South Pasadena, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

448
FXUS66 KLOX 050700
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1200 AM PDT Thu Jun 5 2025

.SYNOPSIS...04/744 PM.

Strong onshore flow and a persistent marine intrusion will
continue night through morning low clouds and fog through
Saturday. Some thinning of the marine layer depth will take place
over the weekend as onshore flow weakens. As a result, low clouds
and fog will retreat to the coast and lower valley areas Sunday
through Tuesday. Cooler than normal temperatures through the end
of the week, then a warming trend will develop for the weekend,
especially away from the beaches.

&&

.SHORT TERM (THU-SUN)...04/854 PM.

The latest fog product imagery indicates the marine layer induced
low clouds to be already well-entrenched along the coast and
making a run into the Ventura County valleys already. Strong
onshore flow in place will continue more of the same with a
persistence forecast in the mix. A cooler weather pattern will
persist into late week with night through morning low clouds and
fog.

Broad troughing aloft will continue to create a favorable pattern
for onshore flow to persist. Another weak trough of low pressure
dropping down through Thursday night will bring more dynamics for
late night through morning drizzle, especially from Santa Barbara
north. EPS ensemble members indicate a majority of solutions with
very light QPF at KSBA, while high-resolution multi-model
ensemble members lean toward possible drizzle along the Central
Coast. NAM BUFR time height section also agree that the greatest
threat of drizzle will be along the Central Coast.

With trough`s dynamics moving over the area and EPS precipitable
water value means hovering around 1 inch, a slight chance of
showers and thunderstorms over mountains looks agreeable at this
time for Thursday afternoon and evening. The pattern will
different from Tuesday as the steering flow is flowing from
southwest to northeast. The flow is concerning though, as the
steering light. If any storm develop over the mountains on
Thursday afternoon and evening, there is a high chance that these
storms will not move much.

An update will be sent to the forecast shortly to add drizzle
overnight and into Wednesday morning.

***From Previous Discussion***

Overall, 12Z models in good synoptic agreement through the short
term period. At upper levels, trough will linger over the area
through Friday then will become a cutoff low that develops west of
Point Conception. Near the surface, moderate to strong onshore
flow will continue.

Forecast-wise, two main issues in the short term will be
convection and the marine layer stratus. With respect to
convection, still looks good (as mentioned in the morning
discussion) for a slight chance of showers/thunderstorms over the
eastern San Gabriel Mountains and adjacent desert foothills this
afternoon. For Thursday, instability parameters (CAPE, K-Indices,
etc.) decrease a bit over the eastern San Gabriel Mountains, but
increase a bit over the Ventura county mountains. Additionally,
PWATs increase over the northern Ventura county mountains and
remain similar to today over the eastern San Gabriel Mountains.
So, still think there is enough moisture and instability to
warrant inclusion of a slight chance of showers/thunderstorms
Thursday afternoon over the eastern San Gabriel Mountains and the
northern Ventura county mountains. Any storms that develop will
likely be a mix of wet and dry. So, both brief heavy rain and dry
lightning strikes will be possible.

The second issue, marine layer stratus, H5 heights remain
virtually unchanged tonight. So, with continued onshore gradients,
inversion will be deep enough for stratus to push into the coastal
slopes tonight. Clearing should be better on Thursday afternoon.
For Thursday night through Saturday, rising H5 heights will
increase, resulting in more shallow inversion and lesser areal
extent of stratus/fog.

As for winds, the onshore gradients will generate the usual gusty
southwesterly winds across interior sections through Saturday.
However, outside of Lake Palmdale, expect winds to remain below
advisory levels.

Finally with respect to temperatures, will expect a gradual
increase in temperatures from day-to-day with lessening marine
influence and rising H5 heights.

.LONG TERM (MON-THU)...04/215 PM.

For the extended period, 12Z models are not in the best synoptic
agreement. The ECMWF and its ensembles indicate more upper level
ridging than the GFS family. However, near the surface, both
models indicate a continued onshore flow.

Forecast-wise, the differences between the models are not expected
to produce any significant issues. Through the period, dry
conditions are expected. As for clouds, marine layer stratus/fog
should remain mostly confined to the coastal plain, before making
a bit further inland Tuesday/Wednesday as H5 heights decrease a
bit. Other than the marine layer stratus, skies are expected to
remain mostly clear through the period. Temperatures will follow
the same trend, with a warming trend Sunday/Monday then some
slight cooling Tuesday and Wednesday. As for winds, will expect
continued onshore breezes each afternoon, but nothing worrisome.

&&

.AVIATION...05/0700Z.

At 0515Z at KLAX, the marine layer was 2400 feet deep. The top of
the inversion was at 5100 feet with a temperature of 18 C.

High confidence in VFR TAFs for KPMD and KWJF.

Moderate confidence in all remaining TAFs. Flight cat change
timing may be off by +/- 90 minutes and cig hgt by +/- 300 ft.

KLAX...Moderate confidence TAF. There is a 30 percent chc of
OVC008 conds 10Z-14Z. SCT conds could arrive anytime between 19Z
and 21Z with a 25% chance of no clearing. No significant east
wind component expected.

KBUR...Moderate confidence in TAF. Flight cat change timing may
be off by +/- 90 minutes. There is a 20 percent chc that cigs will
remain AOA 010.

&&

.MARINE...04/854 PM.

High confidence in unseasonably quiet conditions through Friday
with no Small Craft Advisories (SCA) needed. More seasonally
typical northwest to west winds will form by Saturday or Sunday,
with short period choppy seas likely nearshore. Next week will
bring increasing chances for both SCA winds and seas.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...Hall/Thompson
AVIATION...Rorke
MARINE...Black
SYNOPSIS...Hall

weather.gov/losangeles

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