11/459 PM.
A significant cooling trend will begin Thursday, with temperatures falling to near normal by Friday. Off and on rain is expected Thursday night into early Saturday and more storms are possible next week.
(tdy-Sat), 12/118 AM.
Latest models in good synoptic agreement through the short term period. An upper level low, located west of the area, will move south and east into northern Baja today through tonight. Behind that low, a cold front will sweep across the area Friday and Friday night. With this pattern, cooler and wet conditions can be expected across the area.
The first shot of precipitation, associated with the upper low, will impact the area tonight through early Friday afternoon. Given the trajectory of the upper low, the best shower activity will remain south and east of the area. So, rainfall totals with this first wave will be light, generally on the order of 0.25 inches or less for most areas. However, instability associated with the upper low (MUCAPE in the 500-1000 J/KG range and 500 MB temperatures around minus 16 degrees Celsius) will bring the potential for some thunderstorms to areas south of Point Conception (mainly the coastal waters and coastal plain). So, there could be some locally higher totals with any thunderstorms or heavier showers.
The second shot of precipitation, associated with a frontal passage, will impact the area late Friday afternoon/evening into Saturday morning. This will bring a good chance of more widespread rainfall to the area. At this time, rainfall totals with this second impulse look to be in the 0.25-0.75 inch range with locally higher amounts possible across more favored mountain slopes.
Between the two impulses, rainfall totals are expected to top out in the 0.25-1.00 inch range for most areas with locally higher amounts possible across some mountain slopes and associated with any thunderstorm activity. Rainfall rates are expected to mostly be 0.25 inches/hour or less although local rates around 0.50 inches/hour will be possible.
Other than the rain chances, this pattern will bring noticeably cooler conditions to the area on Friday/Saturday with high temperatures topping out in the 60s to lower 70s. Additionally, there will gusty southwest to northwest winds Friday and Friday night with a chance of some low end advisory-level winds across interior sections.
(Sun-Wed), 12/118 AM.
For the extended, models continue to exhibit decent synoptic agreement. Pattern-wise, the "storm train" is expected to continue with one storm impacting the area Sunday night through Tuesday then another system during the day on Wednesday/Wednesday night.
At this time, the ECMWF is more bullish with rain totals than the GFS. Based on current QPF guidance, the Sunday night-Tuesday system will likely generate 0.10-0.50 inches and the Wednesday and Wednesday night storm will likely generate 0.25-1.00 inches. Of course, given this is in the extended period, these expected totals will likely change from day-to-day. Looking at the respective ensembles, there is a 10-20% chance of totals being higher than the current forecast.
Other than the rain chances, partly to mostly cloudy conditions will be likely through the extended period. High temperatures will be cooler, generally in the 60s with temperatures in the 40s and 50s across the mountains.
12/1051z.
At 1000Z at KLAX, the marine inversion was 1400 feet. The top of the inversion was 2400 feet with a temperature of 21 degrees Celsius.
For the 12Z TAF package, moderate confidence in KPRB, KSBP and KSMX as there is a 50% chance that CIG/VSBY restrictions do not develop this morning. For tonight, high confidence in VFR CIGs (BKN050-070) after 08Z with a chance of showers.
For sites south of Point Conception, high confidence in CAVU conditions through this evening with VFR CIGs (bkn050-070) developing after 08Z with a chance of showers.
KLAX, High confidence in 12Z TAF. Through this evening, CAVU conditions are expected. Overnight, VFR CIGs are expected with a chance of light showers. No significant easterly wind component is expected.
KBUR, High confidence in 12Z TAF. Through this evening, CAVU conditions are expected. Overnight, VFR CIGs are expected with a chance of light showers.
12/118 AM.
For the Outer Waters, high confidence in current forecast. Today through Monday, a combination of Small Craft Advisory (SCA) level winds and seas is expected. Winds look to peak on Friday and Saturday, then again on Monday. Seas are expected to peak on Saturday (15-22 feet) with a secondary peak expected on Monday (12-18 feet).
For the Inner Waters north of Point Sal, high confidence in current forecast. Today through Monday, a combination of SCA level winds and seas are expected. Winds look to peak on Friday, then again on Monday. Seas are expected to peak on Saturday (14-19 feet) with a secondary peak on Monday (11-15 feet).
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. For today, high confidence in winds and seas remaining below SCA levels. For Friday through Saturday, there is a 40-50% chance of SCA level winds. On Sunday, high confidence in winds and seas remaining below SCA levels. On Monday, there is a 60-80% chance of SCA level winds.
With the expected large westerly swell this weekend, there is the threat of dangerous breaking waves at Ventura and Morro Bay harbor entrances.
Today through Monday, there will be the threat of showers, especially Friday/Saturday then again on Monday. Also, there will be a slight chance of thunderstorms south of Point Conception late tonight and Friday.
12/118 AM.
A very large, long-period west to northwest swell originating from a strong Aleutian low pressure system will arrive at the beaches this weekend. Impacts will be focused along west to northwest facing shores and are expected to peak on Saturday. Significant beach erosion and shallow flooding of sea water over low-lying beach walkways, parking lots, and roads is likely, especially in the morning hours near high tide. Large surf will create dangerous rip currents, along with strong long shore currents, potential sneaker waves and large shore pound. Impacts will be less for south-facing shores.
The highest risk will be along the Central Coast with potential for localized damage to the most vulnerable areas - such as to piers, roads, and structures. A coastal flood watch has been issued to highlight the potential for WARNING-level inundation, such as widespread flooding at Oceano Dunes State Park. There is a HIGH chance for WARNING-level Surf which current guidance shows potential for 18-25 ft across northwest facing shores.
For LA/VTA west-facing beaches, there is potential for at least advisory level surf and cannot rule out a High Surf WARNING especially for the Ventura coastline.
Coastal hazards are likely to continue well into next week as the northern Pacific remains very active.
Ca, Beach Hazards Statement in effect through Monday morning for zones 87-349-350-354-362-366. (See LAXCFWLOX). High Surf Advisory in effect until noon PST Monday for zones 340-346. (See LAXCFWLOX). Coastal Flood Watch in effect from late Friday night through Saturday afternoon for zones 340-346. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until noon PST Monday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM this afternoon to noon PST Monday for zone 673. (See LAXMWWLOX). Small Craft Advisory in effect from 6 PM this evening to noon PST Monday for zone 676. (See LAXMWWLOX).
