textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 148 PM PDT Sun Jul 19 2026

- Near or slightly below normal temperatures and higher humidity through the first half of the upcoming week.

- The marine layer and mid to upper level cloud cover will continue to help keep temperatures cooler under building high pressure.

- Approximately 5% chance of elevated showers with isolated thunderstorms Tuesday afternoon through Wednesday evening.

SHORT TERM

Issued at 148 PM PDT Sun Jul 19 2026 (This evening through Monday night)

Marine layer stratus has retreated back to the coastline as of early this afternoon. Increasing coverage of mid/high level clouds streaming northeast out ahead of an upper level low over the EPAC will continue this afternoon and tonight. Elevated showers can be seen on radar approaching our southern outer marine zones and will continue to remain well off shore for the remainder of today and this evening. However, after midnight, elevated shower activity is possible mainly for the Bay Area and the North Bay through mid- morning Monday. Poor lapse rates and thermal instability will limit the chances for thunderstorm activity. Along with the weak instability, very dry air between 700mb-925mb will likely result in little to no precipitation reaching the ground with only a trace to a few hundredths where any rainfall is measured. Temperatures on Monday will be similar to slightly cooler than todays values with the increased cloud coverage.

Expecting a typical stratus intrusion tonight into early Monday morning as onshore flow persists, with high clouds helping to limit some of the radiational stratus cloud top cooling that will result in less mist/drizzle coverage than we saw this morning, and mostly confined to coastal areas.

LONG TERM

Issued at 148 PM PDT Sun Jul 19 2026 (Tuesday through next Saturday)

Chances for another round of elevated showers with isolated thunderstorms is trending upward. Not currently reflected in the official forecast but subsequent updates may see increases in coverage and intensity by Tuesday afternoon into Wednesday, mainly across the North Bay and maybe as far south as the Bay Area. The main source continues to be the moisture associated with what will be the remnants of Elida moving north, well offshore of our area by the end of the day Wednesday. Increasing lift, better thermal instability and slightly improved mid-level lapse rates between 7- 7.5 C/km by late Tuesday afternoon into Tuesday night will provide the best chances for elevated thunderstorms and potentially impactful dry lightning. A similar pocket of dry air from 700mb- 925mb will continue to limit beneficial rainfall. A final wave of elevated instability will move into the North Bay once again late Wednesday afternoon into the evening hours with potentially improved thermal instability, however less lift and weaker lapse rates, with dry air in the mid-levels continuing to limit precipitation reaching the ground. By Thursday into the weekend, the increased mid-level moisture shifts north and we begin to see drier air aloft with a gradual warming trend into the weekend. However, onshore flow will persist will persist through the extended forecast with typical no- sky-July conditions each night and morning.

AVIATION

(00Z TAFS) Issued at 440 PM PDT Sun Jul 19 2026

VFR with IFR-LIFR stratus to return overnight. The marine layer is expected to compress tonight which will lead both to lowered ceiling heights and a smaller inland extent. Confidence in stratus reaching SJC is slightly higher than it was this morning while stratus chances for LVK remain minimal. Have kept higher chances for IFR in at OAK/SFO with confidence increasing. Patchy fog is possible along the coast tonight with LIFR CIGs and reductions in visibility possible. Diurnally breezy onshore winds continue in the afternoon/evening.

Vicinity of SFO...VFR with MVFR-IFR stratus to return overnight. Moderate confidence of timing of stratus return. Satellite imagery shows a less expansive stratus layer than last night which increases confidence in a later stratus arrival (~07Z). MVFR CIGs are the most likely scenario but cannot rule out patchy IFR CIGs given the compressing of the marine layer. Conditions improve by late morning with some potential for stratus to return again late tomorrow evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR with stratus expected to build in over the next few hours. IFR-LIFR CIGs are expected tonight with CIGs to gradually lower early tomorrow morning. There is some potential for fog and reductions in visibility due to the compressing of the marine layer. Moderate confidence in clearing between 17-19Z with a few models indicating stratus could linger longer at MRY.

MARINE

(Tonight through next Friday) Issued at 440 PM PDT Sun Jul 19 2026

Gentle to moderate northwesterly breezes will persist through the upcoming workweek with slight to moderate seas. As tropical cyclone activity continues across the eastern Pacific, long period southerly swell is forecast. Southerly swell heights are anticipated to remain in the slight category but mixed seas may result in hazardous boating conditions through the week. Additionally, there are non-zero chances for high based showers which could result in pockets of gusty outflow winds and subsequent steep seas tonight through mid-week.

FIRE WEATHER

Issued at 148 PM PDT Sun Jul 19 2026

Near to slightly cooler than normal temperatures will continue through the week with typical diurnal intrusion of the marine layer each night and retreat to the coast each morning as onshore flow persists. However, above 1500-2000ft we'll see relatively weak thermal belting the first half of the week with continued warm overnights and poor RH recovery at higher elevations.

Guidance is trending toward an increasing potential for elevated showers and isolated thunderstorms Tuesday afternoon through Wednesday evening. Chances are below 5% in the official forecast but may increase in subsequent updates tonight and Monday. The primary concern is dry lightning strikes across the North Bay, with lesser chances farther south into the Bay Area.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...None.