Issued at 905 PM PDT Fri Mar 13 2026
Strong 500 mb height ridging at 581 decameters on the evening Oakland upper air sounding has decreased a little since morning. Weak upper level jet stream divergence and cirrus clouds continue to move across the forecast area within the medium to broad ridge. The sounding vertical water vapor distribution is dry at 0.36" precipitable water. The dryness in the vertical has helped nightly coastal stratus/fog formation thanks to radiative cooling above the marine layer. The marine layer is currently ~ 1000 feet deep.
The 850 mb temperature on the evening sounding is warm already at 15.2 Celsius which is greater than the 90th percentile for mid March. After a cool to chilly start it did warm up above mid March 30 year normal highs today, but not to the extent it could've warmed if air parcels aloft were compressed closer to the surface and fully mixed vertically with March daytime surface warming. This combination however has a better chance of occurring beginning early next week which will cause daytime temperatures to warm up rapidly to well above normal and record territory once the Sun rises. There is good agreement in the model forecasts showing strong long wave ridging becoming highly focused over the southwestern U.S. while on the periphery the singular high is surrounded by low pressure development downstream and upstream. Late Saturday night and Sunday in fact the WMC-SFO pressure gradient (offshore winds) will temporarily steepen to ~ 10 mb while the 850 mb temperature won't be at its forecast peak quite yet for next week. This may be a good thing that it's out of step from a warming potential for Sunday. 850 mb temperatures then climb next week while the WMC-SFO pressure gradient eases.
Overall as advertised expect warmer to much warmer daytime highs next week. 500 mb wave amplification will take place and it may take much of next week before the high has a chance to move and/or weaken any. There's been some consistency in the GFS showing upstream movement may be a little quicker to arrive here than what recent ECMWF has shown. This may make a difference in when cooler air returns here later next week.
No updates to the forecast anticipated this evening.
, Issued at 244 PM PDT Fri Mar 13 2026 (This evening through Saturday)
Pleasant, above normal temperatures are expected across the region today with forecasted highs running 10-15 degrees above normal. However, there is one caveat to today's high temperatures: cloud cover. Satellite shows high level clouds streaming across much of the Bay Area and Central Coast while a shallow marine layer is bringing low level clouds directly along the coastline. The shallow marine layer is keeping temperatures cool along the coast with both HAF and MRY at 55 degrees as of 1PM. Temperatures are a bit higher (mid to upper 60s) across inland areas where low level clouds have cleared. Made some tweaks to the high temperature forecast for today and bumped afternoon highs down to the low 60s directly along the coast to account for the persistent shallow marine layer. Generally expecting temperatures to peak in the mid to upper 70s across the interior today before cooling down into the upper 40s to low 50s tonight. If you have any outdoor activities today and Saturday will be the best days for them as they are the two coolest days of the upcoming forecast period.
..issued at 244 PM PDT Fri Mar 13 2026 (Saturday night through next Thursday)
Upper level ridging builds in across the region Saturday before fully settling in by late weekend. Temperatures on Saturday will be fairly similar to those observed on Friday with highs in the upper 70s to low 80s across the interior and 60s directly along the coastline. Both HREF and WRF guidance suggest a shallow (500 ft) marine layer is possible again Saturday morning which will keep coastal areas cooler than interior areas.
Saturday will generally be the last "pleasant" day of the Long Term forecast. By Sunday, the center of the upper level ridge will push into California and usher in the start of our prolonged heat wave. The center of the upper level ridge will then remain over the California/Arizona border through late next week, potentially sticking around into next weekend. This unusually strong ridge is bringing us late summer like weather with 500mb heights around 5900 meters. Sunday will act as a transition day between the more pleasant Saturday temperatures to full summer on Monday with highs in the upper 70s to mid 80s. Starting Monday, highs across the interior will rise into the upper 80s to 90s. It will then stay that hot through the remainder of the long term forecast. This has the potential to break numerous daily high temperature records and even some all time high temperature records for March.
It is worth noting that temperatures may in fact go up during the second half of the week (starting Wednesday) as the ridge strengthens further. The NBM 95th Percentile (a reasonable high end scenario) pushes temperatures into the upper 90s to low 100s across the interior Central Coast and portions of the Santa Cruz Mountains/interior valleys Wednesday through late week. There is enough supporting evidence to say that this heatwave will extend through Friday and likely into the weekend given the longevity and restrengthening of the upper level ridge. Currently, Moderate HeatRisk is only forecast Monday through Wednesday but this is likely to expand through the rest of the week as the temperature forecast continues to increase. If you are spending any time outdoors this week, remember to drink plenty of water and allow your body to rest as needed. This heatwave is a marathon not a sprint with overnight conditions to offer at least some respite from daytime heat. Heat Advisories are likely to be issued for much of the urban areas and adjacent Santa Cruz Mountains/Diablo Range starting Monday and continuing through late week. For now, we are not anticipating issuing an Extreme Heat Watch/Warning as overnight temperatures will cool enough to prevent us from reaching Extreme Heat criteria. We will, however, need to keep a close eye on the forecast for the second half of the week as models are signaling that it could be even warmer than the first half.
As small, fine fuels (grass) cure this week, the potential for grass fires will increase. Offshore winds will remain light to moderate which will help mitigate how much any fires that do develop can grow. If you are participating in any outdoor activities (camping, offroading, hiking, etc) exercise caution when using fire and be aware that the risk of grass fires will be elevated next week.
(06z TAFS) Issued at 946 PM PDT Fri Mar 13 2026
Winds are starting to reduce, becoming light for most areas aside from the immediate coast. This means HAF will continue to see moderate winds through the night. Low CIGs look to form in the late night around the Monterey Bay as well as at HAF, then STS looks to have moments of low CIGs and mist into Saturday morning. Moderate winds return Saturday afternoon for most areas, while the coast (and HAF) see strong gusts. Cloud cover erodes into the afternoon, but hazy conditions look to form in most of the valleys and along the coast into the weekend. Winds reduce again into Saturday night.
Vicinity of SFO, VFR through the TAF period. Moderate west winds linger into the night before reducing. Northwest winds build again into Saturday afternoon and last into late that night before becoming light again.
SFO Bridge Approach, Scattered low clouds look to move around the Eastern SF Bay into Saturday morning, with a few passing through the approach until the late morning.
Monterey Bay Terminals, VFR lasts into the night before winds become light and IFR CIGs arrive to MRY. IFR CIGs will be slower to arrive to SNS, but are expected into early Saturday morning while MRY begins to see moments of LIFR CIGS. Expect some mist and reduced visibilities along with the building cloud cover. VFR returns in the mid to late morning as moderate west to northwest winds build. Winds reduce again into Saturday night.
(tonight through next Wednesday) Issued at 842 PM PDT Fri Mar 13 2026
Fresh to moderate north/northwest breezes Continue across the waters causing hazardous conditions through the weekend. Winds and seas ease in the inner waters by Sunday afternoon, and the rest of the waters by mid Monday. Mostly calm conditions will then last through the rest of the forecast period.
Ca, None. PZ, Small Craft Advisory until 3 AM PDT Sunday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory until 9 PM PDT Sunday for Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory until 9 AM PDT Sunday for Pigeon Pt to Pt Pinos 10-60 NM.
