04/1218 AM.
Rain and high elevation snow will affect the area today and tonight as a storm moves slowly over the region. The shower activity will diminish Monday. Drier weather is expected Tuesday through late in the week, with cold nights for many areas Wednesday night through Friday.
(tdy-Wed), 04/219 PM.
Overall, 12Z models in decent synoptic agreement through the short term period. Impulse, currently moving across the Central Coast, will continue to move south and east into Ventura/LA counties this evening and overnight (exiting LA county around sunrise Monday). For Monday through Wednesday, models develop upper low off the Central California coast on Monday then meander it offshore, finally moving across Baja Mexico by Wednesday.
Forecast-wise, no major changes to previous thinking. Impulse moving across the area through tonight will bring moderate rain to the area. At this time, rainfall totals through tonight are expected to generally range between 0.25 to 1.00 inches with up to around 2.00 inches across the foothills and mountains. The best totals will be south of Point Conception. As for rain rates, generally expect 0.25-0.50 inches per hours with local rates up to 1.00 inch per hour (with heavier showers and thunderstorms). Also, sub-hourly rates could briefly be more intense. So, there will likely be nuisance urban flooding as well as some minor mud/debris flows across the area through tonight. Snow levels look to be in the 6000-7000 foot range this afternoon and tonight. So, the resorts should get a few inches of new snowfall.
For Monday through Tuesday, there will be a continued threat of showers across the area as moisture rotates around the upper low offshore. At this time, additional rainfall amounts Monday through Tuesday will generally be around 0.25 inches or less (although northwest San Luis Obispo county could receive up to 1.00 inch). Snow levels will drop into the 5500-6000 foot range, so there could be some additional light snowfall accumulation.
For Wednesday, as the upper low moves into Baja Mexico, it should be dry across the area. With the dry conditions and more sunshine, temperatures will rebound, but still remain below normal.
(Thu-Sun), 04/219 PM.
For the extended, both the 12Z GFS and ECMWF, as well as their respective ensembles, are in good synoptic agreement into next weekend. At upper levels, ridge builds offshore of California Through Friday then move over the state Saturday and Sunday. At the same time, offshore surface flow will begin to strengthen noticeably on Friday and continue through the weekend.
Forecast-wise, the above pattern will bring a welcome period of dry weather to Southwestern California. With the ridge building over the area and the increasing offshore surface flow, skies should remain mostly clear into the weekend. As for the offshore flow, both the GFS and ECWMF have impressive LAX-DAG gradients, bottoming out in the -5 to -7 mb range. The amount of upper level support is still in question, but there will be the chance for some advisory-level Santa Ana winds Friday through Sunday. As for temperatures, will expect a warming trend with coastal/valley areas a couple degrees above normal by Sunday. Overnight lows will likely be on the chilly side in wind-sheltered areas.
05/0049z.
At 2339Z at KLAX, there was no marine layer or inversion.
Low confidence in all TAFs through 12Z as cig and vis will change frequently through the period. LIFR to low IFR are possible in heavier SHRA with MVFR conds most likely. 10-20% chance of a TSTM through 12Z Monday. After 12Z expect rain to end but timing could be off by +/- 3 hours. Sites north of Pt. Conception have -shra chances after 21Z Mon as another storm approaches. Moderate confidence in all TAFs after 12Z with MVFR conds forecast but 30-40% chance CIGs rise to VFR.
KLAX, Low to moderate confidence in the 00Z TAF. CIGs/VSBY could lower to IFR during periods of RA and LIFR conds cannot be ruled out during the worst conditions. There is a 15 percent chc of a TSTM with +RA through 12Z. Moderate confidence that any east wind component will remain under 8kt.
KBUR, Low confidence in the 00Z TAF. CIGs/VSBY could lower to IFR during periods of RA and LIFR conds cannot be ruled out during the worst conditions. There is a 10 percent chc of a TSTM through 06Z.
04/1120 AM.
Another frontal system is currently moving eastward across the coastal waters which will bring periods of rain, low visibility, gusty southerly winds, and a slight risk of thunderstorms and waterspouts. Mariners should consider staying in safe harbor through tonight.
Southerly winds of 20-30 kts will be common along the frontal band. Localized GALE Force wind gusts to 35 kts may occur under heavier cells. As of 11 AM, the frontal band is situated about 20 NM west from the Central Coast shoreline. This activity will move over the inner waters south of Point Conception this afternoon into the evening hours. Also, Isolated to scattered showers are expected well ahead of this activity.
Diminishing winds expected tonight, but seas are expected to remain at SCA levels across Outer waters and along Central Coast through early Monday morning. Moderate chance for another round of Small Craft Advisory (SCA) level southerly winds in similar areas Monday afternoon through Tuesday. After a brief lull in winds, NW winds are likely to reach 20-30 knots Wednesday afternoon through late Thursday, focused across the Outer Waters especially south of Point Conception (with a low chance for GALE force winds).
Ca, Beach Hazards Statement in effect through Monday morning for zones 87-349-350-362-366. (See LAXCFWLOX). High Surf Advisory in effect until 10 AM PST Monday for zones 340-346-354. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until 3 AM PST Monday for zones 645-670-673. (See LAXMWWLOX). Small Craft Advisory in effect until 9 PM PST this evening for zone 676. (See LAXMWWLOX).
