textproduct: San Diego

SYNOPSIS

Persistent high pressure will continue hot days and near-record warm nights through Friday night, with a slight chance of showers and thunderstorms for the mountains this afternoon and Friday afternoon. High pressure will weaken for the weekend into early next week with high temperatures cooling to around average next Monday. For Tuesday and Wednesday of next week, there is a 10 to 20 percent chance for an increase in clouds and a chance of precipitation from a tropical system that has yet to develop.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

This afternoon...Mid and high clouds moving into San Diego County from the south could produce isolated light showers and possibly a tstm or two over the next several hours, mainly in the mountains but a few light showers could develop over the valleys and coastal areas. Temperatures are mostly a few degrees higher than at this time yesterday.

Through friday...High pressure will continue to bring hot weather to Socal. High temperatures will be around 10 degrees above average with low temperatures as much as 15 to 20 degrees above average for the lower elevations of the mountains. High temperatures will range from the 80s near the coast to 100 to 108 for the Inland Empire with 112 to 116 for the lower deserts. Low temperatures will be mostly in the 70s for the coast, valleys, and high desert and in the mid 80s to mid 90s for the lower deserts. Low temperatures will be around 80 for the lower elevations of the mountains. The highest HeatRisk is expected on Thursday with widespread Moderate to Extreme HeatRisk for the valleys, inland coastal areas, and lower deserts. While the high temperatures will likely not tie or exceed existing records, many records for warmest overnight low temperatures could be tied or broken, most likely on Thursday and Friday.

A cooling trend is expected for Saturday into the middle of next week as high pressure aloft weakens and shifts to the southeast in response to a developing trough of low pressure near the California coast which will strengthen lower-level flow onshore. High temperatures will cool to around average for next Monday with low temperatures cooling to slightly above average.

There could be some increase in clouds and a chance of precipitation around Tuesday or Wednesday of next week from moisture from a tropical system that has yet to develop.

AVIATION

261800Z...Coast...VFR conditions prevail through early Thursday morning. Very patchy low clouds based 200-600 ft MSL develop over nearshore waters after 09z Thu, intermittently pushing ashore into coastal areas mainly in San Diego County. Vis reductions of 1SM or less possible where low clouds/FG develop. Greatest chances for cigs/vis reductions at coastal TAF sites will be from 12-15z (20% at KCRQ, 50% at KSAN). Any low clouds scatter out by 16z.

Mountains/Deserts...Cumulus based around 9000 feet MSL with ISO TSRA and CB tops to 40000 feet MSL over mountains into adjacent deserts 20-01Z. Any TS that develops could produce gusty, erratic winds.

Regionwide...FEW high clouds AOA 15000 feet MSL gradually becoming SCT-BKN this evening and tonight.

MARINE

No hazardous marine conditions are expected through Sunday.

BEACHES

A 4-5 ft southerly swell (from 170 degrees) at 12-13 seconds will continue to produce elevated surf through Thursday, particularly for south-facing beaches of northern San Diego County and Orange County. Surf of 3 to 6 feet, with sets up to 7 feet are expected. Check the Coastal Hazard Message for details on Beach Hazards.

FIRE WEATHER

Through Friday...low humidity and locally gusty westerly winds could produce elevated fire weather conditions during the afternoon hours in areas above 2,000 ft, especially in and below mountain passes and canyons. Persistent high pressure will continue hot days and near-record warm nights through Friday night, with a slight chance of showers and thunderstorms for the mountains this afternoon and Friday afternoon. High pressure will weaken for the weekend into early next week with high temperatures lowering to around average next Monday. Dry conditions with stronger onshore flow will produce elevated fire weather conditions, mainly in the mountain passes and canyons.

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 Friday for Orange County Coastal Areas-Riverside County Mountains-San Bernardino County Mountains-San Diego County Coastal Areas.

Beach Hazards Statement through Thursday evening for Orange County Coastal Areas-San Diego County Coastal Areas.

Extreme Heat Warning until 8 PM PDT Friday for Apple and Lucerne Valleys-Coachella Valley-Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Deserts-San Diego County Mountains-San Diego County Valleys-San Gorgonio Pass near Banning-Santa Ana Mountains and Foothills.

PZ...None.