Onshore flow will strengthen through Wednesday with stronger southwest to west winds in the mountains and deserts gusting 35 to 45 mph into Tuesday evening then gusting 45 to 55 mph for late Tuesday night into Wednesday. Onshore flow will also spread cooling farther inland through Wednesday, with high temperatures on Wednesday and Thursday within a few degrees of average. There is a chance of light showers late Tuesday into Wednesday morning. Friday through next weekend will be warmer and drier with high temperatures warming to 10 to 15 degrees above average for inland areas next Sunday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
This afternoon, Patches of marine layer low clouds persist in the coastal areas and southwest winds are pushing the low clouds inland over portions of southern San Diego County. Widespread high clouds cover SoCal ahead of a low pressure system that is still over 1000 miles to our northwest. Temperatures are as much as 11-17 degrees lower than at this time yesterday in the inland valleys. Elsewhere, temperatures are also lower than at this time yesterday but less so. Lower ocean water temperatures and stronger onshore flow have been efficient in spreading the cooler marine air farther inland.
A low pressure system currently about 1000 miles off the coast of NorCal will move inland over SoCal late Tue into Wed. Strengthening onshore flow will bring gusty southwest to west winds through Thursday. These winds will be strongest late Tue through Wed in the mountains and deserts where wind gusts of 35 to 45 mph are likely today and Tuesday becoming 45 to 55 mph for late Tuesday night and Wednesday.
As the onshore flow spreads cooler marine layer air farther inland, Wednesday will likely be the coolest day with high temperatures generally within a few degrees of seasonal averages. Temps will range from the upper 60s to around 70 near the coast to the lower to mid 70s for the valleys and inland Orange County with the lower deserts in the 80s.
This system will also bring deep-layer moisture and more widespread clouds, with chances for light showers from the mountains to the coast. The deserts will likely remain rain- shadowed. Current precipitation estimates are for less than one tenth inch to near two tenths inch in the San Bernardino Mountains. Elsewhere from the coast to the mountains, a few hundredths of an inch or less is expected. The snow level will be mostly above 8000 to 8500 feet through Tuesday night, lowering to around 7500 feet by Wednesday morning.
This system will be followed in short order by a more intense low pressure system moving inland farther north, with a closed upper low moving east over WA/OR Thu-Fri. This will sustain the strong onshore flow through Thursday but as the low pressure system moves eastward into the Rockies, a surface high will move into the Great Basin setting up offshore flow for Fri and Sat. We are likely to see some Santa Ana winds Fri-Sat but the strength of the winds is uncertain at this time.
Next Sunday will likely be the warmest day with a ridge of high pressure bringing daytime temps of 10-15 degrees above seasonal averages west of the mtns and in the deserts. A return of onshore flow will bring lower temperatures to areas west of the mtns but the deserts will remain warm, with temperatures in the mid to upper 90s.
301730z, Low clouds near 1000-1500 ft MSL will slowly clear coastal areas 18-20Z, though some low clouds may stick around within 5 miles of the coastline the entire afternoon with moderate confidence on coverage. Low clouds will push much further inland tonight after 00Z Tue, reaching parts of the Inland Empire after 06Z Tue. Bases will be higher around 800-1200 feet MSL with vis reductions for higher inland terrain.
Above and beyond the marine layer, VFR conditions will prevail today and tonight. High clouds will increase and lower to about 150000 feet MSL tonight into Tuesday.
No hazardous marine conditions expected through Wednesday. Northwest winds increase Thursday to near 20 kts.
Ca, Wind Advisory from 8 PM Tuesday to 11 PM PDT Wednesday for Apple and Lucerne Valleys-Coachella Valley-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.
PZ, None.
