High pressure aloft will strengthen into the weekend with high temperatures for inland areas around 10 degrees above average through Saturday. Nights will be quite warm with low temperatures for the deserts as much as 10 to 15 degrees above average. Gradual drying and slight cooling for the early and middle of next week with high temperatures for the middle of next week still around 5 degrees above average for inland areas. There is some model guidance that has a brief surge of moisture into the area on Sunday which would result in more clouds, high temperatures not as high for some inland areas, and a slight chance of afternoon thunderstorms for the mountains.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
High pressure aloft will continue to build over the area through the weekend, continuing the hot daytime temperatures and elevated overnight lows. Highs today will be 5 to 10 degrees above the seasonal average, locally up to 15 degrees warmer in the valleys and in the coastal mountain slopes. Daily highs will vary little through Saturday with a slight cooling of inland high temperatures Sunday and Monday.
Elevated overnight lows will offer little to no reprieve from the daytime heat. Coastal areas and inland valleys will see overnight lows predominately in the 70s, low deserts in the upper 80s to low 90s, and the high deserts in the mid 70s to low 80s.
These high afternoon temperatures and elevated lows will bring widespread moderate HeatRisk to most of the area with major HeatRisk in the Inland Empire, San Diego mountains and the low and high deserts through Monday. Major to extreme HeatRisk indicates that anyone may be negatively impacted by the heat if the proper precautions are not taken. Make sure to stay hydrated, stay cool, avoid heavy activity and direct sunlight and check on the elderly, children and pets.
Coastal low clouds will continue to form in the late evenings into the early morning hours, pushing inland as far as 20 miles in some areas through the weekend at times. A slight increase in monsoonal moisture will create mid-level clouds over the mountains today and Friday with a 10-12% chance for light rain in the mountains for San Bernardino and Riverside Counties.
A little uncertainty exists in regards to temperature and moisture over the area Sunday. Models differ slightly over the placement of the upper level high pressure. This will affect how much the afternoon highs will cool Sunday and the chances for rain and storms over the area (currently forecasting 5-15%).
Otherwise, afternoon highs and overnight lows are expected to cool slightly by Monday with conditions drying into mid week. Temperatures will warm again by mid to late next week as high pressure aloft once again builds over the area.
231730z. Coast/Valleys, Better clearing today, with only very localized cigs along the immediate coast into the afternoon. Cigs developing after 07z Fri across San Diego County, with less than 20 percent chance of cigs at KSNA. Cigs will be 1000-1500 ft MSL. Low clouds expected to clear coastal areas 15-17z Fri.
Mountains/Deserts, CU over the mtns bases AOA 8000 ft MSL 20Z through sunset. Otherwise, VFR conditions prevail through the TAF period.
Northwesterly winds with gusts 20-25 kts in the outer waters near San Clemente Island to continue this afternoon and evening. Additionally, a mixed swell will cause steep and choppy seas 6 to 7 feet in the outer waters today. Winds and seas will decrease tonight.
A 3 to 4 feet south swell from 190 degrees with 13 second period will bring surf of 5 to 7 feet to area beaches through Sunday. Highest surf will be on south-southwest facing beaches.
Early next week, a longer period (16-18 second) south swell at 2-3 feet from 190-200 degrees is expected arrive. This will prolong elevated surf into next week and increase rip current risk.
In addition to elevated surf, tides are expected be increase Friday to near 5.5, increasing to 6.0 to to 6.5 feet MLLW by Sunday. The combination of surf and tides will result in minor coastal flooding during high tides.
Ca, Beach Hazards Statement through Sunday evening for Orange County Coastal Areas-San Diego County Coastal Areas.
Heat Advisory until 8 PM PDT Monday for Orange County Coastal Areas-Orange County Inland Areas-Riverside County Mountains- San Bernardino County Mountains-San Diego County Coastal Areas-San Diego County Valleys-Santa Ana Mountains and Foothills.
Extreme Heat Warning until 8 PM PDT Monday for Apple and Lucerne Valleys-Coachella Valley-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Deserts- San Diego County Mountains-San Gorgonio Pass near Banning.
PZ, Small Craft Advisory until 9 PM PDT this evening for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
