textproduct: Los Angeles

SYNOPSIS

09/733 PM.

A gradual cooling trend is expected this week, with cooler than normal temperatures expected across much of the area by Tuesday. More robust marine layer cloud coverage is expected, expanding into most coastal valleys by midweek. There remains a low chance of thunderstorms each afternoon through the week, with the highest chances over the mountains through Tuesday.

LONG TERM (THU-SUN)

09/145 PM.

The weak trough off the coast will remain in place into the weekend with heights slowly rising Friday into the weekend. However, there is some disagreement amongst models as to how progressive the increase in heights will be, and to what extent. What does appear likely is that high temperatures are likely to remain below seasonal normals through the extended period, although the slight warming trend Friday into the weekend will bring maximum temps closer to normal. As soon as next Sunday is when we start to see significant differences between the GFS and Euro. The Euro favors another, potentially slightly stronger, trough swinging down through California, bringing another round of cooler temperatures into next week. Meanwhile, the GFS favors the pattern transitioning into a more zonal flow with slightly increasing 500 mb heights.

Southwest flow aloft will help aid the increase of onshore flow region-wide, with enhanced southwest to west winds. Increasing onshore flow over the interior will bring a moderate chance for wind advisories Thursday, lower chances Friday. Marine layer coverage is expected to be expansive, with most folks across the coastal valleys waking up to cloudy skies. The coverage should shrink somewhat this weekend, but still expecting some coastal valley communities to see marine layer clouds into the weekend. Similar to midweek, some immediate coastal areas may not see much in the way of marine layer clearing Thursday due to that enhanced onshore flow.

As mentioned in the short term, the threat of thunderstorms due to the upper level trough along the coast potentially drawing in leftover monsoonal moisture will continue through Friday (5-15% chance), highest chances along the Central Coast. Confidence is quite low in this convective potential, but there is a signal for elevated MUCAPE values, especially Wednesday and Thursday. We will continue to monitor as we get closer.

AVIATION

10/0617Z.

At 0512Z at KLAX, the marine layer was 800 feet deep. The top of the inversion was at 2700 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, with lowest confidence for coastal sites south of KSMX. Cigs may be intermittent through the night, and timing of flight cat changes may be off by 3 hours.

KLAX...Low to moderate confidence in TAF especially tonight into Mon morning. Ocnl period of SCT conds are likely through 15Z. No significant east wind component expected.

KBUR...High confidence in VFR TAF.

MARINE

09/735 PM.

Conditions will remain below Small Craft Advisory (SCA) across all of the southwestern CA coastal waters through Friday night.

BEACHES

09/1239 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 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...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.