, Issued at 1229 AM PDT Fri Mar 13 2026 (Today and tonight)
Cirrus clouds are moving over the CA coast associated with a sharp upper level trough over the Eastern Pacific. This feature is producing southerly winds that are pumping upper level moisture from the tropics to the West Coast. These clouds will likely remain trough the day as the trough slowly weakens and meanders a little closer towards the coast. This will help moderate the temperatures today, but the moderate strength upper level ridge will keep max temperatures similar to yesterday and around 10-15 degrees above normal.
..issued at 1229 AM PDT Fri Mar 13 2026 (Saturday through Thursday)
Saturday's temperatures will be similar to Friday, but for a different reason. The high clouds will clear, but a very weak disturbance will take a quick bite out of the ridge. 500mb heights are expected to drop from around 5850m on Friday to around 5770m on Saturday morning. That's still well above normal (5650m) for this time of year. The ridge starts to rebuild Saturday afternoon while surface high pressure builds over the northern Rockies causing the winds to veer offshore. This upper level ridge will continue to build through Tuesday, eventually becoming as strong as we ever seen in March. Some high clouds are likely to return Sunday before clear skies and unfiltered heat moves in for the peak of the heat wave starting Monday. Tuesday and Wednesday look like the hottest days before the ridge axis moves through. This will cause the temperatures to drop a couple degrees, but the heat wave will persist through the workweek. More noticeable relief will have to wait until the weekend, but temperatures may not return to normal for the rest of the month.
The guidance on the strength of this heat wave is remarkable. I'm going to cover it in detail here, but the bottom line is that I audibly gasped when I saw the ECMWF Extreme Forecast Index for maximum temperatures next week. I have never seen it anywhere near this aggressive with bright red painted across the state. That means the ECMWF ensemble members are showing a 99-100% chance of exceeding the maximum values of M-Climate (20-year database). The upper level support strongly points record breaking heat. There is a 75% chance that the 500mb height will break 5900m Monday evening (March record: 5885m). There is also a 75% chance the 850mb temp will break 20C Tuesday - Wednesday (March record: 19.2C). The 250 mb height is very likely to set a monthly record as well. All of this upper level support, combined with offshore winds, creates the perfect recipe for record breaking heat. As such, we expect a slew of daily records to be broken, and several monthly records are likely to go down as well. One final note on the upper level statistics before the hype train runs off the rails; these numbers are very high for March (near the lowest heights climatologically), but would be typical for early August. As such, expect next week to feel like early August, just without the marine layer.
So what does this mean for you? Temperatures will be warm but comfortable through Saturday with mid to upper 70s inland and upper 60s along the coast, roughly similar to what we saw on Thursday. By Sunday temperatures jump 5-10 degrees before another similar increase Monday. During the peak of the heat wave on Tuesday and Wednesday, most areas will be in the upper 80s and 90s, including many coastal locations thanks to the offshore winds. Temperatures will likely drop a couple degrees later in the week, but not nearly enough to end the heat wave. Much of the area will be under moderate HeatRisk. This level affects people sensitive to the heat, especially those without access to cooling and hydration. Keep in mind this is our first heat wave of the year and we haven't seen these temperatures since September.
(12z TAFS) Issued at 435 AM PDT Fri Mar 13 2026
Upper level moisture riding the ridge is leading to widespread cirrus over the region this morning (SCT-BKN150-250). As the surface, a quasi-marine layer trying to reforming, but it is struggling. VFR most terminals this morning except HAF/MRY with stratus and STS with some patchy fog. Some stratus will linger for HAF, but elsewhere will be VFR today. Stronger onshore flow will lead to some breezy conditions at times. Expect a repeat again tonight into Saturday with some marine stratus impacting the immediate coast and pushing locally inland.
Vicinity of SFO, Breezy NW flow through the GAP with a few low clouds around 500 ft thru AM rush. VFR this afternoon. Didn't buy in on cigs for tonight, but guidance does have some lower cigs with a 20-25% chc of MVFR conditions.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, Low/patchy cigs for MRY. There will be pockets of clearing through 17Z at times. Low cigs again tonight for MRY.
(today through Wednesday) Issued at 435 AM PDT Fri Mar 13 2026
High pressure anchored off the California coast will maintain moderate to fresh northerly breezes over the coastal waters. The stronger winds will result in locally hazardous conditions with fresh very steep swell. Winds and seas ease Sunday evening into the next week.
Ca, None. PZ, Small Craft Advisory from 9 AM this morning to 9 PM PDT Saturday for Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 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 from 9 PM this evening to 9 PM PDT Saturday for Pigeon Pt to Pt Pinos 0-10 nm.
Small Craft Advisory until 9 PM PDT Saturday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.
