Cool and windy this weekend with chances of light precipitation Saturday morning through Sunday night. Warmer early next week, then minor cooling and a slight chance of precipitation towards the middle of the week. Warmer and drier for the end of the week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Evening update, Marine layer low clouds have quickly developed and spread into the coastal mountain slopes in San Diego County and southern Riverside County with far less coverage to the north. Expect clouds to fill in across the entire coastal basin overnight. The 00Z sounding and pilot reports indicate clouds are currently to thin for any drizzle, but some spotty light showers are possible towards Saturday morning should the cloud deck thicken sufficiently as an upper level low approaches. Otherwise breezy conditions continue overnight with wind gusts generally 30-40 mph in the mountains and deserts with isolated gusts near 50 mph in the passes.
Previous discussion, Heights fall quickly after today as the system inches towards the CA Coast, with highs around 5-10 degrees below normal for Saturday and 8-15 degrees below normal Sunday. Clouds remain present for much of the day on Saturday, spreading into the deserts by the afternoon, with on and off light rain showers across much of the region. As the system pushes inland late Saturday night into early Sunday morning, a 500mb jet max will pass just south of the region >80kts, which will struggle to mix down due to the timing of the passage. Regardless, very strong westerly winds will develop late Saturday evening and persist into Sunday morning - 20-30 mph for inland areas and 40 to 55 mph with higher gusts through mountain passes and on the desert slopes of the mountains. Due to this, the Wind Advisory has been expanded to include the Coachella Valley and San Diego County Deserts, both of which are likely to see gusts above 40 mph late Saturday. Make sure to tie down loose items or bring them inside prior to these peak winds. Blowing dust will be possible throughout this period, especially in the deserts, which may reduce visibility at times. Winds weaken a bit after sunrise Sunday as the system sweeps across, but expect strong, gusty winds to prevail into Monday. Peak heating on Sunday may allow some of the stronger winds to mix down to create another round of gusts greater than 30-40 mph at times in the deserts and on the desert slopes.
Outside of the winds, ample moisture and light rain will move across the region early Sunday morning. The snow levels will be falling from 7000ft on Saturday to around 5500ft Sunday morning as the system sweeps through. This will allow for some snow or rain/snow mix for elevations above 6000ft, although little in the way of accumulations are expected. Elevations above 6500ft may see 1-2 inches of snow, while only a dusting is expected below this elevation. Lower elevations aren't expected to see much rainfall through this event given the main corridor of moisture moves southward into San Diego County Sunday morning. Rain totals below the snow level could see anywhere from 0.10-0.30" across Saturday and Sunday, with slightly more expected in SD County closer to 0.25- 0.50", locally higher in the mountains. Any and all precipitation should come to an end by late Monday morning as the system moves up into the Great Basin, with drier air filling in behind it.
Quieter weather expected next week as temperatures slowly warm under weak ridging setting up between a larger trough over the Central US and a deepening low off the coast of CA. This low could be our next chance for precipitation, with some models more aggressive with its approach mid-week, while others slow the system. At this point, moisture seems to be lacking a bit with this low, so timing will impact any rain chances greatly. We will be keeping a close eye on this system but will manage expectations for now.
250400z, Coast/Valleys, BKN-OVC low clouds based 2000-2500 ft MSL have filled into San Diego/Orange County inland areas, slowly filling into the entire Inland Empire by 12z Sat. Spotty light rain in the morning 12-16z, then cloud bases rise to 3-5 kft MSL and scatter out partially with FEW-BKN cigs throughout the afternoon. Breezy afternoon winds gusting 20-25 kts at times, especially in the Inland Empire. ISO -SHRA begins to reach into coastal SD County after 22z in the vcnty KSAN/KCRQ, becoming scattered throughout the coastal basin by 02z Sun. Bases will lower intermittently in the vcnty of -SHRA, yielding to periods of MVFR cigs. Brief periods of IFR cigs/vis possible under each -SHRA.
Mountains/Deserts, Westerly winds gusting 25-35 kts, locally to 45 kts along desert slopes and through mountain passes through tonight. Gusts may weaken slightly in the late morning, then intensify again in the afternoon to 30-40 kts (locally up to 50 kts). Moderate up/downdrafts expected in lee of mtns. Areas BLDU (3-5SM) along desert slopes and locally into deserts. After 19z Sat, gusts in the desert valleys could periodically exceed 35 kts, including vcnty KPSP.
SHRA reach mtns around 01z Sun with intermittent SHSN above 6500- 7000 ft MSL. Mtns shrouded in FG; vis 0-5SM in FG/SNSH.
No hazardous marine conditions are expected through Wednesday, though brisk westerly winds 15 to 20 kts are expected each afternoon and evening through Sunday.
Ca, Wind Advisory from 2 PM Saturday to 11 AM PDT Sunday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
