textproduct: Los Angeles

SYNOPSIS

13/548 PM.

Dry conditions and seasonable temperatures are expected through this weekend. Then, a strong storm system will affect the region late Sunday into Monday, bringing the potential for heavy rainfall, along with flooding and mountain snow, thunderstorms, strong winds, as well as marine and beach hazards. These conditions will continue through much of next week.

LONG TERM (TUE-FRI)

13/310 PM.

Looking further ahead, the large, upper-level cold-core trough will remain anchored across the western CONUS throughout much of the remainder of next week. This will be reinforced by multiple impulses of compact vorticity and accompanying speed maxima pivoting through the western rim of the larger-scale troughing. It appears Southern California will be beneath the trajectory of multiple impulses. Each impulse will have the potential to boost precipitation rates and winds within a rather long duration of on- and-off showers and blustery conditions. Significant dispersion exists amongst models concerning these impulses, though next Tuesday night through-Wednesday is a more-likely period of stronger jet energy passing over the local area, providing more precipitation and gusty winds. Regardless, temperatures through the week in most areas will be in the 50s and lower 60s -- below seasonal normal readings -- while snow levels gradually fall in response to cold advection with each passing impulse. Cold-weather impacts could become of increasing concern through the week.

Regarding precipitation totals through the period, there remains substantial variability from model to model, though most areas will likely experience at least 2-4 inches of liquid-equivalent precipitation (perhaps upwards of a several inches of precipitation). The progressive nature of each impulse following the Monday, more- avorable-for-flooding event may tend to mitigate subsequent flooding impacts. However, increasingly saturated ground conditions could offset the short-duration precipitation character to maintain, or even boost, flooding concerns through the week, and uncertainty regarding hydrological impacts grows quickly through the course of next week.

And then regarding storm-total snow in the mountains, elevations above 6 kft could receive upwards of multiple feet of snow. As snow levels lower, lighter snowfall accumulations -- though still potentially significant -- could impact elevations as low as 3 or 4 kft including the Grapevine of the Interstate-5 corridor, if enhanced mositure can adequately phase with cooling aloft. This will depend on numerous mesoscale factors for which uncertainty is significant.

While a drying trend is anticipated by next Friday, the potential for precipitation cannot be ruled out through late next week as embedded impulses track across the local area.

AVIATION

14/0550Z.

At 0450Z at KLAX, the marine layer was 1700 ft deep. The top of the inversion is near 2200 feet with a temperature of 14 C.

Good confidence in TAFs through 20Z with only a 15 percent chc of MVFR cigs 10Z-16Z and cstl sites. Lower confidence after 20Z for TAFs KOXR, KCMA and sites to the north as cigs might arrive later than fcst and hgts could be off by 2000 ft.

KLAX...Good confidence in TAF through 00Z then lower confidence as BKN conds may arrive as early as 00Z or as late at 07Z. Cig hgts could be as high as BKN060. There is a 25 percent chc of an 8-9kt east wind component 10Z-16Z.

KBUR...Good confidence in TAF through 00Z then lower confidence as BKN conds may arrive as early as 00Z or as late at 07Z. Cig hgts could be as high as BKN060 or as low as BKN030.

MARINE

13/200 PM.

For the Outer Waters, moderate to high confidence in current forecast. Today through Saturday morning, high confidence in Small Craft Advisory (SCA) level northwest winds with seas near 10 ft. For Saturday afternoon through Saturday night, high confidence in winds and seas remaining below SCA levels. For Sunday through Tuesday, high confidence in a combination of SCA level southerly winds and seas. There is a 50-70% chance of GALE force winds during this time period.

For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. SCA level northwest wind gusts this afternoon and evening. For Saturday through Saturday night, high confidence in winds and seas remaining below SCA levels. For Sunday through Tuesday, high confidence in a combination of SCA level winds and seas. There is a 40-50% chance of GALE force winds during this time period.

For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Today through Saturday night, high confidence in winds and seas remaining below SCA levels. Winds gusts could reach SCA levels at times through early this evening across the western Santa Barbara Channel. The Catalina Eddy will spin up overnight with a 30% chance of borderline SCA level SE wind gusts mid-morning tomorrow. For Sunday through Tuesday, high confidence in SCA level southeast to southwest winds developing. There is a 30-40% chance of GALE force winds during this time period.

(Late Sunday night - Monday night) *Timing will be refined later*

A squall line will likely develop in association with the cold front which will result in hazardous marine conditions. These include: GALE force winds, dangerous Lightning, heavy rainfall with reduced visibility, and waterspouts.

BEACHES

13/739 PM.

A High Surf Advisory is in effect for the Central Coast, and is expected to peak overnight with large breaking waves of 9 to 13 feet.

A period of very large waves continues to be advertised by the latest swell model guidance early next week. High confidence in widespread high surf between Monday and Thursday as a combination of SW and W-NW swells affect the SW California waters. Sets above 10 feet will be possible across all beaches, but there is a higher chances for W-NW facing shores. There is a moderate chance of damaging sets (near 20 ft) developing between Tuesday night and Wednesday night, especially along the Central Coast.

Elevated high tides as the new moon cycle approaches will coincide with the arrival of the higher surf and swell. This will bring an elevated chance of coastal flooding, or at the very least, minor tidal overflows especially during the time of the high tides. A coastal flood advisory may be needed should swell guidance remain consistent along with wind-driven factors.

LOX WATCHES/WARNINGS/ADVISORIES

CA...High Surf Advisory in effect until 9 AM PST Saturday for zones 340-346. (See LAXCFWLOX). PZ...Small Craft Advisory in effect until 9 AM PST Saturday for zones 670-673-676. (See LAXMWWLOX).