textproduct: San Diego

SYNOPSIS

Increased HeatRisk expected through Saturday with moderate HeatRisk for the mountains and Inland Empire with areas of major HeatRisk in the deserts. An influx of monsoonal moisture early next week will taper daytime highs in the deserts. Additionally there is a 15-20% chance of showers and thunderstorms over the mountains in the afternoons Sunday through Tuesday, most widespread chances Sunday and Monday. 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...

A persistent area of high pressure will remain over the western United States through the weekend. The position of the high through Wednesday will allow for a shallow influx of moisture into the lower deserts, which may taper daytime highs but elevate overnight lows. The high is expected to strengthen Thursday through Saturday, bringing widespread moderate HeatRisk to the Inland Empire and mountains and areas of major HeatRisk to the deserts.

High temperatures through Wednesday will generally be within a few degrees of average. Thursday through Saturday highs will be above average near the coast to 5 to locally 10 degrees above average for some 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 Empire and mountains, the widespread moderate HeatRisk indicates 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).

For Sunday through Tuesday, the high pressure will begin to slowly weaken with the flow aloft becoming more southeasterly. This would allow for some additional influx of monsoonal moisture into the area and bring a 15 to 20 percent chance of showers and thunderstorms to the mountains each afternoon. Ensemble guidance show precipitable water values and instability peaking Sunday and Monday. Current forecast follows the NBM which has chances each afternoon, with most widespread coverage Sunday and Monday.

Mountains/Deserts

Mostly clear skies and unrestricted VIS through Wednesday morning.

MARINE

No hazardous marine conditions are expected through Saturday.

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 Saturday for Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains.

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

PZ...None.