10/712 PM.
Moderate heat impacts will continue into next week, despite slightly cooler temperatures in the forecast through Monday. Monsoonal showers and thunderstorms will also be possible starting late Saturday night 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.
(Fri-Mon), 10/748 PM.
***UPDATE***
Hot and dry conditions were observed across inland locations today while fairly typical marine influences helped to keep coastal areas closer to seasonal norms. Latest satellite imagery shows the marine layer starting to expand onshore in spots this evening, and expect most coastal areas to see the marine layer fill back in overnight.
As the main upper level ridge of high pressure then continues to shift away from the region on Saturday, 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 of temperatures this weekend along with an increasing chance for a monsoonal shower or thunderstorm - especially towards the latter half of the weekend. While many areas will remain dry, the increasing moisture will also impact how warm it feels, with the added humidity adding to the discomfort experienced from the heat.
***From Previous Discussion***
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, and marginal cooling trends are underway across most of the area today as scheduled. Given these trends, we have been able to trim some areas closer to the coast from the Heat Advisory on Saturday. 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 over the area will develop late Saturday, which will bring moisture into the area, leading to an increase in overall (non-marine layer) cloud coverage and risk of monsoonal thunderstorms. Monsoon shower and thunderstorm potential is on track with a 5 percent chance as early as Saturday night, increasing to 10-20 percent chance Sunday into much of next week. 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.
(Tue-Fri), 10/217 AM.
The upper high will migrate to South Dakota on Monday and then sit there for a while. It will also strengthen and push hgts over CA up from 590 dam to 594 dam. The onshore flow to the east will increase to mdt-stg on Monday and will no change much through the rest of the week. The N/S gradient is a much trickier call with many different solutions possible ranging from weak onshore to mdt offshore. Pinning down this value will be the key to getting next weeks forecast correct.
The monsoon will continue on Monday with partly to mostly cloudy skies and a 10 to 20 percent chc of showers and isold TSTMs over the mtns. The increase in onshore flow will likely bring another round of morning low clouds although there is a chc that the advection of monsoon moisture may disrupt the marine inversion. Max temps will not change much from Sunday's values and will remain above normal.
The long range mdl consensus is that the monsoon will stop on Tuesday and skies will become mostly sunny. 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 to cover the good possibility of these temps.
The mdl consensus points to an increase in onshore flow to the normal next Thursday perhaps a substantial increase. 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.
11/0029z.
At 2353Z at KLAX, the marine layer depth was was 1000 ft. The top of the inversion was at 3600 ft with a max temperature of 26 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.
Moderate confidence in the remaining TAFs. Timing of flgt cat changes could be off by +/- 90 min and cig hgt off by +/- 300 ft.
KLAX, Moderate confidence in TAF. BKN008-BKN015 cigs could arrive anytime between 03Z and 06Z. High confidence that any east wind component will be AOB 6kt.
KBUR, Moderate confidence in TAF. BKN004-BKN008 cigs could arrive anytime between 09Z and 11Z.
10/815 PM.
For the outer waters, Small Craft Advisory (SCA) level NW winds are expected to continue subside from south to north into Saturday night. Across the far northern outer waters there will be gusts up to 30 knots. Large short period NW seas 8 to 10 feet at 8 seconds will gradually diminish through early next week.
For the nearshore waters along the Central Coast, SCA winds should drop off tonight. Otherwise, mainly light winds are then expected through Tuesday morning, then increasing Tuesday afternoon and evening.
For the inner waters south of Point Conception, conditions are expected to remain below SCA levels through the period.
10/814 PM.
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 Saturday for zones 645-673. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Sunday for zone 670. (See LAXMWWLOX).
