High pressure aloft and weak offshore flow will bring record-setting heat today. A return of onshore flow on Saturday will begin to spread cooler marine air inland but with record-setting heat continuing for many areas on Saturday. Cooling will continue through Monday, but with high temperatures remaining above average. There will be stronger and gusty west winds for Sunday and Monday afternoon and evening in the mountains and deserts with gusts 30 to 40 mph in the wind-prone areas. A little warmer and continued dry for Tuesday through Thursday of next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Today through tomorrow night,
A strong ridge remains over the region, although this is beginning to break down as an area of low pressure upstream over the E Pac waters continues to slowly advance towards the west coast. This will allow for onshore flow to become predominant over the next couple of days and cause the marine layer to become more persistent during the overnight hours, especially along the coastal slopes, where there will likely be some fog as well where these clouds intersect. There may also be some patchy areas of dense fog developing within some of the wind-sheltered valleys during the early morning hours. Highs for today will not be as quite as warm as they were yesterday, although there could still be a few daily records either tied or broken for one more day. For tomorrow, temperatures will continue to gradually come down and be slightly cooler than today, and there will likely be more extensive low cloud coverage during the late evening through the early morning hours. By Sunday afternoon, the surface pressure gradient will tighten as the trough approaches SoCal, and this will produce some strong and gusty winds across the higher terrain, although this should predominantly remain below Wind Advisory criteria.
Thursday through early next week,
For Monday, strong winds will continue across the higher terrain as the trough begins to advance eastward, though the associated area of low pressure is going to remain far enough to the north to where there will likely not be any precipitation, except for possibly some drizzle west of the mountains and along the foothills during the early morning hours. High temperatures on Monday will also be notably cooler with passage of the trough, and returning to much more seasonal values for this time of year. There will be a slight rebound in temperatures Tuesday through Wednesday as some upper level ridging moves in behind the trough, but then another trough passing to the north on Thursday will help to cool things off slightly on Thursday. Conditions should remain dry through next week, as ensembles suggest, then there could be more influence by a deepening trough over the western states that could provide more of a unsettled weather pattern shift beginning the following weekend.
281200z, VFR conditions prevail at most TAF sites through the period. Coastal sites will see low clouds and fog development after 08Z Sunday with cigs 200-700 feet MSL and vis restrictions 3-5SM. Low clouds and fog are expected to begin to clear towards the end of the period.
No hazardous marine conditions are expected through Sunday morning. Northwest winds increase over the outer waters Sunday afternoon creating hazardous conditions for small craft. See Small Craft Advisory for more details. Winds will ease Monday in the late evening.
Ca, None. PZ, Small Craft Advisory from 4 PM Sunday to 9 PM PST Monday for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
