07/800 PM.
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.
(Fri-Mon), 07/826 PM.
***UPDATE***
Today was noticeably warmer than yesterday, with many areas in the mid 70s to mid 80s. Warming is on track to continue each day through Sunday or Monday, as the region heads into a Santa Ana Wind and riding pattern. Gusty northeast winds are occuring across the eastern Santa Ynez Mountains, the eastern Santa Susana Mountains, and the Interstate 5 Corridor. Wind Advisories have been issued until 3 AM Saturday for the aforementioned mountains. Gusty winds are also expected starting late tonight into Saturday morning across the San Luis Obispo and Santa Lucia Mountains, and the northeast winds may reach some foothill and valley areas (such as Montecito Hills, Simi Valley, San Luis Obispo, and Morro Bay). Additional Wind Advisories will be possible for some of theses locations.
***From Previous Discussion***
Overall, 12Z models in good synoptic agreement through the short term period. At upper levels, ridge builds over the area, peaking in strength on Sunday and Monday. Near the surface, north to northeast offshore flow will continue.
Forecast-wise for the short term, two main issues are winds and temperatures. With respect to winds, high resolution models indicate northerly offshore gradients will relax through the weekend while the northeast gradients increase. With the northerly offshore gradients, north winds will continue across the Santa Ynez Range and the I-5 Corridor tonight and Saturday, likely reaching advisory-levels tonight (especially across the Santa Ynez Range). So, will keep the WIND ADVISORIES in effect for these areas through 10 PM for the I-5 Corridor and 300 AM for the Santa Ynez Range. As the gradients turn northeasterly on Saturday and increase through Sunday/Monday, the focus of the winds will turn to the usual Santa Ana areas of Ventura/LA counties as well as the Santa Lucia Range (in San Luis Obispo county). LAX-DAG gradients look to peak in the -4.5 to -5.5 mb range and upper level winds top out around 25-35 knots. So, weak to moderate Santa Ana winds can be expected, especially on Sunday and Monday. Looking at high resolution ensembles, there is a 30-40% chance of advisory-level Santa Ana winds. So, will not issue any wind products for these Santa Ana winds right now, but future shifts will need to monitor the situation closely.
The second issue will be temperatures. With the combination of a building upper level ridge and offshore surface flow, afternoon temperatures will be on quite the upswing through the period. By Sunday/Monday, most areas west of the mountains will experience highs in the mid 80s to lower 90s which would be about 10-15 degrees above normal. Overnight lows will also be on the warm side, generally in the 60s to lower 70s across the foothills and in breezy areas. At this time, there looks to be about a 30% chance of heat products being required for Sunday/Monday as the overnight low temperatures are the limiting factor. So, will not issue any heat products at this time, but future shifts will also need to monitor this potential.
Other than winds and temperatures, no issue are expected. Other than some potential stratus/fog tonight across the LAX Basin, mostly clear skies are expected for the area through Monday.
(Tue-Fri), 07/126 PM.
For the extended period, 12Z models continue to exhibit decent synoptic agreement, although disagreeing in the details, especially later in the period.
For Tuesday and Wednesday, models indicate the upper level ridge will break down and shift eastward, as a low approaches from the west. As the ridge breaks down, onshore gradients will be on the increase. So, will expect a noticeable cooling trend, a return of onshore winds and increasing marine layer stratus and fog.
For Thursday and Friday, models indicate wet and unsettled weather, but differ noticeably in the details. The GFS sweeps the upper low across northern California while the ECMWF drops the upper low southward, keeping it offshore of the area through Friday. So, either solution bring a good chance of rain to the area Thursday/Friday, but timing and amounts vary dramatically. Ensembles do not offer much additional information, stressing the same differences as the deterministic models. So, current NBM POPs look good, with likely/chance POPs for the entire area. However, amounts through Friday are very much in questions, ranging from minor to significant. Over the coming days, the models should come to a better consensus and details can be greatly fined-tuned. Essentially, be prepared for some rain beginning Thursday.
08/0557z.
At 0500Z at KLAX, the marine layer was 900 feet deep. The top of the inversion was 2400 feet with a temperature of 23 C.
High confidence in VFR TAFs for desert airfields (KPMD & KWJF).
Low to moderate confidence in remaining TAFs. Timing of CIG/VSBY restrictions may be off +/- 2 hours, with flight minimums off by one category. There is a 25% chance for V/LIFR conditions at KPRB from 10Z-16Z Saturday. There is a 30% chance for NE wind gusts up to 20 kts to surface at KSBP through 15Z Saturday.
LLWS and turbulence is possible over & near mountainous terrain through 12Z Saturday. The terminals most likely to be impacted are KSBP and KSMX.
KLAX, Moderate confidence in TAF. There is a 30% chance VSBYs of <1SM, 15% chance of 1/2SM, & 15% chance of KBUR, Low confidence in TAF. There is a 40% chance that VV001-OVC004 with vsbys 1/4SM-2SM from 11Z-16Z Sat do NOT arrive. VFR conditions expected after 18Z Sat. 07/803 PM. High confidence in a long period northwest swell continuing to create hazardous seas (10 to 12 feet) through Saturday afternoon across the outer waters and nearshore Central Coast waters, but gradually decreasing in height. Northwest winds 20-30 knots will be common through Saturday morning, with localized Gale Force gusts (34-38 knots) southwest of Point Conception. Moderate confidence in conditions improving by Saturday night, 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. Seas will linger between 5-7 feet through tonight. Then high confidence in relatively calm seas into next week. 07/140 PM. All Coastal Flood Advisories and the Beach Hazards Statement (Southern Santa Barbara County) have been allowed to expire. Although surf will diminish some through tonight, High Surf Advisories will remain in effect, and the Los Angeles County High Surf Advisory was extended into late tonight. Minor tidal overflow is possible during peak high tide Saturday morning between 9am and 12pm. Please refer to the CFWLOX and SRFLOX for additional details. Ca, High Surf Advisory in effect until 9 PM PST Saturday for zones 340-346. (See LAXCFWLOX). Wind Advisory remains in effect until 3 AM PST Saturday for zones 351-352-375-378. (See LAXNPWLOX). High Surf Advisory in effect until 3 AM PST Saturday for zones 354-362-366. (See LAXCFWLOX). 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). Marine
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