A slight chance of afternoon showers and thunderstorms will continue for the mountains through Wednesday as monsoonal moisture slowly decreases. High and low temperatures will continue to rise through Thursday, to as much as 10 to 15 degrees above average, with not much change for Friday. The highest HeatRisk is expected for Thursday and Friday with widespread Extreme HeatRisk for the inland valleys and inland Orange County. This will be followed by a cooling trend for the weekend into early next week with stronger onshore flow and drier southwest flow aloft, with high temperatures falling to around average for next Monday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
This afternoon, Skies are clear except over the mountains where cumulus clouds have developed. There is a chance that some showers or tstms could develop over the mtns later this afternoon and may drift into the deserts. Temperatures are generally higher than at this time yesterday, especially in the lower deserts where temperatures are as much as 12 degrees higher.
Extensive ridge of high pressure will continue the warming trend through Thursday, with warmer days and warmer nights. High temperatures on Thursday will range from the 80s near the coast to 106 to 112 for the Inland Empire with 110 to 116 for the lower deserts. Low temperatures on Thursday will be mostly in the 70s for the coast and valleys and in the mid 80s to mid 90s for the lower deserts.
The highest HeatRisk for the coast and valleys is expected on Thursday and Friday with widespread Extreme HeatRisk for the inland valleys and inland Orange County with Major HeatRisk for most other areas with Moderate HeatRisk limited to the beaches.
Mid level monsoonal moisture will remain in place today with a slight decrease on Wednesday and a greater decrease on Thursday. A slight chance of afternoon showers and thunderstorms, mostly for the mountains, will continue through Wednesday.
For Saturday through Tuesday, high pressure will begin to weaken across the area as a low pressure system develops near the California coast, strengthening onshore flow at the surface. High temperatures will fall to around 5 degrees above average on Sunday and a few degrees below average for the mountains and inland valleys on Monday. Monday high temperatures will range from the mid 70s to lower 80s near the coast to the 90s for the Inland Empire with 104 to 108 for the lower deserts.
251800z, Coast, VFR through early Wednesday morning. Patchy low clouds based 600-900 ft MSL redevelop over coastal areas starting 08- 10z Wed. Best chance for cigs will be in San Diego County from 12- 15z. Minor vis reductions of 2-6SM down to sea level and patchy dense FG along elevated coastal terrain where cigs develop. Any low clouds scatter out by 16z.
Mountains/Deserts, Cumulus based around 9000 feet MSL with ISO TSRA and CB tops to 40000 feet over mountains 20-01Z. Any TS that develops could produce gusty, erratic winds. VFR conditions prevail otherwise.
Regionwide, FEW-SCT clouds AOA 15000 feet MSL through the period.
No hazardous marine conditions are expected through Saturday.
A 4-5 foot southerly swell (from 170 degrees) at 12-14 seconds will move into the area Wednesday morning, leading to elevated surf for the south facing beaches of northern San Diego County and Orange County through Thursday. Surf of 3 to 6 feet, with sets up to 7 feet are expected.
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.
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.
