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000
FXUS66 KLOX 130551
AFDLOX

Area Forecast Discussion...CORRECTED
National Weather Service Los Angeles/Oxnard CA
1051 PM PDT Fri Apr 12 2024

.SYNOPSIS...12/846 PM.

Much cooler weather is expected through the weekend as another
late season storm moves into the region. Rain will begin tonight
with showers lasting through Sunday. Snow is expected at higher
elevations. A warming trend will begin Monday with dry weather
next week.

&&

.SHORT TERM (FRI-MON)...12/1050 PM.

Main feature of note will be an unseasonably cold upper level
low pressure system, currently located about 400 miles west of
San Francisco, which will bring some rain and mountain snow to
the area this weekend. This low will meander towards the Central
CA coast tonight/Saturday then will drop southeastward across our
area Saturday night/Sunday.

A deep moist layer in place this evening, with current satellite
imagery showing solid low clouds and fog into the lower coastal
slopes. 00Z NAM model cross section and high resolution model QPF
fields showing potential for drizzle/light rain tonight,
especially overnight when a well established warm front develops
across much of the forecast area. The main cold front will sweep
across the area on Saturday, bringing moderate precipitation to
the area. By Saturday afternoon, much colder air aloft and
associated instability moves across San Luis Obispo County and the
adjacent coastal waters, bringing a slight chance of
thunderstorms along with an increasing threat of small hail.

Behind the front, a showery regime can be expected Saturday
night through Sunday evening. Storm rain total estimates range
from 0.50 to 1.50 inches for much of the region, with 1.50 to
3.00 inches across the foothills/mountains (especially across
SLO/SBA county mountains as well as the western Ventura county
mountains). These totals match up well with NBM/ensemble thinking
of a 30-40% chance of 2.00+ inch totals in those favored
orographic areas. Rainfall rates should generally be around 0.50
inches or less per hour although local rates up to 0.66 inches per
hour will be possible with any thunderstorm activity. These types
of rainfall rates would support the potential for some urban
roadway and small stream flooding, as well as the threat of
additional mudslide/rockslide activity, especially in foothill and
canyon areas that have already been hard hit this winter season.

As for thunderstorms, given the time of year and the cold upper
low with associated instability, a threat of thunderstorms cannot
be ruled out. At this time, there looks to be a slight chance of
thunderstorms across SLO/SBA counties Saturday night then all
areas on Sunday as the upper low moves across the area. Any
thunderstorms that develop would likely produce brief heavy rain,
small hail gusty/erratic winds, and the threat of isolated
waterspouts (with a remote chance of severe- level thunderstorms).
With such cold air aloft (500 mb temperatures in the -26 to -29
degree range), the highest risk with storms will be accumulating
small hail, which could even occur outside of thunderstorms.

In evening update, expanded the wind advisory covearage to
include much of interior SLO County, the Santa Lucia Range,
southwest Santa Barbara county, the I-5 corridor, Santa Clarita
Valley, and Antelope Valley (including adjacent foothills).
Winds already ramping up across the Antelope Valley foothills
and southwest Santa Barbara county this evening, and expected to
expand to the other wind advisory areas tonight into Saturday
when gusts of 40 to 50 mph will become more widespread.

*** From previous discussion ***

For snow concerns, snow levels will drop to the 5000-6000 foot
range tonight/Saturday then down to the 4000-5000 foot range
Saturday night/Sunday. So, some decent snowfall can be expected in
the mountains. At this time, 5-10 inches are expected above 6000
feet with trace to 5 inch amounts between 4000 and 5000 feet. With
southerly winds gusting around 45 MPH, some winter weather
conditions can be expected in the mountains. Therefore, WINTER
WEATHER ADVISORIES are in effect some mountains areas in
SBA/Ventura and LA counties. See LAXWSWLOX for the details.

By Monday, the upper low will move eastward across the
southwestern deserts. So, dry conditions can be expected on Monday
with some warmer temperatures.

.LONG TERM (TUE-FRI)...12/148 PM.

