07/201 AM.
A warming and drying trend will develop through the weekend as offshore flow establishes beneath building high pressure aloft. Temperatures above seasonal levels are likely Saturday through Monday with 80s and 90s being common across most coastal and valley locations. A storm system will likely move over the region the latter half of next week and could bring moderate to heavy rainfall.
(tdy-Sun), 07/835 AM.
***UPDATE***
For the immediate short term, two main issues are the winds and marine layer stratus.
Currently, surface observations indicate northerly winds, gusting anywhere from 30-55 MPH, across the area with the strongest winds across the mountains of San Luis Obispo and Santa Barbara counties. As the day wears on, these winds should gradually diminish in strength into the afternoon, but will likely increase again this evening into the overnight hours. Current WIND ADVISORIES for the Santa Barbara county mountains goes through tonight and will remain. For the mountains of San Luis Obispo county, the WIND ADVISORIES end at 1100 AM, but will either extend them through tonight or let them expire and possibly reissue this afternoon. These decisions will be made through the day.
Second issue is the marine layer stratus. Stratus/fog is pretty widespread across the LAX Basin as well as the Cuyama Valley. Dense fog is reported across the San Gabriel/San Fernando Valleys and a DENSE FOG ADVISORY remains in effect until 900 AM. As the stratus/fog dissipate later this morning, will let the advisory expire at 900 AM.
Overall, will be some updates this morning to the forecast to account for the marine layer and winds.
***From Previous Discussion***
The latest surface observations show offshore flow establishing across the area this morning. Weak to locally moderate offshore gradients are in place currently. Ridging aloft continues to build in over the region as high pressure centered near 26N and 133W amplifies off the West Coast. Some low clouds remain over southern Los Angeles County this morning as the marine layer depth remains wedged in. Some low clouds and fog are spilling over into the interior valleys and mountains, such as the Cuyama and California Valleys and out on the Carrizo Plain.
Gusty offshore winds continue to develop across the region. Mt. Lowe is gusting to 55 mph currently, and Sandberg hit 54 mph earlier in the night. Sundowner winds have been a little more marginal at this point, but a few gusts into 45 to 50 mph were observed last evening. Wind headlines were tweaked to keep the Santa Ynez Range in an advisory through early Saturday morning as winds will retreat into the higher elevations later today then redevelop tonight and into Saturday morning. There is a good chance that an advisory will need to reissued and/or extended into the coastal zones of southern Santa Barbara County. Farther to the north, a wind advisory remains in effect for the Santa Lucia range through 11 am this morning. As winds are progged to reach down a little farther down into the foothills of the Santa Lucia range, this advisory will likely need to be reissued for tonight through Saturday morning and expanded into the Central Coast portion.
With offshore flow developing and the ridge aloft building in, a warming and drying trend will establish through early next week. Warm daytime temperatures expected today will turn hotter over the weekend with 80s to mid 90s being common across coastal and valley locations by Sunday. Near record heat will develop across the region and there is a chance that heat advisories may be needed starting Sunday as heat risk values climb. While daytime record highs are warmer for Sunday, there is a good chance that record values could be tied in some spots.
The latest NAM-WRF solutions continue suggest a low-end advisory level Santa Ana wind event setting up across the usual Santa Ana wind corridor between late Saturday night and early Sunday morning. While EPS ensemble members do not pick up on this event and suggest the NAM-WRF solutions to be an outlier, higher resolution SREF and REFS ensemble members are starting to fall inline with the idea of advisory levels wind developing. Early frames of the 00Z REFS solutions match up well with the ideas presented by the NAM-WRF solutions. In addition, NCEP SREF member means advertise -6 mb KLAX-KDAG surface pressure gradients on Sunday morning, stronger than the latest deterministic NAM-WRF gradient of -4.4 mb. Stay tuned as this wrinkle will hopefully get ironed out here in the next 12-24 hours.
(Mon-Thu), 07/357 AM.
Another hot Santa Ana day is expected Monday, potentially setting records as the record high values are cooler than Sunday. SREF ensemble members suggest KLAX-KDAG pressure gradients near -6 mb again, but with less wind support aloft, it could end up only being breezy to locally windy.
