Below average temperatures with marine layer low clouds and fog reaching into portions of the valleys this weekend. For the first half of the week, 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. The marine layer will become shallower next week, staying confined to coastal locations. Gradual cooling expected for the second half of the week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Thai morning, The marine layer remains about 3,000 ft deep with low-zonal flow over SoCal and weak troughing just to our north. Low clouds are increasing in coverage over the coastal areas and valleys of San Diego County. The cloud coverage seems to be expanding in a similar pattern to yesterday (Friday) morning. The saturated layer is relatively thin and the inversion weak so clearing will likely be as early this morning as yesterday morning.
A warming trend will continue into Thursday as high pressure builds over the western states. Wed and Thu will likely be the warmest days with the center of the upper high over northern Mexico. Daytime high temperatures on those days will likely be 5 to 10 degrees above average for inland locations with localized areas of moderate HeatRisk away from the coast, and areas of major HeatRisk in the low desert. Most model solutions continue to show an influx of mid-level moisture from the south around the middle of the week. If this brings significant cloud cover, it could suppress temperatures during the daytime and inhibit radiation cooling at night - at least on Wed and Thu. The possibility of showers and/or tstms can't be ruled out for Wed afternoon but at this time, the probability is 15 percent or less. The marine layer will be shallower and overnight low clouds may be patchy and disrupted by the moisture aloft.
Beyond the middle of the week, Model solutions are coming into better agreement with respect to a low pressure system moving inland to our north, with a closed upper low over WA state by next Saturday morning. A majority of ensemble members now show the ridge of high pressure beginning to weaken and shift east by Thursday as a low pressure trough approaches the west coast. This will result in a cooling trend beginning on Friday with next Sunday being the coolest day overall. High temperatures will be within a degree or 2 of normal in the coastal areas and low deserts while in the valleys, mtns and high desert daytime high temps will be anywhere from 3 to 11 degrees below normal. The marine layer will again deepen with low clouds spreading inland to the coastal mtn slopes during the nights and mornings.
210530z, Coast/Valleys, Low clouds are meandering in along the San Diego coast and into the adjacent valley. Low clouds with cigs 1500- 2000ft MSL will increase in coverage over the next few hours, spreading north into OC after 09-10Z. The Inland Empire will get some low clouds but not expecting them to fill in all the way to the foothills. Low clouds will scatter out of inland locations after 16- 17Z. Low clouds with slightly lower bases will reform after 03Z Monday.
Mountains/Deserts, VFR conditions expected through the TAF period. Westerly wind gusts of 25-40 kts will continue this evening along desert slopes and locally into deserts. Local VIS reductions 4-6 SM in BLDU during periods of strong gusts and moderate up/downdrafts in lee of mtns. Winds will slowly diminish through 12z Sun. Westerly winds of similar strength will return for the same areas after 18Z.
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 through this evening for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
