Above-normal temperatures and dry conditions Friday through early next week as offshore flow develops, strongest Friday and Saturday. A slow cooling trend starts beginning Monday, with more substantial cooling and increasing precipitation chances late next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
There haven't been many significant changes to the forecast in the past 24 hours. Mid-level water vapor places a high over the Rockies with a shortwave trough over Nevada, and weak riding building in behind the trough over California. Offshore flow was observed this morning through typical windy passes, but remains light elsewhere at or below 15 mph. Still, the drier air has already begun to push to the coastline, evident by the scattering out of low clouds early this morning pre-sunrise. Various weather stations in the Inland Empire show humidity at 10AM around 26-32%, much less than the 55-70% observed at the same time yesterday. Down into San Diego County and even inland Orange County, RH is around 45% whereas yesterday at the same time, values were closer to 65-70%.
Temperatures warm a bit today under the weak upper level ridging and clear skies, around 5 degrees above Wednesday's highs. Offshore flow will continue to increase into Saturday as robust high pressure develops and a low deepens over Arizona. With substantial influence from the high and warm downsloping winds, temperatures will reach the low to mid 80s for nearly every location west of the mountains, around 10 degrees above normal. The Santa Ana winds will be strongest from Friday afternoon through Saturday afternoon, ushering in low humidity around 15-25% for all locations west of the mountains. Despite the drier weather, only weak to locally moderate Santa Ana winds are expected (CW3E) with the upper level pattern not as conducive for a stronger event. Winds may gust as high as 25-30 mph for foothills and Inland Empire, with up to 40-45 mph for wind-prone passes. With recent rainfall and currently sitting at above-normal precipitation for the water year for SoCal, there aren't major fire weather concerns with this event. Still, make sure to do your part and avoid activities that could cause a spark this weekend.
Sunday looks to be the hottest day as the high elongates into SoCal and offshore winds prevail, though weakening significantly Sunday afternoon. Widespread minor to locally moderate HeatRisk will exist for all areas west of the mountains on Sunday as highs hit upper 80s, around 10-20 degrees above normal. While the afternoons will be hot, moderate overnight lows will help offset the heat, limiting HeatRisk.
By Monday, an approaching shortwave trough will help squish the high a bit and a cooling trend will begin. Zonal flow settles over the area and highs drop 2-3 degrees day over day through Tuesday. Latest model guidance shows the high attempting to take hold again mid week, spreading into the Four Corners region which could help keep temperatures above-normal through Wednesday. Regardless, the next system in the form of a massive trough is expected to swing into the region Thursday/Friday. Surprisingly, global model guidance is decently aligned on this next system and the potential for a split off low to form Friday, surging down into Baja. Should this occur, some substantial precipitation would be possible for SoCal, but confidence at this point remains low. For now, the GFS remains the wetter model while the ECMWF attempts to provide precipitation with more tempered expectations.
051800, VFR conditions under FEW-SCT clouds around 20 kft today and tonight. Weak offshore winds expected below mountain passes in the Inland Empire and Coachella Valley today and tonight look to strengthen by 18z Friday. Surface gusts after 18z Fri could be up to 20-30 kts in these corridors, and up to 30-40+ kts within mountain passes and along mountain foothills.
No hazardous marine conditions are expected through Monday.
Increasing high tides will exceed 7 feet by Friday, peaking Sunday and Monday at 7.4-7.6 feet. A NW swell today driving surf near 3-5 feet briefly fades tonight into Friday. However, a fresh northwest swell arriving Friday afternoon/evening will be 2-3 feet from 290 degrees with a period of 14-15 seconds. This will keep surf elevated to 3-6 feet along west-facing beaches through Tuesday, with 3 foot waves more likely along south-facing beaches. This NW swell may even see an increase to 3-4 feet on Monday, which could bring breaking waves up to 7 feet.
The combination of high tides and elevated surf will likely generate minor coastal flooding, with chances for moderate coastal flooding along more west-facing beaches where surf will be higher. A Coastal Flood Advisory remains in effect from 4 AM Friday through noon Tuesday and contains more details.
Reminder, tides mentioned have been corrected to reflect the current trends in actual tide observations.
Ca, Coastal Flood Advisory from 4 AM Friday to noon PST Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
