textproduct: Los Angeles

SYNOPSIS

12/927 PM.

Dry conditions with a warming trend are expected to continue through Saturday. A strong storm system will affect the region starting on Sunday and Monday, bringing the potential for heavy precipitation with flooding and mountain snow, thunderstorms, strong winds, as well as marine and beach hazards. These conditions could last through much of next week.

LONG TERM (MON-THU)

12/219 PM.

The general consensus among guidance is that there is likely to be three storm systems to impact Southwest California next week. Although timing is not set in stone, it appears that the system could arrive to the Central Coast sometime late Sunday night, with fairly good confidence of widespread impacts on Monday. Details will be ironed out with time.

This first system appears the most robust in terms of rainfall amounts and rain rates. One caveat that could dampen hydrologic concerns a bit would be the storm's fast motion. However, this system will take more time to move through the region compared to the last storm system. PWAT values are expected to average around 1" on Monday with 10% of ensembles indicating closer to 1.2". This would be over the 95th percentile. Still with the same general thoughts of 1-2" for coast/valley and 2x that for the mountains on Monday. There is still quite the range with respect to amounts.

Quite a bit of uncertainty regarding the convective potential. There is a handful of models such as the UKMET and ICON that are less favorable synoptically for severe storms. There is a slight chance for thunderstorms as the front moves through on Monday.

There appears to be less discontinuity in guidance between Monday and Tuesday's storm - likely continuing through Wednesday. There could be another shortwave diving southward embedded in NW flow on Thursday but uncertain in how much moisture will be present.

Snow levels will begin near 6000 ft for the first storm and will decrease to 3000-3500 ft by Wed. Significant snow accumulation is possible to likely through this timeframe. Details will be ironed out with time. ECMWF 500mb temps drop to -33 C over the Central Coast by late Wednesday morning with 700-500mb (7-8 C) lapse rates indicating favorable mid-level instability. Despite less low-level moisture compared to Monday, these values will likely be enough to compensate and support thunderstorm potential.

Please continue to monitor the latest information from the National Weather Service in Los Angeles/Oxnard, California, as forecast details become refined over the coming days.

AVIATION

13/0253Z.

At 0017Z, there was no marine layer and no inversion.

High confidence in VFR TAFs except for KPRB, where there is a 20-40% chance for cigs through 18Z. Moderate confidence in winds over the period. There is a 20% chance for north winds 10-15 kt at KSBA through 16Z.

KLAX...High confidence in VFR conds through at least 12Z. After 12Z, there is a 20% chance for VV002 and 1/2SM conds 12Z-18Z. Light east winds are possible from 08Z to 18Z, but east wind component should remain below 7 kt.

KBUR...There is a 30 percent chance of VLIFR to LIFR conditions in ground fog through 16Z, otherwise VFR conditions are expected. No wind impacts are expected at this time.

MARINE

12/730 PM.

A series of storm systems will move over the coastal waters Sunday into Monday, and through the remainder of the week, bringing hazardous winds and seas to the waters, rain and a slight chance of thunderstorms. Confidence is growing in the development of dangerous marine conditions across the waters Sunday night, thus it is encouraged to consider altering plans for next week.

Near Term: Small Craft Advisory (SCA) winds and seas will be common across much of the waters through late Friday night or early Saturday morning then a relative lull is forecast during most of Saturday. For the inner waters south of Point Conception, there is a 30-40% chance for winds to reach SCA levels Friday afternoon and evening. The Catalina Eddy is forecast to spin up again on Saturday morning, bringing a 30% chance of SCA level southeast winds to the inner waters south of Point Conception Saturday morning to early afternoon. Southerly winds will begin to reach the Outer Waters by late Saturday, then spread across the remainder of the waters through Sunday night.

Outlook: All eyes shift to late Sunday through at least Wednesday when moderate to strong southerly to southwesterly flow will impact the entirety of the coastal waters. There is a moderate to high chance of widespread Gale Force winds, especially Monday through Tuesday night. Seas will also build, becoming large and hazardous across all the waters, including nearshore.

Hazardous marine conditions are expected to continue through the late in the week.

BEACHES

12/725 PM.

Surf and swell will build again at area beaches through late Friday night, and a High Surf Advisory was issued for the Central Coast. Local sets to 7 feet are possible at Ventura County Beaches.

A period of very large waves continues to be advertised by the latest swell model guidance early next week. There is a 50-70 percent chance of widespread high surf between Monday and Thursday as a combination of SW and W-NW swells affect the California coast. Sets above 10 feet will be possible across all beaches, but there is a higher chances for W-NW facing shores. There is a 20-30 percent chance of damaging sets developing between Tuesday night and Wednesday night, highest for NW facing shores along the Central Coast.

Elevated high tides as the new moon cycle approaches will coincide with the arrival of the higher surf and swell with storm system early next week. This will bring an elevated chance of coastal flooding, or at the very least, minor tidal overflows during times of the highest high tides each evening. A coastal flood advisory may be needed should swell guidance indicate similar surf and swell and locally wind-driven swell affect the beaches and coastline.

LOX WATCHES/WARNINGS/ADVISORIES

CA...High Surf Advisory in effect from 3 AM Friday to 9 AM PST Saturday for zones 340-346. (See LAXCFWLOX). PZ...Small Craft Advisory in effect from noon to 9 PM PST Friday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until midnight PST tonight for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PST Saturday for zones 670-673-676. (See LAXMWWLOX).