Area Forecast Discussion
Issued by NWS Los Angeles, CA

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316
FXUS66 KLOX 231745
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1045 AM PDT Mon Apr 23 2018

.SYNOPSIS...22/901 PM.

There will be overnight and morning coastal low clouds and fog
for several days this coming week otherwise conditions will be
warm and dry. Temperatures will cool a bit Friday and Saturday as
a weak weather system moves across the region.

&&

.SHORT TERM (TDY-WED)...23/905 AM.

As expected this will be a week of marine layer as weak ridging
along with moderate onshore flow will last most of the week.
Minimal day to day changes with low clouds possibly lingering at
or just inland from the coast through the afternoon. Could again
be some patchy dense fog later tonight.

***From previous discussion***

Just a few little changes Tuesday. The ridge is a little weaker
so the marine layer will be a touch deeper and will extend a
little deeper into the vlys. Max temps will cool a little as well.

An upper low approaches northern CA on Wednesday. It will push the
ridge a little more to the east. Hgts...though...really do not
change much. The lift from the trof should lift the low clouds
into the vlys. The inversion will be a little weaker and this will
allow the morning stratus to clear a little quicker. Max temps
will not change much from Tuesday and will be a few degrees above
normal.

.LONG TERM (THU-SUN)...23/318 AM.

EC and GFS agree that the upper low will not move much on
Thursday. Things will be in pretty static pattern and like
Wednesday there will be a deep stratus pattern extending deep into
the vlys. Hgts and pressure grads do not change much and max temps
will be similar to Wednesday`s.

The EC and GFS begin to disagree on the movement and evolution of
the low on Friday but the disagreement if more of a Northern CA
problem as there is not too much difference between the two mdls
for SoCal. Look for a troffier pattern with lower hgts. The deep
marine layer will continue but the lower hgts will usher in a
cooler trend and max temps will fall to a degree or two blo
normal.

Very large disagreement for the forecast next weekend. The EC
brings a tight cut off 552 DM upper low over Sacramento while the
GFS has only a weak trof over the state. The EC seems a little
exuberant and based the weekend forecast on the GFS. Saturday
will be like Friday but by Sunday there should be enough cool air
mixing up north to prevent the stratus from forming across the
Central Coast. The cooler air will also bring max temps down 2 to
4 degrees across the 4 county forecast area.

&&

.AVIATION...23/1744Z.

At 17Z, the marine inversion at KLAX was based around 1500 feet.
The top of the inversion was 3700 feet with a temperature of 19
degrees Celsius.

Overall, low confidence in coastal TAF sites and high confidence
in inland TAf sites. IFR stratus has been slow to clear away from
coastal terminals, especially for the central coast, and low
clouds should make an early return this evening. Confidence erodes
by 04Z as IFR/LIFR cigs and fog could push back to these sites. For
inland terminals, high confidence in VFR through the period
(although there is a 20% chance of IFR/LIFR conditions developing
by 12Z at KBUR/KVNY).

KLAX...Low confidence in 18Z TAF mainly after 00Z. Cigs have
pulled offshore, but could return shortly after 00Z. IFR
cig/vis expected by 02Z and a 30% chance of LIFR visibility after
08Z.

KBUR...High confidence in 18Z TAF. There is a 20% chance of
IFR/LIFR conditions developing by 12Z tonight.

&&

.MARINE...23/811 AM.

Widespread dense fog with visibilities of one mile or less will
likely persist through Tuesday, and maybe through Thursday. The
afternoon and evening hours should be slightly improved, but areas
of reduced visibilities will likely linger.

High confidence in winds and seas remaining below Small Craft
Advisory (SCA strength everywhere through Wednesday. Winds will be
increasing Thursday through Saturday with widespread SCA
conditions and building short period seas likely.

&&

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

&&

.HAZARD POTENTIAL OUTLOOK (WED-SUN).

No significant hazards expected.

&&

$$

PUBLIC...MW/Rorke
AVIATION...EB
MARINE...Kittell
SYNOPSIS...Kj

weather.gov/losangeles



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