National Weather Service Raw Text Product

092 
FXUS66 KLOX 041841
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA 
1041 AM PST Wed Jan 4 2023

.SYNOPSIS...04/1016 AM.

A strong Pacific storm system will affect the area later today 
into Thursday with strong winds, damaging surf, heavy rain with
flooding, and high elevation snow. Activity will lower Thursday 
night with Friday being dry. A series of storms is forecast to 
bring cloudy skies and wet weather over the weekend and into next 
week. Temperatures will remain cooler than normal through the 
period.

&&

.SHORT TERM (TDY-FRI)...04/1022 AM.

***UPDATE***

All systems go for our storm system, with minimal changes. Rain
amounts and intensity forecast remain unchanged, with the caveat
of mentioning isolated totals to 10 inches and rates to 1.25 inch
per hour. The storm will peak in intensity tonight over SLO and
Santa Barbara Counties, and over Ventura and LA Counties Thursday
morning. The storm looks to move very slowly over Santa Barbara
and Ventura Counties, which is why they will likely see the
highest amounts. This is a lot of water and the threat of flooding
is a real concern. Expect a lot of roadway flooding, including a
few freeway closures. The Thursday morning commute will be bad. 
Several small streams will likely flood and spill over. Stay out 
of and away from any creeks and drainages as these could become 
deadly quickly. 

Snow still expected to be confined to the higher peaks 
with the bulk of the precipitation, but could lower to around 
6,000 feet today and during the showers tomorrow. Thunderstorms 
were already in the forecast, but expanded it tomorrow to cover 
all areas.

Winds remain a concern as well. Already seeing a lot of gusts in
the 40 to 50 mph range in the mountains and Central Coast, where 
High Wind Warnings remain in play. These winds will only increase 
toward the late afternoon and night peak. Wind damage to trees 
and large objects is likely. Many power outages are nearly 
certain, and could be prolonged by the concurrent heavy rain. Plan
ahead now for what you would do if the power was out for several 
hours. Expanded Wind Advisories to all of Ventura and Los Angeles 
Counties, where a few power outages could occur. 

With everything set for this storm, will start to focus more on
the next storms. Stormy weather could return as early as later
Saturday, with significant chance of rain extending through
Wednesday. The potential is growing now for a similar type storm
in the Monday or Tuesday timeframe. 

***From Previous Discussion***

A powerful and dangerous storm system will affect the area today 
and esp tomorrow. While the storm is a few hundred miles to the 
west of the Central Coast its affects will be felt today as a warm
front develops ahead of the main system. The weak lift and more 
importantly the southerly flow assoc with the warm front will 
interact with a 7000 ft deep moist layer that is in place over the
csts/vlys. This will lead to the development of widespread light 
rain or drizzle. The foothills and coastal slopes will be most 
affected as the south wind will drive a good amount of orographic 
lift. This rain will not be too heavy but it will occur over a 
long duration. Rainfall amounts from this warm front should be .25
to .75 of an inch csts/vlys to 1 to locally 2.5 inches south 
facing coastal mountain slopes. The warm southerly flow will lift 
snow levels to above 7000 ft, keeping any accumulating at or above
the resort levels.

As the main front approaches the Central Coast the sfc pressure
gradient will tighten and a low level jet will develop. These two
items will combine to really increase the winds across SBA and 
SLO counties as well as the mtns of VTA county. Warning level 
gusts from 60 to 70 mph will develop across the mtns of 
SLO/SBA/VTA counties. Warning level gusts near 60 mph will also 
occur across the Central Coast. The interior sections of SLO and 
SBA counties will see advisory level gusts to 50 mph. Please see 
the product LAXNPWLOX for all the wind details.

Winter Storm Warnings (see the product LAXWSWLOX) have been issued
for the mtns of LA and VTA counties. This is not a typical warning
as the winds will arrive first when the snow levels are at or
above the resort levels the accumulating snow will arrive as the
winds diminish later Thursday. The major mtns passes will not see
snow but some higher elevation roadways, such as Angeles Crest 
and Big Pines Highways in Los Angeles County and Lockwood Valley 
Road in Ventura County should get snow later Thursday.

