There could be a few sprinkles or light showers over the higher mountains this afternoon. Dry and warm conditions expected over the weekend with weak Santa Ana winds. Pattern change expected next week, bringing cooler conditions, periods of gusty southwest to west winds, and chances of widespread precipitation.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Temperatures at 12 PM were running 5 to 12 degrees cooler than noon yesterday for most locations west of the mountains, with little change from yesterday for the deserts and mountains. A 10 percent chance of a shower or two developing over the mountains (mainly in San Bernardino County) remains, but little to no accumulation is expected. A closed upper level low off the California coast will continue to move south into Saturday morning before moving east into Baja California early Sunday. The southerly track of the low will allow an upper level ridge to build over Southern California and for weak offshore flow to develop. The combination of these will bring an uptick in high temperatures for the weekend. Highs will peak on Sunday at 10 to 18 degrees above average.
A change in the overall upper level pattern is expected for next week. The effects will be felt as early as Monday, with temperatures expected to be 3 to 5 degrees cooler than Sunday. Further cooling is expected through next week as broad troughing prevails over the Western United States. In addition to cooler conditions, marine layer low clouds and fog will likely reach into the valleys, with the potential to reach the mountain slopes at times.
This pattern is also expected to bring periods of widespread precipitation. Current forecast has precipitation chances starting as early as Tuesday, but there remains uncertainty in the timing of the trough passage and the trough's track. About 35 percent of ensemble solutions show the trough axis reaching the central California coast on Tuesday, which would bring precipitation. By Wednesday, the solutions increase to about 60 percent, with similar percentages for Thursday and Friday. Most of the individual ensemble members are indicating light rainfall amounts, with only a few members showing moderate amounts. Mountain snow is possible for the the middle to end of next week. There remains uncertainty in snow level due to uncertainty in the forward progression of the low and it's ultimate track. Nbm 25th and 75th percentile has snow levels between 5500 and 7000 feet respectively. Increased westerly winds over the mountains and into the deserts are also possible depending on the track of the low. Latest ensemble guidance has the peak of the winds Tuesday afternoon, with more spread in wind speeds into Wednesday and Thursday.
061745z. Coast/Valleys, Low clouds have cleared out of the inland areas, with VFR prevailing and generally light southerly winds. Patchy low clouds redevelop again tonight and will move inland up to 20 miles with bases 1500-2000ft MSL beginning around 06z Sat, rising to 2200-3000+ft MSL after 09z. VIS generally should be above 6SM, although areas of the Inland Empire and where clouds intersect terrain may see VIS below 5SM after 08z. Clouds retreat back towards the coast around 16z Sat.
High clouds AOA 15,000ft MSL continuing over the area with high clouds AOA 25,000ft MSL expected after 20Z.
A building northwesterly swell (280 degrees) at 15-16 seconds will bring seas of 6-9 feet in the outer waters near/around San Clemente Island today and Saturday. This may also lead to localized steep, rough conditions near the bay entrances, including the entrance to the San Diego Bay/Zuniga Shoal area and Oceanside Harbor. Otherwise, no hazardous marine conditions are expected through Wednesday.
Increasing long-period (15-16 second) swell from the west-northwest (280 degrees) will bring elevated to high surf of 5-8 feet with locally higher sets to 10 feet this afternoon through early Sunday morning. Impacts will be greatest at west facing beaches, especially across southern San Diego County, and there will be a high risk for rip currents. This may also lead to minor tidal overflow for low- lying beach areas during high tide late tonight into early Saturday. Further information can be found in the High Surf Advisory.
Ca, High Surf Advisory until 6 AM PST Sunday for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
