11/345 PM.
Minor to moderate coastal flooding is likely continue to through at least Tuesday. Periods of light to moderate rain and a low chance of thunderstorms will persist through Monday with below normal temperatures. Beginning Tuesday and continuing through the end of the week, weak to moderate offshore flow will bring warm and dry conditions to the area.
(tdy-Wed), 12/933 AM.
***UPDATE***
Isolated showers or drizzle continued this morning mainly across south facing mountains and foothills and more broadly into Los Angeles County. Any light showers will generally diminish this morning, although LA County, especially eastern mountains and foothills may see an uptick in shower activity late morning to early afternoon thanks to added lift from daytime heating. Amounts and rates will generally be light, although brief moderate showers are possible.
Today will be the coolest for most areas for at least the next week and likely beyond with highs only 60s to near 70.
Thursday through Saturday will be looked at closely for the afternoon forecast package as the first moderate to strong Santa Ana wind event is likely with potential heat and fire weather concerns.
***From Previous Discussion***
A highly amplified upper level pattern has developed over the eastern Pacific and it appears southwest California will be experiencing quite a range of temperatures and weather conditions over the next couple of weeks. The upper low over the area yesterday and today that has brought scattered light showers and much cooler temperatures will evolve into our first real Santa Ana wind event of the season later in the week. For today though, highs will mostly be in the 60s which is 10-20 degrees below with some off and on light showers, mainly in the morning.
As the upper low slowly moves into the Great Basin, onshore pressure gradients will be weakening and a light northeast flow aloft will develop over the area as early as Tuesday afternoon. Not expecting any winds of significance Tuesday but high temperatures will warm up 4-8 degrees area-wide as the air mass dries out and heights rise at least 10dam from Monday.
Wednesday will be noticeably warmer and drier as offshore gradients continue to increase across the area heights climb another 10dam. Still not expecting any significant winds yet except possibly some northeast winds in the San Gabriel mountains up to 35 mph.
(Thu-Sun), 12/339 AM.
Santa Ana winds will really pick up Thursday into Friday as all the ingredients appear be in place and properly aligned. We're still well outside the boundaries of the high res models but given the amplified upper level pattern, confidence is higher than usual at this early stage that a Santa Ana Wind event of at least moderate strength will develop during this period. The latest ensemble pressure gradients indicate that the peak offshore gradient will occur Friday morning somewhere in the 5-7mb range. Couple that with 50kt winds at 850 mb and very strong upper level subsidence, that should result in peak winds of 50-70mph in the San Gabriel mountains and 35-55mph across the LA/Ventura valleys as well as the Ventura County coastal areas and Santa Monica mountains. The ECMWF is already showing peak winds between 25 and 40 mph in Camarillo Thursday and increasing to 35-50 on Friday. As a reminder, Santa Ana winds typically do not impact the LA Metro area and LA coast.
Temperatures will be peaking during these days as well with highs in the upper 80s and 90s across all coast and valleys, including the Central Coast. There is a very strong chance (60-80%) that heat advisories will be needed for coastal areas Fri and Sat. However, mid 90s in the inland areas would not likely meet criteria there.
Temperatures are expected to remain well above normal through Sunday but slowly cooling into next week. And looking out a little further there is fairly high agreement in the models that another cold upper low will move into the area the middle of next week.
12/1757z.
At 18Z at KLAX, there was neither a marine layer nor a marine inversion. A moist layer was present around 4000 to 5000 feet.
Overall, moderate confidence in TAFs. There is a threat of isolated sprinkles or very light showers at all sites throught the evening, but higher chances for LA coast and valley TAF sites. There will be 20-40% chance of MVFR CIGs at all sites, less so around 21Z Mon to 04Z Tue.
KLAX, Moderate confidence in TAF. Short periods of sprinkles or light showers are possible into this afternoon. There is a 30% chance of MVFR CIGs anytime during the TAF period, more likely after 04Z Tue. No significant easterly winds are expected.
KBUR, Moderate confidence in TAF. Short periods of sprinkles or light showers are possible through Monday morning. There is a 40% chance of MVFR CIGs anytime during the TAF period, more likely after 04Z.
12/930 AM.
For the Outer Waters, moderate to high confidence in current forecast. Through this afternoon, high confidence Small Craft Advisory (SCA) level seas subsiding below advisory levels by the evening, with winds below SCA levels today except for near Point Conception in Zone PZZ673. On Tuesday, there is a 40-60% chance of SCA level winds, again mainly around Point Conception. For Wednesday through Thursday, high confidence in winds and seas remaining below SCA levels.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. High confidence in winds and seas remaining below SCA levels today. For Tuesday through Thursday, there is a 30-40% chance of SCA level winds in the afternoon and evening hours, except a 50% chance Wednesday evening.
For the Inner Waters south of Point Conception, moderate confidence in current forecast. Through Wednesday, high confidence in winds and seas remaining below SCA levels for most area, but the only exception is the western half of the Santa Barbara Channel where there is a 50% chance of SCA level winds Tuesday afternoon and evening. On Thursday and Friday, there is a 40-50% chance of SCA level northeast winds from Ventura south to Santa Monica.
Long period swell from the west and the south are affecting the coastal waters, and can create a confused sea state. This can make boating more challenging and dangerous, especially for small vessels.
12/927 AM.
While the peak timing for the most impactful coastal flooding has passed, there is still a threat of minor to moderate coastal flooding through Tuesday, due to continued high tides and elevated to high surf. The highest tides will occur during the mornings and range from 7.0 to 7.5 feet through Tuesday, with secondary high tides during the evenings (around 6 feet tonight decreasing to 5 feet by Tuesday evening). As for elevated surf, a long period southerly swell and long period westerly swell will impact the coastal waters the next several days, and slowly subside further each day.
The Coastal Flood Advisory for the San Luis Obispo and Santa Barbara coasts are in effect until this evening, and the rest of the coasts continuing until Tuesday afternoon. The High Surf Advisory for the Central Coast beaches (surf 8-12 feet) is in effect until this evening. The Beach Hazards Statement for Santa Barbara South Coast will continue into Tuesday afternoon as well, and is due to elevated surf and minor tidal overflow during high tides (lingering after the coastal flood advisory expires).
Please continue to monitor the forecast and refer to the Coastal Hazard Product (CFWLOX) for more information.
Ca, Coastal Flood Advisory in effect until 2 PM PDT Tuesday for zones 87-354-362-366. (See LAXCFWLOX). Coastal Flood Advisory in effect until 10 PM PDT this evening for zones 340-346-349-350. (See LAXCFWLOX). High Surf Advisory in effect until 10 PM PDT this evening for zones 340-346. (See LAXCFWLOX). Beach Hazards Statement in effect through Tuesday afternoon for zones 349-350-354-362-366. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until 5 PM PDT this afternoon for zones 670-673-676. (See LAXMWWLOX).
