06/311 AM.
Temperatures will cool today and Tuesday with increasing onshore flow and areas of low clouds and fog near the coast. Warmer temperatures will return briefly Wednesday before a sustained cooling trend takes us into the weekend with a chance of rain.
(tdy-Thu), 06/253 PM.
Weak upper level trough moving into region today, bringing increased onshore flow and a cooling trend, most noticeable across coastal and coastal valley areas. The bulk of the high level clouds have shifted south of the forecast area today. Most coast and valleys will drop at least 3-6 degrees from yesterday's highs and near the beaches the drop could be as much as 10 degrees.
Onshore pressure gradient are increasing this morning and will further increase across the region this afternoon, when LAX- Daggett pressure gradient could reach +5 to +6 mb range. This will generate increasing onshore winds across the interior this afternoon/evening, and this trend will continue the next few days. Also expecting northwest pressure gradients to increase tonight and the next few nights, with Santa Barbara-Santa Maria expected to reach around -4 mb. A wind advisory has already been posted for later today into tonight for the western Santa Ynez mountains and southwest Santa Barbara coast, with gusts in the 35 to 50 mph range. Winds will be strongest tonight from Gaviota to San Marcos Pass. A wind advisory may need to be expanded to include the I-5 corridor and western Antelope Valley foothills as early as tonight, with increasing probability for Tuesday night. In addition, the sundowner winds are expected to shift eastward into the eastern Santa Ynez range by Tuesday night, which may require wind advisories for that region as well. North gradients will peak Wednesday, and with an increase in support aloft and subsequent downsloping south of the mountains, temperatures are expected to rise anywhere from 3 to 6 degrees, making Wednesday the warmest day of this week.
(Fri-Mon), 06/255 PM.
Light rain will be possible starting Thursday night, particularly for areas north of Point Conception. By Friday, the cold upper low will enter the region, bringing cooler temperatures, rain and thunderstorms chances. Due to the cold and unstable nature of the storm, thunderstorms will be possible. Most rain is likely to fall between Friday and Saturday, with lingering chances for showers and thunderstorms on Sunday. Rain totals with this storm are likely to be between 0.25 inch and 1.0 inch, but locally up to 2 inches will be possible across some mountains and areas impacted by thunderstorms. Ensemble means over the last couple days have been fairly consistent with regards to average rain amounts and timing. However there remains a lot of spread in the exact rain totals between ensemble members, which suggests uncertainty in rain totals and a showery rain pattern that would yield variable rain amounts across the region. By early next week, a gradual warming and drying trend is expected, however at this point there is no strong signal for another storm or heatwave.
06/1808z.
At 1634Z at KLAX, the marine layer was 1200 ft deep. The top of the inversion was at 1900 ft with a temperature of 18 C.
Overall, moderate confidence in 18Z TAF Package. Timing of CIG/VSBY restrictions may be off +/- 2 hours and flight minimums by one category. More confident in CIGs tonight due to less high clouds and the development of a weak to moderate Catalina eddy overnight. With this LIFR CIGs could possibly arrive (40% chance) at KBUR & KVNY between 07/10Z-16Z.
KLAX, Moderate confidence in TAF. Arrival and clearing times of CIGs may be off +/- 2 hours. CIGs likely to range from IFR to low-end MVFR 007-015. No significant east wind component is expected.
KBUR, Moderate confidence in TAF. LIFR CIGs possible (40% chance) between 07/10Z-16Z.
06/157 PM.
Small Craft Advisory (SCA) level winds will become widespread by this afternoon to include all Outer Waters, nearshore along the Central Coast, and the Santa Barbara Channel. SCA winds will continue across all Outer Waters through Wednesday. There is a 60% chance that a GALE Warning will be needed for PZZ676 from Tuesday evening through the overnight hours.
Winds will diminish later in the week with moderate chances for SCA winds lingering south of Point Conception on Thursday and possibly into Friday.
The Inner Waters will reach SCA levels at times mainly during the afternoon and evening hours - lower chances along the Central Coast later in the week. There is a 30% chance of GALE force winds Wednesday night across the Santa Barbara Channel and near the Channel Islands.
A storm system is expected to impact the coastal waters starting Thursday night lasting into the weekend bringing rainfall and the potential for thunderstorms. Confidence is low on exact timing and details for now.
Ca, Wind Advisory in effect until 8 AM PDT Tuesday for zones 349-351. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 3 AM PDT Tuesday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Wednesday for zones 650-670-673-676. (See LAXMWWLOX).
