Area Forecast Discussion

SYNOPSIS

Increase in both high and low temperatures expected for the middle of this week into early next week. Widespread moderate to areas of major HeatRisk away from the coast are expected during this time, with locally extreme HeatRisk in the low deserts. There is a slight chance of showers and 5 percent chance of thunderstorms Thursday and Friday afternoons over the mountains and High Desert. Otherwise, dry conditions expected through the weekend. This week marine layer low clouds will remain patchy and confined to the coast.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

UPDATED AVIATION DISCUSSION

Areas of high clouds are being observed on satellite this morning. Areas of clouds will stick around through the afternoon, but coverage will be much less widespread compared to yesterday. Night and morning low clouds are expected to stay mostly confined to coastal areas this week, with patchy coverage.

Broad ridging is still expected across the southwest this week. Today, the ridge is centered farther east, over New Mexico/Texas. The ridge is expected to strengthen and expand westward Thursday and Friday settling over the Arizona/New Mexico border for Saturday into early next week. High temperatures will start to become above average on Wednesday, peaking at 5 to 10 degrees above average Thursday through the weekend. In addition to above average high temperatures, low temperatures will be running 5 to 10 degrees above average, locally up to 15 degrees above average in the mountains. The combination of elevated high and low temperatures will limit the ability to recover from heat overnight and allow for conditions to quickly warm once the sun rises. Widespread moderate to locally major HeatRisk is expected in inland Orange County, San Diego Valleys, Inland Empire, and area mountains. Major HeatRisk is expected in the deserts, with locally extreme HeatRisk in Coachella Valley and San Diego deserts. Major to extreme HeatRisk indicates that anyone may be negatively impacted by the heat if the proper precautions are not taken.

While there will be a minor uptick in monsoonal moisture in the mountains and deserts Thursday and Friday, chances of showers and thunderstorms stay low. Shower chances are mostly 15 to 20 percent, with only a 5 percent chance of thunderstorms developing. Dry conditions are expected over the weekend into early next week.

AVIATION

220000Z....Coast/Valleys...Low clouds based 800-1300 ft MSL expected to redevelop over coastal areas after 08z Wed. Coverage of BKN cigs should be more uniform and persistent than this morning with low clouds spreading up to 15-20 miles inland by 12z. Patchy minor vis reductions (3-5SM) expected for elevated coastal terrain and western valleys. Clouds scatter back to the coast by 18z, though there is a 30-40% chance for BKN cigs along the immediate SD County coast through the afternoon.

Mountains/Deserts...VFR conditions will prevail through the TAF period. Westerly wind gusts 20-40 kts along desert slopes and locally into deserts expected through this evening. Gusts may exceed 50 kts through the Banning Pass. Winds slowly weaken 06-12z Wed.

MARINE

Northwesterly winds with gusts 20-25 kts in the outer waters near San Clemente Island expected 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 Thursday 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 Warning from 10 AM Thursday to 8 PM PDT Monday for Apple and Lucerne Valleys.

Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Monday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...Small Craft Advisory from noon Wednesday to 9 PM PDT Thursday for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.