Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 261625

925 AM PDT Tue Sep 26 2017

Weak offshore flow will bring a warm and dry conditions with
mostly clear skies to the area through this week and into the
weekend. There will be some gusty north to northeast winds at
times over the region, especially below and through passes and
canyons. A few nighttime marine clouds may sneak into the L.A.
coastal area by mid week. Temperatures will be a few degrees
above normal for many areas early this week, then increase to much
above normal for late this week and into the weekend.



Gradients trending onshore today which was not expected and as a
result coast/valley temps are not climbing as fast as they did
yesterday. Winds also weaker than yesterday though there is still
sufficient upper support to get some localized gusts to around 30
in the LA mtns, mainly right around the highway 14 corridor. So
temps should top out lower than yesterday with an earlier sea
breeze arrival, though still above normal. Main forecast dilemma
for the short term is how the marine layer will respond tonight
and whether low clouds will reform and move up from the south as
the NAM suggests. Models still showing some northeast winds just
off the surface Wednesday morning and a LAX-DAG gradient of
around -2mb so there`s still a little offshore push, though
weaker even than today. It`s a tough call but more signs are
pointing towards at least some return of low clouds for srn LA
County late.

***From previous discussion***

A weak eddy will spin up tonight and its likely (but not certain)
that some marine layer clouds will spread over parts of the LA
county coast as well as Catalina island. The offshore flow will
also be weaker and this along with slightly lower hgts will knock
a few degrees off of temps everywhere but esp across the coasts.

A weak ridge moves into the area on Thursday and hgts rise to
582DM up from Wednesday`s 576 DM. This will lead to an increase in
temps across the vlys and interior sections. The offshore grad
decrease to almost neutral and this trend will counter the
increase in hgts and coastal temps will be similar to Wednesdays.
The weak eddy is forecast to continue and the LA coast will again
see some morning low clouds.


EC and GFS agree that an upper low will move through the pac NW
Friday and flatten the flow over CA. By Saturday the upper low
will be entering Idaho and cyclonic flow will prevail over the
state. There is no eddy forecast and there is enough offshore flow
to keep the marine clouds away so the forecast calls for clear
skies. It is not too difficult to imagine some low clouds forming
and this will need watching. Whatever the case the very warm temps
that were forecast earlier seem rather unlikely now and max temps
now reflect the cooler forecast.

The EC and GFS do not agree on much at all for the Sunday and
Monday forecast. The one thing they do agree on is that onshore
flow will return. Think this will be enough to bring some morning
low clouds to the coasts as well as a cooling trend to the area.
Max temps should be several degrees blo normal both Sun and Mon.



At 0400Z, there was no marine inversion at KLAX.

Overall, good confidence in 06Z TAF package. Weak offshore flow
will keep all sites VFR through the period. There will be some
LLWS/turbulence issues across the valleys and foothills as the
northeasterly flow develops overnight across Ventura and Los
Angeles counties.

KLAX...high confidence in 06Z TAF. There is a 15% chance of east
winds exceeding 7 knots 10Z-18Z. There is a 30% chance of LLWS

KBUR...high confidence in 06Z TAF. There is a 40% chance of
moderate LLWS 08z-20Z.


.MARINE...26/900 AM...

For the Outer Waters, high confidence in current forecast. Winds
and seas will remain below SCA levels through Thursday then will
increase to SCA levels Friday and Saturday.

For the Inner Waters, moderate confidence in current forecast. For
the waters north of Point Sal, winds and seas will remain below
SCA levels through Thursday with a 50% chance of SCA level winds
Friday and Saturday during the afternoon and evening waters. For
the inner waters south of Point Conception, winds and seas are
expected to remain below SCA levels through Saturday although
there is a 40% chance of SCA level winds Saturday afternoon across
the western half of the Santa Barbara Channel.




There will be local fire weather danger through Saturday.



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