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692
FXUS66 KLOX 201301
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
601 AM PDT Thu Jun 20 2024

.SYNOPSIS...20/317 AM.

Some morning low clouds and fog will continue along the coast and
valley areas today. 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 Antelope Valley.

&&

.SHORT TERM (TDY-SAT)...20/321 AM.

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 (SUN-WED)...20/334 AM.

Through the extended period, the region will continue to be under
the western portion of strong high pressure centered over Arizona
and New Mexico. With overall little changes in the upper level
pattern, weather conditions will each day will be similar.
Temperatures will be much cooler at the beaches, with very warm-
to-hot interior temperatures.

However, highs are likely to trend slightly downwards for the
interior, Sunday and Monday. This is a reflection of increasing
precipitable water in the atmosphere that will dampen daytime
heating. With the center of high pressure settling over the
desert southwest, the flow over the region will support the
transport of monsoonal moisture from the southeast. PWAT will
increase quickly on Sunday, and the NAEFS forecast values for PW
are in the 90th to 99th percentile over Los Angeles County much of
the time Sunday through Tuesday. This moisture will serve to cool
daytime highs, however conditions will be more humid and overnight
lows will be on the warm side. There is a small (10-20%) chance
of afternoon showers/thunderstorms over the mountains and Antelope
Valley, with the highest chances on Sunday at this time.

While high hieghts 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.

&&

.AVIATION...
-- Changed Discussion --
20/1300Z.

At 1115Z at KLAX, the marine layer was 1400 feet deep. The top of
the inversion was at 4500 ft with a temperature of 20 deg C.

High confidence in TAFs for KSBA, KVNY, KBUR, KPMD and KWJF.

Good confidence in TAFs for KOXR and KCMA with only a 20 percent
chc of IFR cigs 14Z-17Z.

Moderate confidence in TAFs for KSMX and KSBP. VFR transition may
be an hour later than fcst.

Moderate confidence in TAFs for KLAX, KSMO and KLGB. VFR
transition may be an hour later than fcst. There is a 30 percent
chc of no cigs tonight.

KLAX...Moderate confidence in TAF. There is a 30 percent chc
BKN015 conds hanging on until 18Z. There is a 30 percent
chc of no cigs tonight. Any east wind component should
be less than 5 knots.

KBUR...High confidence in TAF.
-- End Changed Discussion --

&&

.MARINE...20/222 AM.

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) winds are expected through Friday night.
Brief lulls in the winds during the mornings hours are possible.
Seas will be steep and choppy through Friday night. Conditions
are then expected to be below SCA levels Saturday through Monday
night.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. There will be a slight lull in SCA
winds and choppy seas this morning but they will reform this
afternoon and persist through the evening. For Friday through
Monday night, winds and seas should remain below SCA levels.

For the inner waters south of Point Conception, moderate
confidence in current forecast. SCA conditions will be confined to
the western third of the Santa Barbara Channel. Winds should
remain below SCA levels for the waters south of Point Mugu, but
will be stronger over western portions of zone PZZ655. Local winds
near SCA levels are possible again Friday for western portions of
the Santa Barbara Channel and near Santa Cruz Island. Winds and
seas should remain below SCA levels over the weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CA...NONE.
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).
-- End Changed Discussion --

&&

$$

PUBLIC...Schoenfeld/Rorke
AVIATION...Rorke
MARINE...Phillips/ASR
SYNOPSIS...RS

weather.gov/losangeles

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