A major winter storm will continue to bring blizzard conditions, heavy snowfall, icing, and strong winds through Monday across the Upper Midwest and Upper Great Lakes. A line of storms will be capable of producing widespread damaging winds, tornadoes, and some large hail from the Mid-South to the Ohio Valley and the Southeast through tonight, moving into the Mid-Atlantic Monday. Read More >
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979 FXUS66 KMTR 160839 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 139 AM PDT Mon Mar 16 2026 ...New SHORT TERM, LONG TERM... .KEY MESSAGES... Updated at 203 PM PDT Sun Mar 15 2026 - Early season, long duration heat wave brings record-breaking temperatures and Moderate HeatRisk through the week - Elevated potential for grass fires through the week due to warm and dry conditions with periods of moderate offshore winds && .SHORT TERM... Issued at 1225 AM PDT Mon Mar 16 2026 (Today and tonight) After building for the last couple days, the much anticipated heat wave arrives in earnest today. A remarkably strong ridge of high pressure over the far eastern Pacific is meandering towards the coast this morning. This ridge has taken over the pattern and will be the primary driver of the heat wave this week. The early measurements on the strength of this ridge are coming in as expected. The 00Z sounding found an 850 mb temperature of 17.15C. That breaks the daily record of 16.8C. Similarly the 500 mb height was measured at 5880m, breaking the old daily record of 5860m. As the ridge continues to build and move closer over the next 24-36 hours, these benchmark values will only increase. Ensembles show a high likelihood that the 850 temp will reach 20C and the 500 mb height will reach 5900m by the 12Z sounding Tuesday. Those would both set monthly records by a wide margin, and are more typical of early August. This translates to temperatures in the mid to upper 80s across the interior, and 70s along the coast today. The marine layer is still hanging on, but it is being compressed to 500 feet or lower under the high pressure. This keeps the marine influence very localized to the coast. Ocean Beach will feel a nice marine breeze, but don`t expect it to reach over the hill. Offshore winds have become established and will be moderate at times before the ridge moves firmly overhead Tuesday and winds calm. Hot weather combined with dry offshore winds requires taking a look at fire weather conditions, and for good reason. At 10:50 AM Sunday, Mt. St. Helena reported sustained 42 mph ENE winds with 7% relative humidity. We should see something similar later this morning. That would be a slam dunk Red Flag Warning in the Summer. The reason we are holding off is the live fuel moisture content. Fortunately it`s March. The hills are still green and will not be receptive to burn. Live fuel moisture reaches its highest levels in Spring due to peak growing season. Dead fuel moisture, on the other hand, will respond more to the hot dry weather, and the Energy Release Component is expected to set monthly records this week. After the winds die down today, the next period of concern is when the ridge breaks down sometime around next weekend. This brings the potential for strong winds after all the fuel drying has occurred. As always, be cautious with campfires or any other potential ignition source. && .LONG TERM... Issued at 1225 AM PDT Mon Mar 16 2026 (Tuesday through Sunday) After several days of this heat wave building, it will reach the top of the plateau by Tuesday. Interior temperatures will reach the low to mid 90s, with 70s and 80s along the coast. Wednesday through Friday look nearly identical. Hot spots this week include the southern Salinas Valley and Gabilan Range. There is a strong possibility that Pinnacles National Park records the earliest 100 degree day of the year this week. The current record for March is only 93. Along the coast the hot spot looks to be Santa Cruz, where downslope winds will add adiabatic heating to battle any marine influence. We expect low 90s there. Numerous monthly records are expected to be broken this week. Check out the Climate section below for those benchmarks. Overall the big story with this heat wave is how early it is. Yes we`ve seen much hotter days in the Summer and early Fall, but we are a full 30 degrees warmer than normal this week. That`s very unusual any time of year. Finally, when will it end? All ensemble clusters agree that the ridge will start to weaken this weekend. That doesn`t mean temperatures will drop all the way back to normal, but we should see a cooling trend of about 5 degrees per day from Saturday through Monday, effectively ending the heat wave. && .AVIATION... (06Z TAFS) Issued at 932 PM PDT Sun Mar 15 2026 Widespread VFR and moderate winds last into the night. Expect winds to become light across the region overnight, with some slight reductions in visibility from mist and spotty fog. Visibilities improve in the mid to late morning. Winds increase slightly into Monday afternoon. Winds become light again that night. Vicinity of SFO...VFR through the TAF period. West winds are reducing and are becoming light. Winds become light and variable into Monday morning with some slight reductions in visibilities. West winds build again Monday afternoon and last into late that night before becoming light again. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR lasts into the late night. Expect light to moderate winds through the evening that become light into the night. Some pockets of mist look to reduce visibilities in the late night and through the morning. Conditions improve by the late morning and early afternoon as northwest winds build. These winds reduce into the evening and become light and variable into that night. && .MARINE... (Tonight through next Saturday) Issued at 932 PM PDT Sun Mar 15 2026 Breezy to gusty northerly winds linger in the Northern outer waters into Monday night before easing. Winds across the waters will continue to reduce into the work week. Sea heights will stay moderate due to a combination of wind waves and low southerly swell. && .CLIMATE... Issued at 133 AM PDT Sun Mar 15 2026 The following are the record high temperatures at the long term sites for March 15th, 16th, 17th, and 18th. Location Mar 16 Mar 17 Mar 18 Santa Rosa 91 in 2004 87 in 1996 84 in 2010 San Rafael 87 in 1972 84 in 1972 80 in 1996 Kentfield 86 in 2004 87 in 1914 89 in 1914 Napa 88 in 2004 92 in 1914 87 in 1914 Richmond 84 in 1972 83 in 2004 78 in 1996 Livermore 88 in 1972 87 in 1972 86 in 2004 San Francisco 85 in 1914 85 in 1914 86 in 1914 SFO Airport 82 in 2004 82 in 2004 77 in 2004 Redwood City 84 in 2004 85 in 2004 84 in 2004 Half Moon Bay 78 in 1972 83 in 2004 75 in 1978 Oakland Museum 85 in 2004 85 in 2004 81 in 2004 San Jose 85 in 1914 88 in 1914 87 in 1914 Salinas Airport 87 in 2004 87 in 2004 84 in 1960 The following are the record high temperatures at the long term sites for the entire month of March. Location Santa Rosa 91 on March 16, 2004 San Rafael 88 on March 25, 1952 Kentfield 91 on March 28, 1923 Napa 92 on March 17, 1914 Richmond 87 on March 31, 2021 Livermore 90 on March 25 and 26, 2025 San Francisco 87 on March 11, 2005 SFO Airport 85 on March 25, 1952 Redwood City 89 on March 31, 2011 Half Moon Bay 83 on March 31, 2000 and March 17, 2004 Oakland Museum 88 on March 11, 2005 San Jose 89 on March 14, 2015 Salinas Airport 92 on March 14, 2015 && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory from 10 AM this morning to 8 PM PDT Friday for CAZ006-502>506-508>510-512>518-528>530. PZ...Small Craft Advisory until 3 AM PDT Tuesday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Flynn LONG TERM....Flynn AVIATION...Murdock MARINE...Murdock 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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