04/718 PM.
Near to slightly above normal are temperatures expected through Friday, except significant cooling in the mountains and interior areas Thursday and Friday. Temperatures will increase region wide Saturday and Sunday. Strong and gusty northerly winds expected across much of the area Wednesday night into Thursday morning. Moderate to strong Santa Ana winds likely over the weekend.
(Wed-Sat), 04/752 PM.
***UPDATE***
Moderate to strong north winds are forecast for many areas tonight into Thursday morning, strongest over the interior mountains, including the Santa Monicas, with gusts of 55 to 65 mph expected. The Santa Monica Mountains should see gusts between 55 to 60 mph, although there is a chance the stronger winds won't materialize there. However, there is also a chance of stronger wind gusts filtering down to the Malibu coast overnight. Another area to watch will be the San Gabriel Valley where strong winds could develop depending on the location of the upper level jet.
As of 700 PM, the winds are still ramping up over the area with peak gusts between 35 to 55 mph. The FV3 model indicates more significant increases in wind speed this evening through around midnight.
***From Previous Discussion***
The forecast through Friday remains largely unchanged. The first of two upper level lows will move through tonight into Thursday morning bringing significant northerly winds to many areas, but especially the mountains. Winds are expected to reach at least 60 mph across the interior Santa Barbara mountains, in the mountains surrounding the Grapevine area, and in the San Gabriels. There's about a 30% chance of 60 mph gusts in the Santa Monica Mountains and 10-20% across the LA County portion of the Malibu coast. There could also be some isolated gusts 60 mph gusts in and around the Simi Valley hills, Santa Susana Mountains, and in the Porter Ranch area. Also, still expecting windy conditions filtering down into the West LA area and out across the coastal waters, including all the Channel Islands. One area to be mindful of that is currently not included in the current suite of wind hazards is the San Gabriel Valley. This is typically protected by the mountains but if the upper level jet shifts more to the north to align favorably over that area there could be some strong winds at times there as well but chances for that would be under 10% at this time.
Temperatures at higher elevations and far interior areas will drop several degrees Thursday but closer to the coast not much change expected as downslope warming will compensate for most of the cold air advection.
Some light showers are still possible (30-50%) on the northern mountain slopes later tonight into Thursday morning with the snow level lowering rapidly overnight to possibly around 4000 feet, meaning some very light snow is possible near the summit on I5, but only a 5% chance or less of any accumulations at that level.
The pattern will shift from a north flow wind event to a traditional Santa Ana event Friday into Saturday with offshore gradients between 6 and 8mb. Temperatures will be on the rise, especially by Saturday with most coast/valley areas in the mid to upper 70s and possibly an isolated 80. Many of the previous wind advisories and warnings will be back in play Friday and Saturday with the focus shifting to the usual Santa Ana wind favored areas, which would not include the LA Basin, the San Gabriel Valley, or SLO and SB Counties, except possibly the Santa Lucias.
(Sun-Wed), 04/215 PM.
Offshore gradients will continue into Sunday but with slowly weakening upper support and a much warmer air mass. Will likely need continue wind advisories in many of the same areas. Temperatures will be warming up quite a bit with highs in 80s for most coast/valley areas, including the Central Coast. There's event about a 40-50% chance of lower 90s across LA/Ventura Counties.
Above normal temperatures will continue into early next week, though light onshore flow is expected to return Tuesday and highs will be back into the 60s and 70s.
05/0547z.
At 0453Z, the marine layer was around 1100 ft deep at KLAX. The top of the inversion was at 1900 feet with a temperature of 15 degrees Celsius.
High confidence in VFR conds for most TAF sites, except moderate confidence in the Ventura and LA County coastal sites where the flight categories could be off by 1, and the timing could be off by +/- 2 hours. Chance for no cigs at KOXR (30%) and KCMA (40%).
Lower confidence in the wind forecast as timing of wind group changes may be off +/- 3 hours. Mdt LLWS due to increasing winds with height possible at all sites except KPRB and KSBP. Highest confidence for KSBA, KLAX, KSMO, KBUR focused 06Z-18Z. Mdt turbulence also likely, especially over terrain.
KLAX, Low to moderate confidence in TAF. North winds will rapidly increase sometime between 08Z and 12Z. Lower confidence in peak wind gusts, but higher confidence in timing being between 10Z and 18Z, then again 06/00Z-08Z. LLWS likely due to wind speeds rapidly increasing with height 10Z-18Z (+/- 3 hours).
KBUR, Moderate confidence in TAF. North winds will rapidly increase over the next few hours. LLWS possible due to wind speeds rapidly increasing with height 08Z-18Z (+/- 3 hours), however.
04/703 PM.
***UPDATE***
Have pushed back the starting time of GALE WARNING for the waters adjacent to Los Angeles and Orange County (PZZ655) to 1 AM.
Small Craft Advisory level N winds will develop during the late evening hours nearshore from Malibu to Palo Verdes. These winds will spread southward and increase to GALE Force after midnight.
***MAIN DISCUSSION***
Moderate to high confidence in the current forecast. Higher confidence exists in the forecast for winds. Less confidence in the forecast for seas. Seas could be up to 1-3 feet higher than forecast, especially today through Saturday.
Marine weather conditions will deteriorate through tonight with widespread strong Small Craft Advisory (SCA) and GALE conditions expected through at least Thursday night. GALE WARNINGS remain in effect through Friday morning for some waters.
Another period of strong winds will develop across the region as an offshore flow pattern will set up Friday through Sunday. There is a high to likely (40 to 60 percent) chance of SCA level winds between Friday night and Sunday. There is a moderate (30-40 percent) chance of GALE FORCE wind gusts inside the southern California bight, and high (40-50 percent) chance of SCA level winds along the nearshore waters of the Central Coast.
Ca, Wind Advisory remains in effect until 9 AM PST Thursday for zones 87-88-349>352-356-357-366-367-371>375-381>383. (See LAXNPWLOX). Wind Advisory remains in effect until 2 AM PST Thursday for zones 346-347. (See LAXNPWLOX). High Wind Warning remains in effect until 7 AM PST Thursday for zones 353-376>378. (See LAXNPWLOX). High Wind Warning remains in effect from 2 AM to 9 AM PST Thursday for zones 362-369-370. (See LAXNPWLOX). High Wind Warning remains in effect until 9 AM PST Thursday for zones 379-380. (See LAXNPWLOX). PZ, Gale Warning in effect until 9 AM PST Thursday for zones 645-650. (See LAXMWWLOX). Gale Warning in effect until 10 AM PST Thursday for zone 655. (See LAXMWWLOX). Gale Warning in effect until 3 AM PST Friday for zones 670-673-676. (See LAXMWWLOX).
