Upper level high pressure will result in hot weather across inland areas today. A trough dropping through the Pacific northwest and into the Great Basin will bring a cooling trend over the weekend. Some warming is expected early next week, with temperatures a few degrees above normal in most areas Monday through Wednesday. Cooler weather is expected Thursday as a trough moves into the West Coast.
(tdy-Sun), 22/353 AM.
The marine layer was just under 2000 feet deep early this morning, about the same as it was Thu morning at this time. Low clouds were widespread in all coastal and valley areas with the exception of the interior valleys of SLO County, the Cuyama Valley and the Santa Clarita Valley. However, expect some clouds to push into the Santa Clarita Valley for a couple of hours this morning, and clouds could even push into the Salinas Valley as well. Expect skies to clear by mid morning in the valleys and late morning across most of the coastal plain. However, some clouds could linger at some beaches into the afternoon.
Despite the rather deep marine layer, models continue to show warming at 950 mb along with a decrease in onshore pressure gradients this afternoon compared to Thu afternoon. Therefore, expect a few degrees of warming in the valleys and across interior sections of the coastal plain. There may be couple of degrees of warming in the mtns, interior valleys of SLO and SBA Counties and the Antelope Valley, with mostly minor changes in max temps near the coast. Although it will be hot inland, expect temps to remain below Excessive Heat Warning levels in the Antelope Valley. Temps could get close to advisory levels in the interior valleys of SLO County, but believe they will be just below those levels.
An upper low will drop southward through Idaho tonight and Saturday, and heights across the region will drop a bit. Onshore gradients should increase as well. An eddy circulation will develop across the inner waters, which would deepen the marine layer a bit. Overall though, expect a similar low cloud pattern tonight/Sat morning, with widespread clouds in all coastal and valley areas with the exception of the far interior valleys of SLO County and the Cuyama Valley. Max temps should be down a few degrees in most areas, except there will be minor changes near the coast. Cooling should be most pronounce in the warmer valley locations of L.A. and VTU Counties on Sat. Gusty winds in the Antelope Valley could approach advisory levels Sat afternoon.
The upper low will move into the Rockies Sat night and Sun, with a very weak broad trough extending into the forecast area. Models are showing a rather strong southerly surge will be located just east of the region Sat night and Sunday, which should help deepen the marine layer and bring cool marine all the way to the coastal slopes. Models show significant cooling at 950 mb on Sun. Expect plenty of night through morning low clouds, possibly to the coastal slopes, with slower clearing on Sunday. Clouds may well linger through the afternoon in coastal areas south of Pt Conception on Sunday. There should be significant cooling in all areas west of the mtns on Sunday, with the exception of portions of the Santa Ynez Valley and the Central Coast, where downslope southerly winds will provide warming in places like Lompoc and Vandenberg. There will be less cooling in the higher mtns and Antelope Valley.
(Mon-Thu), 22/407 AM.
Heights will rise a bit across the region on Monday, and onshore gradients will relax a bit, especially in the N-S direction. Expect faster clearing on Mon, and with some warming at 950 mb, there should be a few degrees of warming in the valleys and across interior sections of the coastal plain, generally to a bit above normal levels. It will remain hot in the mtns and deserts, with temps several degrees above normal. Do not expect too much change in the weather Tue and Wed, with night through morning low clouds in coastal and most valley areas, and mostly minor changes in max temps. A trough moving into the West Coast should bring cooling to most areas on Thu.
At 1000Z, the marine inversion at KLAX was based at 1900 feet. The top of the inversion was 4600 feet with a temperature of 28 degrees Celsius.
Overall for 12Z TAF package, low confidence in coastal TAFs, moderate confidence in valley TAFs and high confidence in desert TAFs. IFR conditions will dissipate across the valleys by late this morning. For coastal sites (especially south of Point Conception), confidence in CIG/VSBY forecast is low as clouds may or may not dissipate this afternoon.
KLAX, low confidence in 12Z TAF. There is a 50% chance that MVFR CIGs will not dissipate this afternoon. For tonight, low confidence in timing of flight category changes.
KBUR, moderate confidence in 12Z TAF. There is a 30% chance that IFR/MVFR conditions could persist to 18Z. For tonight, high confidence in return of flight restrictions, but low confidence in flight category (equal chance of IFR or MVFR conditions) and timing (could be +/- 3 hours of current 07Z forecast).
For the Outer Waters, high confidence in current forecast. Small Craft Advisory (SCA) level winds will continue through Saturday morning with a 60% chance of SCA level winds continuing into Saturday evening. Winds will remain below SCA levels Sunday and Monday. On Tuesday, there is a 70% chance of SCA level winds.
For the Inner Waters, high confidence in current forecast. For the waters north of Point Sal, winds and seas will remain below SCA levels through Tuesday.
For the waters south of Point Conception, winds and seas will remain below SCA levels through Tuesday. However, both tonight/Saturday morning and again Saturday night/Sunday morning, southeast winds are anticipated with a 50% chance of Southeast wind gusts between 10 and 15 kt.
Ca, NONE. PZ, Small Craft Advisory in effect until 9 AM PDT Saturday for zones 670-673. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Saturday for zone 676. (See LAXMWWLOX).