A heat wave over the Southwest will intensify this week, peaking and expanding into the Intermountain West and northern High Plains this weekend. Severe thunderstorms and heavy rainfall are expected over parts of the Upper Midwest to mid-Mississippi Valley today. Critical to extremely critical fire weather conditions from the Northwest and the northern Great Basin on Saturday and Sunday. Read More >
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523 FXUS66 KMTR 311637 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 937 AM PDT Fri Jul 31 2026 ...New UPDATE, MARINE... .KEY MESSAGES... Updated at 1216 AM PDT Fri Jul 31 2026 - Gradual warming trend through Saturday with Moderate HeatRisk in the interior through the early part of next week - Elevated fire weather threat across the interior North and East Bays, and the Diablo and Santa Lucia ranges through the early part of next week - Hazardous beach conditions across the Pacific Coast with an increased risk for sneaker waves and rip currents through the weekend - Strong and gusty winds develop over coastal waters north of Pt Reyes this weekend && .UPDATE... Issued at 934 AM PDT Fri Jul 31 2026 Patches of stratus along the San Mateo coast and the Monterey Bay region continue to mix out, while smoke from the Woodside Fire continues to flow into the North Bay valleys. Sonoma County is dealing with the most intense smoke impacts with haze extending into Napa and Marin counties. Smoke transport is expected to continue through the day with peak transport expected as the winds pick up in the afternoon and evening hours. At the site of the fire, northwest winds gusting to 25-30 mph are expected this afternoon and evening. Air quality information is available from the Bay Area Air District. DialH && .SHORT TERM... Issued at 1246 AM PDT Fri Jul 31 2026 (Today and tonight) Near term Woodside Fire Weather: Satellite imagery shows some heat still showing up for the Woodside Fire. Thankfully the winds have eased from what was being observed during the evening hours. Still seeing some occasional gusts of 10-15 mph nearby. There is a shallow marine influence still showing up with cooler temps and moderate to excellent humidity recover. However, go up the hill on the east side of Hwy 1 just a few 100 feet and it`s milder and drier. There is a little bit of northerly flow over those ridge tops too, which is likely enhancing the thermal belt. Today`s challenge won`t be the temps or humidity, but the winds. Similar to Thursday NW winds will pick up again and be strongest in the afternoon/evening. Transport flow will be NW again leading to smoke transport to the southeast and east. Weather highlights for Friday: The warming trend observed on Thursday will continue today as high pressure aloft continues to ooze westward. Per 00z model guidance 850mb temps warm an additional 1-3C leading to 3-5F degrees at the surface. That`s assuming a fully mixed atmosphere with no marine layer influence. In other words, across the interior. Thursday`s hottest locations were 100-103 so a max of 105 isn`t out of the question today. Regardless, solid temps in the 90s to low 100s across the interior. Those temps will translate to widespread HeatRisk of Moderate with a few pockets of Major. At the coast and near the bays we still see subtle onshore flow with natural AC. The temp difference between the coast and inland will lead to gusty onshore winds this afternoon again. Given the nearby fire activity added smoke to the forecast with greatest coverage over the Sonoma and Petaluma Valleys of the North Bay. Could see some hazy condition develop over Marin and Napa as well depending on fire activity this afternoon. Clouds maybe lacking early this morning, but a weak cold front will approach from the N on Friday night/Saturday morning with a higher probability for patchy coastal stratus. Given the warm airmass aloft expect thermal belts to be active again with only minor relief expected in the hills. && .LONG TERM... Issued at 141 AM PDT Fri Jul 31 2026 (Saturday through Thursday) The aforementioned cold front fades out during the day Saturday with little to no fanfare. Even with the fading frontal boundary Saturday still appears to be the hottest day for this round of heat. No big change to previous forecast. Hottest interior locations of the Central Coast have the highest probability of exceeding 105 degrees, but less than 10% of reaching 110. Still expecting widespread HeatRisk of Moderate with a few pockets of Major. At the coast/bays temperatures will remain closer to seasonal levels. The large upper level ridge gets buffeted by a passing upper level trough to the north on Sunday. This will pause any additional warming with moderating temperatures to round out the weekend. Cooling 850mb and lower 500mb heights will bring subtle cooling Monday through the middle of next week. Do want to point out that even thought we technically cool next week this will be a prolonged period with max temps in the 90s to lower 100s across the interior. As discussed last night it still looks dangerously windy over the northern coastal waters this weekend, especially Sunday into Monday. The N-S gradient is still projected to reach 8 to 9mb resulting in storm force gusts. The ECMWF EFI has doubled down on tonight`s run and is showing decent confidence for the windy scenario. Thankfully the flow remains