textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 130 PM PDT Sun Jul 12 2026

- Showers continue across the region into Tuesday

- Warming trend through midweek

- Large tidal swings to bring localized coastal flooding at high

SHORT TERM

Issued at 130 PM PDT Sun Jul 12 2026 (This evening through Monday night)

As you read this remember the word nuance. The atmosphere is many moving parts in the x, y, and z axis, as well as time. Mid to upper level monsoonal moisture has been working its way around the western periphery of an area of high pressure dominating the center portion of the US. As it does so this moisture is encountering an upper trough over the East Pacific. The path between the ridge and the trough are providing a road for the moisture to travel, while the trough and embedded shortwaves in the ridge are allowing for some vertical ascent. Models typically struggle with this type of pattern and this scenario is no exception. That said, it is all we have to go on as we look out beyond about 24 hours. In the short term forecast we can look at satellite and upstream soundings and radar. Today's satellite is showing a steady stream of moisture from the south cutting across Monterey County and extending up to Eastern Santa Clara County before exiting out to the NE. The remainder of our service area generally has thin clouds or is clear, which is not always good in an environment like this, because surface heating provides lift. That said, remember this moisture is in the mid to upper levels of troposphere. Even so, surface based heating can have an influence on the mid levels. A shortwave has shown up nicely in satellite data this afternoon over the San Diego and Orange County areas, tracking northward while following the coast. This could prove interesting as this shortwave is taking on a meso-low look, which simply means that it could add a little vertical kick to an already receptive environment. As this shortwave embeds within the larger moisture flow, we could see a a traveling pulse of increased mid to upper level instability this evening and overnight.

This evening and tonight expect bubbly cumulus clouds in the mid layers, meaning the base of the clouds starting at about 10000-15000 feet. This will likely produce virga (rain out of the bottom of the cloud that never reaches the ground). The question is, will it cause lightning? Models (again, which don't handle these patterns well) have been showing a vertical temperature profile that does not support a robust hail growth zone. The -10C range doesn't even start until around 19000 feet in the Vandenberg sounding from this morning. Models do not show a descending hail growth zone during our times of peak instability. So at this point the probability of squeezing out a lightning strike is probably less than 10%. In all likelihood we will probably simply experience virga and an occasional drop of water on the ground. All that said, the probability is not zero. While odds are low, don't be surprised if you see a flash from a cloud or a rumble of thunder.

Monday is looking a little more robust for convective development. With warming temperatures and higher humidity levels, we'll start the day a little warmer than Sunday, meaning we'll have a little jump start on breaking a convective cap. When models do show convective parameters in these high based situations, it is important to take notice. By Monday afternoon models are all showing plenty of moisture across our entire service area with PWAT values in the 1-1.5" range. MU CAPE pops in some select area to a couple hundred J/kg, Total Totals jump into the mid 40s, and K index pulls into the 30s. All the ingredients are there for a convective afternoon on Monday, but again, the depth of convection will be the limiting factor as to any lightning development. Expect more virga, more chances for a few drops to hit the ground, but continued less than 10% chance of lightning. If surface heating and/or an embedded shortwave gives an afternoon kick to break the mid level cap, we could see some solid deep convection. If that occurs these will be dry thunderstorms and outflow boundaries could approach 30-40 mph. In other words, if thunderstorms do develop, expect lightning and locally gusty and erratic winds.

Other things through Monday. Coastal flood advisory remains in place due to high astronomical tides with a little anomaly on top. Warming trend is beginning and will run through mid week. Cloud cover could mute the warming signal, but outside the clouds the warming will be strong. Tuesday and Wednesday will bring inland areas into the 90s and surpass 100 in a few spots.

LONG TERM

Issued at 130 PM PDT Sun Jul 12 2026 (Tuesday through next Saturday)

Convective threat will continue Monday night into Tuesday with the overall pattern shifting East through the day Tuesday. This shift will bring an end to the threat of high based thunderstorms for the Bay Area and Central Coast. The first part of Tuesday will be interesting as the warm minimum temperatures will give us a jump start on upward buoyancy in the low levels, potentially impacting the upper levels. The question will be, is there enough moisture left around as some convective parameters spike again on Tuesday? As it stands now, there could be a small window Tuesday afternoon where we can see another threat of dry thunderstorms, but those odds are in the 5% or less range.

Overall, don't count anything out. With poor model guidance for high based convection and the ever present threat of nocturnal thunderstorms, the atmosphere can and does surprise us. All it takes is one of the parameters breaking from expectation and we could be off to the races.

After the warm up into midweek, the pattern takes on a much more normal look for the second half of the week.

Early next week (yup, talking about that far out), we could see more monsoonal/sub-tropical moisture work its way into the area. Stay tuned.

AVIATION

(00Z TAFS) Issued at 431 PM PDT Sun Jul 12 2026

Radar and satellite show a band of high based showers over the southern part of the forecast area; showers are moving northward. A few patches of coastal stratus and fog may develop tonight and Monday morning. Clouds will slow radiative cooling and redevelopment of coastal stratus and fog tonight and result in a hazy, partly to mostly cloudy sky Monday. Overall conditions favor VFR with the highest probability of LIFR-IFR along the immediate coastline.

Vicinity of SFO...VFR. Northwest to west wind 5 to 15 knots.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR except patchy stratus and fog /LIFR- IFR/ nearby late tonight and Monday morning. Winds mainly varying from northwest to southwest 5 to 15 knots.

MARINE

(Tonight through next Friday) Issued at 425 PM PDT Sun Jul 12 2026

Moderate to fresh northerly winds are outer waters leading to hazardous conditions. Otherwise, expect light to moderate north- northwest winds with moderate northwest swell. Mainly northerly winds become fresh to strong mid to late week, which will have near gale force gusts. Seas will build in response, leading to overall hazardous conditions.

FIRE WEATHER

Issued at 130 PM PDT Sun Jul 12 2026

Warming temperatures this week will cause fuel moistures to plummet. At the same time we are tracking monsoonal moisture moving across the area and any threat of dry thunderstorms. While dry thunderstorms have a 10% or less of development, any strike can start a fire. Not to mention, in and around active thunderstorms winds can become gusty and erratic. For more information on the thunderstorm threat, see discussion above.

MTR WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory until 4 AM PDT Thursday for CAZ006-506- 508.

Coastal Flood Advisory until 4 AM PDT Wednesday for CAZ505-509- 529-530.

PZ...Small Craft Advisory until 3 PM PDT Wednesday for Pt Arena to Pt Reyes 10-60 NM.