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FXUS66 KLOX 171150
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
450 AM PDT Mon Jun 17 2024

.SYNOPSIS...17/345 AM.

Temperatures will gradually trend downwards in most areas this
upcoming week, following the warm to hot conditions this weekend.
Strong northwest to north winds will impact the Central Coast
through interior sections of Santa Barbara County to the Antelope
Valley through Monday night, with fire weather concerns.

&&

.SHORT TERM (TDY-WED)...17/430 AM.

Good eddy circulation in progress across the inner waters. The
marine layer has deepened to about 2000 feet, and clouds have
surged northward from the coastal of L.A. County into the valleys
and into Ventura County as well. By daybreak, expect low clouds in
all coastal and most valley areas of L.A. and VTU Counties with
the possible exception of the Santa Clarita Valley and some of the
interior valley locations of VTU County. There is even a chance
that low clouds will push into southeastern coastal sections of
SBA County, but that remains in doubt given the strong offshore
N-S gradients across SBA County. N of Pt. Conception, skies were
clear. Some patchy low clouds and fog may form in southern
portions of the Central Coast and in the Santa Ynez Valley by
morning, but that should be it.

Any low clouds north of Pt Conception should dissipate quickly
this morning. Across VTU and L.A. Counties, clouds will clear more
slowly today, generally by mid to late morning in the valleys and
by early afternoon across the coastal plain. High res models
suggest that clouds could linger at the beaches today, which is
entirely possibly given the strength of the onshore gradient
between KLAX and KDAG both currently, and during the afternoon.
Otherwise, N-S gradients continue to produce strong NW to N winds
across much of southwestern SBA County, the mountains of interior
SBA County eastward thru the mtns of L.A. County, including the
I-5 Corridor, in the Antelope Valley foothills, and in the Santa
Clarita Valley. There were still some local High Wind Warning
levels gusts in the mtns and through the I-5 Corridor, but winds
were mostly at advisory levels in these areas. Winds had dropped
below advisory levels on the Central Coast and in much of the
Antelope Valley.

An unseasonably strong and cold upper low was moving through
eastern Oregon early this morning and it will push into Idaho and
western Montana later today. A sharpening trough axis extending
south from this low will push across the area today. Behind this
trough, NW flow aloft will increase and there will be increasing
subsidence across the region. In addition, there will be some cold
advection. This should translate to an increase in northwesterly
winds across much of the windy areas this afternoon this evening.
Given this expected bump up in winds again this afternoon and
evening, will keep the warnings and advisories as is. With
lowering heights/thicknesses, increasing onshore gradients
between KLAX and KDAG, and lots of low clouds this morning,
expect several degrees of cooling in most areas today. The
exception will be across southern SBA County, where gusty north
winds may bring a few degrees of warming late this afternoon and
early this evening.

Low level flow will turn more northeasterly across L.A. and
Ventura Counties late tonight, with gradients between KLAX and
KDAG actually turning weakly offshore. N-S gradients across SBA
County will begin to weaken tonight. This should cause the NW
winds to drop below advisory/warning levels in most areas by late
tonight. NE flow at 850 mb will actually briefly increase to 40
to 45 kt across portions of L.A. County and eastern Ventura County
Tue morning, with a corresponding increase in surface winds,
similar to a Santa Ana wind event. Expect a period of strong to
possibly advisory level NE winds in the mtns of L.A. County and
possibly eastern Ventura County Tue morning.

In coastal and valley areas, the forecast is more challenging, and
it all depends on the marine layer tonight. At this point, low
clouds are expected to push into coastal and at least lower valley
areas of L.A./Ventura Counties. Where there are low clouds, the
winds would have to erode the stubborn marine layer to allow them
to surface, which is no small task. Therefore, it will be
difficult for the northeast winds to surface in coastal and lower
valley areas of L.A. and Ventura Counties. Winds are most likely
to make it into the valleys of Ventura County and northern and
western L.A. County for a few hours Tue morning, but that is not a
sure bet, given how unusual this would be for mid June. But there
is still a chance that it will happen, and will have to be watched
closely. Given the offshore gradients, do expect much faster
clearing of any low clouds on Tue. Max temps should jump up
several degrees in most areas Tue, especially in the valleys of
L.A. and VTU Counties. If winds do surface, it will likely be
even warmer than currently forecast on Tue in coastal and valley
areas of L.A./VTU Counties. Expect little change in max temps
across SLO and SBA Counties.

