18/723 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 through Thursday, when moderate heat risk is expected in warmest locations.
(tdy-Fri), 18/227 PM.
Very little change in the forecast today. The large and very warm upper level high continues to sit over the area, stretching all the way to Texas. 500 mb heights will remain around 595/594 dam into Friday (higher than normal for this time of year), with minimal changes in the surface pressure gradients with weak to moderate onshore trends during the afternoons.
Night through morning marine layer clouds will continue to spread into the Central Coast each night, but south of Point Conception, marine layer clouds will struggle to form through at least Thursday due to a combination of the warm sea surface temperatures, lack of an eddy to bring clouds in from the south, and weak onshore flow. If clouds do form south of Point Conception, they will remain confined to the coastal areas due to the shallow marine layer. Periods of high level clouds will stream over the area, but skies will mainly be partly cloudy at most during the afternoons.
Higher than normal heights, weaker than normal onshore flow, and the sunny skies will all combine to bring 2 to 4 degrees of warming today, 1 to 3 degrees on Wednesday and another 1 to 2 degrees on Thursday for areas south of Pt Conception (The Central Coast will cool some as the sea breeze increases). Max temps in the valleys, lower mountain elevations, and far interior will range from 95 to 105 degrees, which is 4 to 8 degrees over normal. The strong inversion, much warmer than normal sea surface temps and the warm atmosphere will also bring above normal overnight low temps to much of the area. Most coast/valley locations will only have lows in the upper 60s to lower 70s.
The combination of warmer than normal high and low temps will bring Moderate HeatRisk to many areas through at least Thursday. Heat advisories are in effect through Thursday for the San Fernando, San Gabriel, and Santa Clarita Valleys as well as the lower mountain elevations. There is a small chance that advisories need to be extended into the Santa Monica Mountains and Ventura County Valleys starting Wednesday. Additionally, there is a 10-20 percent chance that heat advisories will need to be extended into Friday for portions of the area, but it depends on the balance of the humidities and cooling temperatures on Friday (See long term discussion for more details about Friday). Please see the product LAXNPWLOX for all of the details.
Gusty north winds will affect southwest Santa Barbara County and the I-5 corridor near the Grapevine each evening and overnight. The gusts should almost all be below advisory levels with only a chance of isolated advisory level (45 mph) gusts in the Gaviota area tonight.
(Sat-Tue), 18/236 PM.
All medium range models agree that the upper high will shift to the four corners area by Friday, which will set up SE monsoon flow over Southern CA. This SE flow will allow Precipitable Water values to approach 1.5" across southern L.A. County starting Friday afternoon. This influx of moisture will allow for a 5-10 percent chance of showers or thunderstorms to to develop over the LA County mountains and Antelope Valley Friday afternoon through the weekend.
The upper high will shift slowly eastward Saturday through Monday and hgts will fall to 592 dam on Saturday and about 590 dam by 18/2321z. At 2238Z at KLAX, the marine layer was 900 feet deep. The top of the inversion was at 1900 feet with a temperature of 29 C. High confidence in VFR TAFs for KPMD, KWJF, KPRB, KBUR, KVNY, and KSBA. For KSBP & KSMX, timing of flight category changes could be +/- 2 hours of current forecast. (Late tonight through early tomorrow morning) Chances for IFR conditions: KOXR/KCMA/KSMO/KLAX (20%), KLGB (30%). KLAX, Moderate confidence in TAF. There is a 30% chance of IFR conditions 10Z-17Z. No significant easterly wind component is expected. KBUR, High confidence in VFR. No wind issues expected. 18/1209 PM. For the Outer Waters, high confidence in current forecast. Small Craft Advisory (SCA) level winds are expected today through Sunday. For the Inner Waters north of Point Sal, moderate confidence in current forecast. Through Thursday, there is a 30-40% chance of SCA level winds in the afternoon and evening hours. For Friday through Sunday, there is a 50-70% chance of SCA level winds in the afternoon and evening hours. For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. For the western half of the Santa Barbara Channel, there is a 60% chance of SCA level winds late this afternoon and tonight. For Wednesday through Sunday, there is a 30-40% chance of SCA level winds during the afternoon to evening hours. Elsewhere south of Point Conception, high confidence in winds and seas remaining below SCA levels through Saturday. 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 Wednesday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Thursday for zones 670-673-676. (See LAXMWWLOX). Aviation
Marine
Watches, Warnings, Advisories
