Claremont, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

533
FXUS66 KLOX 301639
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
939 AM PDT Fri May 30 2025

.SYNOPSIS...30/938 AM.

Significant warming today with an elevated risk for heat illness.
Cooler but more humid over the weekend as tropical moisture moves
over the region, also bringing a chance for showers or a
thunderstorm. Near normal conditions to follow Monday and Tuesday,
before another warm up arrives for the back half of next week.

&&

.SHORT TERM (TDY-SUN)...30/938 AM.

***UPDATE***

Interesting stratus behavior this morning as the marine layer did
indeed shrink considerably north of Pt Conception where dense fog
has now retreated to the beaches. However, in LA County reports
from pilots still peg the marine layer depth at around 2000 feet.
Looking at the 24 hour temperature change map, the biggest
increase from yesterday is at elevations above 1500 feet
(including the Santa Clarita Valley) where some places are as
much as 25 degrees warmer than yesterday morning. In the lower
valley such as the San Fernando and San Gabriel Valleys rises are
not quite as impressive but still in the 5-15 degree range. With
offshore gradient trends today and building heights aloft the
marine layer should shrink through the day push that warmer air
aloft down towards the lower valley areas. So the heat advisories
there are still on track with highs approaching 100 this afternoon
in the warmest valleys.

Across interior SLO and SB Counties, the marine inversion is much
lower so even the lower valleys such as the Salinas Valley are
seeing much warmer temperatures compared to yesterday morning and
expecting highs near or even slightly above 100 today. Coastal
areas are much cooler with the marine layer but interior parts of
the coast, such as San Luis Obispo, should reach the lower 80s at
least.

***From Previous Discussion***

A shallow marine layer has brought dense fog and low visibilities
to northwest Santa Barbara County this morning, which will likely
linger into the daylight hours. Low confidence on how the low
clouds and fog will behave elsewhere, including off Los Angeles
County as a sudden and much delayed surge is now pushing up from
San Diego County.

Southwest California will be caught in between a narrow upper
level high just to the north and a stationary cutoff low just to
the south (more on the low later). With weakening onshore flow and
a reduced marine layer, expect more sunshine and drastically
warmer conditions on the coastal side of the ranges today when
compared to yesterday. Highs will generally be in the 70s near
the coast, 80s over the inland coastal plains, and 90s to 102 in
the valleys and lower mountains. The previously issued Heat
Advisories look good with no changes planned, highlighting the
elevated risk for heat illness for sensitive populations,
including those active outdoors like hikers. While sunny skies
will be common today, a few afternoon cumulus clouds should bubble
up in the mountains, but look unlikely to result in any showers
at this point.

Temperatures will lower some over the weekend but will continue
to feel warm as humidity rises, especially towards Los Angeles
County as that fairly stationary low draws up tropical moisture
from Mexico. With precipitable water values approaching Monsoon-
like 1.5 inches, expecting a noticeable muggy factor on the rise
from Saturday through Sunday. Combine this moisture with a few
upper level disturbances (with omega values of 10+ at 500
millibars) and marginal instability (MUCAPE 500-1000 and K-Index
around 35), and a few showers or even a thunderstorm is also in
the cards. That potential is highest towards Los Angeles County,
and more so Saturday Night through Sunday. If any shower develops,
it will likely be light or a few fat drops, with the highest
potential of a legit shower over the mountains and deserts. The
thunderstorm potential is highest over the mountains in the
afternoon hours, and over the waters overnight. Winds will be
rather complex with varying wind directions, especially if a
heavier shower or thunderstorm forms.

.LONG TERM (MON-THU)...30/405 AM.

Another low pressure system will drop through California Monday
and Tuesday, but does not look to stall like our weekend system.
This will likely accelerate our return to a more typical June
Gloom pattern with seasonal temperatures. Ensemble projections
show a range of outcomes after that from Wednesday on. While the
majority favor a warm up, little change is also a possibility.

&&

.AVIATION...30/1132Z.

At 0641Z, the marine layer was 1000 feet deep at KLAX. The top of
the inversion was around 2700 feet with a temperature of 23 C.

Overall, low to moderate confidence in the 12Z TAF Package. High
confidence for desert and valley terminals and low for coastal
sites. Most uncertain in regards to cigs returning after 06Z Sat.

KLAX...Low confidence in the 12Z TAF. Most likely outcome is for
cloud coverage to remain FEW-SCT through 17Z Fri, with a 30%
chance of MVFR/IFR cigs. High uncertainty in regards to cig
arrival tonight (+/- 3 hours), with a 25% chance cigs do not
materialize. No significant east wind component expected.

KBUR...High confidence in the 12Z TAF. VFR conditions are
expected to dominate the fcst pd.

&&

.MARINE...30/802 AM.

For the outer waters, moderate confidence in the forecast for the
remainder of today, then high confidence thereafter. Small Craft
Advisory (SCA) conditions are expected to linger into the early
afternoon hours (short period seas for PZZ673) and evening hours
(wind gusts over 21 kts and short period seas for PZZ670) today.
Conditions are then expected to remain below SCA levels through
Sunday morning. Then there is a 50% chance for SCA conds Sunday
afternoon into the overnight hours, with slightly higher
confidence in seas reaching 10 ft than winds reaching 21 kts.
Thereafter, conditions look to remain below advisory criteria
through at least mid-week.

For the nearshore waters along the Central Coast, conditions are
expected to remain below SCA criteria through the middle of next
week. However, there is a 30% chance of local SCA level NW wind
gusts during the afternoon today, and a 40% chance for SCA level
seas Sunday afternoon into late night.

For the Santa Barbara Channel, high confidence in conditions
remaining below SCA criteria through the middle of next week,
with the exception of a 20-30% chance of SCA level wind gusts
over western portion during the afternoon and evening hours on
Sunday.

For the Inner Waters off the Los Angeles and Orange County coasts,
moderate-to-high confidence in conditions remaining below SCA
levels through Tuesday. However, there is a 20% chance of SCA
level wind gusts nearshore around Mailbu this afternoon.

Brief, localized SCA wind gusts may occur across the coastal
waters Saturday afternoon through Sunday morning as an upper level
low pressure system off the coast of Baja California moves north
then east, with the heart of the system evading our waters. This
system brings a 10-20% chance of thunderstorms Saturday afternoon
through Sunday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory remains in effect until 8 PM PDT this evening
      for zones 38-88-343>345-358-372-373. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
      for zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until noon PDT today for zone
      673. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/Kittell
AVIATION...Black
MARINE...Lewis
SYNOPSIS...RK

weather.gov/losangeles

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