textproduct: Los Angeles

SYNOPSIS

09/205 AM.

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 into this evening, with near to above normal temperatures around the beaches. Starting Monday, a gradual cooling trend will last through the week, with near to below normal temperatures by late week. 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)

09/229 AM.

The ridge of high pressure will finally move eastward and weaken as an incoming trough starts to move into the West Coast on Tuesday into Wednesday. At the same time, an upper level low/disturbance will sit off the Central Coast mid-week, getting absorbed by the trough and potentially lingering into late Friday. At the same time, onshore flow will increase both to the north and the east becoming strongly onshore in both directions during the afternoons. The increased onshore flow will allow the marine layer to push into the valleys each night through morning. Slower than normal clearing skies will be likely as the onshore flow strengthens, 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 this week in southern Santa Barbara County.

AVIATION

09/1745Z.

At 1722Z at KLAX, the marine layer was 900 feet deep. The top of the inversion was at 2800 feet with a temperature of 27 C.

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

Low to moderate confidence in remaining TAFs after 03Z Mon, with lowest confidence for sites south of Point Conception. Mid-level moisture and warm SSTs will likely continue to disrupt the formation of marine layer clouds S of Point Conception. There is a 40%-50% chance that conds remain VFR at KLAX, KSMO, and KLGB through Mon morning. Timing of flight cat changes may be off by 3 hours, and any CIG heights should be accurate within +/- 200 ft of current forecast.

KLAX...Low to moderate confidence in TAF especially tonight into Mon morning. There is a 50% chance that conds remain VFR through the fcst period. Small chance (20%-30% chance) of intermittent CIGs (007-010) after 04Z Mon. Better chance (50%) of these cigs 14Z-17Z Mon. No significant east wind component expected.

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

MARINE

09/808 AM.

Conditions will remain below Small Craft Advisory (SCA) across the coastal waters through Thursday night. The only exception is a 20% chance of SCA level NW winds across the extreme northwest portion of the outer waters north of Point Sal (PZZ676) this afternoon and evening.

Dense fog may affect portions of the coastal waters through this morning and possibly the next night through morning periods through Tuesday.

BEACHES

09/808 AM.

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 on 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 this evening for zones 38-377-381>383. (See LAXNPWLOX). Heat Advisory in effect until 8 PM PDT this evening 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...NONE.