17/832 PM.
Temperatures are expected to change little over the next few days, and most areas will be near normal. Morning low clouds and fog will return to many coastal areas each night to morning period through early next week. A warming trend is expected by the middle of next week as upper level high pressure builds into the area while onshore gradients weaken.
(tdy-Mon), 18/325 AM.
The 500 mb heights will remain fairly similar over the region (around 589-592 dam) through Monday as a large/wide high pressure system hangs out over the Utah/Colorado/Wyoming area. Meanwhile, Tropical Storm Elida, currently about 1300 NM South of Point Conception, is forecast to move northward, well off the coast to the west, and rapidly weaken. Upper level flow will shift from the S today to more SE on Sunday with Elida's movements and slight shifts in the aforementioned high pressure system.
Sunday afternoon into late Monday morning, some of the moisture from Elida could reach the Central Coast, with the most likely outcome resulting in an increase in mid to high clouds. However, there is a 5-10 percent chance of a shower for the Central Coast Sunday. At the same time, slight shifts in the high pressure system to the NE, will help bring some monsoonal moisture from the SE Sunday afternoon through Monday. This will result in an influx of mid to high level clouds across the region, as well as a 5-10 percent chance of a shower or thunderstorm focused over Ventura and L.A. County interior Mountains, mainly on Monday.
At the surface, little change in the pressure gradients will result in similar marine layer coverage each night. The little change in marine layer clouds, pressure gradients, and 500 mb heights will mean little change in temperatures through the weekend. Temperatures will be near normal, with highs in the 70s to low 80s for the coast, mid 80s to mid 90s for the valleys and lower mountains/foothills, and 90s to around 100 for the deserts.
As for winds, Sub-advisory SW winds 25 to 40 mph can be expected each afternoon/evening across the Antelope Valley/adjacent foothills. Localized terrain enhancement could result in a few areas gusting to 45 mph (i.e Lake Palmdale).
(Tue-Fri), 18/236 AM.
The large western U.S upper level high pressure center is forecast to drift South from Colorado on Monday to the area around New Mexico and the northern Texas panhandle by Thursday. Southwestern CA will continue to be on the western periphery of this large upper level high, with 500 mb heights slowly increasing to 592-594 dam during the extended period.
As a result, the flow aloft will mostly be from the SE, bringing monsoon moisture into the region through much of the week. Precipitable Water (PWATs) values are forecast to be 1.25 to 1.50 inches through much of the week for areas south of Point Conception and through mid-week for north of Point Conception. These PWATs are about 150 percent of normal for this time of year. Although the deepest moisture and is forecast to remain east of L.A. County during the extended period, it does look like the best chance of afternoon convection will come Wednesday and Thursday over the mountains of at least Ventura and L.A. Counties. However, right now chances remain around 10% for thunderstorms across the mountains, and are too low to include in the official forecast at this time. As we draw closer to early next week, we should have a better idea of the chance and extent of afternoon convection for the middle of next week.
Otherwise, it look like varying amounts of night and morning coastal low clouds and fog will prevail during the extended period, with a warming trend through the middle of next week. Moderate to high heat risk may expand into Wednesday or Thursday as pressure gradients weaken and maybe turn lightly offshore in the mornings with the potential for 500 mb heights building to 594-596. There is a moderate (50-60 percent chance) that at least Heat Advisories will be needed in some areas, including potentially near the coast.
18/1307z.
At 1218Z at KLAX, the marine layer was 1800 ft deep. The top of the inversion was at 3400 ft with a max temperature of 23 C.
High confidence in VFR TAFs for desert airfields (KPMD & KWJF).
Low to moderate confidence in remaining TAFs. Timing of CIG/VSBY restrictions may be off +/- 2.5 hours and flight minimums off by one category.
KLAX, Low to moderate confidence in TAF. Arrival and clearing times of CIGs near 012 (+/- 300ft) and within +/- 2.5 hours of current forecast. There is a 30% chc east wind component reaches 7-8 knots between 08Z-16Z both Sat and Sun.
KBUR, High confidence in TAF.
18/1247 AM.
Conditions are expected to remain below Small Craft Advisory (SCA) levels through Monday except for localized SCA level northwest wind gusts across the Outer Waters more than 20 NM from shore. Northwest winds will begin to strengthen Tuesday to SCA levels by late Tuesday afternoon and last through late in the week.
A series of moderate period southerly swells will move through the waters late Sunday through much of next week which may impact south facing harbors, including the Port San Luis area.
18/1208 AM.
Over the eastern Pacific, Tropical storm Elida is forecast to move to the north and west well off the Baja coast. Another tropical disturbance is expected to develop in the same area and follow a slightly more westerly track along 20 N Latitude. Both systems will produce moderate period southerly swells. High Surf Advisories and Beach Hazards Statements have been issued across Southwest California from Sunday evening through Tuesday night.
The secondary system on the heels of Elida and an incoming long period southern hemisphere south swell arriving later next week will contribute to continued and potentially more hazardous beach conditions into the following weekend. Additional High Surf Advisories and/or Beach Hazards Statements are likely next week.
Ca, High Surf Advisory in effect from 5 PM Sunday to 11 PM PDT Tuesday for zones 87-354-362-366. (See LAXCFWLOX). Beach Hazards Statement in effect from Sunday afternoon through Tuesday evening for zones 340-346. (See LAXCFWLOX). PZ, NONE.
