-- Discussion containing changed information from previous version are highlighted. --
737
FXUS66 KLOX 202127
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
227 PM PDT Thu Jun 20 2024

.SYNOPSIS...
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20/134 PM.

Temperatures will trend upwards each day into the weekend, as
high pressure builds aloft. Above normal temperatures expected
Friday into early next week, especially for areas away from the
coasts. Dangerously hot conditions are possible this weekend,
especially for the mountain areas and Antelope Valley. There is a
slight change of rain showers Saturday through Tuesday.
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&&

.SHORT TERM (TDY-SUN)...
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20/835 AM.

***UPDATE***

Have added an excessive heat watch for the Los Angeles, Ventura,
and interior Santa Barbara County Mountains for Saturday morning
to Sunday evening. Antelope Valley will be in the 100s, but not
likely to reach EHW conditions. Temperatures are up a degree or
two along the south coast today with less extensive marine clouds
and less onshore flow. No impactful changes from the previous
discussion.

***From Previous Discussion***

The upper level pattern currently features weakening trough over
the region. Heights will gradually trend upwards throughout
the day. Gradients are trending less onshore, thus marine layer
clouds will struggle to make it into much of coastal LA County
this morning, and daytime clearing will be rapid. Gusty Sundowner
Winds will continue early this morning across southwestern Santa
Barbara County, and the wind advisory has been extended through 5
AM PDT. Currently, Refugio and Gaviota RAWS stations report
northerly winds gusting around 50 mph. The Summer Solstice will
occur at 151 PM PDT today, marking the day of the year with the
maximum amount of daylight hours. This extensive sunshine will
allow for very warm conditions this week for areas that are
unaffected by marine layer stratus or seabreezes. Temperatures
today will mostly be within 5 degrees warmer than normal, but will
increase compared to yesterday by around 4 to 8 degrees for
inland areas, as a result of reduced onshore flow and cloud cover,
and increasing heights.

Upper level heights will rise rapidly on Friday, as a broad
region of high pressure nudges into the area from the east.
Additionally, onshore pressure gradients at the surface will
continue to trend downwards. Marine layer clouds will struggle to
develop overnight, and clearing will again be very good during
the day. Daytime highs will trend upwards by around 2 to 6
degrees, with highs ranging from 100-105 degrees across the
Antelope Valley, in the low 80s to low 90s across the valleys, and
in the upper 90s for Paso Robles.

Saturday will be the peak of the heat for many inland locations,
as the high pressure settles over the region, due to a
stationary high pressure centered over the central southern
United States. Pressure gradients will trend less onshore from
the west, but more onshore from the south. This will likely
result in shallow marine layer status overnight. However with a
very strong temperature inversion capping the marine layer,
enforced by the very warm airmass, low clouds may cling to the
beaches all day. This will create a large temperature difference
between the beaches and inland valleys. The Antelope Valley is
expected to see highs from 103-108, coastal and interior valleys
will be in the mid 80s to upper 90s, and inland coastal areas will be
in the 80s. Only the beaches will stay in the upper 60s to mid
70s. There is around a 60% chance of a heat advisory for the
Ventura and LA County Mountains, and 25% chance of an excessive
heat warming for the Antelope Valley and foothills. The atmosphere
is expected to be on the dry side Saturday, but as the overall
flow becomes more favorable for monsoonal moisture, there is
around a 10% chance of a significant amount of precipitable water
entering the region from the southeast which would lead to some
afternoon convection.

.LONG TERM (MON-THU)...20/226 PM.

The region will continue to be under the western portion of
strong high pressure centered over Arizona and New Mexico through
the extended period. With only minor changes in the upper level
pattern, weather conditions will will be similar from day to day.
Temperatures will be much cooler at the beaches, with very warm-
to-hot interior temperatures. Monday and Tuesday could also see a
slight chance of showers/thunderstorms.

While high heights will remain though the extended period, the
center of the high pressure will migrate to the west by Wednesday.
This will change the positioning of the anticyclonic flow, and
will stifle the stream of mositure into the region.
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&&

.AVIATION...
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20/2116Z.

At 2000Z at KLAX, the marine layer was 1700 feet deep. The top of
the inversion was at 3600 ft with a temperature of 20 deg C.

High confidence in desert TAFs, and moderate to high confidence
in TAFs for coastal areas and coastal valleys. CAVU conditions
expected to continue for the rest of today and into tonight for
all areas, with cig/vsby restrictions returning to the coasts and
coastal valleys late tonight continuing through mid-morning
Friday. Timing of onset and dissipation of cig/vsby restrictions
may be vary by +/- 2 hours from current forecasts, and there is a
20% chance that these restrictions do not occur. By early
afternoon Friday, CAVU conditions are expected for all sites.

KLAX...Moderate confidence in TAF. There is a 20% chance of no
cig/vsby restrictions tonight. No significant east wind component
is expected.

KBUR...High confidence in CAVU TAF.
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&&

.MARINE...
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20/219 PM.

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) winds are expected through Friday evening.
Thereafter, SCA conditions are not expected through at least
early next week.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. SCA winds will remain possible
through Friday evening. Thereafter, SCA conditions are not
expected through at least early next week.

For the inner waters south of Point Conception, moderate to high
confidence in current forecast. SCA winds are expected over the
western Santa Barbara Channel through tonight. Otherwise, SCA
conditions are not expected through at least early next week.

In addition, there will be some possibility for a few
thunderstorms to impact the local waters this weekend, as remnant
upper-level moisture from Tropical Cyclone Alberto advances into
the region. Please reference the Marine Weather Statement for
additional information.
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&&

.LOX WATCHES/WARNINGS/ADVISORIES...
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CA...Heat Advisory in effect from 10 AM Saturday to 8 PM PDT
      Sunday for zones 38-88-343>345-372-373-548. (See LAXNPWLOX).
     Excessive Heat Watch remains in effect from Saturday morning
      through Sunday evening for zones 353-376>382. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Friday for zone
      650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Saturday for
      zones 670-673-676. (See LAXMWWLOX).
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&&

$$

PUBLIC...Schoenfeld/Rorke/jld
AVIATION...Cohen
MARINE...Cohen
SYNOPSIS...jld

weather.gov/losangeles

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