11/407 AM.
Warm temperatures will continue for the interior and interior mountain into this coming week. Monsoonal showers and thunderstorms will also be possible starting late tonight and continuing well into next week. Temperatures will rise again on Tuesday, potentially reaching Major Heat Risk levels across parts of the area, with the monsoonal moisture adding to the discomfort from the heat.
(tdy-Mon), 11/353 AM.
***UPDATE***
Latest satellite imagery shows the marine layer expanding deeper into the coastal valleys and foothills, along with additional upper level clouds moving through from the south. Still expecting a fairly unbroken marine layer from the coasts to the valleys this morning, that will burn off late morning into the afternoon. However, will likely see low clouds linger near the immediate coasts throughout the day.
As the main upper level ridge of high pressure then continues to shift away from the region today, expect a slight moderation of temperatures across the local area as heights aloft decrease, with southeasterly flow around the periphery of this high pressure system helping to steer some monsoonal moisture towards the region. This should result in a slight cool down, and the marine layer clouds reaching further onshore.
A high pressure system over the Southern California region will travel to the northeast and settle over the Four Corners region for the weekend. 500 mb heights will trend slightly downwards over the next couple days. Given these trends, coastal plains and coastal valleys have been removed from the heat advisory (now in effect for the interior mountains and northern interior areas) for today. Going forward, there is a chance of the advisories being trimmed for Sunday or Monday, but an expected increase in humidity will enhance the heat impacts regardless of the temperature. Additionally some offshore flow on Sunday may lead to some warming.
Southeast flow will lead to an increase in overall (non- marine layer) cloud coverage and risk of monsoonal thunderstorms towards the latter half of the weekend, with the best chances over the LA and Ventura County mountains. Monsoon shower and thunderstorm potential is on track with a 5 percent chance as early as tonight, increasing to 10-20 percent chance Sunday and Monday. There is a risk of lightning, gusty winds, and brief flash flooding with thunderstorms. The highest probability for storms will be across interior and mountain areas of Los Angeles and Ventura Counties, however smaller chances do extend to coastal areas, including Santa Barbara and San Louis Obispo Counties. The monsoon will continue on Monday with partly to mostly cloudy skies and a 10 to 20 percent chc of showers and isolated TSTMs over the mountains. It is important to note that while some areas could see showers and isolated thunderstorms, many areas will remain dry.
(Tue-Fri), 11/402 AM.
The long range mdl consensus is that the monsoon will stop on Tuesday and skies will become mostly sunny, likely as a result of a break in the moisture as upper level flow shifts to the southwest. The marine layer and temp forecast begins to get problematic due to the uncertainty in the N/S pressure gradient. Right now it looks like the best bet is for continued onshore flow which means a good chc of morning stratus and only a degree or two of warming due to the increase in sunshine.
Rising hgts and a better chc of weak onshore or even offshore flow in the N/S direction will bring 3 to 6 degrees of warming to most areas. Vly temps will likely range from 95 to 105. A heat watch is in effect Tuesday through Thursday to cover the good possibility of these hotter temps.
The mdl consensus points to an increase in onshore flow starting Tuesday afternoon, growing stronger Thursday and Friday. This will likely increase the morning clouds and bring 3 to 6 degrees of cooling to the area. Even with this cooling max temps will remain above normal. The is also a chc of a return of the monsoon with a 10 to 20 percent chc of showers/TSTMs developing over the mtns for Thursday.
11/0653z.
At 0503Z at KLAX, the marine layer depth was was 1000 ft. The top of the inversion was at 4800 ft with a max temperature of 24 C.
High confidence in TAFs for KPMD and KWJF.
Low-to-moderate confidence in TAF for KPRB with a 40 percent chc of LIFR conds from 12Z-16Z. Cigs may fail to reach the TAF site, or will be short-lived.
Moderate confidence in the remaining TAFs. Timing of flgt cat changes could be off by +/- 1-2 hrs and cig hgt off by +/- 300 ft.
KLAX, Moderate confidence in TAF with southeast winds possible through 15Z. High confidence that any east wind component will be AOB 6kt.
KBUR, Moderate confidence in TAF. BKN004-BKN008 cigs could arrive anytime between 07Z and 11Z.
11/315 AM.
For the outer waters, Small Craft Advisory (SCA) level NW winds have ended over most of the waters, but gusty winds linger for the outer waters north of Point Sal through at least this afternoon. There is a 30-40% chance for SCA level winds to return Sunday evening. NW seas around 7-9 feet are decreasing over the next few days.
For the nearshore waters along the Central Coast, SCA winds have ended. Mainly light winds are expected through Tuesday morning, but winds increase Tuesday afternoon and evening with a 50% chance for SCA winds.
For the inner waters south of Point Conception, conditions are expected to remain below SCA levels through the period.
11/315 AM.
A south to southwest swell will continue to affect the coastal waters through next week. With this longer period swell, the potential for larger surf and a greater risk for rip currents will continue. High tides are expected to increase this weekend going into next week with Monday expected to be the highest tide of 7.0 to 7.6 ft above MLLW. There is the potential for some minor coastal flooding next week with the high tides and south swell. One thing that will need to be watched into next week will be the potential of a greater south to southwest swell from potential tropical development.
Thunderstorms will be possible along the beaches starting Sunday and going through next week (10-20% chance). For more information, please refer to the Beach Hazard Statement.
Ca, Heat Advisory remains in effect until 10 AM PDT Tuesday for zones 38-343>345-353-376>380. (See LAXNPWLOX). Extreme Heat Watch in effect from Tuesday morning through Thursday evening for zones 38-88-341>345-347>358-362-366>376-378>383-548. (See LAXNPWLOX). Heat Advisory remains in effect from 10 AM Sunday to 10 AM PDT Tuesday for zones 88-368-372-373-375-548. (See LAXNPWLOX). Beach Hazards Statement in effect from Sunday morning through Wednesday evening for zones 340-346-349-350-354-362-366. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until 3 AM PDT Sunday for zone 670. (See LAXMWWLOX).
