textproduct: Los Angeles

SYNOPSIS

12/316 AM.

Patchy dense fog has developed across coastal areas and the coastal waters south of Point Conception, and dense fog is expected to expand to the north and impact coastal areas and the waters through Sunday. A gradual cooling trend is expected into the weekend as high pressure weakens. Temperatures will trend warmer again next week.

LONG TERM (MON-THU)

12/316 AM.

Were not out of the woods yet when it comes to the December warmth. The upper level ridge will build back up Monday through at least Tuesday. Offshore flow from the north will increase Monday and Tuesday, continuing through the period, but it is forecast to be weaker than this past week. The LAX-DAG gradient is forecast to turn back offshore during the same period, but also remain weaker than this past week. High temps are currently forecast to be 10 to 15 degrees above normal Monday and Tuesday, with isolated areas up to 20 degrees above normal.

There is some discrepancy between the GFS ensemble (GEFS) and EC ensemble (ENS) for the Wednesday through Thursday period. The ENS keeps the upper level ridge overhead through the period, while the GEFS turns the upper levels more zonal. The ENS does weaken the upper level ridge, but this solution would still result in some warmer temperatures through the week. The GFS turns the LAX-DAG gradient back onshore Wednesday while the EC keeps the weak offshore flow going, which will also result in cooler temperatures in the GFS scenario compared to the EC scenario. Went ahead and kept the NBM max temperatures for Wednesday and Thursday due to this discrepancy, but these temps are still likely to be too cool regardless of which scenario plays out.

AVIATION

12/1116Z.

At 11Z at KLAX, the marine layer was a 300 feet deep. The top of the inversion was 3000 feet with a temperatures of 22 Celsius.

60+% chance of VLIFR FG affecting KLGB, KLAX, KSMO, KOXR, KCMA, KSBA through 16Z. Moderate confidence in MVFR/VFR conditions by 19Z, but there is a 20% chance of lingering IFR conditions at KOXR and KLAX into the afternoon hours. Low confidence on how the low clouds evolve Friday Night into Saturday, but the clouds will likely cover a greater area and likely be LIFR or VLIFR. In addition to the above airports, there is a 50% chance of clouds in KSMX and KSBP forming Friday night.

High confidence in all other airports staying VFR through Saturday.

KLAX...There is a 60% chance of VLIFR conditions 12-16Z today. Improvement to VFR likely by 19Z, but there is a chance of MVFR HZ lingering into the afternoon. IFR conditions could form as early as 23Z, with LIFR conditions likely sometime Friday night into Saturday. Low confidence on timing.

High confidence in any east winds staying under 8 knots.

KBUR...High confidence in VFR conditions through at least Saturday with weaker than normal winds.

MARINE

12/227 AM.

Areas of dense fog with very low visibility will affect the coastal waters through at least Saturday. This fog could form anywhere at anytime, wwith indications of it expanding in coverage through Saturday. While the focus will be in the overnight and morning hours, some pockets will likely through the afternoon and evening hours.

High confidence in unusually light winds and lowering seas through the weekend. More typically gusty NW-W winds will likely return, Monday and Tuesday. These winds will strengthen further Wednesday and Thursday, when there is a 30% chance for Gale Force winds from Point Sal to San Nicolas Island including portions of the Santa Barbara Channel. This increase of winds will increase choppy seas over most of the waters.

LOX WATCHES/WARNINGS/ADVISORIES

CA...Dense Fog Advisory in effect until 10 AM PST this morning for zones 350-354-355-362-366-368. (See LAXNPWLOX). PZ...NONE.