textproduct: San Diego

SYNOPSIS

Through Sunday moderate HeatRisk expected for the inland valleys and mountains with major HeatRisk in the deserts. There are chances of showers and thunderstorms in the mountains each afternoon through Tuesday. There are lower chances today and Saturday with increased thunderstorm chances early next week. Coastal areas will continue to see low clouds each night and morning through the forecast period.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

An isolated convective cell developed around 8 AM along the San Diego coast starting in La Jolla and eventually moving offshore near Encinitas. A few lightning strikes occurred near Solana Beach/Encinitas. Rainfall totals out of that cell ranged from 0.03 inches of rain to 0.36 inches between La Jolla and Encinitas. For the rest of the day, dry conditions are expected west of the mountains but there remains slight chances of showers and isolated thunderstorms in the mountains and High Desert. Latest high resolution guidance is indicating showers that develop today and Saturday will see rainfall rates 0.10 inch per hour or less, with only a 10 percent chance of rainfall rates exceeding that.

Through Sunday high temperatures are expected to run 5 to 10 degrees above average for inland areas. Low temperatures will also run above average, most noticeable in the mountains and deserts where lows will be 10 to 15 degrees above average. For the inland valleys and mountains moderate HeatRisk is expected which means that folks who are sensitive heat, especially those without consistent cooling/hydration will be most impacted. In the deserts, major HeatRisk indicates anyone may see negative impacts from the heat if precautions aren't taken. Make sure to stay hydrated and if possible avoid strenuous activity during the hottest parts of the day (10 AM to 4 PM). High temperatures are expected to gradually decrease next week, bringing temperatures back down to near or slightly below average by the middle of next week.

Sunday through Tuesday, the ridge of high pressure will shift east more over the Four Corners region. This will allow for additional influxes of moisture into the area and increase our chances for showers and thunderstorms. Latest guidance doesn't show a forcing mechanism outside of the usual daytime heating from the sun but that could change as we get closer. The current forecast keeps thunderstorm chances confined to the mountains, locally into the High Desert, in the afternoons each day Sunday through Tuesday. For Sunday, the latest REFS 90th percentile hourly rainfall rate peaks at 0.55 inches per hour, with only 10 percent chance of exceeding that.

Valleys/Mountains/Deserts

VFR with FEW-SCT clouds AOA 20,000ft MSL through Saturday. Low chance (10%) for TSRA over the mountains this afternoon between 20z-02z.

MARINE

No hazardous marine conditions are expected through Tuesday.

SKYWARN

Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions.

SGX WATCHES/WARNINGS/ADVISORIES

CA...Heat Advisory until 8 PM PDT Sunday for Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains.

Heat Advisory from 10 AM Saturday to 8 PM PDT Sunday for Orange County Inland Areas-San Diego County Valleys-Santa Ana Mountains and Foothills.

Extreme Heat Warning until 8 PM PDT Sunday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...None.