Warmer through Saturday with moderate HeatRisk for the coast and western valleys Friday and Saturday. Night and morning low clouds and fog will stay confined to the coastal areas for the next few nights. There is a slight chance of showers and thunderstorms over the mountains this afternoon. Tropical mid and high level moisture will bring more clouds and cooler temperatures late weekend early next week. Warming trend after Monday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION, MARINE, AND BEACHES DISCUSSIONS,
Ample cloud cover this morning from a very robust and shallower marine layer, with satellite still showing some inland coverage as of 11am. Areas of patchy fog were reported, mostly in part thanks to increasing heights as a weak ridge attempts to take hold of SoCal and a shortwave trough moves eastward today. The morning sounding already shows drier air in the mid and upper levels with the departure of the trough, also evident on mid-level water vapor satellite with additional subsidence 150 miles southwest of San Diego. This lack of moisture will be a main limiting factor for storms in the mountains this afternoon, although a few thunderstorms remain possible for primarily the San Diego and Riverside County Mountains. Anything that develops will be diurnally driven and unlikely to produce flash flooding, with storms ending by sunset.
Southern California will be in a push-and-pull for the remainder of the week between a deepening low over the PacNW, high pressure over Texas, and two tropical cyclones in the eastern Pacific. The aforementioned weak ridge will hold through at least Friday and keep temperatures well above normal with highs in the 90s for inland and High Desert, 80s for the coast and mountains, and 100-103 for the low deserts. Things start to change this weekend as the ridge is compressed and the high over Texas shifts southward, allowing for tropical moisture to shift up Baja and into Southern California and western Arizona. This could mean some very warm morning temperatures both Saturday and Sunday as the moisture reduces radiational cooling, and temperatures in the afternoon remain elevated as heights will be slow to fall. This is likely to bring about some Moderate HeatRisk for the coastal areas on Saturday with temperatures around 10-12 degrees above normal and warm overnight lows above 71 degrees. A lot of this will depend heavily on cloud cover associated with the tropical cyclones well to our south, which could impact peak heating on Saturday, limiting our warming.
By late weekend, a trough off the aforementioned larger low in the PacNW will swing down and become a closed low by Monday. This could help initiate some convection while mixing with the influx of moisture. For now, much of any precipitation looks to stay east of the region, as drier air on the backside of the trough looks to push in as tropical moisture is shunted east of the mountains. Should SoCal get dry slotted (80-90% confidence), Sunday and Monday would at least feature cooler weather thanks to the deepening low as it meanders into Arizona and Utah. Meanwhile, other states in the Desert SW may experience multiple rounds of precipitation and some heavy rainfall. At this point, the tracks of Polo and Odalys and where the larger upper level pattern will be are not conducive to precipitation for SoCal.
With building high pressure to the west and drier air filter in, the region will return to a warming trend after Monday along with quieter weather.
A few impacts that may be observed early next week due to the tropical cyclones: -higher humidity for the deserts, especially the low deserts, late weekend into early next week. -coastal flooding and coastal erosion, especially for south-facing beaches, Sunday through Tuesday. Additional details on this can be found in the Beaches discussion below.
241800z, Coast/Valleys, Low clouds from last night's marine layer intrusion have lifted (with bases now around 1500-1700ft MSL) and been scattering out this morning. While CIG scattering is expected at the coastal TAF sites (KSAN, KCRQ, KSNA) by 19z Thurs, SCT-BKN clouds may linger along the beaches/immediate coasts through the afternoon. Low clouds begin to fill back in as early as 02z Friday, but could be somewhat limited in pushing ashore until around 06-07z. Afterwards, clouds will fill back in with similar areal coverage and bases compared to this morning. Clouds clear back to the coast by 17- 19z Friday.
Otherwise, Mostly clear today and tonight. Except for SCT cumulus based near 10 kft over mountains and isolated SHRA/TSRA 20-01z. Any storm that develops will be capable of producing gusty, erratic winds, lightning, and vis reductions in SHRA/BLDU.
No hazardous marine conditions are expected through Tuesday.
Southwesterly swell (3-4 ft at 12 seconds from ~210 degrees) from Hurricane Odalys begins to increase on Friday, bringing surf up to 3- 5 feet with sets up to 6 feet to most beaches. This swell from Odalys is expected to persist into this weekend. Given tides are already observed over 6 feet and are expected to gradually increase into this weekend, a Beach Hazard Statement has been issued for Friday morning through Sunday evening. Minor tidal overflow and minor coastal erosion are the primary impacts during this period.
The swell associated with Hurricane Polo (4-5 ft at 14 seconds from ~160 degrees) increases on Monday. However, given this direction, most of San Diego County beaches will be largely sheltered from this swell, but Orange County beaches still look to be impacted by this swell. Meanwhile, a northwesterly swell (3-4 ft at 8 seconds from ~290 degrees) from an incoming storm system will also be building Sunday into Monday. Between these two swells, surf of 4-6 feet look to remain possible along all beaches into Tuesday. Tides see their bi-monthly astronomical peak Monday-Wednesday morning, with peak tides near 7.0 ft Between the combination of higher tides and the expected surf, there is a risk for minor-moderate coastal flooding during the late morning/early afternoon high tides. Stay tuned as details continue to become more clear in the coming days.
Please note - listed tide predictions have been adjusted to reflect actual measured tide observations.
Ca, Beach Hazards Statement from late tonight through Sunday afternoon for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
