13/649 PM.
A cooler weather pattern with night through morning low clouds and fog will linger into Saturday as a weak trough of low pressure remains along the California coast. A warming trend will begin over the weekend as high pressure to the east gradually expands over the region. Temperatures will remain below normal through at least Sunday then warm above normal by Tuesday.
(Thu-Sun), 13/812 PM.
***UPDATE***
A trough along the West Coast extends from the Pacific Northwest to northern California, then southward over the offshore waters of Southern California. The placement of this weak upper trough supports southwest winds aloft, and mid-level clouds continue to stream over the area in this flow. There will be continued low chances (10% or less) of convective showers and thunderstorms with this moisture flow, mainly during the afternoon to early evening hours into the weekend. But with limited moisture and instability the storms will struggle to get started.
The combination of upper troughing near the coast with moderate to strong onshore gradients has caused a fairly deep marine layer to form. Low clouds are expected to move well inland overnight, with a chance of some drizzle occurring. The overnight low clouds and patchy drizzle may recur the next couple of nights as well, due to the proximity of the upper trough to the coastline. The clouds may struggle to clear along the coast in some areas tomorrow afternoon, especially along the Central Coast.
Cooler temperatures are expected to persist through Friday, with 70s to 80s across most of the area except for low 90s in the Antelope Valley. Gusty onshore winds will occur in the afternoon to overnight hours, as onshore gradients persist. Peak gusts over the interior will be around 25 to 35 mph.
***From Previous Discussion***
The trough will start to weaken over the coming days and 500 mb heights will climb into the weekend. The marine layer depth will start to shrink on Saturday as onshore flow weakens. Temperatures will gradually warm through the weekend as high pressure aloft starts to press down on top of the marine layer. Low clouds will start to retract from the valleys area and become confined to the coast.
(Mon-Thu), 13/246 PM.
The latest forecast ensembles suggest a steady warming trend taking place through at least Tuesday as 500 mb heights climb to near 594-595 decameters. Any night through morning low clouds and fog should become confined to the coast by Sunday or Monday. Temperatures should approach August during this time. After Tuesday, the spread ensemble member solutions diverge some. Two of the cluster analysis panels suggest a warming trend continuing, while one of the panel would bring some cooling.
A northerly surface pressure gradient could develop between Sunday and Tuesday. Gusty northerly winds could develop across southern Santa Barbara County and through the Interstate 5 Corridor. Advisory level Sundowner winds could develop during this time, but there is some uncertainty in the timing and the actual strength of the winds.
14/0213z.
At 0029Z at KLAX, the marine layer was 2000 feet deep. The top of the inversion was near 4400 feet with a temperature of 19 C.
High confidence in VFR TAFs for KPMD & KWJF.
Moderate confidence in remaining TAFs. Timing of change groups may be off +/- 2 hours, with CIGs between 015 to 30.
KLAX, Moderate confidence in TAF. Timing of cat changes could be off by +/- 3 hours. No significant east wind component expected.
KBUR, Moderate confidence in TAF. Timing of cat changes could be off by +/- 2 hours. No wind issues expected.
13/809 PM.
High confidence that conditions will remain below Small Craft Advisory (SCA) criteria across all coastal waters through Saturday morning. There is a 30-50% chance of SCA winds across the outer waters and the western portion of the inner waters starting Saturday afternoon, with the highest chances for the waters south of Point Conception and the Santa Barbara Channel during the afternoon/evening hours. Chances increase Sunday afternoon, and at least SCA conds will continue through mid-week. Gusts of 30-35 kt will be possible starting Monday, with highest likelihood around Point Conception. Seas may approach 10 ft across portions of the Outer Waters Tuesday and Wednesday.
Ca, NONE. PZ, NONE.
