03/119 AM.
A moderate Santa Ana wind event will bring gusty northeast winds to portions of southern California Wednesday morning through Thursday. Cold overnight low temperatures will occur through the work week, coldest Wednesday night into Thursday morning in wind protected areas. A significant warming trend will begin this weekend and peak next Tuesday and Wednesday at 10 to 20 degrees above normal.
(tdy-Fri), 03/852 AM.
***UPDATE***
Gradients are now offshore to the east and the north and we're observing some near-advisory level gusts across the San Gabriels and Santa Susanas. Although winds are offshore across coasts and coastal valleys, they are generally in the 10-20 mph range. Multiple higher resolution models, including the REFS ensemble and a local WRF model, are indicating an increase in Santa Ana Wind speeds in virtually all wind prone areas later this morning, so we'll keep the Wind Advisory as is. There is still a chance for winds to remain relatively light at the coasts today.
A relative lull in Santa Ana Wind speeds will occur this afternoon and evening. Confidence is higher in stronger, more widespread advisory level winds from late tonight into Thursday afternoon.
Another focus will be the overnight lows, which will likely be some of the coldest of the year, especially for areas absent of Santa Ana Wind influences. Widespread Frost/Freeze products are on the table for tonight, so look for the afternoon forecast for more information.
***From Previous Discussion***
A cold upper level trough is passing through the southern portion of the Great Basin this morning, creating thick cirrostratus over the region but no precipitation locally. The marine layer has jumped up over 2500 feet and pressure gradients to the east have gone from 2-3mb offshore to over 5mb onshore. Some stratus is trying to develop but the thick high clouds are making that difficult to form and also see from space.
The main story for today and Thursday is the rapid shift back to offshore and the expected development of the next round of Santa Ana winds across portions of Ventura and LA Counties and the Santa Lucias. Given the existence of a 2500 foot marine layer there remains still quite a bit of uncertainty when the northeast winds will begin and how strong they will be. High res models seem to be a little too strong for today given the current conditions, especially near the coast, while confidence in increasing winds is certainly higher inland and especially in the mountains. The most likely outcome is for most of the advisory level winds to stay up in the mountains today while lower elevations have breezy but sub advisory level winds by mid to late morning. However, there's a 20% chance of much lighter winds closer to the coast today.
Going into tonight and Thursday with zero marine layer influence and more favorable easterly flow aloft the chances for 30-50mph winds are much higher and would likely include gusty winds out to Catalina Island as well, especially tonight.
This is again a fairly cool Santa Ana event so high temperatures will top out in the lower 70s, warmest at the coast and coolest across the far interior where highs will be in the 50s. And overnight lows in wind protected locations will be quite cold, hence the flurry of frost and freeze products out.
By Friday morning gradients will have swung back to onshore which will result in cooling at the coast but warming inland. Overall highs will be near or slightly above seasonal norms.
(Sat-Tue), 03/212 AM.
Strong high pressure will be building rapidly over the eastern Pacific this weekend and especially the first half of next week. 500mb heights are expected to exceed the 95th percentile and with increasing offshore flow, particularly Monday through Wednesday, temperatures locally are expected to be 10-20 degrees above normal. Local historical guidance suggests widespread highs in the 80s across coast and valleys with about a 20% chance of lower 90s. There will be some northerly flow developing Sunday night through Tuesday that will bring dry and gusty winds to north exposed areas which includes most of the mountains as well as southern Santa Barbara County.
Temperatures will start cooling next Thursday and Friday but still well above normal.
03/1126z.
Around 09Z, there was a deep moist layer up to around 3400 feet with a inversion above up to 6500 feet.
Low to moderate confidence in the current forecast through 18Z as ceilings could form rapidly and dissipate. Moderate confidence in the forecast thereafter.
KLAX, There is a 60 percent chance of MVFR to VFR conditions with ceilings at or below 6000 feet through at least 14Z, then VFR conditions should develop through 17Z. There is a 30 percent chance of east winds between 7 and 10 knots through 19Z. There is a moderate chance of moderate wind shear after 06Z Thursday.
KBUR, There is a 60 percent chance of MVFR to VFR conditions with ceilings at or below 6000 feet through at least 14Z, then VFR conditions should develop through 16Z. There is a moderate to high chance of moderate wind shear through 18Z, and again after 05Z Thursday.
03/824 AM.
Moderate confidence in the current forecast. Slightly higher confidence in the forecast for seas versus winds.
For the waters southwest through northwest of the Channel Islands beyond 10 NM offshore of the Central Coast and outside the southern California bight, there is a 40 to 60 percent chance of Small Craft Advisory (SCA) conditions this morning, diminishing to a 30 to 50 percent chance this afternoon through Thursday morning. Winds and seas should drop below SCA levels Thursday afternoon through Friday morning, then there is a 40 to 60 percent chance of SCA level winds between Friday afternoon and Saturday night, highest from near Point Conception south to San Nicolas Island.
Inside the southern California bight and for the nearshore waters along the Central Coast out to 10 NM offshore, there is a 30 to 50 percent chance of gusty northeast to east winds through early this afternoon, increasing to 40 to 60 percent chance overnight tonight and into Thursday morning, highest between Rincon Point to Santa Monica and into the San Pedro Channel. There is a 40-50 percent chance that east winds could affect east facing harbors on Thursday morning. Winds and seas should drop below SCA levels Thursday afternoon and remain below SCA levels through the weekend.
Ca, Wind Advisory remains in effect until 3 PM PST Thursday for zones 88-354-355-358-362-369>371-374>376-378>380. (See LAXNPWLOX). High Surf Advisory in effect until 3 AM PST Thursday for zones 340-346. (See LAXCFWLOX). Beach Hazards Statement in effect through Saturday morning for zones 349-350-362-366. (See LAXCFWLOX). Coastal Flood Advisory in effect until 10 AM PST this morning for zone 354. (See LAXCFWLOX). High Surf Advisory in effect until noon PST Thursday for zone 354. (See LAXCFWLOX). PZ, Small Craft Advisory in effect from 9 PM this evening to 2 PM PST Thursday for zones 655-676. (See LAXMWWLOX). Small Craft Advisory in effect until 10 AM PST this morning for zone 670. (See LAXMWWLOX).
