25/1237 PM.
Dry and warm conditions will continue through the first half of this week. Cooler conditions will follow, with a growing potential for a storm system towards next weekend.
(tdy-Wed), 25/1210 PM.
Near neutral pressure gradients with night to morning light offshore breezes focused across interior areas to afternoon to early evening sea breeze onshore winds closer to the coast will continue into Monday. Seasonably warm and dry conditions will continue with daytime highs near 70 to near 80 for most areas. The dry air mass and generally light winds will allow temperatures to drop off pretty quickly in the evening.
Monday evening through Wednesday and weakening front will set up dry northwest to onshore flow. This will support a gradual cooling trend for most save some south facing foothills and adjacent valleys/coast such as the Santa Barbara South Coast where the downslope winds from the northwest flow will delay the cooling trend.
Night-to-morning low clouds and fog may return as early as tonight for the Central Coast with a good (70% chance) of returning by Tuesday morning. There is a 30-50 percent chance of low clouds returning to other coastal areas (especially the LA County coast) as early as Tuesday morning.
(Thu-Sun), 25/1240 PM.
Northwest flow aloft will transition to the southwest with a digging trough just to our west. Light rain may begin as early as Thursday night for Friday in response to this pattern change. Either way cloud cover will be on the increase, contributing to continued cooling with highs only in the 60s to near 70 by Friday.
Guidance is trending slower and stronger with the potential weekend storm. While confidence is growing, it still remains below normal, especially for Santa Barbara and San luis Obispo Counties. There is a 90 percent chance of widespread rain SOMETIME between Friday and Monday, again focused Saturday (Halloween) or Sunday. We have a decent (30-60% chance) shot of a moderate storm (0.5-1.5 inches except 1.5-3 inches south facing mountains/foothills) and slight (10-20%) chance of a strong storm (2+ inches except 4+ inches mountains/foothills). Odds of both of these scenarios are highest for Los Angeles and Ventura Counties, lowest San Luis Obispo and Santa Barbara Counties) due to the best moisture and possible track of the storm focused towards the south. Other significant impacts such as strong winds and coastal flooding are possible in the strong storm scenario.
Snow levels will generally be high, although light snow may occur at high elevations on the backside of the storm.
Again just to repeat, confidence remains low on this time period and may remain low, especially on forecast details, for another couple of days.
An active weather pattern may continue behind next weekend, with a 50-60 percent chance of above normal precipitation into the following week.
25/1541z.
At 15Z at KLAX, there was a surface-based inversion. The top of the inversion was 2400 feet with a temperature of 19 degrees Celsius.
For 18Z TAF package, high confidence in CAVU conditions through the period for KSBA, KOXR, KCMA, KBUR, KVNY, KPMD and KWJF.
For KSBP, KLAX, KLGB and KSMO, there is a 10-20% chance of LIFR/VLIFR conditions 08Z-16Z.
For KSMX, there is a 50% chance that CIG/VSBY restrictions do not develop tonight.
KLAX, High confidence in 18Z TAF as CAVU conditions are likely through the period. There is a 10-20% chance of IFR/VLIFR conditions 10Z-17Z. No significant easterly wind component is expected.
KBUR, High confidence in 18Z TAF as CAVU conditions are expected through the period.
25/1227 PM.
For the Outer Waters, moderate to high confidence in current forecast. Through Monday morning, high confidence in winds and seas remaining below Small Craft Advisory (SCA) levels. For Monday through Wednesday, high confidence in winds increasing to SCA levels. On Thursday and Friday, there is a 50-60% chance of SCA level winds continuing.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Through Monday morning, high confidence in winds and seas remaining below SCA levels. For Monday afternoon and evening, there is a 60-80% chance of SCA level winds. For Tuesday through Friday, there is a 30-50% chance of SCA level winds each afternoon and evening.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Today through Friday, high confidence in winds and seas remaining below SCA levels for most of the southern Inner Waters. The only exception will be the western half of the Santa Barbara Channel with a 50-60% chance of SCA level winds in the late afternoon and evening hours Monday and Tuesday, then again on Friday.
Dense fog is likely to form over portions of the coastal waters over the next 48 hours, but low confidence on exactly when and where.
A significant storm system will impact the area sometime in the late Friday through early next week timeframe. There is a wide range of outcomes, but there is at least a low threat of a 12-24 hour period of strong winds and step seas.
25/1227 PM.
Very high tides between 7.5 and 8.0 feet (roughly 1.0-1.5 feet above astronomical predictions) are expected during the morning hours through Thursday over all coastal areas, with the highest towards Los Angeles County. Monday through Wednesday could produce the highest on record (current record at San Pedro is 7.93 feet set on Jan 10, 2005 with records going back to 1924).
Minor coastal flooding is likely purely based on the high tides. While these tides might be the highest of all-time, similar extreme tides in the past tell us that coastal communities should expect shallow flooding of harbor walkways, beach parking lots and bike paths. With swells and surf on the lower-end during these extreme tides (2-3 feet), the threat of more significance/damaging impacts should be limited to the most vulnerable areas that have little-to-no sandy beach left and have already seen water damage.
With that said, these is a small change for more elevated surf on south-facing shores around Wednesday as waves from a southern Hemisphere storm arrive. The majority of computer projections keep this wave energy on the small side, but a couple are a little larger.
With all of these considerations in play, Coastal Flood Advisories are in effect today through Thursday. There is a low potential for targeted Coastal Flooding Warnings if a larger swell develops and produces elevated surf on top of the very high tides.
Ca, Coastal Flood Advisory in effect until 1 PM PDT Thursday for zones 340-346-349-350-354-362-366. (See LAXCFWLOX). PZ, Small Craft Advisory in effect from 3 PM to 9 PM PDT Monday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect from 5 PM Monday to 3 AM PDT Tuesday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM Monday to 3 PM PDT Tuesday for zones 670-673-676. (See LAXMWWLOX).
