textproduct: Los Angeles

SYNOPSIS

07/258 AM.

Night through morning low clouds and patchy fog will be common over coastal areas and the coastal valleys through the weekend. Over the interior areas, hazardous heat will continue through this weekend, with near to above normal temperatures across the coasts and coastal valleys. Aside from the chance of a few mountain showers during the afternoon and evening hours through sunday, dry conditions will prevail.

LONG TERM (MON-THU)

07/257 AM.

The aforementioned ridge of high pressure will start to finally weaken over the area on Monday as a series of upper level troughs move into the Pacific Northwest down into NorCal. 500 mb heights will drop to at least 592 dam Monday through Thursday, and maybe even lower. At the same time, onshore flow will increase both to the north and the east becoming strongly onshore in both directions in the afternoons. The marine layer will respond to this and low clouds will likely begin to extend into the valleys. Look for slower than normal clearing and some west facing beaches may see only limited clearing each afternoon and evening.

The combination of a deeper marine layer, stronger onshore flow, and falling heights will bring 2 to 3 degrees of cooling each day Monday through Thursday. Max temps will approach normals on Tuesday and then most areas will see below normal max temps on Wednesday and Thursday, with valley temps in the mid 80s to lower 90s.

PWs will remain elevated through the period, however. In combination with warmer than normal ocean temperatures off the immediate coast, conditions will continue to feel a little stickier than normal. It will also keep overnight lows a little warmer than normal. The region will remain on the fringe of the monsoonal moisture through at least Wednesday, with the elevated moisture and increased instability keeping the low chance (10 to 15 percent) of afternoon mountain convection going.

Additionally, the strong onshore flow to the east will produce near advisory level wind gusts across the western Antelope Valley and the western foothills each afternoon and evening.

AVIATION

07/1258Z.

At 1212Z at KLAX, the marine layer was 1100 feet deep. The top of the inversion was at 2400 feet with a temperature of 25 C.

High confidence in VFR TAFs for KPRB, KBUR, KVNY, KPMD & KWJF.

Low to moderate confidence in remaining TAFs through 17Z Fri and after 06Z Sat due to mid level moisture and warm sea surface temperatures disrupting the formation of the Marine Layer. Timing of flight cat restrictions may be off +/- 3 hours, and CIG heights by +/- 200 ft. Cigs may scatter and reform frequently, with a 40% chance of VFR conds persisting at KSMO and KLAX through this morning, and IFR conds at KLGB through 16Z.

KLAX...Low confidence in TAF through 16Z, then moderate confidence. There is a 40% chance VFR conds prevail through this morning. Intermittent CIGs (009-012) likely after 06Z Fri. No significant east wind component expected.

KBUR...High confidence in VFR TAF. No wind issues expected.

MARINE

07/1257 AM.

Winds and seas are expected to remain below Small Craft Advisory (SCA) criteria into this weekend, with the exception of northwest winds locally gusting to 20-25 knots in typically windy areas around and to the south of Point Conception each afternoon and evening through Saturday. There is a 20-30% chance of SCA level NW winds across the outer waters northwest of the Channel Islands Sunday afternoon into early Monday morning.

Dense fog may affect portions of the coastal waters each night through morning, especially this weekend across the waters north and west of Point Conception.

LOX WATCHES/WARNINGS/ADVISORIES

CA...Extreme Heat Warning in effect until 8 PM PDT Sunday for zones 38-377-381>383. (See LAXNPWLOX). Heat Advisory in effect from 10 AM Saturday to 8 PM PDT Sunday for zones 88-342-343-348-349-351-352-356>358-367>374-548. (See LAXNPWLOX). Heat Advisory in effect until 8 PM PDT Sunday for zones 344-345-353-375-376-378>380. (See LAXNPWLOX). PZ...NONE.