, 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.
..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.
(12z TAFS) Issued at 410 AM PDT Mon Mar 16 2026
Widespread VFR through the TAF period with patches of MVFR-IFR visibilities possible along the immediate coast, although confidence is low enough to bump up visibilities at HAF and SNS. High clouds coming through the region should inhibit the widespread formation of stratus this morning. Light winds through the morning, with a pulse of gentle to moderate northwest flow in the afternoon and evening before light winds return overnight.
Vicinity of SFO, VFR through the TAF period with light winds through the morning. A pulse of moderate west-northwest flow arrives this afternoon and evening with light winds resuming overnight.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, VFR through the TAF period. A gentle to moderate pulse of northwest flow should arrive in the afternoon and evening. Otherwise, light winds prevail at the terminals.
(today through Saturday) Issued at 410 AM PDT Mon Mar 16 2026
Breezy to gusty north winds linger in the northern outer waters through the day before easing tonight. Winds across the waters continue to decrease through the work week. Sea heights remain moderate due to a combination of wind waves and low southerly swell.
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 9 AM PDT Tuesday for Pt Arena to Pt Reyes 10-60 NM.