For the extended, dry and warmer conditions can be expected. A
ridge will build along the West Coast Tuesday/Wednesday then will
flatten out to a zonal flow Thursday/Friday. At this time, the
warmest days of the period will be Wednesday/Thursday. Skies will
range between mostly clear and partly cloudy levels with the
potential for some coastal stratus/fog during the night and
morning hours.

&&

.AVIATION...13/0201Z.

At 0115Z at KLAX, the marine layer was 4000 ft deep. The top of
the marine inversion was at 4800 feet with a temperature of 10 C.

Low to moderate confidence in TAFs. A frontal system will bring
widespread rain tonight and tomorrow, as well as gusty south
winds. Wind speeds may be off by +/- 5 kts during peaks. Cigs may
be off by a category at times, especially during rain.

KLAX...Low to moderate confidence in TAF. Timing of onset of
rain/drizzle may be off by +/- 2 hours, and cigs/vsby may briefly
be off by a category, especially during rain. A southeast wind
direction is expected until around 21-23Z, then winds will shift
SW. Gusts up to 25 kts are possible from 12Z-18Z.

KBUR...Moderate confidence in TAF. Timing of onset of
rain/drizzle may be off by +/- 2 hours, and cigs/vsby may briefly
be off by a category, especially during rain.

&&

.MARINE...12/845 PM.

For the northern two outer water zones (PZZ670/673), a period of
SCA level S winds is likely this evening thru Sat morning. Wind
are expected to shift to the W Saturday afternoon and stay at SCA
level for the northernmost waters. Winds will stay below SCA until
Monday, when NW SCA level winds will build and last through Wed.
SCA level seas are expected Sat night thru Mon, with a 50% chance
of returning Tues night thru Wed.

In the southern outer waters zone (PZZ676), there is just a 30%
chance of SCA level S winds tonight/early Sat. SCA level seas are
likely Sat night-Mon. SCA level NW winds are likely Sun night-Wed.

In the inner waters north of Pt. Sal, a period of SCA level S wind
is likely this evening thru Sat morning. There will be a 40%
chance of SCA winds early Sunday morning. Then, winds will stay
below SCA until Monday afternoon, when NW SCA level winds will
build and last much of the time through Wed. There is a 60-70%
chance of SCA level seas Sat night thru Sun morning, and a 50%
chance on Wed.

For the inner waters S of Pt Conception, there will likely be a
period of SCA level SE winds in the SBA Channel late tonight/Sat
morning, with a 50% chance of SCA level winds in the southern
inner waters zone. SCA level W-NW winds are likely in the SBA
Channel Sun night-Tue, with a 30% chance in the southern inner
waters during that time.

There will be a chance of dense fog through the weekend.

&&

.BEACHES...12/845 PM.

Low-level high surf is expected this weekend with strong rip
current activity. Surf will peak Saturday night through Sunday
morning at 6 to 10 feet for the Central Coast, highest on west and
northwest facing shores. For beaches south of Point Conception,
surf will peak on Sunday around 4 to 7 feet, highest on west
facing shores.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 3 PM PDT Saturday for zones
      38-344. (See LAXNPWLOX).
     High Surf Advisory in effect from 9 PM Saturday to 9 PM PDT
      Sunday for zones 340-346. (See LAXCFWLOX).
     Winter Weather Advisory in effect from 5 AM Saturday to 5 PM
      PDT Sunday for zones 353-376-377. (See LAXWSWLOX).
     High Surf Advisory in effect from 9 AM to 9 PM PDT Sunday for
      zones 354-362-366. (See LAXCFWLOX).
     Winter Weather Advisory in effect from 11 AM Saturday to 5 PM
      PDT Sunday for zones 379-380. (See LAXWSWLOX).
PZ...Small Craft Advisory in effect until 9 AM PDT Saturday for
      zones 645-650-670-673. (See LAXMWWLOX).

&&

$$

PUBLIC...Gomberg/Thompson
AVIATION...Schoenfeld
MARINE...Gomberg
BEACHES...Schoenfeld
SYNOPSIS...Gomberg

weather.gov/losangeles

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