textproduct: Los Angeles

SYNOPSIS

15/1057 PM.

A powerful storm system will move into and through the region today, bringing the potential for severe thunderstorms, burn- scar debris flows, flash flooding with rock and mud slides, damaging winds, heavy mountain snow, and high surf with coastal flooding. Cold and blustery conditions with periodic rain will occur through at least the middle of this coming week.

LONG TERM (THU-SUN)

16/1216 AM.

On Wednesday evening the entire state will be under fast moving moist cyclonic NW flow. There will be enough lift and moisture to bring chc (30-40 percent) of rain to SLO and north and west SBA counties. South of Pt Conception there will only be a 10 to 20 percent chc. Rainfall amounts, if any will be under a tenth of an inch. Snow levels will remain at or under 3000 ft and the Tejon (I-5) pass will see snow flurries.

On Thursday a fast moving trof will ripple through the NW and will likely (70 percent chc) bring rain to most of the area. This is a drier system (PWATs ~ .60") and slightly unstable so it will be a showery system. Early rainfall estimates call for a third to a half inch with slightly higher amounts in the mtns. The showery nature of the system may make the rainfall a little less homogeneous than typical. Snow levels will be around 3500 ft but could be lower under convective bursts. Max temps will be solidly in the mid to upper 50s or 10 to 15 degrees blo normal.

Cold cyclonic flow will wring out a few showers Thursday night but for the most part it will be partly cloudy cool and dry.

Not the best mdl agreement on the Friday forecast with ensembles splitting between weak troffing and weak ridging. Enough ensembles are wet to allow for a slight chc of showers in the morning, but really think the day will be dry. Skies should be, at worst, partly cloudy. Max temps will rise a few degrees but still will come in only a degree or two either side of 60.

Saturday will provide a brief respite in the parade of storms as a weak ridge should pop up and make for a dry day with mostly sunny skies. Max temps will respond in kind, rising 3 to 6 degrees and ending up in the 60s (still 2 to 4 degrees under normal)

A cold 522 dam move towards the PACNW on Sunday and will set up another round of fast moving SW flow over the state. Clouds will increase through the day and areas north of Pt Conception will end up mostly cloudy. A chance of rain will also develop north of Pt Conception in the afternoon. The warmer SW flow is forecast to add a few degrees of warming, but if the clouds arrive earlier or are thicker this warming may not materialize.

Looking at both long range AI mdls there appears to be a chance of rain each day Mon Tue and Wed (The 23rd, 24th and 25th)

AVIATION

16/1113Z.

At 0823Z at KLAX, there was no marine layer or inversion.

Moderate confidence in TAFs for KPMD and KWJF.

Fair confidence in TAFs through 15Z then low confidence in all TAFs. A cold front will move through the area and both cigs and vis will vary frequently. MVFR flight conds will occur most of the time, but there will be periods of IFR conds and a chance of LIFR conds during heavier rains. Good confidence in improving condition after 00Z. There is a 20 percent chc of a TSTM (13Z-19Z KPRB, KSBP and KSMX and 16Z-22Z for the rest of the sites)

KLAX...Good confidence in TAF through 15Z with a 20 percent chc of BKN025 conds. Low confidence in TAF 15Z-00Z as cig and vis will vary frequently. During this time cigs will mostly be between 010 and 020, but BKN008 conds are possible and brief period of BKN004 1SM +RA BR are also possible. Better confidence in improving conditions aft 00Z. High confidence in east winds through 20Z (strongest 15Z-19Z) with a 30 percent chc of them lasting through 22Z.

KBUR...Good confidence in TAF through 15Z with a 20 percent chc of BKN025 conds. Low confidence in TAF 15Z-00Z as cig and vis will vary frequently. During this time cigs will mostly be between 010 and 020, but BKN008 conds are possible and brief period of BKN004 1SM +RA BR are also possible.

MARINE

16/156 AM.

A squall line is expected to develop in association with the cold front through tonight, which will result in extra hazardous marine conditions. These may include STORM FORCE winds (above 48 kts), dangerous lightning, heavy rainfall with reduced visibility, small hail, and waterspouts.

A large mixed medium period west swell of 8 to 13 feet Monday and Tuesday will likely build further to 12 to 16 feet Tuesday night into Wednesday. Highest in the outer and northern waters. Seas around 10 feet may continue across the outer waters through Friday morning.

For the Outer Waters and Inner Waters north of Point Sal, moderate confidence in current forecast. Through Wednesday morning, high confidence in GALE force winds. There will likely be a 4 to 8 hour break in widespread GALES Tuesday morning into the afternoon, however, Small Craft Advisory (SCA) seas will continue through Friday morning.

For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Through Wednesday, there is a 50-70% chance of GALE force winds after through Monday night, and again Tuesday night into Wednesday morning. Otherwise, SCA winds and seas will continue through Wednesday.

BEACHES

16/156 AM.

A period of very large waves is expected to move into the waters on Monday, with surf generally peaking Tuesday and Wednesday across west facing beaches. High Surf Advisories and Beach Hazard Statements are in effect for all coasts, see the CFWLOX and SRFLOX products for more details.

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 minor tidal overflows, especially during the time of the high tides on Tuesday and Wednesday. A coastal flood advisory may be needed should swell guidance remain consistent, along with wind- driven factors.

LOX WATCHES/WARNINGS/ADVISORIES

CA...High Wind Warning remains in effect until 6 PM PST this evening for zones 38-344-345-353-376-378-379-381-382. (See LAXNPWLOX). Wind Advisory remains in effect until 6 PM PST this evening for zones 87-88-340>343-346>352-354>358-366>375-383-548. (See LAXNPWLOX). Flood Watch remains in effect from 9 AM PST this morning through this evening for zones 87-88-348>358-362-366>380-548>550. (See LAXFFALOX). High Surf Advisory in effect from 10 AM this morning to 6 PM PST Thursday for zones 340-346-362-366. (See LAXCFWLOX). Beach Hazards Statement in effect from 10 AM PST this morning through Wednesday morning for zones 349-350. (See LAXCFWLOX). Winter Storm Watch remains in effect from Tuesday evening through Thursday morning for zones 353-376-378-379-381-382. (See LAXWSWLOX). High Surf Advisory in effect from 10 AM this morning to noon PST Thursday for zone 354. (See LAXCFWLOX). Winter Storm Warning remains in effect until 9 AM PST Thursday for zones 377-380. (See LAXWSWLOX). High Wind Warning in effect from 9 AM this morning to 3 PM PST this afternoon for zones 549-550. (See LAXNPWLOX). PZ...Gale Warning in effect until 8 AM PST Wednesday for zones 645-670-673-676. (See LAXMWWLOX). Gale Warning in effect until 2 AM PST Tuesday for zones 650-655. (See LAXMWWLOX).