Gradual warming through Sunday with periods of weak to moderate Santa Anas winds. Temperatures will be as high as 5-15 degrees above normal by Saturday when offshore winds peak. Gradual cooling Monday through Wednesday as offshore winds weaken and eventually turn back onshore.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION, MARINE, AND BEACHES DISCUSSIONS,
Patchy stratus has developed across San Diego County this morning and a band of scattered high clouds is beginning to move in from the northwest. At the surface, pressure gradients are trending offshore - currently around -5.3 mb SAN-TPH and -1.6 mb SAN-DAG. Winds are gusting 20-30 mph in the Cajon Pass but remain weak elsewhere. Weak offshore flow will persist through the late morning followed by a weak sea breeze this afternoon. Otherwise warmer today with highs near normal and scattered high clouds through the day.
An upper level short-wave trough moving inland across the Pac NW this morning will dig southeast into the Great Basin later today before a closed low develops in the base of the trough over Arizona on Friday. This will drive stronger offshore pressure gradients and provide a bit of upper level support as northeasterly mid-level flow develops over the region on the back side of the low. The EC ensemble remains stronger with forecast gradients than the GEFS, however the GEFS mean is much closer to observed gradients this morning. Expect Santa Ana winds to increase on Friday but generally be confined to the wind-prone passes, canyons, and coastal slopes/foothills. Gradients continue to strengthen on Saturday, especially to the east, though we lose some of the upper level support as the upper low shifts south and east. Winds both days are forecast to gust to around 25-40 mph, first focused in the Cajon Pass/Santa Ana Mountains on Friday as winds are northeasterly, then the San Gorgonio Pass/San Diego County Mountains on Saturday as winds turn more easterly. Gradients and winds weaken for Sunday and Monday, eventually turning back onshore towards the middle of next week.
With offshore winds and high pressure building in from the west, expect much warmer weather into Sunday, especially west of the mountains. By Friday, highs will be as much as 5-10 degrees above normal for the western valleys and coastal areas (highs in the low to mid 80s), but remain near to slightly below normal for the mountains and deserts due to cold air advection from the north. For this weekend, highs will be closer to 7-15 degrees above normal for the coastal areas and valleys, and near to around 3 degrees above normal elsewhere. Highs could push the 90 degree mark on Sunday.
The upper level ridge weakens and a cut-off low passes by to the south Monday and Tuesday allowing for slow cooling. An upper level low moves towards the West Coast on Wednesday, though depending on its position we could see more cooling (further east position), or still be under a ridge with little cooling (further west position). The progression of this trough will have a larger influence on the weather late in the week, not only in terms of how much cooling, but precipitation chances as well. For now there is a slight (15-20%) chance beginning on Thursday, though significant spread exists in the ensembles regarding the timing and amounts for late in the week. It looks like that will also begin a fairly active weather pattern, and the CPC 8-14 day outlook is showing a 60-70% chance of above normal rainfall along the entire CA coast.
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.
