Area Forecast Discussion
Issued by NWS Los Angeles, CA

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459
FXUS66 KLOX 232311
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
411 PM PDT Tue Apr 23 2019

.SYNOPSIS...23/116 PM.

Expect warm temperatures this afternoon as high pressure moves
into the region. Coastal areas will be a little cooler as winds
become westerly. Onshore flow will persist through the week
keeping the coast cool. Temperatures will remain warm inland. There
is a slight chance for a mountain shower or thunderstorms on
Thursday. Expect near normal temperatures for the weekend with
possible showers.

&&

.SHORT TERM (TDY-FRI)...23/156 PM.

Temperatures for coast/valleys peaking today as onshore flow
increases through the rest of the week. Already seeing some marine
layer clouds off the LA Coast today and expecting those to expand
westward overnight, possibly getting as far west as Pt Conception
by Wednesday morning. Probably not too much inland push yet but at
least enough to cover the coastal plain and some of the coastal
valleys.

Cooler onshore flow will set in Wednesday and last through the end
of the week bringing temps back to near normal by Friday. Low
clouds will push a little farther inland each night and also push
north up the SLO/SB coastal areas by Wednesday afternoon and night.

Models have started to show some rather robust instability across
the Ventura/SB mountains starting Thu and a fairly shallow but
significant increase in moisture between 850 and 700mb, the source
of which is unknown at this time so confidence is not particularly
high. But if these factors come together there would likely be
some convective activity the latter half of the week.

.LONG TERM (SAT-TUE)...23/216 PM.

Not too much change in the pattern over the weekend. The ridge
aloft remains in place but a cutoff upper low will be approaching
from the west Sunday that will continue the cooling trend through
Monday. Models in surprising agreement on the track and strength
of the low which is expected to move through the area Monday
morning. As it does it will likely deepen the marine layer over
3000` and possibly generate some light showers or drizzle,
especially in LA County. There is some instability with it as it
moves through south of Pt Conception which would provide
additional support for the showers and can`t rule out thunder
chances, though too low confidence to include at this time.
Current forecast of partly cloudy Monday may be optimistic
depending on the timing of the upper low passage. And temps may be
too warm, especially if showers develop and clouds linger into the
afternoon.

Heights rise Monday night and Tuesday as the low moves into AZ.
However, models maintain a very strong onshore flow so even if the
marine layer clears out faster than Monday temps will remain near
to slightly below normal.

&&

.AVIATION...23/2311Z.

At 2300Z, the marine inversion at KLAX was based at 1000 feet.
The top of the inversion was 2100 feet with a temperature
of 26 degrees Celsius.

Overall, moderate to high confidence in 00Z TAF package. High
confidence in return of CIG/VSBY restrictions to coastal sites
south of Point Conception, but only moderate confidence in timing
and flight category. For all other sites, high confidence in CAVU
conditions through TAF period.

KLAX...Overall, moderate confidence in 00Z TAF. Timing of MVFR to
IFR change may be +/- 2 hours of current 03Z forecast. Timing of
IFR to MVFR change may be +/-4 hours of current 16Z forecast.

KBUR...Overall, high confidence in 00Z TAF. There is a 10-15%
chance of MVFR VSBYs 11Z-17Z.

&&

.MARINE...23/129 PM.

For the Outer Waters and the near shore waters north of Point
Sal, high confidence in current forecast through the this week.
Northwest winds are expected to remain below Small Craft Advisory
(SCA) levels, and there is a 60-70% chance that winds and seas
will remain below SCA through at least Friday. Then, there is
moderate confidence that seas will remain below SCA levels this
weekend.

For the Inner Waters south of Point Conception, there is good
confidence in the current forecast. Winds and seas are expected to
remain below SCA levels through Saturday. Light offshore winds
are likely near shore between Point Mugu to Santa Monica this
morning through around noon, but should remain below SCA levels.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (FRI-TUE).

No significant hazards expected.

&&

$$

PUBLIC...MW
AVIATION...RAT
MARINE...Sweet
SYNOPSIS...Phillips

weather.gov/losangeles



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