Weak to locally moderate Santa Ana winds continuing today, waning this evening with onshore flow returning Tuesday afternoon. Chances increase for another round of weak to moderate Santa Ana winds late Wednesday into Friday, peaking late Wednesday into Thursday. Gradual warming Thursday into next weekend with highs near seasonal normals.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
No significant changes to the forecast this evening under a relaxing offshore wind regime. Will continue to monitor for radiational fog formation across the area ahead of a return to onshore flow.
Previous discussion from December 1st at 13:42 PST
, On the heels of the inside sliding upper trough now ejecting into the Great Plains, a 1032 mb surface high pressure has pushed through the Great Basin, establishing our offshore pressure gradient with weak to moderate Santa Ana winds already in place. The strongest winds remain primarily through mountain and just below passes where wind gusts of 30-50 mph have been observed with 20-30 mph gusts stretching into inland valleys. The offshore pressure gradient quickly relaxes later today with offshore gusts ceasing by midnight. Onshore flow resumes by Tuesday afternoon. Temperatures today should reach the mid 70s for most locations beyond 10 miles inland due to the offshore winds. The marine layer has also been completely pushed out today, but could low marine clouds/fog sneak into portions of southern coastal San Diego County Tuesday morning. With onshore flow resuming tomorrow and ahead of the next trough coming Tuesday night, the marine layer deepens, likely stretching well into inland valleys come Wednesday morning. High temperatures cool a few degrees for Tuesday afternoon as well.
The trend away from light precipitation in favor of a dry offshore wind event is now complete, with less than a 5% chance of precipitation. If anything, the deeper marine layer will be what ends up providing any moisture to the coasts/valleys Wednesday morning. With fairly high confidence in another inside slider Tuesday into Wednesday, offshore Santa Ana winds are expected to pick up again Wednesday, likely persisting through Friday. The track of this trough follows a very similar track to the one earlier in the week and wind strength will be similar to today's event as a result. Winds peak late Wednesday into Thursday with gusts of 30-50 mph in mountain passes and 20-30 mph within downstream corridors of inland valleys. Weak offshore flow continues into Friday morning with the return of onshore flow by Friday afternoon. Temperatures continue to gradually warm Wednesday through the weekend with the persistent offshore flow giving way to weak upper ridging building this weekend.
020400z. Coasts/Valleys, Offshore northeast winds locally gusting to 20-30 kts in coastal foothills and inland valleys will continue to calm overnight. Currently clear skies, with a 20-30% chance for low clouds to develop and intermittently impact coastal sites (KSAN/KSNA) early Tues morning, generally 07-15Z. If low clouds do develop locally, vis and cigs will likely be very low, with a chance for dense fog vis 0-2 SM and bases 100-300 ft MSL. Widespread if patchy low clouds will return after 02Z Wed. Bases could start out fairly low 800-1500 ft MSL but will rise overnight to 1800-2500 ft MSL.
.Mountains/Deserts, VFR conditions through the period. Locally gusty northeast surface winds 20-35 kts on the coastal slopes of the mountains through about 06Z, diminishing afterwards. Mod up/down drafts possible in the vicinity of the mountain peaks.
No hazardous marine conditions are expected today through Friday.
Astronomical high tides are forecast to occur each morning Wednesday through Friday, threatening minor tidal overflow and beach erosion. Chances of these impacts are higher Wednesday and Thursday mornings as elevated surf of 4-6 feet combines with the high tides, especially for San Diego County.
Ca, Beach Hazards Statement from Tuesday evening through Friday morning for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
