Fair and seasonal weather will continue for the coming week, with a gradual warming trend. The marine layer will gradually decrease in depth with night and morning low clouds not spreading as far inland nor lasting as long. Subtropical moisture will bring some higher level clouds this holiday weekend, but with seasonal temperatures.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Our deep marine layer covered the entire coastal basin in clouds this morning. In what has become a typical pattern over the last couple weeks, low clouds cleared this morning in San Diego County before Orange County and much of the Inland Empire. Also, typical of this recent marine layer pattern, clouds will move ashore and inland in San Diego County early this evening, while developing much later in Orange County and the Inland Empire. High pressure aloft softly and gradually builds over the next week. However, the low clouds by Friday morning will not have the extent of overall coverage as they did this morning. On Saturday, the fourth of July, copious high level subtropical moisture arrives from the south. With no real triggers to lift this moisture to produce showers or thunderstorms, there is less than a slight chance of any preciptation with this moisture this weekend. Upper levels dry out Sunday night and Monday. The marine layer will get disrupted by the high level moisture this weekend, and the higher pressure aloft will suppress it. These factors will combine to reduce the spatial coverage and duration of coastal clouds. Friday morning will already begin the decreasing low cloud trend, continuing through the weekend. Low clouds should become more uniform again for Monday morning, as the upper level disruption exits. Models and associated ensembles agree on higher pressure aloft next week over the Southwest, but disagree on the timing, location, and strength of this upper ridge. With confidence, we believe there will be a warming trend next week, felt most noticeably in the mountains and deserts, where temperatures will rise to about 4-8 degrees above normal. On Wednesday, our forecast high temps show 110-113 degrees for the low desert, 96-102 for the high desert, and 90-100 for the Inland Empire. This time of year, that means a moderate HeatRisk for the deserts, with isolated major levels in the lower deserts Tuesday and beyond. The marine layer, reestablishing itself after the weekend disruption, will continue to moderate temperatures in coastal areas and valleys, remaining only a few degrees above seasonal.
021800z. Coast/Valleys, Marine layer clouds (based 2000-2500ft MSL) have quickly cleared out across San Diego County this morning, but will take until 1830-19z to clear out across Orange County and western portions of the Inland Empire. Low clouds redeveloping along the coast after 02z Friday, initially across San Diego County, eventually spreading into Orange County around 06-09z, and into portions of the Inland Empire around 12z. Bases will be slightly lower than this morning, around 1200-1800 ft MSL. Good confidence (80% chance) in CIGs reaching KONT by 12z with lower confidence (~40% chance) to reach KSBD between 12-16z. Similar timing and progression for cloud clearing tomorrow morning as what is occurring today.
Mountains/Deserts, Clear skies with unrestricted VIS through Friday morning.
No hazardous marine conditions are expected through Monday.
Ca, None. PZ, None.
