16/651 PM.
Generally quiet weather expected with cooler than normal temperatures and a robust marine layer through Thursday. Slight warming and a shrinking marine layer expected Friday into the weekend.
(Wed-Sat), 16/842 PM.
***UPDATE***
Thanks to a very deep marine layer today, some areas struggled to clear (mainly near the mountains south of Point Conception), but the remainder of the region saw sunny afternoon skies. The majority of the region saw a few degrees of cooling compared to yesterday, with highs in the high 60s to 70s along the Central Coast, and 70s to low 80s elsewhere. These temperatures are quite a bit below normal, around 5 to 10 degrees, locally 15 degrees below normal away from the coast for this time of year. At the coast, however, temperatures were within a few degrees on either side of normal.
Another round of deep marine layer clouds are expected overnight into tomorrow morning, with better late morning clearing compared to today (thanks to a slight decrease in onshore flow). Temperatures will be similar to today, with only a few degrees different.
Forecast looks to be in shape and no evening updates were needed.
***From Previous Discussion***
Thanks to the influence of the upper level low to our north and the persistent onshore flow, an extremely deep marine layer brought a June Gloom day to us here in Southwest California in mid-September. We're expecting another night of a fairly robust marine layer which will bring another gray morning to most folks, likely with better clearing tomorrow compared to today.
Only minor changes for tomorrow's temperatures, then a slight warming trend will occur Friday into the weekend as onshore flow weakens quite a bit and a short-lived pop up ridge moves into the area on Saturday. We'll likely see some light to locally moderate northerly winds across the interior mountains, and northeast winds across the Santa Lucias. This combo should dramatically reduce the coverage and extent of the marine layer cloud coverage each night through morning starting Friday morning. Otherwise mostly clear skies are expected Friday and much of Saturday.
(Sun-Wed), 16/1228 PM.
Quiet weather continues Sunday and most likely through the extended period. A weak upper level low will swing into the area Sunday, most likely remaining overhead through Monday and potentially Tuesday. While the most likely outcome is generally slightly cooler temps with a deeper and more expansive marine layer and the potential for morning drizzle, there is a very small chance for isolated shower or thunderstorm activity (likely focused over the interior mountains). Most European ensemble members show increasing PWATs as the upper low's cyclonic flow attempts to pull in some moisture from the fetch to our south and east, but PWAT values are not very substantial with a mean just over 1". Additionally most members also show some increasing CAPE over the area. However QPF output is very limited to nil, so it appears that the still limited moisture and the weakness of the trough will limit any sort of convective initiation. We will continue to monitor this very low chance for some "exciting" weather in an otherwise quiet pattern.
For Tuesday-Wednesday the most likely outcome is for that upper low to be replaced by weak ridging with slightly increasing 500 mb heights and weakening onshore flow, resulting in region-wide warming. There does remain a very low chance for that mountain focused convective activity continues.
17/0029z.
At 2337Z at KLAX, the marine layer was 3300 feet deep. The top of the inversion was at 6500 feet with a temperature of 17 C.
High confidence in TAFs for KPMD and KWJF.
Moderate to high confidence in remaining TAFs. Timing of flight cat changes could be off by +/- 3 hours, especially for VFR transitions south of Point Conception. Low VFR cigs may not scatter out through the period.
KLAX, Moderate to high confidence in TAF. Timing of flight cats changes may be off by +/- 3 hours. There is a 15% chance of an east wind component of 6-8 kts 09-19Z Thursday.
KBUR, Moderate to high confidence in TAF. Timing of flight cats changes may be off by +/- 3 hours.
16/754 PM.
For the outer waters, moderate to high confidence in the current forecast. Winds and seas will remain below Small Craft Advisory (SCA) levels through Thursday. Winds are likely to increase to SCA levels Thursday night and continue through Monday night, most prevalent and long-lasting for the waters west and south of Point Conception. Expect steep, choppy seas with the SCA conditions.
For the inner waters N of Point Sal, generally high confidence in the current forecast. Conds are expected to be below SCA levels through Friday morning, then SCA wind gusts are likely during the afternoons and evenings from Friday through Sunday.
For the inner waters S of Point Conception, moderate confidence in the current forecast. Conds are expected to be below SCA levels for the most part through Monday night. However, for the western Santa Barbara Channel, there is a 60% chance of SCA wind gusts Friday evening, a 50% chance of these gusts Monday evening, and a 30% chance of these gusts Saturday evening and Sunday evening.
Ca, NONE. PZ, Small Craft Advisory in effect from 3 PM Thursday to 3 AM PDT Saturday for zones 673-676. (See LAXMWWLOX).
