textproduct: Los Angeles

SYNOPSIS

19/245 AM.

Night through morning marine layer clouds will be confined to the coastal areas, mostly north of Pt Conception, through much of this week. Warmer and drier conditions are expected away from the immediate coast, with the heat peaking today and Thursday, when moderate heat risk is expected in warmest locations.

LONG TERM (SUN-WED)

19/159 PM.

For the extended, 12Z models continue to exhibit decent synoptic agreement. Main feature of note will be the upper level high over the desert Southwest. Through the extended period, it is forecast to just meander around the 4-Corners area.

Forecast-wise for the extended period, main focus will continue to be the heat. With this continued synoptic pattern, temperatures will remain noticeably above seasonal normals through the period. The one thing to watch will be the surface pressure gradients. The GFS indicates weak to moderate onshore gradients through the period. Conversely, the ECMWF actually indicates some weak offshore gradients by the Tuesday/Wednesday time frame. If the ECMWF is correct then conditions will be warmer than currently forecast which will be watched closely.

As for winds, there will be a gradual increase in northerly winds, in the usual locations (Santa Ynez Range and I-5 Corridor), through the period as northerly offshore gradients increase. As for any easterly offshore winds, the ECWMF forecast of weak offshore gradients would result in some northeasterly winds, but nothing approaching advisory concerns.

This pattern will limit the areal coverage of marine layer stratus and fog through the period, with the best coverage likely across the Central Coast. As the upper high meanders about, there will be the continued potential for some incursions of monsoonal moisture. So, there will be a 5-10% chance of mountain showers/thunderstorms Sunday and Monday with about a 10-15% chance on Tuesday and Wednesday.

AVIATION

19/2325Z.

At 2250Z at KLAX, the marine layer was 800 feet deep. The top of the inversion was at 3000 feet with a temperature of 29 C.

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

Good confidence in TAF for KSBP & KSMX, timing of flight cat changes may be off +/- 2 hours of forecast. Min cig height may be off +/- 200 feet.

Low confidence in remaining TAFs, especially 06Z-18Z. There is a chance for low clouds at KSBA (15%), KOXR (30%), KCMA (20%), KSMO (50%), KLAX (60%), and KLGB (60%). Low clouds would likely develop over LA County between 08Z-12Z, then KOXR/KCMA/KSBA possible 10Z-16Z. Lower confidence in cig heights, but likely between 003-008, except higher at KLGB. Lowest heights possible at KOXR/KCMA/KSBA.

KLAX...Low confidence in TAF 06Z-18Z, good confidence otherwise. There is a 40% chance of no low clouds tonight, but if they do occur, likely BKN005-010 arriving between 06Z-12Z. Any east wind component is expected to remain below 8 kt.

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

MARINE

19/722 PM.

Moderate confidence in periods of Small Craft Advisory (SCA) level winds (20-30 knots) across the Outer Waters each afternoon and evening into next week, with lowest chances Thursday (40-60% chance of SCAs to be issued). Local gusts of 20-25 kt will be possible across the nearshore waters along the Central Coast through tomorrow, then a moderate chance for more widespread wind gusts reaching 25 knots Friday-Sunday.

Aside from gusts of 20-25 knots reaching the western half of the Santa Barbara Channel this evening, and again each afternoon/evening over the weekend, widespread SCA conditions are not likely across the nearshore waters south of Point Conception. Localized gusts near 20 knots are possible near Point Dume and the San Pedro Channel at times.

LOX WATCHES/WARNINGS/ADVISORIES

CA...Heat Advisory in effect until 8 PM PDT Thursday for zones 38-88-343>345-351-353-371>373-375-376-379-380-548. (See LAXNPWLOX). PZ...Small Craft Advisory in effect until 3 AM PDT Thursday for zones 670-673-676. (See LAXMWWLOX).