23/926 AM.
A persistent marine layer with stronger onshore flow will keep a cooler weather pattern in place through Saturday. Night through morning low clouds and fog with drizzle will be a staple of the forecast with clouds struggling to clear from beaches each day. Gusty onshore winds are possible across the interior portions of the area through the end of the week. A warming trend is expected for next week.
(Wed-Sat), 23/843 PM.
***UPDATE***
The marine layer is now 3800 ft the onshore push is an impressive 7.5 mb onshore to the east (down from a very impressive 9.5 mb). Marine layer stratus covers all of the csts/vlys and coastal slopes of VTA/LA counties. Low clouds are filling back in over the Central Coast. The SBA south coast is cloud free and will remain that way for a while. Low clouds will again spread across all but the farthest inland areas and highest peaks again. Drizzle is likely again in the morning esp near the foothills.
Max temps today would have been considered cool for January with cst/vly highs in the upper 50s and lower 60s. There may be some warming tomorrow but max temps will remain many degrees blo normal. The clouds showed some signs of disruption this afternoon and there may be slightly better clearing tomorrow afternoon.
Latest NAM continues to show a well defined cold front moving into the area Saturday morning.
Forecast was updated for the short term clouds.
***From Previous Discussion***
No real change in the forecast through the week as a trough of low pressure maintains cool conditions along with lots of marine layer stratus. The marine layer depth rose to 4000 feet this morning across the LA Basin and only slightly lower along the Central Coast. In theory tomorrow will be almost a carbon copy of today as forecast soundings indicate little change in the marine layer depth and onshore gradients. Temperatures again mostly in the lower 60s for coast/valleys and low to mid 70s in the deserts, which is 5-10 degrees cooler than normal. And some areas of drizzle or light rain, especially near the foothills south of Pt Conception.
On Friday a slightly deeper upper low will approach the Bay Area with even colder air aloft that will push the marine layer up to at least 5000 feet and possibly as high as 7000 feet. The additional rising motion created by the colder air aloft should theoretically generate more widespread drizzle or light rain but at the very least it will maintain a cool and cloudy pattern with minimal chances of sunshine for coast/valleys. The one exception could be the immediate coastal areas if a reverse clearing scenario develops.
As that upper low moves onshore near the Monterey/SLO County border Saturday morning, chances for light rain will increase area-wide. Official NBM Pops are still on the lower side and probably not representative of the actual chances for rain due to how light it will be. Virtually all the EPS and now also the GEFS ensembles are showing at least some light measurable rain across the Central Coast Saturday morning. This percentage drops to around 75% across Ventura County and around 40% for southern LA County and 10-15% across the Antelope Valley. Some areas, especially eastern Ventura and LA Counties may not actually receive measurable rain Saturday but that doesn't mean it won't be damp from drizzle.
In addition, with the close proximity of the upper low, can't rule out an isolated thunderstorm across SLO County, particularly the interior which could see some sunshine and surface heating in addition to the instability aloft. There are still a handful of EPS solutions indicating around a half inch of rain and this could be in part from convective cells with heavier rain rates.
(Sun-Wed), 23/218 PM.
The upper low is expected to be moving into NV Sunday morning but temperatures will still be 5-10 degrees below normal. Skies may still be cloudy in some areas Sunday morning but rapidly rising heights and increasing subsidence should clear most areas out by afternoon if not sooner.
High pressure will continue to build over the region into early next week bringing high temperatures to 3-6 degrees above normal in most areas. The one exception may be the immediate coast where persistent onshore flow and cool ocean temps will keep temperatures closer to normal or even slightly below.
24/0016z.
At 2346Z at KLAX, the marine layer was 2700 feet deep. The top of the inversion was around 4800 feet with a temperature of 13 C.
High confidence in TAFs for KPMD AND KWJF.
Moderate confidence in remaining TAFs. Flight Cat changes may be off by +/- 2 hours. There is a 25% chance for IFR cigs at KPRB, KSBP, KSMX. Better confidence in clearing fcst for sites Thursday afternoon.
KLAX, Moderate confidence in TAF. Low clouds may reform as early as 05Z or as late as 09Z. There is a 30% chance of cigs remaining AOA 022. There is a 15% chance of an east wind component reaching 8 kt from 11Z-17Z.
KBUR, Moderate confidence in TAF. There is a 30% chance of no clearing. There is a 30% chance of cigs remaining AOA 022.
23/1012 PM.
In the Outer Waters, good confidence in the forecast. Winds will be close to low-end Small Craft Advisory (SCA) levels at times thru Fri night. SCA level wind gusts are likely (50-60% chance) across much of the Outer Waters this afternoon through late tonight. There is a 20-40% chance of low-end SCA level winds anywhere across the outer waters Thu afternoon thru Thurday night. However, best chances for SCA winds will be south of Point Conception Thursday. SCA level conds are likely (70% chance) Sat afternoon thru Mon night.
For the Inner Waters north of Pt. Sal, moderate to high confidence in the forecast. There is a 30% chance of SCA level winds tonight and Friday afternoon/evening. SCA conds are likely (60% chance) during the afternoon/eve hours Sat thru Mon.
For the Inner Waters south of Pt. Conception, moderate confidence in the forecast. SCA level winds are expected over western and southern portions of the Santa Barbara Channel Thursday afternoon/evening, but most likely will not affect the Santa Barbara Harbor. Gusty winds look more widespread throughout the Santa Barbara Channel Friday, but may not be strong enough to reach SCA levels. Then SCA conds are likely (60% chance) during the afternoon/eve hours Sun thru Mon. There is a 40% chance for SCA level winds to enter the western portion of the southern Inner Waters Sun afternoon/eve. Otherwise, SCA conds are not expected thru Mon night.
Ca, NONE. PZ, Small Craft Advisory in effect until 3 AM PDT Thursday for zones 650-670-673-676. (See LAXMWWLOX).
