, Issued at 1226 AM PDT Mon May 11 2026 (Today and tonight)
Upper level ridge still remains locked over CA, but that will change after today. Let's first take a look at the marine layer situation. Similar to yesterday we still have a marine layer. You can definitely tell there's a ridge overhead due to compressed nature and discontinuous coverage of the stratus. Satellite fog product does show decent coverage along most of the coast, but inland coverage is lacking and less than 24 hours ago. Expect some additional expansion through sunrise. Will need to rely on the building May Sun angle to help erode the stratus by this afternoon. Not much surface forcing to get rid of it. Regardless, today will be the peak of our little warm spell. 850 mb temps are still on track to be 20-22C, which under ideal conditions would yield max temps in the mid 90s. However, we still have some marine layer influence. The last three days NBM guidance was just too warm across the interior and think today will be the same. Did shave a few degrees from the NBM for today. Max Temps will be in the 60s to 70s coast and bays and 80s to mid 90s far interior. The slight downward trend on temps has now kept Moderate HeatRisk confined mainly to the East Bay interior valleys.
By tonight the ridge shifts eastward and gets replaced by an approaching upstream trough. As such, 500 mb heights begin to fall and the airmass cools. The marine layer will develop again and with the exiting ridge coverage will be more and deeper.
..issued at 1226 AM PDT Mon May 11 2026 (Tuesday through Sunday)
Tuesday will be a transition day as the ridge is to the east and a cut-off low develop off the NorCal coast. Deeper marine layer to start the day and cooling airmass will lead to cooler temperatures with no HeatRisk concerns. Temps will still be still above normal, but trending toward seasonal averages.
There was more uncertainty regarding the longwave pattern midweek, but the latest cluster run and ensemble guidance has given a more clear picture. The cut-off low from Tuesday night deepens and then sweeps through NorCal - taking the more northern track. So wait does that mean? Will still have some light rain and/or drizzle in the forecast for the N Bay/ SF/ SF Peninsula late Tuesday night through early Wednesday. Not expecting much in the way of accum. Higher confidence this passing low will bring temps back to seasonal averages.
Zonal flow then develops for the rest of the work week into next weekend with dry conditions and moderating temps.
(12z TAFS) Issued at 449 AM PDT Mon May 11 2026
Conditions are a mix of stratus and patchy fog /IFR-LIFR/ and cirrus clouds /VFR/ over the forecast area. Patchy light drizzle is possible this morning. Conditions improving to MVFR-VFR by late morning or early afternoon. Areas of coastal stratus and fog /IFR- LIFR/ move inland tonight and Tuesday morning.
Vicinity of SFO, Tempo /IFR/ in stratus 13z-16z this morning otherwise VFR today. VFR tonight except stratus /IFR/ returns 08z Tuesday morning. West wind 5 to 15 knots.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, Stratus, fog and a few patches of light drizzle /IFR-LIFR/ this morning. Conditions improving to MVFR-VFR by late morning or early afternoon. Stratus, fog and possibly a few patches of light drizzle /IFR-LIFR/ return tonight and Tuesday morning. Mainly west to northwest winds 5 to 15 knots.
(today through Saturday) Issued at 437 AM PDT Mon May 11 2026
Winds ease across the inner waters then across the outer waters today becoming a moderate to fresh northwest breeze. Seas subside in response, but remain moderate with 4 to 5 foot seas by mid week. Locally gusty conditions are likely across the San Pablo and San Francisco Bays where terrain promotes wind funneling. Winds increase and seas build again late Wednesday into Thursday.
Ca, None. PZ, Small Craft Advisory from 3 PM to 9 PM PDT Tuesday for Pt Arena to Pt Reyes 0-10 nm-SF Bay N of Bay Bridge.
Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory until 9 AM PDT this morning for Pigeon Pt to Pt Pinos 10-60 NM.