mostly parallel to the coast so a wind advisory win`t be needed. The passing system to the north will help to set the stage for bursts of offshore flow Saturday and Sunday nights. The setup isn`t ideal for strong winds, but still a change to NE wind. The NE flow will enhance fire weather concerns. More details below. && .AVIATION... (12Z TAFS) Issued at 525 AM PDT Fri Jul 31 2026 Satellite imagery and surface observations show a few areas of coastal stratus and fog /MVFR-IFR-LIFR/ from Point Reyes to the Monterey Bay otherwise it`s clear /VFR/. Wildfire smoke in the North Bay will lower surface visibility to MVFR. Diurnal surface warming and mixing will mix out the stratus, fog and help mix out the wildfire smoke today. Coastal stratus and fog /MVFR-IFR-LIFR/ return tonight and early Saturday morning under nocturnal radiative cooling. A dry surface cool front moves southward over the coastal waters Saturday. Vicinity of SFO...VFR today and tonight then stratus is likely by 10z Saturday, mixing out to VFR by 18z Saturday. West winds up to 15 to 25 knots today, decreasing to 10 knots tonight and Saturday morning. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Stratus and fog /IFR-LIFR/ mixes out to VFR by late morning then redevelops tonight and Saturday morning. Onshore winds 5 to 15 knots. && .MARINE... (Today through Wednesday) Issued at 934 AM PDT Fri Jul 31 2026 Fresh northwest breezes strength by Saturday into gale force across the northern waters and strong in the southern coastal waters. Wind driven moderate seas build to very rough by Sunday in response to the stronger winds. Occasional storm force gusts are likely in the northern waters. Wind and very rough seas gradually subside by mid next week. Distant tropical activity continues to send long period swells to our coastal waters. && .FIRE WEATHER... Issued at 1216 PM PDT Thu Jul 30 2026 The overall fire weather picture remains similar to the previous discussion, with elevated fire weather threats persisting at the higher elevations through the weekend and possibly beyond. Overnight RH recovery remains moderate to poor at locations at or above 2,000 feet with values between 35 to 45 percent, with some favored locations struggling to even reach 25 percent. This will be particularly true across the Mayacamas, highest peaks of the East Bay Hills, the Diablo Range, the Santa Cruz Mountains, the Santa Lucia and Gabilan Ranges. Nocturnal drying (rapid decrease in RH through the pre- dawn hours) may also transpire which will increase the burn period or time in which fire behavior may remain active. Afternoon RH remains critically dry with values between 15 and 30 percent, with far southern portions of the interior Central Coast potentially seeing min RH near 10 percent. Energy Release Components (ERC) are projected to climb above the 97th percentile across the interior Central Coast. Individuals across the area are advised to avoid activities that may spark a fire. Fire crews are urged to exercise extra caution when executing any prescribed burns, especially where fuels, topography, and weather align. && .BEACHES... Issued at 1216 PM PDT Thu Jul 30 2026 Long period southerly to southwesterly swell of 14-17 seconds continues to impact our coastline through at least Saturday afternoon, bringing hazardous beach conditions to the Central Coast and the San Francisco Bay Area. Sneaker waves and strong rip currents will be the primary threats, with breaking waves up to 10 feet along some south and southwest facing beaches and break points, such as Santa Cruz, Pacifica, and parts of Stinson or Ocean Beach. This can be particularly surprising when wave heights increase suddenly after a period of seemingly tranquil wave action. In fact, sneaker waves can have 20+ minutes in between the larger sets (breaking waves) with significant "flat/calm looking" times between them. Due to the long period, sneaker waves are powerful and can catch beachgoers by surprise, resulting in people and pets being swept into the cold, turbulent ocean. Rip currents are strong enough to pull even the strongest swimmers away from shore. Check marine conditions before you head out! Swim near a lifeguard, if possible. Maintain a safe distance from the water, and stay away from jetties, piers, beachside rocks, and other waterside infrastructure. Never turn your back to the ocean and if you have small children or pets at the beach, please keep an eye on them. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement through Saturday afternoon for CAZ006- 505-509-529-530. PZ...Small Craft Advisory until 9 AM PDT Saturday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM. Gale Warning from 9 AM to 9 PM PDT Saturday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory from 3 PM this afternoon to 9 PM PDT Saturday for Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt to Pt Pinos 0-10 nm. Small Craft Advisory from 9 AM to 9 PM PDT Saturday for Pigeon Pt to Pt Pinos 0-10 nm. Small Craft Advisory until 3 PM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning from 3 PM to 9 PM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory until 9 PM PDT Saturday for Pigeon Pt to Pt Pinos 10-60 NM. && $$ SHORT TERM...MM LONG TERM....MM AVIATION...Canepa MARINE...Navarrete 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 |
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