Warming trend for the first half of the week brings widespread moderate to areas of major HeatRisk possible for the deserts and widespread minor to locally moderate HeatRisk for inland Orange County, valleys, and mountains for Wednesday. The marine layer will become shallower through midweek, staying confined to coastal locations. A few stray showers/storms are possible over the mountains on Wednesday. Gradual cooling expected for the second half of the week with the marine layer becoming deeper.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Current satellite and 500mb analysis reveals largely zonal flow aloft and a weak upper ridge across northern Mexico, with marine layer clouds clearing out to the coasts for the day. Temperatures early this afternoon are running near to slightly warmer than yesterday, but is still coming in 5-10 degrees below normal for most across the region. However, today looks to be the coolest day of the next several as model guidance remains consistent in the upper level ridge strengthening and sliding northward over the next few days, becoming centered near El Paso by Tuesday afternoon. The placement of this ridge also establishes southeasterly flow aloft, allowing for an influx of mid level moisture into the area. The ridge and the moisture will likely serve to limit the vertical depth and inland extent of the marine layer through midweek. The main consequence will be the notable warming trend, that takes afternoon temperatures 5-10 degrees above normal by Wednesday. More importantly, the moisture will inhibit overnight cooling, leading to mild nights, with low temperatures running 5-10 degrees above normal as well and limiting overnight relief from he warm daytime temperatures. This brings areas of moderate HeatRisk into the inland valleys on Wednesday, with locally major HeatRisk for the deserts. Additionally, the increased mid level moisture could support the development of a few showers/storms over the mountains Tuesday or moreso Wednesday afternoon. A weak shortwave rounding the western periphery of the ridge Tuesday into Wednesday may provide enough synoptic support for updrafts to overcome inhibiting cloud cover and dry air above the moist layer, but these are 2 main factors that will likely keep any impacts from these precipitation chances little to none.
Ensembles continue to push a longwave trough into the Pacific Northwest for Thursday into Friday, which should help weaken the ridge and nudge it south/east as well as kick out the mid level moisture. This results in a cooling trend into the weekend with the marine layer deepening again. Temperatures return to near average for Thurs/Fri with the potential for afternoon highs 10 degrees or more below normal for the weekend.
211800z, Coast/Valleys, Lingering low level clouds along the coast will clear offshore by 19Z. Low clouds reform and move into SD coastal regions after 03Z at 1700-2200 ft MSL, then into inland SD/Orange County after 06Z. There is a 30-40% chance for clouds to reach into the southern and northwest portions of the Inland Empire, including vcnty KONT, 11-16Z Monday. Cigs likely to lower slightly overnight to 1500-2000 ft MSL, then scatter out 16-18Z Mon.
Mountains/Deserts, VFR conditions with periods of upper level clouds AOA 20k ft expected through the TAF period. Westerly wind gusts of 25-40 kts along desert slopes and locally into deserts expected through about 06Z this evening. Local VIS reductions 4-6 SM in BLDU during periods of strong gusts and moderate up/downdrafts in lee of mtns.
No hazardous marine conditions are expected through Thursday.
Elevated surf and strong rip currents are set to continue through this weekend with a persistent long period southwesterly swell. Surf of 3-5 feet with local sets to 6 feet are expected at southwest- facing beaches. Expect locally hazardous swimming conditions with high rip current and longshore current risk. See the Beach Hazards Statement for more details.
Ca, Beach Hazards Statement until 11 PM PDT this evening for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
