12/759 PM.
Temperatures will increase each day into mid-week, resulting in widespread Moderate to Major HeatRisk Tuesday through Thursday. Monsoonal moisture moving over the area will add to the discomfort, also bringing the potential for showers and thunderstorms each day, highest in the mountains.
(Sun-Wed), 12/903 PM.
***UPDATE***
CLouds continue to move northward over the region in a stream of subtropical moisture originating from Mexico and the Gulf of California. Satellite derived PW values over land are between 1 to 1.3", and up to 1.5" over the waters south of LA County. Some isolated light showers have affected the area, with some locations seeing a trace of very light rain, but with 0.01 to 0.03" along the Central Coast of Santa Barbara County and northward. Diminishing shower chances are expected overnight into early Monday, mainly over the mountains, and with very light or no rain expected to hit the ground.
Cloud cover over much of the area helped to moderate the muggy conditions resulting from the subtropical moisture and warm temperatures. Highs today were mainly in the 70s along the coast, with 80s to 90s further inland through the far interior. Onshore winds gusting 20 to 35 mph affected interior sections today, strongest through passes and canyons into the Antelope Valley.
Hot and muggy conditions are expected through the week. A strong upper level high has shifted from the Four Corners Region northward across Wyoming and the northern plains. The location of the high will help to pull ample subtropical moisture into the area, resulting in a risk of showers and thunderstorms at times at least through the short term. The best chances of this occuring will be over the mountains and deserts, Monday and Tuesday in the afternoon hours. Temperatures will rise through the short term, peaking on Wednesday with many locations over 100 degrees and up to 110 degrees. Weak offshore gradients will shut off the typical sea breezes, and work to enhance the heating caused by strong high pressure aloft over the area.
***From Previous Discussion***
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. This could bring 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 and close to that in the southern Salinas Valley on Wednesday. There is 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.
13/0055z.
At 0014Z at KLAX, the marine layer was 800 ft deep. The top of the inversion was at 2600 ft with a max temperature of 26 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 tonight, and any cigs that do form (30-40% chc) are likely to be patchy and scatter and reform frequently later tonight into Mon morning.
KLAX, Moderate confidence in TAF. There is a 30% chance of BKN010-25 CIGs between 09-17Z Mon. High confidence that any east wind component will be below 6kt.
KBUR, Moderate to High confidence in TAF. There is a 10-20% chance of brief OVC008-015 cigs 12Z-16Z Mon.
12/829 PM.
For the outer waters, winds and seas are expected to be below Small Craft Advisory (SCA) levels through Tuesday morning. Then there is a 50%-60% chance of SCA winds and seas developing late Tuesday afternoon and continue through Thursday night or Friday morning, with a 20% chance of Gale Force winds Wednesday. Thereafter, conds will be below SCA levels Friday afternoon through the weekend.
For the nearshore waters along the Central Coast, mainly light winds are expected through Tuesday morning, then increase to SCA levels Tuesday afternoon and persist (60% chance) through Thursday night. Seas will increase to SCA levels Wednesday through Thursday. Conds should then drop below SCA levels late Thursday night through the weekend.
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 level wind gusts over the western portions of the Santa Barbara Channel during the afternoon and evening hours Tuesday through Wednesday.
Monsoonal moisture is expected to push over the coastal waters during the next couple of days. As a result, there is a 10% of isolated showers and thunderstorms over the coastal waters through Tuesday. Any thunderstorm that develops could produce dangerous cloud-to- ocean lightning.
12/830 PM.
A longer period, 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 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), and again late week into the following weekend. 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.
