Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 271405
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
605 AM PST Fri Jan 27 2023

.SYNOPSIS...27/213 AM.

Sunny skies and near normal temperatures will be the order of the
day today. Much cooler temperatures are expected over the
weekend, with a chance of light rain Sunday and Monday. Dry but
cool weather is expected Tuesday through Thursday next week.

&&

.SHORT TERM (TDY-SUN)...27/259 AM.

Chamber of Commerce day today. An upper level ridge nosing in from
the NW and weak offshore flow will combine to bring sunny skies
and near normal temperatures to the entire area. The weaker
offshore flow will bring cooling to the coasts due to less
compressional warming, but the rest of the area will warm as ydy`s
cool air advection will not be present. There will be some 15 to
25 mph canyons winds but nothing near advisory levels.

The anticyclonic flow will switch to cyclonic tonight as the state
comes under the west side of a very large CONUS spanning trof. A
rapid switch from offshore to onshore flow will likely bring
marine layer low clouds to the Central Coast.

Aside from the morning low clouds across the Central Coast
Saturday should be a mostly sunny day with little or no wind
issues. The switch to onshore flow and decreasing hgts will knock
5 to 10 degrees off of the max temps which will end up 3 to 6
degrees blo normal.

The marine layer will rapidly deepen Saturday night into Sunday as
a cold trof rotates into the state from Idaho. Heights will
fall rapidly and onshore flow will increase. The marine layer will
rapidly deepen to be around 5000 ft Sunday morning. The rapid
deepening will bring local drizzle to the area (esp near the
foothills) as well as clouds deep into the vly and into the mtns
passes.

The marine layer will further deepen to 8000 ft by the afternoon.
As PVA form the approaching trof interacts with the marine layer a
chc of light rain will develop just about anywhere. Rainfall
amounts, however, will be spotty and total no more than a quarter
inch. 6 to 12 degrees of cooling will keep all cst/vly max temps
in the 50s or 10 to 15 degrees blo normal. Snow levels will be
falling quickly through the day to as low as 3500`.

An upper low will develop in the base of the trof Sunday night and
will retrograde to just west of Pt Conception. This will set up a
showery regime. The sfc winds assoc with this pattern will be
fairly light (under 20kt) and from the west to southwest. This
will limit the upslope flow to only the SLO county foothills and
the San Gabriel range. Since this storm originated over land and
is so cold it will not hold much water and PWAT`s are expected to
be around .4". This will limit the amount of rain that will fall
to under a quarter inch except in the areas with upslope flow.
Light snow could fall as low as 2500 to 3000`.

.LONG TERM (MON-THU)...27/312 AM.

The GFS and EC deterministic mdls as well as their respective
ensembles are in good agreement through the extended period giving
a greater than normal confidence in the fcst.

The upper low will across the area Monday. The cold air aloft will
destabilize the atmosphere and will keep the shower chances
going. It is likely that there will be some breaks in the clouds
as well esp in the afternoon. Rainfall will be very non
homogeneous and totals for the day will generally be under a
quarter inch and storm totals should almost all be under a half
inch, except the eastern San Gabriels which could see a half inch
to inch of rain. Light snow will fall down to 2500-3000 feet.
Graupel will be possible anywhere even over the coasts. A winter
weather advisory may be needed for the eastern San Gabriels where
5-10 inches of snow is possible. And it will be a cold day with
cst and vly max temps only in the mid 50s.

Skies will clear out Monday night and will bring very cold
overnight lows with frost or freezes likely in the valleys and
some coastal zones.

East pac ridging will develop Tuesday and persist through
Thursday. Rising hgts and weak offshore flow will keep the skies
mostly clear. There will be warming each day, but despite this
warming trend Thursday`s max temps will still be 2 to 4 degrees
blo normal.

&&

.AVIATION...27/1404Z.

At 12Z at KLAX, there was no marine layer. There was a surface-based
inversion with a top near 300 feet with a temperature of 17 C.

Clear skies expected through this evening. Low clouds are
expected on the Central Coast late tonight with IFR to LIFR
conds. There is a good chance of low clouds in coastal sections of
L.A. County late tonight with low MVFR of IFR conditions.

KLAX...High confidence in CAVU TAF through at least midnight.
Expect some low clouds late tonight, with low MVFR conds, and
a 30% chance of IFR conds. High confidence that any east wind
component will remain below 7 knots.

KBUR...High confidence in CAVU TAF.

&&

.MARINE...27/442 AM.

Across the outer waters, NW winds are expected to increase to
Small Craft Advisory (SCA) levels this afternoon, then continue
at those levels through Sat evening. SCA NW winds are likely again
Sun afternoon and evening, in the norther two zones PZZ670/673
and there is a 40% chance they will linger into Mon. Across the
southern zones (PZZ676(, there is a 40% chance of SCA level winds
Sun afternoon through Mon.

Across the inner waters N of Pt. Sal, there is a 30% chance of
SCA level winds during the afternoon/evening hours today thru Mon.

Across the inner waters S of Pt. Sat, SCA level W winds are
expected across western portions of the SBA Channel this afternoon
thru late tonight, then there is a 40% chance of SCA level W winds
Sun afternoon thru late Sun night. Otherwise SCA conds are not
expected thru Tue.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PST Saturday for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 9
      PM PST Saturday for zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke
AVIATION...DB
MARINE...DB
SYNOPSIS...MW/CS

weather.gov/losangeles

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


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