15/249 AM.
A moderate to strong Santa Ana Wind will bring widespread strong winds and critical fire weather conditions to much of Southwest California through Saturday. Additionally, very warm temperatures bring a high risk of heat illness to all coastal areas. A significant cool down with a chance of widespread rain is expected next week.
(tdy-Sat), 15/248 AM.
All systems go for the first Santa Ana of the season and it is going to be a strong one. At the upper levels a 592 dam ridge will nose into Humboldt County while a pos tilt trof pinches off a retrograding low that will set up over Yuma. This will set up NE upper level flow from LA county north to Monterey county. At the sfc building high pressure in the Great Basin will bring 4 to 8 mb of offshore flow from the north and the east (strongest from the east). The winds will exhibit a typical diurnal pattern starting to ramp up a few hours before dawn peaking mid morning and then tapering off slightly in the afternoon and evening. The winds will occur all the standard Santa Ana Wind Corridor (~10 miles either side of a line from Newhall to Mugu NAS. Today's strongest winds will be in the 40 to 50 mph range with isolated gusts to 60 mph across favored mtn canyons and ridgetops. Friday will be the peak of the event with wind speed about 10 mph greater than today's. Much of LA/VTA counties are covered by wind warnings or advisories please see the product LAXNPWLOX for details. The downsloping winds will create very dangerous fire weather conditions as well. Please see the detailed Fire Weather Discussion below for details.
Totally sunny skies and downsloping winds will combine to bring 4 to 8 degrees of warming across the csts/vlys (3 to 6 further inland) with an additional 3 to 6 degrees (1 to 3 further inland) likely on Friday. By Friday cst/vly temps will be in the upper 80s and 90s with a 10 percent chc of a few 100 degree readings. Heat advisories are in effect to cover these 10 to 15 degree warmer than normal temps.
Offshore trends and a weakening of the upper support will bring weaker winds to the area but some advisory level gusts are still likely in the windiest areas. The offshore push from the north will weaken more than the one from the east and this will tilt the winds in a more easterly direction which may make some areas that did not see much wind Thu or Fri windier. The weaker offshore flow will allow for a return of a weak sea breezy and this will cool the csts and to a lesser degree the vlys by 2 to 4 degrees. Further inland there will be little change in temps.
(Sun-Wed), 15/231 AM.
Upper level support collapses on Sunday. Offshore flow will remain by it will be down to 1 to 2 mb. The much weaker offshore flow will bring about 3 to 5 degrees of cooling (4 to 8 degrees across the Central Coast). Even with the cooling max temps will end up 4 to 8 degrees above normal.
More cooling is in store on Monday as an upper low moves down the coast. Hgts will fall from 580 dam Sunday afternoon to 576 dam Monday afternoon. Actual onshore flow will develop and will increase through the day. Some morning marine layer clouds may even develop over the Central Coast. Max temps will fall 4 to 8 degrees. This will bring max temps down to near normals.
Forecast confidence drops off quickly starting Tuesday. The cold upper low is forecast to continue down the coast and into and over Srn CA during the time period. There is still much mdl and ensemble disagreement on the timing and track of this system. A more inland track would limit the chc/amt of rain while a more westward over ocean track would bring increased chcs of rain and more of it. Timing is very uncertain. Do think some sort of rain will fall during the Tue to Thu time period but due to all of the uncertainty no more than a 30 percent chc during any 12 hour period. Early and certainly subject to change rainfall totals call for around a quarter to half inch for the entire period. Good confidence in much cooler conditions with highs mostly in the upper 60s and lower 70s.
15/0949z.
At 0832Z at KLAX, there was no marine layer nor inversion.
High confidence in CAVU TAFs, moderate confidence in winds. Timing and strength of gusty NE winds may be off by 2-3 hours and 10kt respectively.
KLAX, High confidence in CAVU TAF. Any east wind component will be AOB 7 kts 12Z-16Z.
KBUR, High confidence in CAVU TAF. Moderate confidence in winds, and N to NE winds may begin as early as 14Z.
15/248 AM.
Gusty northeast to easterly winds will affect the coastal waters over the next few days. Moderate to strong Santa Ana winds will affect the waters south of Point Conception today through Saturday morning, and the near shore waters will see gusty easterly winds Friday, possibly reaching Small Craft Advisory (SCA) levels.
These hazardous Santa Ana NE-E winds will be focused from Ventura to Santa Monica and out past Anacapa Island starting today, and conditions could also become hazardous across the San Pedro Channel Friday morning with a 25% chc of 25 kt gusts at Avalon Harbor. The worst conditions are expected Friday morning, and Gale Watches have been issued to target these waters. Refer to MWWLOX for more details. Small Craft Advisory (SCA) may be needed for the nearshore waters along the Central Coast Friday morning due to gusty offshore winds.
There is a solid signal for a trough early to mid next week which could bring hazardous boating conditions along with rain chances to our coastal waters. Will monitor this system.
Long period swells from the west and the south are affecting the coastal waters, and can create a confused sea state. This can make boating more challenging and dangerous, especially for small vessels.
Ca, Wind Advisory in effect from 6 AM this morning to 8 PM PDT Friday for zones 88-354-355-358-362-370>374-376-377. (See LAXNPWLOX). Heat Advisory in effect from 10 AM this morning to 8 PM PDT Saturday for zones 340-341-346-347-349-350-354-355-362-366>368. (See LAXNPWLOX). Beach Hazards Statement in effect until 2 PM PDT this afternoon for zones 354-362-366. (See LAXCFWLOX). High Wind Warning in effect from 6 AM this morning to 8 PM PDT Friday for zones 369-375-378>380. (See LAXNPWLOX). Red Flag Warning in effect from 6 AM this morning to 8 PM PDT Saturday for zones 288-354-355-358-362-369>382-548. (See LAXRFWLOX). Red Flag Warning in effect from 3 AM to 6 PM PDT Friday for zones 345-353. (See LAXRFWLOX). PZ, Small Craft Advisory in effect from 9 AM this morning to 3 AM PDT Friday for zones 650-655. (See LAXMWWLOX). Gale Watch in effect from late tonight through Friday afternoon for zones 650-655. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT early this morning for zones 673-676. (See LAXMWWLOX). Small Craft Advisory in effect from 2 AM to 5 PM PDT Friday for zone 676. (See LAXMWWLOX).
