Area Forecast Discussion
Issued by NWS Los Angeles, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS66 KLOX 301004

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
304 AM PDT Fri Jul 30 2021

.SYNOPSIS...30/303 AM.

High pressure aloft over the West will keep a warm air mass in
place through the period. After slight cooling over the weekend
due to an area of low pressure brushing the area, high pressure
aloft will build back in for next week. Isolated afternoon and
evening thunderstorms are possible across the Los Angeles County
mountains and Antelope Valley today and Saturday.


.SHORT TERM (TDY-SUN)...30/239 AM.

Latest GOES-W Fog Product Imagery indicated widespread stratus
across the Central Coast and moving into the Santa Ynez Valley.
For areas S of Point Conception, low clouds have been less
organized similar to the past few mornings, except stratus has
filled in nicely across the Ventura County Coastal Plain and just
above the Conejo Grade in Newbury Park. Otherwise, it has been
more patchy in nature for the L.A. County coast. The marine layer
was around 1100 ft deep from a recent AMDAR Sounding. Not
anticipating any low clouds reaching the San Fernando or San
Gabriel Valleys this morning. However, the eastern portion of L.A.
County will continue to see variable high clouds move from south
to north this morning. The wind advisory for the Santa Barbara
South Coast and adjacent mountains will be allowed to expire at 3
AM as winds have lowered well below advisory thresholds.

Synoptically, A persistent and large upper ridge will remain
centered across the central the west coast through the
weekend. There will continue to be S-SE flow aloft moving across
the forecast area through Saturday before a weak upper level
disturbance moves closer to the coast and causes the winds to
shift to the SW allowing the atmosphere to dry out. Latest models
continue to pick-up on some mid level moisture getting pulled into
eastern L.A. County mainly focused over the Eastern San Gabriel
Mtns and Antelope Valley. NAM- WRF model soundings indicated
decent CAPE over 1000 j/kg along with some pooled mid level
moisture over the Eastern San Gabriel Mtns and Antelope Valley
this afternoon. A slight chance for showers and or isolated
thunderstorms is in the forecast for this afternoon and early
evening. There will continue to be some mid level clouds hanging
around into Saturday morning, but some clearing Saturday morning is
expected and should help with surface heating and add some more
instability for the potential of another round of showers and
thunderstorms over the same area Saturday afternoon.The best
chance of storms to fire up would be near the San Bernardino
County Line.  If storms do initiate, the main impact will be
locally chaotic winds as storms collapse along with occasional
cloud to ground lightning strikes.

For Sunday, drier SW flow aloft will move over the region as the
high pushes east as the weak trough off the coast pushes inland.
This will put an end to any monsoonal moisture and showers over
the mountains and deserts but there could be a few flat cumulus
over the mountains. At the lower levels, sfc high pressure will
build into NV and will set up weak offshore flow inland to weak
onshore flow at the coast. This will greatly limit the stratus
formation and low clouds will be patchy at best south of Pt
Conception. There will likely be better coverage across the
Central Coast. This will also bring a few degrees of warming to
the area, especially the coasts.

.LONG TERM (MON-THU)...30/301 AM.

High pressure aloft will continue to dominate much of the west
through the extended period. A persistent upper low over the Gulf
of Alaska and associated trough will dig a little south into
Northern California, but wont have much affect on cooling the
forecast area. There will be increasing onshore flow at the
surface on Monday and continuing through much of the week. This
will help with keeping coastal areas mild with with highs
remaining in the 90s for most valleys and lower 100s for the
Antelope Valley. There will be gradual warming Tuesday and
Wednesday as hgts increase over the area. By Wednesday most of the
interior (including the lower mtn elevations) will see triple
digit heat. The vlys will have max temps in the 90s with an
outside chc of some 100 degree readings in the warmest locations.
These max temps, excluding the coasts, will be 3 to 6 degrees
above normal.

There will continue to be night through morning low clouds through
the extended period, but H5 heights will keep the marine layer
fairly shallow and low clouds should be limited to coastal areas
and the Santa Ynez Valley. Still a chance for some coastal valleys
to see some patchy low clouds and dense fog occur.



At 07Z, the marine layer depth was around 1100 ft deep at KLAX.
The top of the inversion was around 2700 ft with a temperature of
near 28 degrees Celsius.

Moderate to high confidence in the current forecast. Higher
confidence in the forecast for valley and desert terminals,
less confidence in the forecast for coastal terminals.

For coastal terminals, LIFR to IFR conditions will be prevalent
through 16Z, then improve one category. There is a moderate (30-50
percent) chance of VLIFR conditions between through 16Z. There is
a moderate (30-50 percent) chance that IFR to MVFR conditions may
linger up to four hours longer than forecast. An early return of
LIFR to IFR conditions should be expected late this afternoon and
this evening.

For terminals away from the coast, VFR conditions are expected
through the period. There is a low (around 10 percent) chance of
a shower or thunderstorm impacting KPMD or KWJF between 20Z and

KLAX...There is a 50 percent chance of LIFR conditions between 12Z
and 16Z. There is a 40 percent chance that IFR to MVFR conditions
may linger until as late as 20Z. IFR to MVFR conditions could
return as soon as 01Z or as late as 05Z.

KBUR...VFR conditions are expected through the period. No wind
impacts are expected at this time.


.MARINE...30/227 AM.

For the water southwest through northwest of the Channel Islands
and along the Central Coast, there is a 60 percent chance of
Small Craft Advisory (SCA) level winds with choppy seas this
afternoon and evening from near Point Sal to San Nicolas Island,
decreasing to a 50 percent chance on Saturday afternoon and
evening. Wind and sea conditions should remain below SCA levels
Sunday. There is a 40 percent chance of SCA level winds Monday for
the waters northwest of the Channel Islands, increasing to 50
percent on Tuesday afternoon and evening.

Inside the southern California bight, there is a moderate to high
chance of SCA level winds with choppy seas each afternoon and
evening through Tuesday. The highest chance of SCA level will be
for the Santa Barbara Channel, but local afternoon and evening SCA
gusts cannot be ruled out near Point Dume and into the San Pedro
Channel. There is a 60 percent chance of SCA winds in the Santa
Barbara Channel this afternoon and evening, increasing to 60-70
percent on Saturday afternoon and evening. Wind should diminish
some on Sunday, but there is an increasing (40-50 to 50-60
percent) chance of SCA level winds with choppy seas each afternoon
and evening Monday and Tuesday.


PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Saturday for zones 650-673-676. (See LAXMWWLOX).



Gusty Sundowner winds are possible at times between Monday and
Thursday across southern Santa Barbara County. A return
of monsoonal moisture could bring showers and thunderstorms to
the mountains and desert for the latter part of next week.



SYNOPSIS...Kaplan/Hall is the U.S. government's official web portal to all federal, state and local government web resources and services.