Scattered light rain possible through the afternoon. An isolated thunderstorm or two cannot be ruled out today. Hot conditions expected for the middle to end of the work week, resulting in areas of moderate to major HeatRisk. Slight chance of mountain showers and thunderstorms Tuesday and Wednesday. Gradual cooling for the weekend.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Radar reflectivity has been quite active this morning, with consistent returns across the area north of San Diego County. It's likely the majority of that precipitation is not actually reaching the ground with only an additional 0.01-0.08 inches of rain recorded since 4 AM. Light rain is possible through the rest of the day, with accumulations expected to be light and scattered in nature. An isolated thunderstorm or two cannot be ruled out, most likely for the coast, valleys, and mountains north of San Diego County and in the High Desert.
High cloud coverage continues to be widespread today, but is expected to thin out tomorrow. Precipitable water values are expected to remain elevated which will keep overnight lows elevated and conditions feeling tropical. The tropical feeling airmass is expected to disrupt marine layer low cloud and fog development and may result in a weaker afternoon sea breeze. This will contribute to high and low temperatures along the coast running 10 to 15 degrees above average. Further inland, daytime highs will be 5 to 10 degrees above average with a more notable increase in low temperatures which are expectd to run 8 to 15 degrees above average. Hottest conditions are expected Tuesday through Thursday for the coast, valleys, and mountains below 5000 ft with hottest conditions expected in the low desert Wednesday through Friday. Widespread moderate to areas of major HeatRisk are expected.
The lingering moisture and increased sunshine for Tuesday and Wednesday will increase chances of afternoon showers and thunderstorms over the mountains. There is expected to be little to no additional forcing outside of the usual diurnal heating so coverage of any thunderstorms should be fairly isolated. By Thursday, a transient ridge of high pressure is expected to move directly over Southern California. This would result in an airmass likely too stable for thunderstorm development, although with lingering moisture in the air a few showers cannot be ruled out over the mountains.
There is a spread in potential outcomes for the upper level pattern over the upcoming weekend. 32 percent of ensemble solutions have a trough over the Pacific Northwest, which would bring noticeable relief from the heat and humidity. 17 percent of solutions keep the ridge overhead which would prolong the heat event. The rest of the solutions are somewhere in between, with a slower passage of the trough but a weakening of the ridge. Current forecast follows the NBM and is more inline with the "in between" solutions with a gradual decrease in both high and low temperatures Friday through Sunday.
071800z, VFR conditions expected across the region through Tuesday morning. SCT-BKN high clouds around 10-20 kft will continue through tonight, slowly thinning out on Tuesday. ISO-SCT -SHRA will continue for areas north of San Diego County for the next few hours with no impacts expected.
No hazardous marine conditions are expected through Friday.
A large south swell from Hurricane Marie will continue to produce large surf of 4 to 7 feet, with sets up to 10 feet this morning, highest on south and southwest facing beaches. This will result in elevated to high surf and strong rip and longshore currents, creating hazardous swimming conditions. Additionally, high tides during the evenings will combine with the high surf to produce minor tidal overflow, coastal flooding, and localized beach erosion. Swell and surf will gradually diminish tonight through Tuesday night. Check the Coastal Hazard Message for details.
Ca, Coastal Flood Advisory until 11 PM PDT Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.
High Surf Advisory until 11 PM PDT Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.
Heat Advisory from 10 AM Tuesday to 8 PM PDT Thursday for Orange County Coastal Areas-Orange County Inland Areas-Riverside County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Coastal Areas- San Diego County Mountains-San Diego County Valleys-Santa Ana Mountains and Foothills.
Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Friday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
