Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 211200
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
500 AM PDT Thu Jun 21 2018

.SYNOPSIS...21/203 AM.

High pressure aloft will result in well above normal temperatures
for inland areas through the weekend. For coastal and coastal
valley areas, a strong marine influence will moderate temperatures
through the weekend. For the first half of next week, high
pressure will strengthen slightly, resulting in slightly warmer
temperatures and a little less stratus and fog for the coasts and
coastal valleys.

&&

.SHORT TERM (TDY-SAT)...21/203 AM.

Overall. 00Z models in good synoptic agreement through the period.
At upper levels, flat ridge will remain over the area today/Friday
then will be shunted to the southwest on Saturday as a trough
moves into the Great Basin. Near the surface, onshore gradients
will continue through Saturday.

Forecast-wise, a very quiet and typical pattern for the official
first day of Summer. Main issues through the short term period
will be stratus/fog and temperatures. Currently, marine inversion
ranges from around 1000 feet across the Central Coast to around
2100 feet across the LAX basin. Expect the inversion to remain
around this depth through Friday then deepen a little on Saturday
(due to H5 heights falls). So with good onshore gradients, stratus
should be able to push well into the coastal valleys each
night/morning. Stratus should dissipate pretty well each
afternoon although some areas along the immediate coast could be
slow to clear (due to strength of the marine inversion).

As for temperatures, no major changes to previous thinking. For
the coasts and coastal valleys, expect persistence/slight cooling
today due to more expansive marine influence. On Friday, the
onshore gradients slacken a bit which should allow for some
slight warming. However on Saturday, expect cooler temperatures
due to weakening upper ridge and strong onshore gradients. For the
mountains/deserts/interior valleys, a couple degrees warming
today and Friday then some slight cooling on Saturday.

As for winds, moderate to strong onshore gradients will generate
gusty afternoon/evening winds across the mountains and deserts
today through Saturday. However, do not anticipate any widespread
advisory-level winds.

.LONG TERM (SUN-WED)...21/203 AM.

For the extended, 00Z models continue to exhibit good synoptic
agreement. At upper levels, flat ridge will strengthen over the
area Sunday/Monday then persist in strength Tuesday/Wednesday.
Near the surface, moderate to strong onshore gradients will
continue.

Forecast-wise, expect only minor day-to-day changes through the
extended period, mainly due to the whims of the marine layer.
Marine inversion should show only minor variations in depth each
day. So with good onshore gradients, stratus/fog should be able to
push into the coastal valleys each night/morning. Other than the
marine layer stratus, skies should remain mostly clear through the
period. As for temperatures, will expect a little more cooling on
Sunday with some slight warming on Monday then near-persistent
temperatures Tuesday/Wednesday.

&&

.AVIATION...21/1159Z.

At 1130Z, the marine layer at KLAX was around 1800 ft deep. The
top of the inversion was around 3800 ft with a temp of 28C.

Widespread stratus in all coastal and valley areas with the
exception of the Santa Clarita Valley and the interior valleys of
SLO and SBA Counties. Conds were mostly IFR to LIFR, except low
MVFR in some locations south of Point Conception. Expect skies to
clear by mid morning in the valleys and by noon across most of the
coastal plain. However, clouds may linger at some beach areas,
especially south of Point Conception.

KLAX...Moderate confidence in the 12Z TAF. There is a 20-30%
chance of IFR cigs between 12Z and 16Z. There is a 20-30% chance
that cigs will linger through the afternoon. Any southeast winds
this morning should remain below 7 knots.

KBUR...Moderate confidence in the 12Z TAF. There is a 20-30%
chance of IFR cigs between 12Z and 16Z. There is a 20% chance
that skies will remain clear tonight and conds will remain VFR.

&&

.MARINE...21/329 AM.

For the Outer Waters, high confidence in the forecast, with winds
increasing to SCA levels this morning, and continuing thru late
Fri night or Sat morning, then winds will diminish. Winds may drop
below SCA levels briefly at times.

For the Inner Waters, north of Point Sal, good confidence in SCA
level winds mainly during the afternoon/evening hours thru Fri.

For the inner waters south of Point Conception, winds and seas
are expected to remain below SCA levels thru Sun. However, there
is a 30% chance of SCA level winds across the western half of the
Santa Barbara Channel each afternoon/evening thru Fri.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
      for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 AM PDT Saturday for
      zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Saturday for
      zone 676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (SAT-WED).

No significant hazards expected.

&&

$$

PUBLIC...Thompson
AVIATION...DB
MARINE...DB
SYNOPSIS...Thompson

weather.gov/losangeles


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