The most intense part of this weather event will occur later this
evening and last through noon Thursday. A slow moving cold front 
will entrain the moisture from a moderate atmospheric river 
(containing high precipitable water values up to 1.25 inches). The
front will be further enhanced by and a strong low level jet (850
winds up to 60 mph) and the dynamics from the let front region of
130 kt upper level jet. Widespread moderate to heavy rain will 
last 6-9 hours along and ahead of the front. Peak rainfall rates 
of 0.5 to 1 inch per hour will be common with this feature, with 
locally higher rainfall rates possible for south facing mountain 
slopes, especially for Santa Barbara and Ventura Counties. 
Rainfall totals will generally be 2-4 inches coasts and valleys 
with 4-8 inches south facing mountains, highest across Santa 
Barbara and Ventura Counties. These rates and amounts could cause 
significant flash flooding or debris flows across the region in 
and outside of recent burn scars with significant small stream and
urban flooding possible. A Flood Watch (see FFALOX for details) 
for this threat will be in effect for all of Southwest CA later 
this evening and into Thursday afternoon.

In addition this amount of rain will bring significant flow to
many of the main stem rivers Thursday or early Friday. At this
time no river is forecast to reach flood stage. 

Temperatures throughout the event will be fairly steady in the 
50s to near 60 lower elevations and 40s to near 50 in the 
mountains.

Short range ensemble and deterministic guidance all show weak
ridging moving into the area behind the front later Thursday
evening and continuing into Friday. Look for mostly dry conditions
as well as a reduction in cloud cover and a few degrees of
warming.

.LONG TERM (SAT-TUE)...04/306 AM.

Both the EC and the GFS deterministic mdls as well as their
ensemble means show a series of storms of varying intensity moving
into the PAC NW and dragging cold fronts through CA

The system moving through the area over the weekend is not too
strong and Central Coast will see the best chc of rain. Rainfall
amounts will not be too significant.

A stronger system should affect all of the area Monday through
Tuesday. Early rainfall estimates (which could certainly change)
call for 1 to 3 inches of rain.

Wednesday look dry for now, but another system is slated for late
next week.

Max temps will remain 3 to 6 degrees below normal for the period.

&&

.AVIATION...04/1834Z.

At 1750Z at KLAX, there a 12000 ft moist layer with no inversion.

Low confidence in all TAFs. Cigs and Vis will vary frequently
through the period. There is a chc of rain at all sites through
the period becoming more and more likely after 20Z. With strong
winds arriving overnight, there will be the distinct possibility
of LLWS and UDDFS just about anywhere. Expect a good possibility
of IFR cigs and vis just about anywhere with VLIFR conditions near
the mountains.

KLAX...Low confidence in TAF. Cigs and Vis will vary frequently 
through the period. There is a 30-40 percent chc of rain through 
21Z. There will likely be periods of rain 21Z-04Z. Good confidence
in east wind fcst with a 30 percent chc of 21010KT winds arriving
early at 01Z.

KBUR...Low confidence in TAF. Cigs and Vis will vary frequently
through the period. There is a 20 percent chc of rain through 21Z.
There will likely be periods of rain 21Z-04Z.

&&

.MARINE...04/1021 AM.

A strong pacific storm system will bring significant hazards and 
dangerous ocean conditions to the coastal waters through 
Thursday night. Seas will peak at 18-25 feet along the Central 
Coast, and 10-18 feet from Santa Barbara to Los Angeles County. 
Large breaking waves will create dangerous conditions at harbor 
entrances, especially for Morro Bay and Ventura Harbors around low
tide. The storm will also bring a slight (10-20%) chance for 
thunderstorms, possible waterspouts, and lightning. Mariners 
should remain in safe harbor for the protection of life and 
property. Refer to the Marine Weather Statement (LAXMWSLOX) for 
additional details about the storm. 

For all the Outer Waters and the Inner Waters north of Point Sal,
high confidence in current forecast. Through Thursday, southeast 
winds will increase to Gale force this morning and continue 
through Thursday morning with seas well above 10 feet. 
Additionally, there is a 20% chance of Storm Force winds (50 
knots) tonight through Thursday morning. By Thursday afternoon, 
the winds will diminish and are expected to remain below Small 
Craft Advisory (SCA) levels through Sunday. However, seas will 
likely remain at SCA levels through Sunday.

For the Inner Waters south of Point Conception, moderate
to high confidence in current forecast. High confidence in 
southeast winds remaining at SCA levels through this evening.
Then, winds will increase to Gale Force for the Santa Barbara 
Channel this evening with the winds over the waters south of
Anacapa Island following suit late tonight. Moderate confidence 
in timing of winds decreasing below advisory levels as it may be 
earlier for the Santa Barbara Channel, but good confidence that 
winds will be below SCA levels by late Thursday evening. High 
confidence in seas reaching SCA levels by late tonight and
continuing through Friday afternoon. For Saturday and Sunday, 
high confidence in winds and seas remaining below SCA levels.

