07/218 PM.
Gusty Santa Ana winds will continue through Sunday, bringing a warming and drying trend. Briefly cooler conditions are likely early next week, with another warm and dry spell expected to start on Wednesday and continue through at least Friday.
(Sat-Tue), 07/804 PM.
***UPDATE***
Winds have lightened across the area, and thus the High Wind Warnings across the mountains were replaced with Wind Advisories. Additionally, Wind Advisories across the LA Basin, the San Gabriel Valley, and Catalina Island have been allowed to expire. Wind Advisories remain in effect through 3 pm Sunday for the typical Santa Ana wind prone corridor of LA and Ventura Counties. The forecast remains on track, with continued (but slightly weaker) Santa Ana winds and very warm temperatures expected tomorrow.
***From Previous Discussion***
A 555 dam upper low is retrograding to the SW and by late afternoon it will be a couple hundred miles SSW of San Diego. This system is bringing strong northeast wind flow aloft from 850 mb to 500 mb level today. This upper level support is combining with 3 to 4 mb offshore sfc flow from both the north and east to continue the moderate to locally strong Santa Ana wind event. Today is the strongest and most widespread for the offshore winds. The strongest winds have occurred across the San Gabriel, Santa Susana, and Santa Monica mountains, as well as Malibu, with damaging gusts from 60 to 70 mph observed today. In addition to the typical Santa Ana wind corridor areas, have seen gusty north to northeast winds in areas that typically do not see much offshore winds such as the LA basin (especially west LA) and the San Gabriel Valley (especially foothills near Highway 210 corridor), due to the strong upper level wind support and associated mountain wave wind activity. As of 1 pm today, have seen a number of observing stations seeing wind gusts between 35 and 50 mph across the LA Basin and San Gabriel Valley, with locally higher gusts up to 55 mph across the hills. Some of the High Wind Warning and Wind Advisory products are set to expire at 3 pm today, but some areas may need to be extended in time. The potential impacts today associated with the gusty winds include downed trees and powerlines as well as isolated power outages and blowing dust, including the populated urban areas of the LA Basin and San Gabriel Valley.
On Sunday, the upper level wind support will not be as strong, and will become more easterly in direction. The surface pressure gradients actually become more offshore and will be in the 5 to 6 mb range from both the N and E. The weaker upper level wind support, however, will overshadow the increasing offshore surface flow, keeping most of the offshore winds focused in the more typical Santa Ana wind prone corridors of LA/Ventura counties, and overall wind speeds are not expected to be as strong as today in most areas. No high wind warning level winds anticipated on Sunday, but will likely continue to see many wind advisories in effect, with gusts mostly in the 35 to 50 mph range.
The offshore winds are bringing significant downslope warming and drying to the wind prone areas today, with even more significant warming expected tomorrow. With this type of event, coastal areas will likely see the most significant compressional heating, with temperatures likely climbing into the lower 80s today, and around 90 on Sunday (about 15-20 degrees warmer than normal), which could approach record levels in a few locations. A heat advisory has been issued for Sunday across all LA county coastal zones, the San Fernando Valley, San Gabriel Valley, and Santa Monica mountains. The heat is especially impactful since it is very early in the year, and the large LA Marathon race takes place on Sunday, with temperatures expected to approach 90 degrees by the end of the event. While Red Flag Warnings have not been issued for this event due to the continued moist vegetation levels, the hot, dry (humidities falling into single digits), and windy conditions will bring the possibility of small fire activity through the weekend.
The great basin high is expected to weaken considerably by early Monday, while a pronounced eddy circulation develops. It does appear that low clouds and fog may return as early as Monday morning, and even more likely by Tuesday morning. The onshore pressure gradients and increased marine influence will likely bring significant cooling to the region on Monday and Tuesday, with temperatures retuning to the 70s in most areas, and upper 60s near the beaches.
(Wed-Sat), 07/216 PM.
On Wednesday, an upper level ridge of high pressure will rebuild over the area, resulting in the start of another warming and drying trend. The heat is then expected to peak on Thursday and Friday as offshore pressure gradients and boundary layer temperatures peak. During this time, it will likely be more of a northerly offshore wind, favoring such areas as southern Santa Barbara county and the I-5 corridor. The most likely outcome for max temperatures on Thursday and Friday will be upper 80s to lower 90s for warmer coastal/valley areas, but some ensemble members show the potential for localized readings into the mid 90s. These max temperatures are 15 to 20 degrees above normal. As a result, there is the chance of heat advisory headlines needed in the Thursday/Friday time frame.Long range models also showing no signs of rain in the next 10 days.
08/0540z.
At 0526Z at KLAX, there was no marine layer or an inversion.
High confidence in CAVU TAFs through forecast period. Moderate confidence in winds for sites across Ventura and Los Angeles counties, with timing of wind shifts may be off by +/- 2 hours, and gusts may be off by 10 kts during peak winds.
Light to occasionally moderate LLWS and turbulence is likely over and near mountainous terrain across Los Angeles and Ventura Counties.
KLAX, High confidence in CAVU conditions. Moderate confidence in wind forecast as direction may be off by 20 degrees and gusts may be off by +/- 10 kt during peak winds.
KBUR, High confidence in CAVU conditions. Moderate confidence in wind forecast as direction may be off by 20 degrees and gusts may be off by +/- 10 kt during peak winds.
07/912 PM.
For the Outer Waters, moderate to high confidence in current forecast. Small Craft Advisory (SCA) level N-NE winds to persist through early Sunday afternoon across the far southern waters (PZZ676). A lull in winds is likely thereafter followed by a likely chance of SCA NW-N winds during Sunday evening into the overnight hours. Similar chances these winds reach SCA level confined during the evening hours northward to Point Sal. For Monday through Wednesday, high confidence in a combination of SCA level winds and seas for majority of Outer Waters, with a 20-30% chance of GALE FORCE winds across PZZ670 Monday evening into Tuesday. Moderate chances for SCA winds through the work week. Waves will flirt with SCA levels during this period.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Conditions will remain below SCA levels through the weekend. For Monday through Thursday, there is a 30-40% chance of SCA level winds in the afternoon and evening hours.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Through Sunday SCA level NE winds are expected from Ventura south to Santa Monica and across the San Pedro Channel - with winds and seas remaining at or below SCA levels elsewhere. Localized GALE Force wind gusts are likely nearshore from Point Mugu to Malibu Sunday morning. For Monday through Wednesday, high confidence in winds and seas remaining below SCA levels for all of the southern Inner Waters.
Ca, Wind Advisory remains in effect until 3 PM PST Sunday for zones 88-354-355-358-369>380. (See LAXNPWLOX). Heat Advisory remains in effect from 10 AM to 6 PM PST Sunday for zones 362-366>370-372-373-548. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 3 PM PST Sunday for zones 650-655-676. (See LAXMWWLOX).