A broad trough will sag southward through the West Coast Tue night
and Wed. N-S gradients should still be strong enough for some
gusty winds during the late afternoon thru late evening hours
across SBA County Tue/Tue night, but much there should be much
less in the way of wind across L.A. and VTU Counties. Expect more
widespread night thru morning low clouds and fog in coastal and
valley areas Tue night/Wed morning, with low clouds likely
returning to areas N of Pt. Conception as well. Max temps should
be down several degrees in most coastal and valley areas south of
Pt Conception Wed, with somewhat less cooling elsewhere.

.LONG TERM (THU-SUN)...16/223 PM.

The axis of broad mid and upper troughing will shift slightly
offshore for Thursday and Friday, as small-scale impulses
pivoting through the surrounding cyclonic flow reposition its
primary axis. This will favor continued deepening of the marine
layer, with abundant night and morning marine stratus and fog over
the coasts and coastal valleys. As a subtropical ridge builds
westward from the south-central CONUS for late in the week into
next weekend, larger-scale onshore pressure gradients will
substantially strengthen. This will reinforce low clouds and fog
at the coast while supporting stronger heating over the interior.

With the midlevel ridging, high temperatures are forecast to
reach the 90s to around 100 degrees over many interior valleys,
and upwards of 105 degrees in the Antelope Valley next weekend. In
addition, as midlevel heights rise next weekend, more substantial
diurnal clearing may occur over inland areas away from the coast
owing to increasingly shallow marine-layer depths. This could
expand the areal coverage of very warm to hot temperatures closer
toward the coast next weekend.

&&

.AVIATION...
-- Changed Discussion --
17/1149Z.

At 08Z at KLAX, the marine layer was 1400 feet deep. The top of
the inversion was at 3900 ft with a temperature of 19 deg C.

Moderate confidence in KPMD KWJF and KPRB, due to uncertainty in
gusty winds and the potential for FU from distant fires. Gusty W
to NW will affect the Antelope Valley through the period. Blowing
dust and sand will locally reduce visibilities to one half mile or
less at times thru this evening

Low to moderate confidence in other TAFs. There could also be
some reduced vsbys from FU at L.A. County airports this morning.
Additionally, there is uncertainty with the timing of stratus
clearing and development tonight.

Weak to moderate LLWS is possible through 15Z, focused near KSBA,
KBUR, and KVNY. There will be mdt to locally strong uddf at times
near the mountains.

KLAX...Low to moderate confidence in TAF. There is some
uncertainty in the timing of status dissipation and then arrival
late tonight. There is a 20% chance of the east wind component
reaching 6 to 8 kt between 06Z and 16Z Tue.

KBUR...Low to moderate confidence in TAF. There is a 30% chance
of reduced vsbys from FU from the Post Fire until 16Z today. There
is some uncertainty in the timing of status dissipation and then
arrival late tonight.
-- End Changed Discussion --

&&

.MARINE...17/349 AM.

For the Outer Waters, high confidence in current forecast. Winds
are expected to remain at Gale force levels into late tonight.
Seas will peak today around 10 to 13 feet. For Tuesday through
Friday night, winds will subside, but remain at Small Craft
Advisory (SCA) levels. Seas drop below 10 feet Tuesday night.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. SCA level winds will persist
through tonight, and seas will peak today at around 9 to 12 feet.
Then Tuesday and Wednesday, there is a 60-80% chance of SCA level
winds, in the afternoons and evenings. For Thursday through
Friday night, winds and seas should remain below SCA levels.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Noon today through this evening,
Gale Force winds are likely for the Santa Barbara Channel.
Tuesday and Wednesday, there will be a 60-80% chance of SCA level
winds across the western half of the Santa Barbara Channel, during
the afternoons and evenings. South of the SBA Channel, there is a
50-70% chance of SCA level winds for the western and northern
portions of the inner waters, this afternoon into evening.
Otherwise and elsewhere, SCA conditions are not expected.

&&

.BEACHES...17/315 AM.

Short-period wind waves, due to gale force winds over the nearby
coastal waters, will generate elevated-to-high surf conditions and
dangerous rip currents across the beaches through today. West and
northwest facing beaches will see the highest surf.