&&

.BEACHES...04/1040 AM.

A very strong Pacific storm system will bring large surf to all 
beach areas beginning Wednesday. Surf heights will hover around 20
feet on the Central Coast Thursday and Friday and a HIGH SURF 
WARNING has been issued. South of Point Conception, warning level 
surf (around 14 feet) is expected for the Ventura Beaches and a 
HIGH SURF WARNING is in effect for these beaches also. Elsewhere 
south of Point Conception, high surf conditions are anticipated 
and HIGH SURF ADVISORIES have been issued.

Along with the high surf, minor coastal flooding is possible across
the Central Coast and the Ventura county coast on Thursday and 
Friday. Flooding of sea water is likely over vulnerable low-lying
coastal areas such as parking lots, beaches, and walkways. 
Therefore, a COASTAL FLOOD ADVISORY was issued for the Ventura, 
San Luis Obispo and western Santa Barbara County coasts from 
early Thursday morning through Friday morning. The best chance for
coastal flooding is during high tide. Tides peak Thursday morning
and Friday morning at just over 6 feet around 8 AM. Rip currents 
will become even stronger as the tides begin to peak.

Frequent, dangerous rip currents will occur at all beach areas
Thursday through Friday. Large waves will top rock jetties that 
have a history of fatalities along southwest California beaches. 
Be on the lookout for waves that move well up the beach during 
times of high tide, and some much larger waves may occur without
warning. Stay well back from the water's edge and stay off of
rocks and jetties. 

Additionally, a moist and unstable airmass with the storm will 
bring a 20% chance of isolated thunderstorms to the beaches north
of Point Conception late tonight through Thursday morning. If  
thunder roars, go indoors.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Storm Warning in effect until 10 PM PST Thursday for
      zone 53. (See LAXWSWLOX).
     Flood Watch in effect from 10 PM PST this evening through
      Thursday afternoon for zones
      53-54-59-87-88-354>359-362>365-547-548. (See LAXFFALOX).
     Winter Storm Warning in effect from 6 PM this evening to 10
      PM PST Thursday for zone 54. (See LAXWSWLOX).
     Wind Advisory in effect from 6 PM this evening to 10 AM PST
      Thursday for zones 59-87-88-354>359-362>365-547-548. (See LAXNPWLOX).
     High Surf Advisory in effect from 6 AM Thursday to 10 AM PST
      Friday for zones 87-349-350-362-364. (See LAXCFWLOX).
     High Wind Warning in effect until 6 AM PST Thursday for zones
      340>342-345>349-351-353. (See LAXNPWLOX).
     High Surf Advisory in effect until 6 AM PST Thursday for
      zones 340-346-354. (See LAXCFWLOX).
     Flood Watch in effect from 4 PM PST this afternoon through
      Thursday morning for zones 340>353-549-550. (See LAXFFALOX).
     Coastal Flood Advisory in effect from 4 AM Thursday to 1 PM
      PST Friday for zones 340-346-354. (See LAXCFWLOX).
     High Surf Warning in effect from 6 AM Thursday to 10 AM PST
      Friday for zones 340-346-354. (See LAXCFWLOX).
     Wind Advisory in effect until 10 PM PST Thursday for zones
      343-344. (See LAXNPWLOX).
     Wind Advisory in effect until 6 AM PST Thursday for zones
      350-352. (See LAXNPWLOX).
     High Wind Warning in effect from 6 PM this evening to 6 AM
      PST Thursday for zones 549-550. (See LAXNPWLOX).
PZ...Gale Warning in effect until 9 AM PST Thursday for zones
      645-670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 PM PST this evening
      for zone 650. (See LAXMWWLOX).
     Gale Warning in effect from 9 PM this evening to 2 PM PST
      Thursday for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PST Thursday for
      zone 655. (See LAXMWWLOX).
     Gale Warning in effect from 3 AM to 2 PM PST Thursday for
      zone 655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PST this afternoon
      for zone 676. (See LAXMWWLOX).
     Gale Warning in effect from 3 PM this afternoon to 9 AM PST
      Thursday for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke/Kittell
AVIATION...Sweet/Rorke
MARINE...Sweet/Lund
BEACHES...Sweet/Lund
SYNOPSIS...RK

weather.gov/losangeles

Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox