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.
(Wed-Sat), 11/1015 PM.
***UPDATE***
Today was warm again, especially for the valleys. Most of the coasts saw a cooling trend as onshore flow returned, with highs in the 70s to 80 degrees. Heights have already started to fall as the low pressure system approaches from the west, and will continue to fall dramatically through Thursday night. High temperatures Thursday are expected to be about 5 to 10 degrees cooler than today's for northern areas, and 3 to 8 degrees cooler for Ventura county and southward. Highs in the mid 70s will be common, with some warmer 80s forecast for the southern valleys and coasts. High temperatures Friday may need to be cooled a 3-5 degrees, with upper 60s to low 70s common, but otherwise the forecast looks on track.
The chance for showers begins for the coastal waters Thursday night, reaching the coasts early Friday morning. Showers may be scattered to isolated in nature (meaning some areas will get missed), favoring coastal areas and coastal slopes, and there is a slight chance for thunderstorms or heavier showers south of Point Conception early Friday and through the afternoon. The low is forecast to pass to the south, bringing some instability with colder -16 to -18 degree temperatures at 500 mb for our southern most areas. MUCAPE ranging from 500 to 1000 J/kg should be sufficient to support thunderstorms, but if lightning does not develop, showers still look convective enough to create heavy downpours at times. The second round of rain comes late Friday afternoon/evening and looks more widespread, starting in the northwest, reaching LA County in the early morning hours Saturday.
***From Previous Discussion***
Big cooling coming Thursday and Friday as the next storm approaches. Rain timing has sped up slightly with the latest models and we could see some light showers as early as 10pm Thursday night from Santa Barbara west and by 5am Friday everywhere else except the far interior areas. High res models also indicating a small chance of some lightning as this first impulse moves in though most of those chances are from Orange County south. In terms of rain rates, models are showing around a 30-40% chance of 0.50/hr with this first impulse south of Point Conception, but for most areas hourly rates should be under a quarter inch.
The next impulse will hit the Central Coast late afternoon on Friday and advance south of Pt Conception Friday night into early Saturday morning. Any areas that don't get wet Friday morning should get wet Friday night. Peak rain rates will be about the same so still not expecting any significant impacts. For most areas rain will be finished before sunrise Saturday. Rain totals in most areas through Saturday are expected to be between a half and one inch.
(Sun-Wed), 11/220 PM.
Sunday should be a pleasant day as a little pop up ridge moves over the area. Highs will be in the mid 60s to lower 70s, very close to seasonal norms.
Another storm is expected Monday, though could be as late as early Tuesday depending whether the system tries to dig farther south before moving inland as the latest GFS is hinting at. The EC is more progressive. The ensembles seem to favor the earlier arrival. Then a potential third system late Wednesday into Thursday. Neither of them appear to be too impactful at this time, though there are maybe 10-20 percent of the solutions showing a potential 1-3" of rain with that Thursday system.
12/0454z.
At 0450Z at KLAX, the marine inversion was 600 feet. The top of the inversion was 1400 feet with a temperature of 24 degrees Celsius.
For the 06Z TAF package, moderate confidence in KPRB, KSBP and KSMX as there is a 50% chance that CIG/VSBY restrictions do not develop overnight.
For sites south of Point Conception, high confidence in CAVU conditions through the period.
KLAX, High confidence in 06Z TAF as CAVU conditions are expected through the period. There is a 10% chance of IFR/LIFR conditions 10-17Z. No significant easterly wind component is expected.
KBUR, High confidence in 06Z TAF as CAVU conditions are expected through the period.
11/217 PM.
For the Outer Waters, moderate to high confidence in current forecast. Seas will remain slightly below SCA levels through Wednesday, except for PZZ670 where seas will hover near 10 ft. Expecting 10+ ft seas to return Thursday through at least early next week, with models indicating potential for wave heights 15 to 20+ ft this weekend - peaking on Saturday. A secondary but lower peak in seas is expected Monday. SCA winds are likely near and south of Point Conception Friday night through Saturday night, and for a shorter time north of Point Conception as the front moves through.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Conditions are expected to remain below SCA levels through Thursday. SCA level seas could return as early as late Thursday night or Friday, peaking over the weekend. Gusty SCA level winds are possible nearshore Friday night through Saturday afternoon.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Winds and seas are expected to remain below SCA levels for the southern Inner Waters through Thursday. SCA winds will then be possible at times Friday night through Saturday.
There is concern for a large westerly swell this weekend which could produce dangerous breaking waves at Ventura and Morro Bay harbor entrances.
There is a chance of showers sometime from Thursday night into the weekend across the coastal waters.
11/804 PM.
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 from 3 AM Thursday to noon PST Monday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM Thursday to noon PST Monday for zone 673. (See LAXMWWLOX). Small Craft Advisory in effect from 6 PM Thursday to noon PST Monday for zone 676. (See LAXMWWLOX).
