FXUS66 KLOX 271023

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
323 AM PDT Sun May 27 2018

.SYNOPSIS...27/257 AM.

A weaker onshore flow pattern will occur across the area through
early this week and bring a warming trend through Tuesday with
night through morning low clouds expected to persist across the
region much of this week. A cooling trend is forecast for
Wednesday and Thursday with a deeper marine layer as another
trough drops into the region. Warmer weather possible next weekend
as high pressure aloft could establish over the West Coast.


.SHORT TERM (TDY-TUE)...27/322 AM.

Latest GOES-16 Fog Product imagery indicated low clouds filling in
across much of the Central Coast and Santa Ynez Valley and the
Salinas River Valley early this morning. A Catalina Eddy was late
in developing, but low clouds were starting to fill in across the
L.A. Basin, San Gabriel Valley, and should continue to surge
north across the coast and valleys of Ventura County to the
southern potion of Santa Barbra County closer to sunrise. The
marine layer was around 2500 ft deep with a very weak inversion,
therefore low clouds should be able to scour out fairly quick this
morning or closer to noon at the coast. Also, northerly flow
across the San Joaquin Valley has allowed clouds to bank up
against the northern slopes of the Ventura/SBA County Mountains
and through the Grapevine this morning but should clear out
through this afternoon.

Gusty NW to N winds across the western portion of the Santa
Barbara County coast have not diminished, therefore have extended
the wind advisory through 9 AM this morning. Mainly from the hills
around Gaviota to the San Marcos Pass including Refugio. Gusts
were over 45 mph at Refugio and near 40 mph at San Marcos Pass.
Winds should decrease some by sunrise and continue through mid
morning. Winds will restrengthen once again this afternoon across
the same area, but not expecting advisory level gusts late this
afternoon through this evening.

Synoptically, An upper low was over the Great Basin Region and
will remain fairly stationary over the area through early Monday
before filling in and pushing into the Central and northern
Plains. H5 Heights will start to rise as a weak upper ridge builds
in behind the exiting trough through mid-week. At the lower
levels, onshore gradients will start to weaken over the next few
days. The combination of weaker onshore flow and building upper
ridge will cause high temps to trend higher anywhere from 2-5
degrees along the coast, except slightly cooler or similar across
SBA South Coast, to 6-10 degrees warmer in the valleys, and as
much as 10 to 14 degrees higher for the mountains and Antelope
Valley to around normal for this time of year. High temps will
continue to trend higher through Tuesday with the warmest valleys
reaching the upper 80s for areas S of Point Conception, and lower
to mid 90s for the interior SLO valleys and Antelope Valley.
Expect night through morning low clouds to continue through
Tuesday, but the marine layer depth should lower to around 1000 to
1500 ft continuing to affect most coastal valleys. With the
stronger inversion expected, low clouds should become more
organized and may not scour out to the coast until early afternoon

.LONG TERM (WED-SAT)...27/256 AM.

Both the 00Z GFS and ECMWF models continued to remain in good
agreement with large scale synoptic features across eastern Pac
and Western U.S. through the extended period. Another broad upper
level trough will deepen as it approaches the California Coast
Tuesday night into Wednesday.

H5 heights will go from 580 DM on Tue to 573 DM by Wednesday
night into Thursday. Expect significant cooling from Tue to
Wednesday. In fact high temps should lower between 8-15 degrees
for valley and interior locations while coastal areas to 2-7
degrees for coastal areas. Most areas will be in the 60s and 70s
to around 80 in warmest valley locations while the Antelope Valley
reach the mid 80s. The coolest day should be on Thursday with the
trof axis over the region and a deep marine layer in place. Clouds
should linger well into the afternoon hours with a possible
reverse clearing scenario Thursday. High temps will be well below
normal and low clouds should linger into the afternoon hours.
Flat upper level ridging can be expected for Fri thru Sat, with H5
heights over srn CA increasing to 588 to 589 dm by Sat. High
temps will warm to slightly below normal Fri and several degrees
above normal away from the coastal plain for Sat.



At 2130Z AT KLAX, there was a deep moist layer up 60 5800 feet. An
inversion was beginning to form at 1200 feet.

Good confidence in TAFs through 09Z then lower confidence due to
timing issues with stratus formation with a 20 percent chc of no
stratus forming at all.

KLAX...Good confidence in VFR TAF through 08Z then low confidence
with cloud arrival time which could be anytime between 08Z and
12Z. There is a 20 percent chc of no cigs. Good confidence in
east wind component remaining under 8kt.

KBUR... Good confidence in VFR TAF through 08Z then low confidence
with cloud arrival time which could be anytime between 08Z and
12Z. There is a 20 percent chc of no cigs.


.MARINE...27/321 AM.

Across the outer waters, high confidence in SCA conds thru late
tonight, though there is a 20% chance that winds will remain below
SCA levels across the northern outer waters zone. Conds are expected
to remain below SCA levels Mon thru Tue, with a 20-30% chance of
SCA level winds across the northern two outer waters zones Tue
afternoon. SCA conds are likely across the northern two zones Tue
night thru Thu, and across the southern zone Wed thru Thu.

Across the northern inner waters, there is a 20-30% chance of SCA
level winds this afternoon and evening. Otherwise, SCA level conds
are not expected thru Wed morning, with SCA level winds likely Wed
afternoon thru Thu.

Across the inner waters s of Pt Conception, SCA conds are not
expected thru Wed night. There is a 30% chance of SCA winds Thu.

Choppy short period seas are expected across all waters thru tonight.


CA...Wind Advisory in effect until 9 AM PDT this morning for zones
39-52. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Monday for
zones 670-673-676. (See LAXMWWLOX).



Strong rip currents and elevated surf could develop at Central
Coast beaches late Tuesday through early next Thursday.




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