20/306 AM.
Night through morning marine layer clouds will be confined to the coastal areas, mostly north of Pt Conception, through much of this week. Warm conditions are expected away from the immediate coast slight cooling is forecast Friday through the weekend.
(tdy-Sun), 20/112 PM.
Overall, 12Z models in good synoptic agreement through the short term period. At upper levels, high will "wobble" around the 4 Corners through Friday, before drifting southeast across New Mexico. At the surface, moderate onshore flow will continue to the east with some weak northerly offshore flow.
Main concern in the short term will continue to be the heat. Based on current trends, today will be the hottest day in the short term period. So, current HEAT ADVISORIES for interior sections still looks good through this evening. For Friday, there is expected to be some slight cooling across most area with some slight decrease in thicknesses and more extensive mid-level clouds. There will be a slight uptick in humidity on Friday which will counteract the slightly cooler temperatures. For Saturday and Sunday, near persistent temperatures are expected with most areas away from the coast remaining 5-10 degrees above seasonal normals. Looking at Heat Risk grids, the moderate areas decrease in areal coverage on Friday. So, at this time, will not extend the HEAT ADVISORIES through Friday. Although no additional advisories are expected, residents should still exercise caution this weekend in this above normal heat.
Secondary concern in the short term period will be the possibility of some showers and thunderstorms. With SE-S flow aloft, there will be an increase in PWATs tonight and Friday. Models indicate a weak disturbance moving across Ventura/LA counties late tonight which could generate some isolated showers and thunderstorms. By Friday afternoon, this disturbance will be out of the area, but there will still be enough moisture around to warrant a slight chance of afternoon showers and thunderstorms over the eastern San Gabriel Mountains and the northern Ventura county mountains. Any thunderstorms that may develop will likely not produce much rain, resulting in gusty outflow winds and dry lightning as the main hazards. 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.
Finally with respect to winds, there will continue to be some northerly offshore gradients through the weekend. So, there will be locally gusty north winds across the western half of the Santa Ynez Range, but any advisory-level winds will remain localized around the Gaviota and Refugio areas.
(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.
20/1730z.
At 1615Z at KLAX, the weak marine layer was 1200 feet deep. The top of the inversion was at 2900 feet with a temperature of 28 C.
High confidence in VFR TAFs for KPMD, KWJF, KBUR, and KVNY.
Good confidence in TAF for KPRB with a 15% chance for LIFR conds after 10Z.
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.
Moderate confidence in TAF for KOXR and KCMA as timing of flight cat changes may be off +/- 3 hours. 30% chance for no low clouds.
Low confidence in TAFs for KSBA, KLAX, KLGB, and KSMO, with a 40-50% chance for VFR conds to prevail, highest at KSBA/KSMO. Timing of arrival of cigs may be off +/- 3 hours.
All LA/Ventura county sites have a 15-20% chance of SHRA/TSTM from 03Z-15Z.
KLAX, Low confidence in TAF after 21/05Z with good confidence before. There is a 40% chance of no low clouds. Timing of arrival of cigs may be off +/- 3 hours. 20% chance for cigs 003-004. 15-20% chance of SHRA/TSTM from 03Z-15Z. Any east wind component is expected to remain below 8 kt.
KBUR, High confidence in CAVU TAF. No wind issues expected.
20/1152 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. Local gusts of 20-25 kt will be possible across the nearshore waters along the Central Coast today, then there is a moderate chance for more widespread wind gusts reaching 25 knots starting Friday.
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.
Ca, Heat Advisory in effect until 8 PM PDT this evening for zones 38-88-343>345-351-353-371>373-375-376-379-380-548. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 9 AM PDT Sunday for zones 670-673-676. (See LAXMWWLOX).