&&

.FIRE WEATHER...
-- Changed Discussion --
16/223 PM.

GOES-16 satellite imagery indicates that the ongoing Post Fire
complex in the vicinity of the I-5 corridor in northwest LA
County and adjacent northern Ventura County continues to grow in
size and intensity. Weather conditions will become increasingly
conducive for further growth and intensification of this complex,
especially tonight, and a Red Flag Warning has been issued for the
I-5 corridor in northwest LA County and the Ventura County
Mountains. For these areas, the latest data suggest that northwest
to north winds will gust to 45 to 55 mph today, increase to 60 to
70 mph range tonight, and then gradually decrease to 30 to 50 mph
through the day Monday. Sustained wind speeds will generally be
in the 20 to 40 mph range. These strong winds, with the notable
uptick tonight, will be caused by increasing upper support
overspreading Southern California in the base of a deepening
cyclone centered well north of the area. The upper pattern will
also bring an influx of abundant dry air into the area, and
minimum afternoon relative humidity values are expected to range
from 15 to 25 percent, locally as low as 10 percent in downslope-
flow favored areas -- with only poor to moderate overnight
recovery to around 25 to 40 percent tonight. While live fuel
moisture readings are still quite high, ample fuel loading of
dead fuels is likely contributing to the extreme fire behavior
with the Post Fire complex, and increasingly favorable
meteorological conditions are expected to foster further growth
and intensification of this fire complex or any other fires
developing in the Red Flag Warning area. The Red Flag Warning is
currently set to expire at 3PM PDT Monday, however, conditions
will be re-evaluated for possible extension of the Warning in
subsequent forecasts, given the potential for gusty winds to
continue into Monday night and Tuesday. There is a 40 percent
chance that the Red Flag Warning is extended into Monday night or
Tuesday. There is also the potential for winds to shift to the
northeast Monday night and Tuesday.

Elsewhere across the region, gusty northwest to north winds are
expected to continue through Monday, peaking in intensity tonight
with a secondary peak Sunday night into early Monday. Wind gusts
of 30 to 50 mph will be common at times through the period for the
Central Coast, mountains of Santa Barbara, Ventura and northwest
LA County as well as the Antelope Valley (strongest in the
mountains and deserts). Isolated gusts to 65 mph will be likely in
the strongest periods of wind across western the Santa Ynez Range
and adjacent western Santa Barbara County South Coast, primarily
in the evening and overnight hours in conjunction with Sundowner
wind enhancements and nocturnal drainage processes. Meanwhile, a
warm and dry air mass will remain in place, with widespread 8 to
15 percent humidities across the interior today, and 12 to 20
percent on Monday. Poor overnight recoveries in the foothills are
also expected. The warm and dry air will continue to descend into
some coastal foothills on Sunday, including portions of southern
Santa Barbara County. The combination of gusty winds, warm
temperatures, and low humidities will continue to bring elevated
to brief critical fire weather conditions across southern Santa
Barbara county through Sunday night, and all interior areas
through Monday. There is an increased risk for fast-growing grass
fires over much of the area, that could transition into wildfires
where the fuel beds are most abundant and dry.
-- End Changed Discussion --

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through this evening for
      zones 87-340-346-362-366. (See LAXCFWLOX).
     Wind Advisory remains in effect until 3 AM PDT Tuesday for
      zones 88-340-341-346-347-353-356-383. (See LAXNPWLOX).
     High Wind Warning remains in effect until 3 AM PDT Tuesday
      for zones 349-351-376>378-381. (See LAXNPWLOX).
     Wind Advisory in effect until 3 AM PDT Tuesday for zone 352. (See LAXNPWLOX).
     High Surf Advisory in effect until 7 PM PDT this evening for
      zone 354. (See LAXCFWLOX).
     Red Flag Warning in effect until 3 PM PDT this afternoon for
      zones 376>378. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until noon PDT today for zone
      650. (See LAXMWWLOX).
     Gale Warning in effect from noon today to 9 PM PDT this
      evening for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 9
      PM PDT this evening for zone 655. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Tuesday for zones
      670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...DB/Cohen
AVIATION...DB/Schoenfeld
MARINE...Sirard/Schoenfeld
BEACHES...Sirard/Schoenfeld
FIRE...Cohen/Gomberg
SYNOPSIS...Cohen/RS

weather.gov/losangeles

Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox