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), 11/857 AM.
***UPDATE***
Low clouds and patchy fog returned in full force across most coastal areas and most of the lower coastal valleys thanks to a marine layer around 1000-1500 feet deep (shallower on the Central Coast). The marine layer has already begun to burn off away from the coasts, with low clouds burning off through this morning. However, skies will transition to partly to mostly cloudy by this evening as high clouds stream into the state.
Two main concerns in the near (and long) term periods of the forecast. First of all, the warm weather will continue, however, today is expected to be the "coolest" through the remainder of the forecast, but temperatures will still be warm. Sunday will tick up a few degrees in most places, but it will likely feel warmer as moisture streaming in from the south with raise humidities, so we are expected a very warm and muggy period to commence tomorrow. We will be looking at potentially trimming back some of the Heat Advisories for Sunday, but that will come later today if we do.
Regarding the mositure streaming in from the south, some higher resolution guidance is hinting at the potential for some isolated showers or thunderstorms tonight along the Central Coast, so we will be introducing a 15-20 percent chance on the Central Coast later today. Elsewhere a 5 percent chance exists due to the uncertain nature of this type of setup. Sunday will feature a 10-20 percent chance of thunderstorms and showers over the LA, Ventura, and far interior Santa Barbara County mountains into Tuesday, while a 5-10 percent chance exists elsewhere (including lower elevations). Moisture will be somewhat limited tonight, so rainfall accumulations are expected to be light with any, which leads to more of a concern for dry lightning impacts in regards to fire weather. Storms are expected to be wetter Sunday, and especially Monday and Tuesday.
***From Previous Discussion***
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.
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.
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.
11/1247z.
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. Cigs may fail to reach the TAF site, and if they do, they will be short-lived.
Moderate confidence in the remaining TAFs. Clearing times may be 1-2 hours later than forecast, and if clouds last later into the day, could see earlier arrival times tonight.
KLAX, Moderate confidence in TAF with southeast winds possible through 15Z. High confidence that any east wind component will be below 6kt.
KBUR, Moderate confidence in TAF due to uncertainty in marine layer clouds clearing times and if cigs will reach BUR tonight.
11/843 AM.
For the outer waters, winds and seas are largely expected to be below Small Craft Advisory (SCA) levels today through Tuesday, then there is a 50% chance of SCA winds developing Tuesday night and continuing through Wednesday night.
For the nearshore waters along the Central Coast, mainly light winds are expected through Tuesday, but winds increase Tuesday afternoon and evening with a 50% chance for SCA winds Wednesday and Wednesday night.
For the inner waters south of Point Conception, conds are expected to remain below SCA levels through the period, except for a 50% chance of SCA wind gusts at times western portions of the Santa Barbara Channel Wednesday and Wednesday night.
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, NONE.
