For Wednesday and Thursday, onshore flow will strengthen spreading greater cooling inland. A low pressure system from the northwest will bring additional cooling for Thursday night and Friday along with showers and a slight chance of thunderstorms. There could be another round of more widespread showers on Saturday. Chances for showers are less on Sunday with additional precipitation possible for early next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
.Morning Update,
Low clouds and fog will continue to clear near the beaches this morning as high clouds stream overhead through the afternoon hours across the entire region. Today will be the the last very warm day for valleys west of the mountains with a low to moderate chance in seeing highs reach 90 degrees by this afternoon. The chance for 90 degrees is high today for the lower deserts, with only a moderate chance by Wednesday. As far as precipitation goes, timing continues to lean slightly later as hi-res model guidance points to rain showers beginning sometime early Friday morning across the north, a bit later into San Diego County. While the heaviest precip will occur on Friday, wrap-around moisture from the northern part of the low pressure system will move across the area from the east to west on Saturday. Chances of precip increase again by early next week as the pattern remains semi-active.
.Previous Discussion (448 AM Tuesday),
(today through Thursday), A strong shallow marine inversion remains in place early this morning. High temperatures will cool for the coast and valleys today with greater cooling spreading inland for Wednesday through Friday. In addition to the coastal low clouds, there will be increasing high clouds for later today into Thursday.
With the cooling, high temperatures on Thursday will range from the mid to upper 60s near the coast to the lower to mid 70s for the valleys with the lower to mid 80s for the lower deserts. There will be stronger onshore flow for Wednesday night and Thursday with southwest winds for the mountains and deserts gusting to 35 to 45 mph, locally to 50 to 60 mph.
(Thursday night through Sunday), A low pressure system from the northwest will bring showers for late Thursday through Friday with another round of more significant showers possible on Saturday. There is also a slight chance of thunderstorms.
The deterministic NBM has trended significantly wetter over the past 24 hours for Thursday through Saturday with forecast rainfall for Orange and southwestern San Bernardino Counties now ranging from around 1.75 inch near the coast to 2 to 3 inches in the mountains with local amounts exceeding 4 inches on the coastal slopes of the San Bernardino County mountains. For San Diego County, amounts range from 1.25 to 1.5 inch near the coast to 1.5 to 2.5 inches in the mountains. For the deserts, amounts range from one-half to one inch for the high desert and one-quarter to one-half inch for the lower deserts. Chances for two inches or more of rainfall for the mountains has increased to 55 to 65 percent.
Snow levels will rise to around 10000 feet for Thursday morning, fall to around 7000 feet on Friday, then rise to around 8000 feet on Saturday. On Friday, the NBM 25th percentile snow level is 5500 to 6000 feet with the 75th percentile snow level 8000 to 9000 feet.
Chances for showers are less on Sunday, then increase again for Monday through Wednesday of next week.
111715z, Coasts/Western Valleys, Low clouds have largely cleared out though CIGs (bases 300-500ft MSL) will linger across northwestern Orange County for the next hour or two before clearing. Low clouds will push back ashore after 02z Wednesday with bases initially near 600-1000ft MSL. Bases will gradually lift overnight to 1000-1200ft by 09-12z with clouds spreading further inland. Scattering back to the coasts around 17-18z Wednesday.
Otherwise, VFR conditions will continue today and tonight under increasing clouds AOA 20 kft.
A storm will bring strong winds and steep seas late Thursday through Friday as a front passes through the coastal waters. There is also a slight chance of thunderstorms Thursday night through Friday.
Ca, None. PZ, None.
