Acton Weather

000
FXUS66 KLOX 180507
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1007 PM PDT Wed Apr 17 2024

.SYNOPSIS...17/938 PM.

High pressure keeps dry conditions in the area for the near
future, and low clouds and fog during the nights and morning will
reoccur through Friday. A warming trend is expected for the
weekend before cooler temperatures return next week.

&&

.SHORT TERM (WED-SAT)...17/1007 PM.

***UPDATE***

Another warm day of high pressure was in store for today, with the
exception of the southern coastal waters and coasts where a solid
deck of marine layer clouds lingered south of Point Conception.
Temperatures warmed into the upper 70s and 80s over much of the
region, however most coastal valleys and coasts south of Point
Conception ended up a few degrees cooler than yesterday due to
more onshore flow.

Tonight, marine layer clouds have been slow to form in part due
to all the high clouds in the region. Low clouds and patchy fog
are expected to move into most coasts and coastal valleys
overnight. There is still potential for dense fog close to the
ocean early Thursday morning. Low pressure moves through the
region Friday, so expecting a deepening marine layer pushing
further deeper into the valleys Friday morning. Expecting warming
temperatures Saturday as ridging returns. The current forecast
looks on track, but will need to consider if more marine layer
clouds will form Friday night/Saturday AM.

***From Previous Discussion***

A relatively quiet period of weather coming up over the next
several days. A weak trough is approaching the West Coast with a
ton of high clouds. Otherwise the main impact will be increasing
onshore flow and marine layer stratus (as those near the coast
south of Pt Conception today can attest to) and cooler
temperatures through Friday. Forecast soundings only indicate
minor deepening of the marine inversion tonight so there will
still be areas of dense fog near the coast and just very little if
any valley fog intrusion expected. The cooler onshore flow mainly
just reached the coastal areas but by tomorrow and Friday cooling
will reach all the way into the interior with highs topping out
in the mid to upper 70s versus the 80s today.

The cooling trend will reverse over the weekend with a brief but
effective ridge over California this weekend. Temperatures should
bounce back to the 80s inland with a 10-20% chance of an isolated
90 or two in the warmest valleys Sunday.

.LONG TERM (SUN-WED)...17/207 PM.

The weekend ridge will be short lived as the next weak trough is
expected to hit the West Coast late Monday and likely remain in
place through the week. This will generate significant cooling
across the area with a likely return of a deep marine layer by mid
to late week. Ensembles have been hinting at some precipitation
chances as well, though those were likely associated with a small
percentage of solutions that showed the upper low cutting off and
dropping much farther south along the coast. A majority favor an
open wave solution with the upper low over Oregon and extreme
northern California. There are some deeper trough solutions later
in the week and into next weekend that could squeeze out some
light precip by next weekend, probably more in the form of deep
marine layer drizzle. In any case, it looks like a long duration
of well below normal temperatures across the area starting next
week.

&&

.AVIATION...18/0347Z.

At 00Z, the marine layer at KLAX was about 600 ft deep. The top
of the inversion was at 2200 ft with a temp of 19 deg C.

High confidence in desert and valley TAFs. Low confidence for
coastal TAFs with widespread low clouds are expected tonight, with
IFR to LIFR conds, and local VLIFR conds on the Central Coast.
High clouds may disrupt low clouds from forming.

KLAX...Moderate to low confidence in the 00Z TAF. There is a 20%
chance that cigs tonight will be in the MVFR category and a 20%
chance that cigs will not arrive until as late as 12Z. Any east
wind component should remain less than 6 knots.

KBUR...High confidence in the 00Z TAF with VFR conds thru the pd.
There is a 20% chance of LIFR cigs after 11Z Thu.

&&

.MARINE...17/947 PM.

A very shallow marine layer will continue to bring dense fog to
most waters south of Point Conception into this morning. There is
a chance that dense fog will also form off the Central Coast, but
low confidence. Improved but still reduced visibility is expected
during the day.

High confidence in generally light winds through Friday.
Southeast winds around 10 knots are expected each morning from the
Santa Barbara Channel to Orange County, with some local
enhancements through the Anacapa Passage and San Pedro Channel.

Northwest winds will be increasing over the weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Thursday for
      zone 670. (See LAXMWWLOX).

&&

$$

PUBLIC...Phillips/MW
AVIATION...Phillips
MARINE...Kittell/Schoenfeld
SYNOPSIS...Phillips/MW

weather.gov/losangeles

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