textproduct: Los Angeles

SYNOPSIS

17/816 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.

LONG TERM (TUE-FRI)

17/1224 PM.

The large western U.S upper level high center is forecast to drift S from Colorado on Mon to the area around New Mexico and the northern Texas panhandle by Thu. Southwestern CA will continue to be on the western periphery of this large upper level high, with H5 heights slowly increasing to 592-594 dam during the extended period.

The flow aloft will mostly be from the SE with monsoonal moisture expected to continue to push into the area. Precipitable water values are forecast to be in the 1.25 to 1.40 inch range for the most part which is about 150 to 160 percent of normal for this time of year. Although the deepest moisture and instability 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. For now, there is only a minimal chance of showers late Thu in the fcst for the eastern L.A. County mtns. Otherwise, there is a non-zero chance (10%) for a thunderstorm to develop in the mtns especially Wed and Thu. 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 thru 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 potential near the coast.

AVIATION

18/0027Z.

At 2300Z at KLAX, the marine layer was 1200 ft deep. The top of the inversion was at 3000 ft with a max temperature of 24 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) should be accurate within +/- 2.5 hours of current forecast. There is a 30% chc east wind component reaches 7-8 knots between 18/08Z-16Z.

KBUR...Moderate confidence in TAF. There is a 30% chance of IFR CIGs from 18/12Z-18Z. Otherwise, VFR conditions with no wind issues are expected.

MARINE

17/814 PM.

Small Craft Advisory (SCA) northwest winds (15-25 kt) and seas will impact the waters beyond 20 NM from shore through tonight. Localized gusts to 25 kt may occur in the far western portion of the Santa Barbara Channel through around midnight. Conditions are then expected to remain below 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 and SCA conditions are expected to occur from around Tuesday night 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.

BEACHES

17/801 PM.

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.

LOX WATCHES/WARNINGS/ADVISORIES

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...Small Craft Advisory in effect until 9 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Saturday for zones 670-673-676. (See LAXMWWLOX).