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350
FXUS66 KLOX 271616
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
916 AM PDT Thu Jun 27 2024

.SYNOPSIS...
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27/807 AM.

Slight cooling is expected today and Friday as high pressure
aloft weakens. Gusty northwest winds will affect southwestern
Santa Barbara County and the Interstate 5 Corridor tonight. Warmer
weather is expected over the weekend as high pressure returns,
and above normal temperatures may continue through next week.
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&&

.SHORT TERM (TDY-SAT)...
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27/812 AM.

***UPDATE***

Low clouds are beginning to push into Long Beach and southern LA
County from the southeast, otherwise skies are mostly clear. The
push may make it into Ventura County for a few hours. The warmer
temperatures along the coast is a reflection of the lack of
stratus, but slightly cooler temperatures are still expected by
this afternoon. Temps are already down 3-5 degrees in the interior
this morning.

***From Previous Discussion***

Low clouds were rather slow to develop this morning, and were
confined to southern portions of the Central Coast. Clouds may
become a bit more widespread on the Central Coast and could spread
into the Santa Ynez Valley by daybreak. Elsewhere, low clouds
developing south and west of L.A. County may affect coastal
sections of L.A. County and possibly VTU County for a few hours
this morning. Any low clouds should burn off by mid/late morning.

Good N to S offshore pressure gradients across SBA County brought
low-end advisory level winds to southwestern SBA County last
evening, with gusty but below advisory level winds thru the I-5
Corridor. Those winds have dropped below advisory levels, so the
advisory was allowed to expire.

An upper low in Washington state early this morning will push
across northern Idaho and Montana later today and tonight, with a
broad trough extending southward into the forecast area. There
will be very little change in heights and thicknesses across the
region, and there is just a touch of cooling at 850 mb and 950
mb. Onshore gradients between KLAX and KDAG also change very
little. Expect max temps today to be similar to those on Wed, or
possibly a couple of degrees cooler in most areas.

N-S gradients are forecast to increase very slightly across SBA
County tonight, so expect another round of low-end wind advisory
level NW winds across the western portions of the south coast of
SBA County and the western Santa Ynez Range. Have issued wind
advisories there for late this afternoon thru late tonight. Gusty
winds thru the I-5 Corridor should stay below advisory levels.

High resolution models suggest more in the way of low clouds in
coastal areas tonight, so expect more widespread low clouds,
affecting most coastal areas (with the exception of the S coast
of SBA County due to the N flow). Clouds could even push into the
lower valleys. However, confidence in the low cloud forecast is
not great given the dearth of low clouds this morning.

A weak short wave trough will approach the West Coast Fri. Heights
will actually fall a bit, as will temps at 850/950 mb. Should
stratus become widespread tonight/Fri morning, clouds may linger
into the afternoon, especially near the coast. Max temps may be
down a couple of degrees in most areas on Fri.

Heights will rise across the region Fri night and Sat as a large
upper high over the southeastern U.S. expands westward. There
should be areas of low clouds and fog in coastal and some lower
valley areas Fri night/Sat morning, but clearing should be rather
quick Sat. Height rises and warming at 950 mb should bring several
degrees of warming in most areas Sat, especially away from the
coast. The best warming will likely be in the valleys as the
marine inversion lowers, decreasing the marine influence there.
High temps may rise well into the 90s in the warmest locations in
the valleys of L.A. County on Sat.

.LONG TERM (SUN-WED)...27/543 AM.

The upper high will continue to expand westward Sat night/Sun
causing heights to rise. Onshore flow will weaken, and the marine
layer will become increasingly shallow. Low clouds Sat night/Sun
morning should be confined to locations within a few miles of the
coast. Max temps will likely exceed 100 degrees in the Antelope
Valley and the interior valleys of SLO County, with highs near 100
degrees in some of the warmer locations in the valleys of VTU/L.A.
Counties. Heights will change little Sun night/Mon, so expect only
minor changes in night/morning low cloud coverage or max temps Mon.

N-S gradients should be steep enough for some gusty winds in
southwestern SBA County and thru the I-5 Corridor Sat night and
Sun night, possibly to advisory levels.

There are some differences between the deterministic runs of the
GFS and the EC for Tue/Wed. Both models show minor changes in the
upper pattern Tue, but the GFS shows lower heights with perhaps
some slight cooling Tue as a very weak upper low approaches the
area from the SW. The EC is stronger with a developing upper high
in the eastern Pacific Tue and Wed, and shows heights rising
across the region, with continued hot weather, (possibly very hot
by Wed), especially across the interior.
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&&

.AVIATION...
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27/1614Z.

At 17Z over LAX, the marine layer was 800 feet deep. The top of
the inversion was 3500 feet and 25 degrees Celsius.

Moderate confidence in all sites staying VFR today through at
least 02Z. High confidence in VFR conditions through Friday at
KPRB KWJF KPMD. All other sites have a chance of ceilings tonight
into Friday: KSBP (40%) KSMX (60%) KSBA (50%) KOXR (70%) KCMA
(60%) KSMO (60%) KLAX (60%) KLGB (60%). High confidence that if
ceilings form, flight categories will be LIFR-IFR at KSMX KSBP
KSBA and IFR-MVFR elsewhere.

KLAX...Moderate confidence in VFR conditions through at least 04Z.
Low confidence on ceilings tonight. 60% chance of BKN008-012
starting as early 04Z and as late 12Z. Southeast winds will
likely form after 09Z, but high confidence that they will stay
under 8 knots.

KBUR...There is a 20% chance of IFR ceilings Friday 10-16Z,
otherwise high confidence VFR conditions through at least
Friday. High confidence in seasonal winds.
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&&

.MARINE...
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27/906 AM.

Dense fog will impact the waters off the Central Coast this
morning, with reduced visibilities possibly lasting through the
afternoon and evening. There is a moderate threat for dense fog
again tonight into Friday for the same area.

Moderate confidence in low-end Gale conditions for the offshore
waters from the Central Coast to San Miguel Island by this
afternoon. There is a 20 percent chance of these Gales extending
south to San Nicolas Island, otherwise high confidence in Small
Craft Advisory (SCA) winds. SCA level west to northwest winds
will push into the Santa Barbara Channel as well but high
confidence that they will stay confined to the western half. There
is a 30 percent chance tonight that enough of the channel will be
covered with these winds to warrant an SCA.

High confidence that winds will decrease each day Friday through
Saturday, but will increase again Sunday and Monday.
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&&

.LOX WATCHES/WARNINGS/ADVISORIES...
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CA...Wind Advisory in effect from 4 PM this afternoon to 3 AM PDT
      Friday for zones 349-351. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Friday for zone
      645. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Friday for zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT this afternoon
      for zone 673. (See LAXMWWLOX).
     Gale Warning in effect from 3 PM this afternoon to 3 AM PDT
      Friday for zone 673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Saturday for
      zone 676. (See LAXMWWLOX).
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&&

$$

PUBLIC...DB
AVIATION...Kittell
MARINE...Kittell
SYNOPSIS...jld

weather.gov/losangeles

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