12/906 AM.
Temperatures will increase each day into mid-week, resulting in widespread Moderate to Major HeatRisk Tuesday through Thursday. Monsoonal moisture moving into the area will add to the discomfort, bringing shower and thunderstorm potential each day, highest in the mountains.
(tdy-Wed), 12/139 PM.
A hot and muggy week expected as an upper level high over the northern plains tops out around 600dam, and is also favorably placed to import tropical moisture from Mexico. PW's peak tonight and Monday around 1.5" and slowly fall the remainder of the week but remaining as high as 1.35" Thursday. The best chance for any precip reaching the ground remains today and Monday but can't rule out a few drops through mid week. And there also remains a 10-20% chance of thunderstorms through that time, but the best chance of those would be in the mountains. So far rain amounts have been mostly non-measurable but as much as 0.02 has fallen along the Central Coast.
The heat and humidity will be the biggest concern this week with temperatures peaking on Wed. Models continue to indicate a significant offshore trend to the east, with actual gradients possibly 1-2mb offshore, effectively delaying the typical cooling sea breeze and providing an additional heating source in addition to the strong high aloft. For this reason there is high confidence that Extreme Heat Watches will become Warnings on Tuesday for most areas except possibly along the immediate coast and continuing through Thursday, though there is a 20-30% chance that warnings will extend to the coast as well, especially the Santa Barbara South coast where hot and strong Sundowners are expected to peak Tuesday and Wednesday evenings, possibly bringing temperatures at the beach into the 90s with very warm overnight temperatures as well. Current projections indicate a 30-40% chance of 110 degrees in the western San Fernando Valley as well as the southern Salinas Valley on Wednesday and a 60-80% chance of 95 or higher in Downtown Los Angeles. Given the extreme heat and humidity it's highly recommended to complete outdoor activities as early as possible.
(Thu-Sun), 12/158 PM.
High pressure will begin to slowly weaken Thursday as a low pressure system moves into the Pac NW. In addition, onshore flow will return much earlier in the day bringing temperatures back down to within a few degrees of normal in most areas by Friday.
However, one factor to keep a close eye on will be the next tropical system off the coast of Mexico this weekend. While the storm is expected to weaken considerably as it moves northwest, there is a chance of another tropical moisture surge across the area. Models are indicating PW's increasing again to around 1.5" as early as Saturday and remaining high into early next week. At the very least there will be some increasing mid level clouds along with higher humidities. But also can't rule out isolated showers and/or thunderstorms. Temperatures are expected to remain within a few degrees or normal, but the increase in humidity could lead to an increase in heat risk. And there will likely be some increase in south swells as well.
12/1742z.
At 1721Z at KLAX, the marine layer depth was was 1700 ft. The top of the inversion was at 3200 ft with a max temperature of 24 C.
High confidence in TAFs for KPMD, KWJF, KBUR, KVNY and KPRB.
Moderate confidence in the remaining TAFs. Mid and high clouds will likely continue to disrupt the marine layer cloud formation through tonight, and any cigs that do form are likely to be patchy and scatter and reform frequently later tonight into Mon morning.
KLAX, Moderate confidence in TAF. There is a 40% chance of no MVFR cigs forming late tonight into Mon morning, and if any do form they may bounce between BKN015 and BKN250. High confidence that any east wind component will be below 6kt.
KBUR, Generally high confidence in TAF. There is a 10%-20% chance of brief OVC008-015 cigs 12Z-16Z Mon.
12/115 PM.
For the outer waters, winds and seas are largely expected to be below Small Craft Advisory (SCA) levels through Tuesday, then there is a 50%-60% chance of SCA winds and seas developing Tuesday night and continue through Thursday night or Friday morning. This will be followed by conds below SCA levels Friday afternoon and Friday night.
For the nearshore waters along the Central Coast, mainly light winds are expected through Tuesday morning, but winds and/or seas will begin to increase to SCA levels Tuesday afternoon and persist (60% chance) through Thursday night. Conds should then drop below SCA levels late Thursday night through Friday night.
For the inner waters south of Point Conception, conds are expected to remain below SCA levels through the forecast period, except for a 60% chance of SCA wind gusts over the western portions of the Santa Barbara Channel Tuesday night through Wednesday night.
Monsoonal moisture is expected to push over the coastal waters during the next couple of days. As a result, there is a very small non-zero chance (10%) of a thunderstorm over the coastal waters through Tuesday. Any thunderstorm that develops could produce dangerous cloud-to-ocean lightning.
12/119 PM.
A south to southwest swell will continue to affect the coastal waters through this week. With this longer period swell, the potential for larger surf and a greater risk for rip currents will continue.
Evening high tides are expected to increase this week with Monday expected to be the highest tide of 7.1 to 7.7 ft above MLLW. There is the potential for some minor coastal flooding this week with the evening high tides and south swell. One thing that will need to be watched late this week into the weekend will be the potential of a greater south to southwest swell from potential tropical cyclone over the eastern Pacific.
In addition, a non-zero chance of thunderstorms will be possible along the beaches at times into Tuesday (around a 10% chance overall). Any thunderstorms that develop could produce dangerous cloud-to-ground lightning. For more information, please refer to the Beach Hazard Statement.
Ca, Heat Advisory remains in effect until 10 AM PDT Tuesday for zones 38-88-343>345-353-368-372-373-375>380-548. (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). Beach Hazards Statement in effect through Wednesday evening for zones 340-346-349-350-354-362-366. (See LAXCFWLOX). PZ, NONE.
