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-Thu), 18/953 AM.
***UPDATE***
Temperatures will warm up by a few degrees today, bringing temperatures into the 70s and 80s near the coast, and 90s to low 100s away from the coasts. These high temperatures away from the coasts are around 3 to 7 degrees above normal for this time of year. Gusty W-NW winds will impact southwest Santa Barbara County, the I-5 Corridor, and the western Antelope Valley once again this afternoon through evening, but expected to remain below advisory levels. Night through morning marine layer clouds are expected to reoccur along the Central Coast, but struggle to form for the areas south of Point Conception tonight.
Forecast looks on track, and no changes were needed for the morning update.
***From Previous Discussion***
Very little change to the forecast thinking for the next 7 days. A large and very warm upper high stretching from TX to Srn CA will remain in place through the period. Hgts will be around 594 to 595 dam. SFC gradients will also be fairly static. The W/E gradient will be weakly onshore during the mornings and moderately onshore during the afternoons, while the N/S gradient will be near neutral in the mornings becoming weakly onshore in the afternoons.
There will not be much of an eddy to generate low clouds south of Pt Conception so there will only be patchy morning low clouds at most across the VTA/LA csts as well as the SBA south coast. The Central Coast will see a fairly robust marine layer cloudy pattern each morning as the onshore flow up there will be stronger.
Higher than normal hgts, weaker than normal onshore flow and 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 vlys, lower mtn elevations and far interior will range from 95 to 105 degrees or 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 highs and lows will bring Moderate HeatRisk to many areas. Heat advisories start later this morning and continue through Thursday for the San Fernando, San Gabriel, and Santa Clarita Valleys as well as the lower mtn elevations. The VTA county valleys, and the Santa Monica mtns will also need heat advisories starting Wednesday. Additionally, there is a small chance that heat advisories will need to be extended into 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 chc of isolated advisory level (45 mph) gusts in the Gaviota area.
(Fri-Mon), 18/159 AM.
All medium range mdls 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. Hgts fall a to 592 dam and there will be an increase in mid and high level clouds as well. These two things will likely bring 1 to 3 degrees of cooling. Future shifts will have to weigh the opposing effects of the cooler temps vs the increased humidities and consider extending the heat advisories for one more day. Right now this appears to be about a 30 percent chc.
The upper high will shift slowly eastward Saturday through Monday and hgts will fall to about 590 dam. The onshore gradients do not change much so the pattern of plenty of morning low clouds over the Central Coast and minimal low clouds for areas south of Pt Conception should continue. 1 to 2 degrees of cooling each day should bring most max temps down to a few degrees under normal by Monday.
18/1618z.
At 1600Z at KLAX, the marine layer was 600 feet deep. The top of the inversion was 3100 feet with a temperature of 25 degrees Celsius.
For 18Z TAF package, high confidence in KBUR, KVNY, KPMD, KWJF and KSBA.
For KSBP, KSMX and KPRB, timing of flight category changes could be +/- 2 hours of current forecasts.
For all other TAFs, there is a 30% chance of IFR conditions 08Z-17Z.
KLAX, Moderate confidence in 18Z TAF. There is a 30% chance of IFR conditions 08Z-17Z. No significant easterly wind component is expected.
KBUR, High confidence in 18Z TAF as VFR conditions are expected through the period.
18/708 AM.
For the Outer Waters, high confidence in current forecast. Small Craft Advisory (SCA) level winds are expected through Saturday. Building short-period seas will also affect the Outer Waters, rising to the 6-9 foot range.
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 Saturday, 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. Then there is a 30-40% chance of SCA level winds during the afternoon to evening hours Wednesday through Saturday. 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 from 3 PM this afternoon to 3 AM PDT Wednesday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Wednesday for zones 670-673-676. (See LAXMWWLOX).
