04/201 PM.
Cloudy and cool conditions will continue through Tuesday, with increasing chances of mostly light rain. Warming and drying to follow Wednesday through the next weekend, with high temperatures approaching 90 degrees in some areas by Friday.
(Mon-Thu), 04/839 PM.
***UPDATE***
Today was rather cool as the low moved over southern California bringing some winds, clouds and a chance for showers. High temperatures were generally in the 60s, with some cooler 50s at at higher elevations. The Antelope Valley foothills, especially near the Hwy 14 corridor was quite gusty, with south wind gusts reaching 40 to 55 mph. Rainfall totals were spotty throughout the region but were more focused on higher terrain, with amounts below a quarter of an inch. Tonight, the low pressure system overhead is keeping plenty of clouds and a chance of light rain in the area. Rain chances linger into Tuesday morning, mostly over the Ventura County mountains and the San Gabriel mountains. Expecting little change in temperatures for Tuesday, with warming on Wednesday as high pressure builds in. Coastal areas may see a return in marine layer clouds as the influence of the low wanes.
***From Previous Discussion***
An upper level low, currently centered just south of Monterey, will slowly move to the southeast and into Arizona by late Tuesday. As this colder airmass moves overhead, it will continue to destabilize the atmosphere. This will make showers possible, but without much mositure (precipitable water readings around 0.8 inches), most shower activity will be limited in terms of coverage and intensity. As such, much of the area will likely not see any precipitation between now and Tuesday, but some will and that is especially true in the mountains (btw, snow levels are 6,000+ feet). High resolution models continue to show increased activity forming tonight over the LA/Orange County border, and a cell or two looks rather healthy. So considering all of this, rain impacts will overall be minimal to none, but there is a low risk of isolated minor road flooding and traffic issues. The potential for anything more significant beyond that is not zero, but pretty close to zero. Breezier than usual onshore winds are also likely through Tuesday over most areas. The Antelope Valley looks the windiest and the low-end Wind Advisory remains in effect, but might need to be cancelled early as winds so far have been a step under Advisory levels.
With the cold airmass in place, temperatures will remain 10 to 20 degrees below normal through Tuesday, with highs in the upper 50s to mid 60s common.
Big changes coming Wednesday through Thursday. Low pressure aloft will be quickly replaced with building high pressure, as 500 millibar heights go from 560 decameters on Tuesday to 580 decameters on Thursday. Meanwhile, onshore pressure gradients will weaken with light offshore flow forming Thursday morning. This has all the ingredients for a sharp warm up, with high temperatures likely jumping 15 to 20 degrees from Tuesday to Thursday when mid 70s to mid 80s will be common. The marine inversion should reestablish itself around Thursday to a more traditional height, and there are some signals of a weak coastal eddy. Coastal low clouds and fog will likely be in the area as a result, which will moderate the warming near the coast. Very unsure however exact what areas will be in the May Gray.
(Fri-Mon), 04/213 PM.
High confidence in high pressure aloft continuing its building over the region into early next week. At this point, 500 millibar heights peak Monday or Tuesday of next week around 588 decameters. At the very least, this means that mountains and deserts will continue to warm Friday through Tuesday, with highs in the mid 80s to mid 90s by Sunday or Monday all but a certainty at this point. The coastal and valley areas however will be tricky. There is a fair spread in the onshore and north-to-south gradients, between moderate onshore and moderate offshore. The offshore scenario would bring high 90s to the coastal valleys, while the onshore scenario would keep highs in the high 80s. Climatology would favor the onshore scenario. Our official forecast is fairly conservative and pretty much going down the middle between the two scenarios, which seems like a good way to go this far out.
05/0211z.
At 2216Z at KLAX, there was a deep moist layer up to 8000 ft.
Moderate confidence in TAFs. Lower confidence in cigs through 06Z with MVFR conditions at times. There is a 20-30 percent chc -SHRA from 22Z-04Z.
KLAX, Moderate confidence in TAF. High confidence that any east wind component with be less than 5 kts.
KBUR, Moderate confidence in TAF. There is a 10-20 percent chance of -SHRA until 04Z.
04/809 PM.
Across the nearshore waters inside the SoCal Bight, Small Craft Advisory (SCA) west winds are likely Tuesday afternoon and evening. In the Santa Barbara Channel, there will be a 30-40% chance of SCA winds Wednesday night, followed by a higher chance (40-50% chance) Thursday night through Friday night over the western Channel.
Nearshore along the Central Coast there is a 40-60% chance of SCA NW winds Tuesday night and a 30-40% chance Wednesday night. Starting Thursday afternoon, SCA winds are likely each afternoon to evening period through Saturday. The winds will be strongest Friday afternoon and evening, with winds 20 to 30 kt, and SCA conds may persist through late Friday night.
For the outer waters, SCA NW winds are likely (50-70% chance) on Tuesday. After a slight lull on Wednesday, winds will increase again Wednesday night into Thursday and will remain at SCA levels through late Saturday night. Short period seas will build under the persistent NW winds, reaching 10 feet by Friday peaking at 11 to 13 feet Friday night through Saturday night.
Ca, Wind Advisory in effect until 9 PM PDT this evening for zones 381-383. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from noon to 9 PM PDT Tuesday for zones 645-650. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM to 9 PM PDT Tuesday for zone 655. (See LAXMWWLOX). Small Craft Advisory in effect from noon Tuesday to 3 AM PDT Wednesday for zones 670-673-676. (See LAXMWWLOX).
