Increase in both high and low temperatures expected for the middle of the week into early next week. This will bring widespread moderate to areas major HeatRisk away from the coast. Shower and thunderstorm chances are slim to none for the first half of the week. Shower and thunderstorm chances for Thursday and Friday remain in the forecast, but have decreased over the past few forecast cycles. Through the week the marine layer will remain mostly confined to the coast.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
Widespread high cloud coverage is being observed at 12 PM on visible satellite. Light radar returns are being observed in the deserts and mountains, although only an isolated hundredth of rain has been observed in area rain gauges. Any additional rain that falls should just be a few sprinkles and will not have any impacts. Showers chances continue to look unlikely through Wednesday.
The weather pattern this week will be mainly influenced by broad upper level ridging across the southwest United States. Today and Tuesday will see minor day to day changes in temperatures with highs remaining near to slightly above normal as the high drifts east over the Midwest. Starting Wednesday, the upper level high is forecast to shift south and west more over New Mexico and Texas which is when it will begin to have more of an influence on our weather. Highs on Wednesday will be 5 to 10 degrees warmer than Tuesday for inland locations and a few degrees warmer along the coast. Conditions will continue to warm Thursday through the upcoming weekend as the upper level high's position moves more west over Arizona/Nevada.
For the middle of the week through the upcoming weekend, both high and low temperatures will be running 5 to 10 degrees above average. The combination of elevated high and low temperatures will limit the ability to recover from heat overnight and allow for conditions to quickly warm once the Sun rises. Widespread moderate to locally moderate HeatRisk is expected in inland Orange County, San Diego Valleys, Inland Empire, and area mountains. Major HeatRisk is expected in the deserts. Major HeatRisk indicates that the general population may be impacted by the heat if precautions are not taken.
While there remains chances of showers and thunderstorms in the mountains Thursday and Friday afternoons, chances are continuing to decrease over the last few forecast cycles. Guidance is also indicating a decrease in precipitable water values, with the GFS indicating a more notable decrease than the ECMWF ensemble guidance. Less of a moisture influx would allow for a greater warming, while more moisture would put a limit on how warm highs will get it would also increase humidity which would make conditions muggier.
210500z. Coast/Valleys, FEW-BKN mid-high level (12-15 kft) clouds this evening, significantly limiting low cloud formation for most of the evening. Very patchy low clouds (~1000-1500 ft MSL bases) expected to form near the coast after 08z, yielding very intermittent low cloud cigs to the coastal TAF sites, if any. Chance for over 1hr of MVFR/IFR cigs tonight: 50% for KSAN (09-14z), 40% for KCRQ (10-13z) and 20% for KSNA (11-14z). Remaining patchy clouds scatter out 14-16z Tue, then VFR conditions prevail with FEW-SCT mid level clouds through Tuesday evening.
Mountains/Deserts, SCT-BKN clouds 12-15 kft MSL. West winds gusting 15-25 kts along desert slopes and up to 35 kts through the Banning Pass expected through 07z Tue, then once again after 00z Wed.
There is a 75% chance for NW wind gusts to exceed 20 kts in the outer waters near San Clemente Island both Wednesday and Thursday afternoons. Additionally, a mixed swell will cause steep and choppy seas during the day Thursday, especially in the outer waters.
Ca, High Surf Advisory until 11 PM PDT Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.
Heat Advisory from 10 AM Wednesday to 8 PM PDT Monday 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 Watch from Wednesday morning through Monday evening for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
