Through Sunday moderate HeatRisk expected for the inland valleys and mountains with major HeatRisk in the deserts. The HeatRisk decreases through next week. There are chances of showers and thunderstorms in the mountains and deserts each afternoon through Tuesday. There are lower chances today with increased thunderstorm chances early next week. Coastal areas will continue to see low clouds each night and morning through the forecast period.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
This morning, The marine layer remains about 1500 ft deep and low clouds are slowly developing and increasing in coverage over the coastal areas. Low cloud formation could be disrupted by mid-level debris clouds moving in from the southeast as mesoscale Convective Systems over AZ and northern MX collapse. However, SoCal is unlikely to see a repeat of the nocturnal convection we saw Thursday night due to a less unstable environment.
Numerical models are in good agreement through the middle of next week with respect to the large-scale pattern. High pressure centered over the Inter-Mountain West will dominate our weather through Monday then a low pressure trough will deepen along the west coast for the middle through the end of next week.
Although temperatures will very slowly trend lower, daytime high temperatures will remain about 5-10 degrees above normal for most areas through Monday while overnight low temps will remain 5-10 degrees above normal only in the mountains and deserts. The monsoonal flow will persist and continue to bring us significant deep-layer moisture. This will maintain some chances for afternoon/evening showers/tstms through Tuesday. The marine layer will remain shallow and the night and morning low clouds will mostly be restricted to the coastal areas.
Conditions begin to change more noticeably for the middle through the end of next week as models consistently show a trough of low pressure deepening along the west coast and displacing the high pressure center as far to the southeast as the FL Panhandle by next Friday. This will bring us cooler and drier conditions with a deeper marine layer. By next Thursday, daytime high temps will be near normal along the coast and 5-10 degrees below normal for inland areas. The below-normal temps will likely continue into next weekend. The trough will bring dry southwest flow aloft, ending the chances for pm showers/tstms by Wed. Low clouds and fog could spread inland to cover most of the area west of the mountains by Thursday night.
081730z. Coast, Patchy low clouds with bases 800-1200 feet MSL will develop gradually but intermittently overnight, with cigs most likely between 11-15Z Sunday. Any cigs should scatter out Sunday by 15-16Z.
Valleys/Mountains/Deserts, Mostly clear across the region through tonight, except for SCT cumulus at 10000 feet MSL over mountains 20- 01Z.
Regionwide, Increasing clouds AOA 10000 feet Sunday morning.
No hazardous marine conditions are expected through Wednesday.
Ca, Heat Advisory until 8 PM PDT Sunday 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 until 8 PM PDT Sunday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
