31/247 AM.
Rain chances continue through much of the weekend, with the peak of the rain likely occuring Saturday evening into Sunday morning. Warmer and drier conditions expected next week.
(tdy-Tue), 31/1250 PM.
Overall, latest models remain in decent synoptic agreement through the short term period. At upper levels, a low will impact the area through Sunday (bringing widespread shower activity) then a ridge will build over the area on Monday before getting "flattened" on Tuesday. At the surface, weak onshore flow will prevail through Sunday with weak offshore flow developing on Monday and Tuesday.
Forecast-wise for the short term, main issue remains rain chances for the area. Based on latest guidance, no major changes to previous forecast thinking. Scattered showers will continue through this afternoon, before more substantial rain moves into the area tonight/Sunday morning. As has been the case over the last several days, models indicate heaviest rainfall will remain south of the LA county. So, for our area, most locales can expect between 0.25 and 0.75 inch rain totals through Sunday afternoon. However, based on high resolution models (HRRR, RRFS, etc.), there may be some locally moderate to heavy showers through Sunday morning. Local totals between 1 and 2 inches will be possible with any heavy shower activity. As for any thunderstorm threat, the chances look to be in the 5-10% range for our area. So, that potential will need to be monitored through tonight. As for rainfall rates, hourly rates of 0.10 to 0.33 will be common, but isolated rates of 0.50+ inches/hour will be possible with any heavier showers.
After the system moves east and shower activity ends Sunday evening, the upper level ridge and weak offshore flow will bring dry and warmer conditions to the area on Monday. At this time, upper level support looks minimal, so any offshore winds on Monday are expected to remain below advisory levels. On Tuesday, the ridge will flatten, but weak offshore flow will still prevail. So, there may be a degree or two of warming on Tuesday.
(Wed-Sat), 31/1250 PM.
For the extended period, models continue to exhibit broad synoptic agreement through the period. Cyclonic flow aloft will prevail over the area Wednesday/Thursday then an upper level ridge builds in from the west on Friday/Saturday. At the surface, weak diurnal flow will likely prevail although the ECMWF indicates a bit of weak offshore flow in the Thursday-Saturday time frame.
Overall, the above synoptic pattern will result in benign weather for Southwestern California. Dry conditions will prevail through the period. High temperatures will remain relatively persistent on Wednesday/Thursday with some warming expected on Friday and Saturday. There may be some gusty offshore winds through the period, but nothing that looks to be near advisory levels.
31/1501z.
At 15Z at KLAX, there was no inversion or marine layer.
Occasional -SHRA with MVFR-VFR ceilings and visibility at most airports through 24Z, becoming more persistent with -RA tonight. Isolated and brief IFR conditions are possible tonight, especially from KSBA through KLGB. Improvement likely 12-18Z Sunday. Wind wind gusts of 20-30 knots likely at most coastal sites starting Sunday 21Z.
KLAX, High confidence in VFR ceilings common through 02Z, with occasional -MVFR SHRA possible. -RA with MVFR ceilings will likely become more common by 06Z, with possible brief IFR RA under and heavier cells. Improvement likely by 15-18Z. East winds likely each morning with a chance of reaching 8-10 knots through 17Z today (20%) and 06-15Z Sunday (30%). West winds 20-30 knots likely starting 21Z Sunday.
KBUR, High confidence in VFR ceilings common through 02Z, with occasional -MVFR SHRA possible. -RA with MVFR ceilings will likely become more common by 06Z, with occasional IFR RA under and heavier cells. Improvement likely by 15-18Z.
31/1144 AM.
Moderate confidence in winds and seas staying well below Small Craft Advisory (SCA) through this evening, except for a low chance of brief gusty downdraft winds with any heavier showers.
High confidence in post-frontal SCA-level W-NW winds and choppy seas are likely to form later tonight from the Central Coast to San Nicolas Island, then spread to most coastal waters on Sunday including the entire Santa Barbara Channel and the Santa Monica Bay. The winds turn to NE on Monday and will likely stay below SCA-levels. NE winds under SCA- levels likely to follow on Monday. There is a chance for another round of post-frontal winds on Tuesday, but likely a step below in strength compared to Sunday.
Ca, NONE. PZ, Small Craft Advisory in effect from 11 AM to 9 PM PDT Sunday for zones 645-650-655-670. (See LAXMWWLOX). Small Craft Advisory in effect from 2 AM Sunday to 2 AM PDT Monday for zones 673-676. (See LAXMWWLOX).
