20/438 PM.
Night through morning marine layer clouds will be confined to the coastal areas, mainly along the Central Coast, through much of this week. Warm conditions are expected away from the immediate coast. Slight cooling is forecast Friday through the weekend.
(Thu-Sun), 20/821 PM.
A persistent ridge of high pressure remains more or less centered over the four corners region, with higher 500 mb heights at times extending westward over southern California. This will continue to maintain above normal temperatures across the area, and will also allow monsoonal moisture to move into the area from the southeast. Surface gradients remain weak to moderate, with onshore gradients from LAX to Daggett currently around +4 mb, and northerly gradients between KSMX and KSBA.
Highs today were between 100 to 105 for the interior, including Woodland Hills at 104 degrees. From the coast to coastal valleys highs were in the 70s to low 90s. Most areas have been between 5 to 10 degrees above normal. A few degrees of cooling are expected on Friday, with little change on Saturday, then an uptick on Sunday. The Heat Advisories in effect for interior sections will be allowed to expire this evening, however warm conditions will continue and the slight increase in monsoonal moisture will add to this effect.
Moderate gusty onshore winds are affecting the interior passes and canyons into the Antelope Valley this evening, with gusts up to around 35 mph. At the same time, the northerly gradients are causing Sundowner wind gusts to around 25 mph across southwest Santa Barbara County. High resolution models show the winds decreasing after 03Z, so expect that winds are near their peak now, with decreasing speeds through late in the evening.
Finally, there is a slight chance of showers and thunderstorms over portions of LA County, especially from the foothills/mountains to the Antelope Valley, and also over eastern interior Ventura County. The timing will be late this evening into Friday morning. There is a weak disturbance in southeast flow created by the position of the ridge aloft, and some monsoonal moisture moving into the area. While the mid level moisture likely to remain over the area through Friday night, the disturbance will shift out of the area by Friday afternoon so precip chances will decrease through the day (from 10-20 percent to around 10 percent). Any thunderstorms that may form will likely not produce much rain, but may produce gusty outflow winds and dry lightning. For Saturday/Sunday, the mid- level moisture will decrease and there will only be a 5-10% chance of afternoon showers and thunderstorms over the higher terrain.
(Mon-Thu), 20/112 PM.
For the extended, a rather stagnant pattern is expected. At upper levels, high will remain centered over Arizona and New Mexico through the period with little change in H5 heights over Southwestern California. Models continue to exhibit some differences at the surface with the ECMWF indicating weak diurnal gradients while the GFS indicates weak to moderate onshore gradients.
Forecast-wise, only minor day-to-day changes are expected in the sensible weather. There will be some slight cooling on Monday, but then some warming in the Tuesday-Thursday time frame. So, areas away from the coast will generally remain 5-10 degrees above seasonal normals. Depending on how things develop, there is a chance of some heat products being needed next week. Also, if the ECMWF is correct with the weak diurnal pressure gradients, then high temperatures could be warmer than currently forecast.
As for winds, there will continue to be some weak northerly offshore gradients. So, continued Sundowner winds can be expected across southern Santa Barbara county each night, mainly around the Gaviota and Refugio areas. It will not be out of the question to see some wind products for these northerly wind-prone areas sometime next week.
As for clouds and precipitation chances, the area will remain on the periphery of any monsoonal moisture. So, any convection will likely remain south and east of the district, but there will still be a 5-10% chance of afternoon convection over the mountains. The marine layer will likely continue to cause "fits" with regard to areal coverage, but many coastal areas will continue to deal with night/morning stratus and fog.
20/2331z.
At 2232Z at KLAX, the marine layer was 700 feet deep. The top of the inversion was at 2000 feet with a temperature of 29 C.
High confidence in VFR TAFs for KPMD, KWJF, KBUR, KVNY, & KPRB.
Good confidence in TAF for KSBP and KSMX as timing of flight cat changes may be off +/- 2 hours of forecast. Cig height may be off +/- 200 feet.
Fair confidence in TAF for KOXR and KCMA. There is a 30% chance of LIFR/IFR CIGs from 21/08Z-16Z.
For LAX and LGB, arrival and clearing times of CIGs may be off +/- 2 hours of current forecast. Cig height may be off +/- 200 feet. 30-40% chance of no low clouds.
There is a 30% chance of SHRA at KPMD and a 20% chance at KWJF from 21/09-16Z.
KLAX, Fair confidence in TAF. Arrival and clearing times of CIGs 006 (+/- 200 ft) may be off +/- 2 hours. There is a 40% chance of no low clouds. There is a 5-10% chc of -SHRA 21/05Z-11Z.
KBUR, High confidence in TAF. No wind issues expected.
20/647 PM.
Moderate to high confidence in periods of Small Craft Advisory (SCA) level winds (20-30 knots) across the Outer Waters each afternoon and evening into next week, thus a long duration SCA has been issued through Sunday morning. This may need to be extended into next week as we progress through the weekend. Local gusts of 20-25 kt will be possible across the nearshore waters along the Central Coast through Friday, then there is a moderate chance for more widespread wind gusts reaching 25 knots starting Saturday.
Aside from gusts of 20-25 knots reaching the western half of the Santa Barbara Channel each afternoon/evening starting Friday, 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 during the afternoon through early evening hours starting Friday. Winds may pick up in strength a bit early next week, with low to moderate chances that conditions become widespread enough to warrant an advisory.
Ca, NONE. PZ, Small Craft Advisory in effect until 9 AM PDT Sunday for zones 670-673-676. (See LAXMWWLOX).
