Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 230157

657 PM PDT Tue Aug 22 2017

A low will bring an overnight coastal marine layer, otherwise mostly
clear skies into next week. The temperatures will be around normal
into midweek. Then a high will move in for a warming trend from
Friday into next week, with Monday and Tuesday the peak heat days.



There are some low clouds across the Central Coast and between
Catalina Island and Orange County. Max temps today were about the
same at the coast...a couple of degrees up over the
mtns...Antelope Vly and the interior Vlys. The biggest jump in
temps was across the vlys where there was 4 to 8 degrees of

Biggest issue tonight is the return of the low clouds. Its likely
that by sunrise all of the coasts will be covered in clouds but
there is a fair chc that the San Fernando Vly will be clear
through the morning.

Current forecast is in good shape and no updates are planned.



Models also show moisture filling in below the inversion base
south of Pt Conception tonight as well so better coverage overall
is expected by Wednesday morning. Along with this there is a 1-2mb
onshore trend. So in addition to an increase in low clouds
tomorrow most coast/valleys should be a degree or two cooler as
well for highs.

After that we should begin a slow warming trend through the rest
of the work week. Gradients trends weakly offshore each day
leading to a weaker onshore flow.


Little change or slight warming Saturday, then more significant
warming as we get into Sunday, Monday, and especially Tuesday
where light offshore flow could finally bring some of that inland
heat to the coast. Warmer valley spots should see triple digits by
Sunday and likely 105 or higher by Tuesday. Inland coastal areas
like downtown LA probably won`t see 90 until Monday or Tuesday but
still above normal by Sunday. Temps expected to keep on climbing
through most of next week as well, possibly leading to some heat
advisories and/or excessive heat warnings by as early as Tuesday.
Models still so far not showing any monsoon moisture with this
heat wave so thunderstorms remain out of the forecast.




AT 2345Z, the marine layer at KLAX was near 1500 feet deep. The
top of the inversion was 3600 feet with a temperature of 26 degrees

Good confidence in TAFs KSBA and south through 08Z. Then fairly
low confidence from 08Z to 13Z as timing of low cloud arrival
could be off by 2 hours. Lower confidence for coastal TAF sites
cloud dissipation as well with a 30 percent chc of no clearing.

Moderate confidence in Central coast TAFs timing may be off by +/-
1 hour.

KLAX...Good confidence through 08Z then low confidence. IFR cigs
could arrive any time from 08Z to 11Z. There is a 30 percent chc
of no afternoon clearing.
KBUR...high confidence through 08Z then low confidence. IFR cigs
could arrive any time between 10Z and 13Z. There is a 20 percent
chc of no cigs at all.



22/100 PM

For the outer waters, good confidence in current forecast. Rather
smooth conditions through Wednesday, then northwest winds increase
Thursday and Friday before decreasing late Saturday. Small Craft
Advisory (SCA) levels will likely develop Thursday afternoon with
building seas to around 7 ft into Saturday morning. There will be
a small S swell mixed with the W-NW swell at times.

For the inner waters, good confidence in the current forecast.
For the waters north of Point Sal, winds and seas will remain
below SCA levels through Wednesday. On Thursday and Friday, SCA
level winds are likely each afternoon and evening with winds
diminishing below SCA levels on Saturday and Sunday. For the
waters south of Point Conception, winds and seas are expected to
remain below SCA levels through the weekend.




A significant heatwave could develop this upcoming weekend and
continue into early next week.



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