textproduct: Los Angeles

SYNOPSIS

08/657 PM.

Night through morning low clouds and patchy dense fog will affect some coastal areas and coastal valleys through the weekend. Away from the coast, hazardous heat will continue through this weekend, with near to above normal temperatures around the beaches. Other than a small chance of mountain showers during the afternoon and evening hours through early next week, dry conditions will prevail.

LONG TERM (WED-SAT)

08/122 PM.

Heights will continue to fall during the extended period as the ridge of high pressure weakens and shifts to the east. An upper level low pressure system is expected to develop off the coast by Wednesday or Thursday, and potentially linger into Friday. 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 cooling Tuesday through Thursday. Maximum temps will largely be below normal by Wednesday and Thursday.

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 more humid 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. In the Thursday-Friday time frame, medium-range models continue to indicate the potential for an upper low to develop off the Central California Coast, east of which large-scale ascent and convective chances could modestly increase sometime between Thursday and Friday. At this time, the convective chances are still in the 5-15 percent range across the area, with the highest chances focused across the Central Coast. Latest ECMWF ensemble date showing a weak convective signal in that Thursday-Friday time frame with a slightly uptick in MUCAPE values. If convection were to develop, the main concern would be the potential for isolated dry lightning strikes with minimal rainfall, adding to the fire weather threat. This will need to be monitored closely especially considering the dry fuels in place after this prolonged heatwave.

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. Gusty sundowner winds will also be possible early next week in southern Santa Barbara County.

AVIATION

08/2339Z.

At 1242Z at KLAX, the marine layer was 800 feet deep. The top of the inversion was at 2200 feet with a temperature of 30 C.

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

Low to moderate confidence in remaining TAFs after 04Z Sun. Mid-level moisture and warm SSTs will disrupt the formation of Marine layer. This will likely result in intermittent CIGs especially for KLAX, KSMO, & KLGB. CIG heights accurate within +/- 200 ft of current forecast.

KLAX...Fair confidence in TAF. Intermittent CIGs (007-010) possible 04Z-15Z Sun. IFR CIGs may return around 10/05Z. No significant east wind component expected.

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

MARINE

08/727 PM.

Small Craft Advisory (SCA) NW winds will continue across the waters around Point Conception down south and west to San Nicolas Island through this evening (PZZ673/676). Otherwise, winds and seas are expected to remain largely below SCA levels across the coastal waters through at least Wednesday night.

Dense fog may affect portions of the coastal waters each night through morning this weekend and possibly into early next week.

BEACHES

08/114 PM.

High astronomical tides are expected to affect low-lying beaches south of Point Conception with the possibility of minor coastal flooding starting with the evening high tide Monday and continuing through at least Wednesday. As a result, a Coastal Flood Advisory has been issued.

Predicted tide heights of up to 7.5 feet are expected between about 8 and 10 PM each evening. These tides, combined with a small increase in a long-period southerly swell, could result in minor flooding of sea water around the time of high tide over low-lying coastal areas such as parking lots, beaches, and walkways. Beaches most susceptible to potential minor coastal flooding issues include those around Point Dume and near Long Beach.

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 until 8 PM PDT Sunday for zones 88-342>345-348-349-351>353-356>358-367>376-378>380-548. (See LAXNPWLOX). Coastal Flood Advisory in effect from 6 PM Monday to midnight PDT Wednesday night for zones 349-350-354-362-366. (See LAXCFWLOX). PZ...Small Craft Advisory in effect until midnight PDT tonight for zones 673-676. (See LAXMWWLOX).