17/201 PM.
Well above normal temperatures will continue away from the coast through Friday. Unsettled weather is possible this weekend along the Central Coast, spreading to all areas with a potentially significant storm near the middle part of next week.
(tdy-Sat), 18/1221 AM.
The gradients are transitioning from a strong N push to more of a NE push. The winds are subsiding some and should mostly be below advisory criteria by dawn. The offshore winds have pushed all of the coastal low clouds away save for the western SBA county beaches. The Long Beach area may see some low clouds and dense fog for a few hours this morning as the offshore flow in that area is weakest. The otherwise sunny skies will team up with the offshore flow to bring warming to most of the area, but esp the VTA/LA county csts/vlys where 8 to 12 degrees of warming is likely. Look for max temps in the 70s across the csts and 80s in the vlys or 12 to 18 degrees over normal.
On Friday the ridge will be pushed to the south and flat westerly flow sets up over the area. Hgts will fall to about 585 dam (still well above normal). Low clouds will be similar to Wednesday and pretty much confined to the Long Beach area. Much weaker offshore flow at the sfc will lead to 3 to 6 degrees of cooling across the csts/vlys. The lack of cool air advection from the San Joaquin Vly will lead to 2 to 4 degrees of warming across the interior.
Flat westerly flow continues over the area on Saturday. Hgts will dip down to 582 dam. Onshore flow to the east will increase from 1 mb in the morning to about 3 mb in the afternoon, the offshore flow from the north will be 3 mb weaker in the afternoon compared to Friday. The onshore flow and falling hgts will bring some coastal low clouds to the area in the morning. At the same time the southern edge of an atmospheric river (AR) affecting the northern portion of the state will move south enough to south to bring mostly cloudy skies to most over the area save for LA County which will end up partly cloudy. The AR could (20 percent chc) bring some light rain to SLO county. The cooling trend will continue as falling hgts and better onshore flow combine to lower most temps 3 to 6 degrees. The Central Coast will be the exception with little change in temps. Max temps, however, will remain above normal (3 to 6 degrees csts, 5 to 10 degrees vlys and 10 to 15 degrees mtns and far interior).
(Sun-Wed), 18/258 AM.
Sunday and Monday will be fairly similar days. The upper flow pattern will slowly tilt more and more into a SW to NE direction on Sunday as the AR system sags a little more to the south. A slight chc or chc (20 to 30 percent) of rain will develop over SLO and Western SBA counties. Other areas will just see increasing clouds. Rainfall totals during the two day period will most likely be under a tenth of an inch with perhaps the exception of the far NW tip of SLO county which could see more. Skies will turn mostly cloudy Sunday and will persist through Monday. Max temps will fall 2 to 4 degrees across almost all of the area Sunday and then will change little on Monday. Max temps will remain 3 to 6 degrees over normals for the csts and vlys.
Tuesday romaines the day of transition. The AR will sag south and the flow will become even more southwesterly. Rain chances will overspread the entire area. Rain chances have increased with the latest forecast and now sit around 40 percent for LA county, 50 percent for VTA county, 50 to 60 percent for SBA county and 60 to 70 percent for SLO county. The forecast rainfall amounts have also been increased. SBA and SLO counties will now likely see a half inch to an inch of rain, while a quarter inch to a half inch is possible for VTA and LA counties.
There has been a slight change in the current thinking for the Wed/Thu storm. Both the EC and esp the GFS (as well as most ensembles and the AI enhanced mdls) are now speeding up the system (hence the wetter Tuesday fcst). This forecast (Which very well might change since it is 7 to 8 days away) now call for the bulk of the rain to fall Wednesday through Thursday (Christmas) morning. Very preliminary (and subject to change) rainfall totals for the Wed/Thu time period call for 2 to 4 inches of rain csts/vlys, 4 to 6 inches across the mtns and 1 to 2 inches for the interior sections. It is too early to get a handle on rainfall rate predictions. Snow levels will be over 8000 ft but will start to fall later Thursday.
Model agreement falls off pretty rapidly after Thursday, but there is a potential for another system over the weekend of the 27th and 28th.
18/1008z.
Around 0815Z, the marine layer depth was near 500 feet deep at KLAX. The top of the marine inversion was near 1500 feet with a temperature around 21 degrees Celsius. There was another inversion up to around 3000 feet.
Low-to-moderate confidence in the current forecast through 18Z and again after 08Z Friday for coastal terminals and KPRB, otherwise moderate-to-high confidence. There is a moderate-to-high chance of LIFR to IFR conditions through 18Z and again after 06Z Friday at coastal terminals and KPRB, otherwise VFR conditions are expected through the period.
KLAX, There is a 40 percent of LIFR conditions through 16Z, and again after 06Z Friday. An easterly winds will be less than 7 knots through the period.
KBUR, VFR conditions are expected through the period. No wind impacts are expected at this time.
18/119 AM.
Moderate-to-high confidence in the current forecast. Higher confidence exists in winds through early Saturday morning, then lower confidence thereafter. Lower confidence exists in the sea forecast through Friday night.
For the waters southwest through northwest of the Channel Islands and the nearshore waters along the Central Coast, there is a likely-to-imminent (60-90 percent) chance of Small Craft Advisory (SCA) level winds through Friday night, highest during the afternoon and evening hours and from near Point Concpetion south to San Nicolas Island. There is a moderate (30-40 percent) chance of widespread GALES through tonight, but local GALE force gusts are possible this afternoon and evening from Point Conception south to San Nicolas Island. Winds will likely diminish some with SCA chances decreasing to a moderate-to-high (30-50 percent) chance between Friday night and Saturday, then to a low-to- moderate (20-40 percent) chance over the weekend and into Monday.
Inside the southern California bight, there is a moderate-to-high (30-50 percent) chance of SCA level winds each afternoon and evening through Friday evening, highest across the western portion of the Santa Barbara Channel. Otherwise, winds and seas should be below SCA levels through Monday.
Ca, Wind Advisory remains in effect until 3 AM PST early this morning for zones 88-356-362-369>375-383. (See LAXNPWLOX). Wind Advisory now in effect until 3 AM PST early this morning for zones 349-351. (See LAXNPWLOX). Wind Advisory now in effect until 6 AM PST early this morning for zones 352-353-376>381. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from noon today to 9 PM PST this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PST early this morning for zones 650-655. (See LAXMWWLOX). Small Craft Advisory in effect until 9 PM PST Friday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PST Saturday for zones 673-676. (See LAXMWWLOX).
