MVFR ceilings continue through the night. Stratus clears out through Friday morning with low to moderate confidence in timing at MRY. Breezy onshore winds gusting to 15-20 knots develop Friday afternoon and last into the evening. Model output suggests that the region remains clear through the end of the TAF period and some portion beyond. && .MARINE... (Tonight through next Wednesday) Issued at 1102 PM PDT Thu Jun 13 2024 Fresh to strong northwest winds persist over the northern waters with gale force gusts expected Friday afternoon and evening. Strong north to northwest winds will spread southwards over much of the coastal waters late Friday into Saturday, with widespread gale force winds anticipated. Significant wave heights up to around 12 to 15 feet in the outer waters and 10 to 14 feet in the inner waters continue into the weekend. Hazardous conditions for small craft continue through the weekend and early next week. && .FIRE WEATHER... Issued at 408 PM PDT Thu Jun 13 2024 ...Elevated Fire Weather Conditions Through The Weekend... Elevated fire weather conditions are expected to persist through the weekend into the beginning of next week across our area. A lack of recent rainfall amid warmer and drier conditions has dried fuels, especially grasses. Although temperatures have moderated back down to around normal after the recent heat, a relatively dry airmass associated with an upper level Pacific trough will result in gusty surface winds mixing to the surface across our inland locations and higher terrain. Min RH values for locations susceptible to potential wild fires will generally be between 10 to 30 percent Friday through Monday, and possible beyond. The public should be discouraged from activities that may spark a wildfire, especially weekend campers with campfires. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 PM PDT Friday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM. Gale Watch from Friday afternoon through late Friday night for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory from 3 AM to 9 PM PDT Friday for Pt Reyes to Pigeon Pt 0-10 nm. Gale Watch from Friday evening through Saturday afternoon for Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory from 9 AM Friday to 3 PM PDT Saturday for Pigeon Pt to Pt Pinos 0-10 nm. Small Craft Advisory from 3 AM Friday to 3 AM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Watch from Friday afternoon through Saturday afternoon for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...SO LONG TERM....SO AVIATION...DialH 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