21/357 AM.
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 today with increased humidity.
(tdy-Sun), 21/116 AM.
The upper level high centered around the four corners is bringing southerly, monsoonal flow to southern California. Already, a cluster of showers have formed southeast of Los Angeles County, and they may reach LA and Ventura Counties early this morning. Shower and thunderstorm chances last into this afternoon, focused over the interior mountains. There is a weak disturbance in southeast flow created by the position of the ridge aloft that could help initiate convection, and while the mid level moisture likely to remain over the area through tonight, the disturbance will shift out of the area by this 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.
Heights are forecast to be around 593-594 mb through Saturday before the high begins slowly advancing east, translating to above normal temperatures across the area. Surface gradients remain weak to moderate, with onshore gradients from LAX to Daggett peaking around +3 to +4 mb, and northerly gradients between KSMX and KSBA.
Expecting highs today between 97 to 104 for the interior, 90s for the coastal valleys, and 70s to 90 degrees for the coastal plains. In general, warm temperatures will continue through the weekend, with increased humidity due to moist monsoonal flow. Expect to see a bit of cooling today with the potential for some additional clouds, little change on Saturday, then a little uptick in temperatures on Sunday.
Gusty onshore winds are expected again for this afternoon and evening over the Antelope Valley and valley foothills, with gusts around 35 to 40 mph are possible for this afternoon and evening. There will be a weakening trend Saturday into early next week. Sub advisory level Sundowner winds will reoccur each evening through the weekend, possibly reaching advisory levels by Monday evening.
(Mon-Thu), 21/352 AM.
For the extended, a rather stagnant pattern is expected. At upper levels, southwestern California remains on the western edge of the high pressure, which shifts slightly from centered over the Texas New Mexico border to the Arizona New Mexico border. Not seeing significant changes in day to day heights, so warm weather should persist. The onshore LAX-DAG pressure gradient continues to trend weaker through Tuesday, but is forecast to strengthen somewhat mid-week.
Forecast-wise, only minor day-to-day changes are expected in the sensible weather. There will be some warming Tuesday-Wednesday, 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. There is a significant spread in the model gradients, so confidence is lower in terms of the strength of the onshore flow. 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 northerly Sundowner winds can be expected across southern Santa Barbara county each night, mainly around the Gaviota and Refugio areas. Tuesday evening currently has the best chance for wind advisories, but cannot rule out Monday or Wednesday evenings as well.
As for clouds and precipitation chances, the area will remain on the periphery of any monsoonal moisture. Upper level flow is forecast to shift more southwesterly as early as Saturday, 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 be patchy in areal coverage (especially south of Point Conception), but many coastal areas will continue to deal with night/morning stratus and fog.
21/1244z.
At 0353Z at KLAX, there was no marine layer. The top of the inversion was at 3100 feet with a temperature of 29 C.
High confidence in VFR TAFs for KPMD, KWJF, KBUR, KVNY, & KPRB.
Moderate confidence in KSBP and KSMX due to uncertainty in cig heights and visibility. Low confidence in KOXR and KCMA with a 40% chance of no low clouds, or CIGs that appear for a short time. If CIGs occur, LIFR/IFR conds are most likely.
Low to moderate confidence for the LA Coastal sites with a 30% chance of no low clouds, or periodic/short lived CIGs. If CIGs occur, cig heights and vis may be off one category.
There is a 20-30% chance of -SHRA at KPMD and KWJF from through 18Z.
KLAX, Low to moderate confidence in the 12Z TAF. Brief cigs are possible, with an early clearing time. There is a 30% chance of no low clouds.
KBUR, High confidence in TAF.
21/324 AM.
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. Gusts of 20-25 kt will be possible across the nearshore waters along the Central Coast through this evening, 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 today, 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 today. 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 from noon today to 2 AM PDT Saturday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PDT Sunday for zones 670-673-676. (See LAXMWWLOX).
