Near seasonal temperatures through the first half of the week with an increase in both high and low temperatures for the middle to end of the week. An isolated shower or two may develop over the highest mountain peaks this afternoon and Monday afternoon, no impacts expected. Drier conditions expected Tuesday and Wednesday, with increased chances for afternoon/evening showers and thunderstorms over the mountains Thursday and Friday. Through the week the marine layer will remain mostly confined to the coast, reaching into portions of the valleys at times.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Highs today will be within a few degrees of Saturday, maintaining conditions that are within 3 degrees of normal for inland areas, and up to 7 degrees above average for the coast. The atmosphere is quite stable this morning based on the 12Z KNKX sounding. An isolated slight chance of showers has been maintained over the San Bernardino mountains this afternoon and Monday afternoon, but no thunderstorm development is expected. The forecast has trended drier for Tuesday and Wednesday so slight chances have been removed from the forecast.
The first half of the week will see minor day to day changes in temperatures with highs remaining near to slightly above normal. For the latter half of the week, the upper level high is forecast to shift south towards Oklahoma/Texas Wednesday/Thursday, then will slowly shift westward into next weekend. The forecast position of the ridge indicates at least a modest warming for the latter half of the week. Thursday is currently forecast to be the warmest day with high temperatures 5 to 10 degrees above average. Widespread moderate HeatRisk is expected west of the mountains with areas of major HeatRisk in the deserts, mainly due to elevated low temperatures. Limited overnight cooling will exacerbate impacts from the heat, especially for vulnerable populations and those without air conditioning. Similar levels of HeatRisk are expected to be maintained through the upcoming weekend.
The position of the upper level ridge looks most favorable to support an increase in precipitation for Thursday and Friday. Current forecast follows the NBM which has increased chances of precipitation Thursday and Friday afternoons (20 to 40 percent chance). Nbm is supported by global ensemble guidance showing modest increases in precipitable water and instability. A limiting factor is the position of the upper level ridge's axis. If the axis ends up directly over us, that would limit our shower/thunderstorm chances.
191800z. Coast/Valleys, Low clouds moved out relatively quickly this morning, with CIGs clearing at KSAN and KCRQ by 13-14z. VFR conditions and mostly clear skies will prevail through the afternoon. Low marine layer clouds are expected to redevelop and push ashore after 00z Monday, with CIGs for KSAN/KCRQ anticipated around 04z and 07z for KSNA. Similar cloud bases and inland extent as this morning, with VIS obscurations where clouds intersect higher terrain. Clouds and CIGs expected to clear out 15-17z Monday.
.Mountains/Deserts, VFR conditions expected through the period with FEW-SCT mid-level clouds generally AOA 15,000ft MSL. FEW-SCT Cu based 10-12 kft MSL may develop over the mountain ridgetops this afternoon, with a small (5-10%) chance for ISO SHRA/TSRA, most likely after 21z through 01z Monday. Elevated west winds expected this afternoon/evening from 00-09z Monday, with gusts 20-35 kts along desert slopes and up to 45 kts through the Banning Pass.
Wednesday afternoon, there is around a 50% chance for northwesterly wind gusts to exceed 20 kts in the outer waters near San Clemente Island. Otherwise, no hazardous marine conditions are expected through Thursday morning.
High amplitude southerly swell (4-5 ft with a period of 11-13 seconds) is building today, and is set to bring elevated to high surf and strong rip and longshore currents through Tuesday. Surf generally 5-7 feet with sets to 8 feet is expected through Tuesday, with the highest surf focused on south and southwest facing beaches. Surf sets up to 8 feet have already been reported across Orange County this morning and the High Surf Advisory has been tweaked to go into effect as of 11AM this morning. This High Surf Advisory remains in effect until 11PM Tuesday evening.
Southerly swell and surf falls through the day on Tuesday, remaining low into Wednesday. Another increased southerly swell from a forecast tropical cyclone well off the coast is expected later this week. This swell is expected to be around 4-5 ft with a period of ~15 seconds which would once again bring high surf of 6-8 feet, especially for south-southwest facing beaches.
Ca, High Surf Advisory until 11 PM PDT Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
