, Issued at 1116 PM PDT Mon Jul 13 2026 (Tonight through Wednesday)
While the 12Z HRRR showed some interesting thunderstorm potential early Tuesday morning, the 18Z backed off, and the 00Z continued that trend. The radar picture is also losing steam and it now seems unlikely that thunderstorms will develop. By sunrise, the clouds will be gone and the threat will basically be over. There's another 5% chance Tuesday afternoon during peak daytime heating, but the best chance for convection is now behind us.
The big weather story now shifts to heat. According to commercial aircraft soundings, the 850mb temperature was around 22C at 00Z. That's somewhere between the 75th and 90th percentile. Even with the cloud cover, temperatures were around 5-10 degrees warmer than normal on Monday. The 850 mb temperature will be broadly similar Tuesday, but we won't have the overcast mid level clouds to take the sting out of the heat. Surface temperatures will increase a few degrees, but the HeatRisk will increase more substantially for a few reasons; the radiant heat from direct sunlight, the cumulative effect of multiple hot days, and very warm overnight temperatures. In fact, we may see the warmest minimum temperature of the year for many locations thanks to the lingering altostratus acting as a blanket for the first half of the night. All these factors combine to bring widespread moderate HeatRisk Tuesday. Max temperatures will be in the 90s inland and 70s along the coast.
On the other hand, the humidity will be a little lower and a decent onshore breeze will pick up in the afternoon. While low humidity and a breeze help people deal with the heat, they also contribute to elevated fire weather conditions. Refer to the fire weather section for more information.
..issued at 1116 PM PDT Mon Jul 13 2026 (Wednesday night through next Monday)
The hot weather will continue through Wednesday before a cooling trend starts on Thursday. A trough will move in from the Eastern Pacific, bringing a weak cold front Thursday morning. Inland temperatures will drop by as much as 10 degrees, bringing us back to normal for this time of year. The cooling trend will continue, and Friday and Saturday will actually be about 5-10 degrees cooler than normal while the marine layer expands back to around 1,000 feet. The low pressure system will generate some gusty winds, particularly in the afternoon as the mixing depth increases and higher momentum is transfered to the surface.
At 500 mb the high pressure over the Rockies will remain in place as the trough approaches the coast. This pattern will keep mid-level winds out of the south to southwest through the week. That means the tropical moisture conveyer belt will remain open. While dry air will dominate the middle of the week, there is an increasing chance that one of the many robust tropical waves off the coast of Mexico will develop into a tropical cyclone this week aided by the warm El Nino waters. If that happens, there is a chance that some of the associated moisture will be drawn into the SW winds and advect over the Bay Area, bringing us similar impacts and considerations that we saw with recent monsoon moisture event. Depending on the strength of the TC, there could also be impacts from ocean swell at the beach. The uncertainty is still high, but it's been trending more likely recently. The ECMWF 50 member ensemble has a mean PW returning above 1.0" by Sunday- Monday. That's around the 90th percentile for this time of year. I also noticed 7 of the members have a PW over 1.5", and 2 members are over 2". The highest we've ever recorded is 1.79", and that was on 8/16/2020, when the remnants of Tropical Storm Fausto brought a major dry lightning outbreak to the Bay Area and sparked several wildfires. I'm certainly not predicting a repeat of August 2020, but it's worth keeping an eye on this next potential moisture push given the current warm temperatures and dry fuels.
(12z TAFS) Issued at 411 AM PDT Tue Jul 14 2026
Currently VFR at all terminals with the exception of HAF which is currently oscillating between LIFR and MVFR. High confidence in VFR through the afternoon with low to moderate confidence on IFR ceilings returning to the coastal terminals of HAF, MRY, and SNS tonight. Diurnal winds will prevail. Haze will reduce slant range visibilities.
Vicinity of SFO, Currently VFR with westerly flow. High confidence in VFR and diurnal winds prevailing through the TAF period.
SFO Bridge Approach, Low probability (30% chance) of low clouds below FL045 developing across the San Mateo Bridge Approach tonight. Reasonable best case scenario is the marine layer is too shallow to make it through the Golden Gate Gap or it remains on the north side of the terminal.
Monterey Bay Terminals, Currently VFR with easterly flow at MRY and VFR and calm at SNS. Moderate confidence in IFR ceilings returning to the terminals tonight. The forecast has trended towards a later arrival and a lower ceiling with MRY having a higher probability of occurrence than SNS.
(today through Sunday) Issued at 411 AM PDT Tue Jul 14 2026
Moderate to fresh northwesterly breezes are expected through most of the week. Hazardous conditions for small craft will result, especially across the northern waters and along the Big Sur Coast. Northwesterly breezes will increase on Thursday to become fresh to strong, bringing widespread hazardous conditions for small craft. Moderate seas will prevail, building to become rough in the outer waters over the weekend.
Ca, Coastal Flood Advisory until 4 AM PDT Thursday for CAZ006-506- 508.
Heat Advisory from 10 AM this morning to 10 PM PDT this evening for CAZ503-504-506-510-513>517-528.
Coastal Flood Advisory until 4 AM PDT Wednesday for CAZ505-509- 529-530.
Heat Advisory from 10 AM to 10 PM PDT Wednesday for CAZ516-517.
PZ, Small Craft Advisory from 3 PM this afternoon to 3 PM PDT Wednesday for Pt Arena to Pt Reyes 0-10 nm.
Small Craft Advisory from 9 PM this evening to 9 AM PDT Wednesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory until 3 PM PDT Wednesday for Pt Arena to Pt Reyes 10-60 NM.
