textproduct: San Diego

SYNOPSIS

There will be slow inland warming through Wednesday. There will be greater warming on Thursday with widespread moderate to locally major HeatRisk for Thursday through the weekend for the mountains below 6500 feet, the inland valleys, inland Orange County, and the Apple and Lucerne Valleys with major to locally extreme HeatRisk for the lower deserts. There is a slight chance of showers for the mountains on Thursday afternoon and a slight chance of showers and thunderstorms for the mountains on Friday afternoon. Night and morning coastal low clouds will spread into the far western valleys at times late each night.

SHORT TERM (Today through Thursday)

There will be drying of monsoonal moisture for today and Wednesday, an increase for Thursday into Friday, then a greater decrease for the weekend into early next week. For this afternoon and Wednesday afternoon, there will just be some clouds over the mountains and maybe a few sprinkles. A slight chance of showers will return for Thursday afternoon. The marine layer will remain around 1500 feet deep with night and morning coastal low clouds spreading into the far western valleys at times late each night.

High temperatures for today and Wednesday will be a few degrees cooler for areas near the coast into the San Diego County valleys. For the mountains, deserts, and inland valleys, high temperatures will warm a few degrees today and a few to around 5 degrees on Wednesday. High temperatures on Wednesday will be within a few degrees of average for most areas, ranging from the mid to upper 70s near the coast to the 90s for the Inland Empire with 108 to 112 for the lower deserts.

There will be greater warming on Thursday of a few degrees near the coast to around 4 to 8 degrees for inland areas with the greatest warming for the mountains and inland valleys. High temperatures on Thursday will be few degrees above average near the coast to around 4 to 8 degrees above average for inland areas. High temperatures on Thursday will range from the mid 70s to around 80 near the coast to the mid 90s to 107 for the Inland Empire with 112 to 116 for the lower deserts.

For Thursday into the weekend, there will be widespread moderate HeatRisk for the mountains below 6500 feet, for the inland valleys, inland Orange County, and the Apple and Lucerne Valleys with widespread major HeatRisk for the lower deserts.

Beginning on Wednesday, there is an Extreme Heat Watch for the deserts and a Heat Advisory for the mountains, valleys, and inland Orange County, though the greater heat and HeatRisk will begin on Thursday.

LONG TERM (Friday through Monday)

Not much change in high temperatures is expected through Sunday with high temperatures a few degrees cooler possible on Monday. An increase in moisture and some mid and high clouds for Thursday night will result in low temperatures a few to around 5 degrees warmer than Wednesday night with a corresponding slight increase in HeatRisk on Friday. For Friday for the mountains below 6500 feet, inland valleys, and Apple and Lucerne Valleys, the HeatRisk will increase to moderate to locally major with the HeatRisk for the lower deserts increasing to major to locally extreme.

There is a slight chance of showers and thunderstorms for the mountains on Friday afternoon followed by drying for the weekend into early next week.

AVIATION

210915Z....Coast/Valleys...FEW mid level clouds with very patchy low clouds starting to develop at the coast (~800-1200 ft MSL bases) Very intermittent low cloud cigs expected for the coastal TAF sites (and other coastal areas) through around 14z. VIS reductions locally where clouds intersect with terrain. Remaining patchy clouds scatter out 14-16z Tue, then VFR conditions through Tuesday evening. Low clouds with slightly higher bases begin re-developing at the coastline by around 08z Wed.

Mountains/Deserts...VFR prevailing with FEW mid-level clouds clearing out Tuesday evening. West winds gusting 20-40 kts along desert slopes and up to 50 kts through the Banning Pass expected Tuesday afternoon and evening, 00-07z Wed.

MARINE

There is a 75% chance for NW wind gusts to exceed 20 kts in the outer waters near San Clemente Island both Wednesday and Thursday afternoons. Additionally, a mixed swell will cause steep and choppy seas Thursday and Friday, especially in the outer waters.

BEACHES

Southerly swell of 4-5 ft with a period of 11-13 seconds will continue to bring elevated to high surf and strong rip and longshore currents through this evening. Surf 3-6 feet with sets to 7 feet is expected through tonight, with the highest surf focused on south and southwest facing beaches of Orange County. A High Surf Advisory remains in effect until 11 PM tonight.

While this current swell diminishes tonight, another elevated southerly swell (4-5 feet, 15 second period) from a tropical cyclone far off the coast is expected to develop Wednesday evening and elevate surf through late Saturday. This would once again bring high surf of 6-8 feet, especially for south-southwest facing beaches.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...High Surf Advisory until 11 PM PDT this evening for Orange County Coastal Areas-San Diego County Coastal Areas.

Heat Advisory from 10 AM Wednesday to 8 PM PDT Monday for Orange County Inland Areas-Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains- San Diego County Valleys-Santa Ana Mountains and Foothills.

Extreme Heat Watch from Wednesday morning through Monday evening for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...None.