Near-record high pressure for late August will continue hot days and near-record warm nights through Friday night with a slight chance of showers and thunderstorms for the mountains for this afternoon and Friday afternoon. High pressure will weaken for the weekend into early next week with high temperatures cooling to around average on Monday of next week. 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.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
(today through Friday), 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. Through Friday, high temperatures will range from the 80s near the coast to 100 to 110 for the Inland Empire with 112 to 118 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 mostly not tie or exceed existing high temperature records, many records for warmest overnight low temperatures will likely be tied or broken with the greatest number on Thursday and Friday.
Swell from Tropical Storm Iselle and former Tropical Storm Julio will bring elevated surf of 4 to 6 feet to the beaches for today through Thursday evening.
There may be enough residual monsoonal moisture for a few showers or thunderstorms for the mountains for this afternoon with additional drying for Thursday.
(Saturday through Tuesday), A cooling trend is expected for Saturday into the middle of next week as high pressure aloft weakens and a developing weak trough of low pressure near the California coast strengthens onshore lower-level flow. 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.
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.
No hazardous marine conditions are expected through Sunday.
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.
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.