The flow regime will change between Monday afternoon and Tuesday afternoon as the pattern will shift from offshore to onshore. A cooling trend should begin for Tuesday along with a return of low clouds and fog. With the low clouds and fog returning in a shallow layer, dense fog issues could develop.
Models continue to advertise a storm system moving over the region late next week. There is still large range of possible outcomes ranging from little to no rain (for portions of the area) to heavy rain. The timing of the rain continues to bump to a later time. The most likely outcome is a moderate storm impacting the area with 1-3 inches of rain later Thursday into Friday. However, the timing in the models ranges anywhere from as early as Wednesday to as late as the following Tuesday. For now, NBM values remain in the forecast for PoPs, but temperatures were nudged to match time periods for rainfall.
07/1158z.
At 0921Z at KLAX, the marine layer was 600 feet deep. The top of the inversion was 3000 feet with a temperature of 21 C.
High confidence in VFR TAFs for desert airfields (KPMD & KWJF).
Overall, moderate confidence in remaining TAFs. Timing of CIG/VSBY restrictions may be off by +/- 2 hours, with flight cats off by one or two when CIGs are present. There is a 30% chance of LIFR conditions developing at KPRB through 16Z Fri.
In addition, LLWS and Turbulence is possible over & near mountainous terrain. The terminals most likely to be impacted are KSBP (best chc) and KSMX. Concern is highest for both sites thru 18Z Fri, and again from 06Z to 12Z Saturday.
KLAX, Moderate confidence in the 12Z TAF. OVC005-008 expected thru around 17Z (+/- 1.5 hours). CIGs could periodically lower to LIFR OVC003-004. Subsequent arrival of ~OVC005 CIGs after 06Z Sat could be off by +/- 2.5 hours. Good confidence in any east wind component remaining below 7-8 kts.
KBUR, Moderate confidence in the 12Z TAF. LIFR conditions expected through around 16Z Fri. Then, VFR conditions expected.
07/834 AM.
High confidence in hazardous seas (up to 16 feet) from a moderately long period northwest swell and winds (20-30 knots) across the outer waters and Central Coast nearshore waters through Saturday. Localized Gale Force gusts (34-38 knots) may occur this afternoon and evening south of Point Conception. High confidence in conditions improving Saturday, then remaining relatively calm into next week.
High confidence in winds remaining below Small Craft Advisory (SCA) criteria across the waters south of Point Conception through early next week, with a 20% chance of NW to W winds reaching 20-25 knots Monday afternoon and evening. Seas will linger between 5-7 feet through tonight. Then high confidence in relatively calm seas into next week.
07/209 AM.
A long-period northwest swell will continue to bring high surf, dangerous rip currents and some coastal flooding to the local beaches through Friday night and Saturday.
Coastal Flood Advisories, High Surf Advisories, and a Beach Hazards Statement remain in effect for all coastal areas.
Please refer to LAXCFWLOX and LAXSRFLOX for the latest details.
Ca, Coastal Flood Advisory in effect until 2 PM PST this afternoon for zones 340-346-354-362-366. (See LAXCFWLOX). High Surf Advisory in effect until 9 PM PST Saturday for zones 340-346. (See LAXCFWLOX). Wind Advisory remains in effect until 11 AM PST this morning for zones 342-345. (See LAXNPWLOX). Beach Hazards Statement in effect until 2 PM PST this afternoon for zones 349-350. (See LAXCFWLOX). Wind Advisory remains in effect until 3 AM PST Saturday for zones 351-352. (See LAXNPWLOX). Wind Advisory remains in effect until 9 PM PST this evening for zones 353-376>378. (See LAXNPWLOX). High Surf Advisory in effect until 3 AM PST Saturday for zone 354. (See LAXCFWLOX). High Surf Advisory in effect until 2 PM PST this afternoon for zones 362-366. (See LAXCFWLOX). Dense Fog Advisory in effect until 9 AM PST this morning for zones 372-373-548. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 3 AM PST Saturday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 4 PM PST Saturday for zones 670-673-676. (See LAXMWWLOX).
