02/100 AM.
Stagnant pattern through Friday with below normal temperatures, occasional patchy marine layer clouds, and weak to moderate Sundowner winds. Several potential scenarios exist for the Labor Day weekend, with anything from benign conditions to tropical rain, or even hot offshore winds.
(tdy-Sat), 02/218 PM.
For the short term period, 12Z models in good synoptic agreement for the area. At upper levels, a low will develop over the Pacific Northwest tonight/Thursday then wobble over the Pacific Northwest through Saturday. At the surface, moderate onshore flow will persist to the east with some northerly offshore flow.
For tonight through Friday night, rather benign sensible weather is expected. Main issue in this time period will be Sundowner Winds across southern Santa Barbara county. High resolution models have the SBA-SMX bottoming out in the -2.0 to -3.0 range tonight with the northerly gradients weakening Thursday night and Friday night. So, will expect another round of advisory-level north winds across the western half of the Santa Ynez Range tonight. Therefore, WIND ADVISORIES have been issued for these areas. For Thursday night and Friday night, the northerly gradients are forecast to weaken, resulting in weaker Sundowner Winds. So, the chances for advisory-level Sundowner winds Thursday night and Friday will be lower. Otherwise, the marine layer is expected to make a more widespread return to the coastal plain, and even the interior valleys of San Luis Obispo county, through Friday night. However, confidence in the exact areal coverage of stratus/fog will remain quite low. Other than any low clouds/fog, skies should remain mostly clear through Friday night. Finally with respect to temperatures, there will be little day-to-day changes through Friday with most areas remaining 2-6 degrees below seasonal normals.
On Saturday, things start to get a bit more "interesting" as moisture from Marie is expected to start moving into the area. 12Z models indicate PWATs increase to the 1.00-1.50 inch range across Los Angeles county during the day on Saturday. So, there will be chance of showers across LA county on Saturday with a slight chance of showers developing across Ventura county by Saturday evening. At this time, rainfall amounts, if any, are expected to be very light through Saturday evening. Otherwise, partly cloudy to mostly clear skies can be expected on Saturday with some coastal stratus/fog in the morning. As for temperatures, there will be a few degrees of warming for most areas which will be accompanied by some increase in relative humidity. So, it will feel bit more "tropical" on Saturday for most areas.
(Sun-Wed), 02/218 PM.
For the extended period, focus remains firmly on Hurricane Marie and its potential impacts upon Southwestern California. Currently Marie is located around 17N and 111W. Current official track from the National Hurricane Center has Marie moving to the west and northwest through the Labor Day weekend. This forecast track matches up very well with a majority of the ensemble members from all models.
Given the above-mentioned guidance, the potential for Marie to directly impact Southwestern California as a tropical system remains VERY LOW. However, there still will be impacts that the area should be aware of through the holiday weekend. Latest model guidance indicates the best moisture will move into LA and Ventura counties with lesser amounts across SBA and SLO counties. Based on current deterministic model QPF forecasts, the GFS is now much less bullish on rain while the ECMWF is more bullish (a complete reversal from the last several days). So, definitely a good idea to follow the respective ensemble forecasts. To that end, the ensemble forecasts indicate a good chance of light rainfall across the area from Saturday afternoon through Tuesday, and a pretty low chance of moderate or heavy rainfall. As for any thunderstorm chances, they look to remain in the 5-10% range through the period. As for the potential significant coastal hazards, check out the details in the Marine and Beaches segments of this discussion.
As has been mentioned the last several days, Southern California residents need to keep up-to-date with the latest forecast info. Any change in the track of Marie could result in notable changes to the forecast and the expected impacts.
02/1706z.
At 1640Z at KLAX, the marine layer was 2000 feet deep. The top of the inversion was 3300 feet with a temperature of 18 degrees Celsius.
For 18Z TAF package, high confidence in CAVU conditions for KPRB, KSBA, KOXR, KCMA, KBUR, KVNY, KPMD and KWJF.
For KSBP and KSMX, moderate confidence in 18Z TAFs as timing of flight category changes could be +/- 3 hours of current forecasts.
For KSMO, KLAX and KLGB, moderate confidence in 18Z TAFs as timing of flight category changes could be +/- 3 hours of current forecasts. Additionally, there is a 30-40% chance that CIG/VSBY restrictions do not develop tonight.
KLAX, Moderate confidence in 18Z TAF. Timing of flight category changes could be +/- 3 hours of current forecasts with a 50/50 chance of either IFR or MVFR conditions. There is a 30-40% chance that CIG/VSBY restrictions do not develop overnight. No significant easterly wind component is expected.
KBUR, High confidence in 18Z TAF as CAVU conditions are expected through the period.
02/151 PM.
For the Outer Waters, moderate to high confidence in current forecast. Today through Friday, high confidence in Small Craft Advisory (SCA) level winds across PZZ673/676, with a 20-30% chance of SCA level winds across PZZ670. For Saturday through Sunday, there is a 30-50% chance of SCA level winds across all of the Outer Waters.
For the Inner Waters north of Point Sal, moderate confidence in current forecast. Today through Sunday, there is a 30-50% chance of SCA level winds in the afternoon and evening hours.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. For a majority of the southern Inner Waters, there is a 20-30% chance of SCA level winds today through Sunday, mainly across western sections. For the western half of the Santa Barbara Channel, there is a 60-80% chance of SCA level winds in the late afternoon through overnight hours today through Thursday with a 30-40% chance of SCA level winds Friday through Sunday.
Expecting increasing southerly swell Friday through Labor Day Weekend weekend due to tropical activity to the south. The details and timing are very much dependent on the track of soon to be Hurricane Marie, but confidence is high in larger than normal southerly swell through the holiday weekend and into Tuesday.
Ca, Wind Advisory in effect from 6 PM this evening to 6 AM PDT Thursday for zones 349-351. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 8 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Thursday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Friday for zones 673-676. (See LAXMWWLOX).
