South San Gabriel, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

065
FXUS66 KLOX 191316
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
616 AM PDT Thu Sep 19 2024

.SYNOPSIS...19/336 AM.

An unsettled weather pattern will develop across the region
through tonight as an early season low pressure system moves over
the region through Friday. A cool air mass will remain in place
through Friday, but turn more showery through tonight. While not
every location will see showers and thunderstorms, any shower
activity will be capable of producing heavy rainfall, especially
across interior portions of Ventura, Santa Barbara, and San Luis
Obispo Counties through this evening. Some showers or
thunderstorms could linger into Friday before the low pressure
area and the associated air mass exits the region. A warming and
drying trend should develop over the weekend and into early next
week.

&&

.SHORT TERM (TDY-SAT)...19/455 AM.

The latest satellite imagery shows a vigorous early season trough
off the central California coast early this morning. This trough,
located near 35N and 122W, or about 80 miles west of Point
Conception will wobble around the Point Conception area through
this afternoon while digging slowly southeast. Shower activity is
already developing across interior San Luis Obispo County this
morning, while a weaker band is currently located just offshore
closer to the trough. Isolated thunderstorms cannot be ruled out
for northern San Luis Obispo County this morning as the most
favorable lifted index values will push along the San Luis
Obispo-Monterey County border this morning. A few lightning
strikes have been observed to the north in Monterey County.
Shower and thunderstorm activity should become more expansive as
the day progresses and daytime heating steepen lapses rates and
destabilizes the atmosphere. PoPs mostly remain untouched through
this afternoon with only a few minor tweaks, but PoPs were
increased and a slight chance of thunderstorms were added to the
forecast tonight through Friday morning as the 500 mb cold pocket
will move across the southern California bight tonight through
Friday morning. High-resolution multi-model ensemble members keep
the highest probability of rain across the interior portions
across San Luis Obispo, Santa Barbara, and Ventura Counties this
afternoon and tonight. A flood watch remains in effect for these
areas where the highest probability of the heaviest rainfall
exists and includes Hurricane and Apache burn scars.

To south, low clouds and fog are filling in across the Southland
and into southern California bight and Santa Barbara Channel, but
low confidence exists in the cloud forecast as middle and high
level clouds streaming over the region are disrupting the marine
layer stratus formation. Where there are clouds, the instability
with the trough will likely produce patchy drizzle this morning as
the instability interacts with the deep marine layer depth in
place. The latest AMDAR soundings from KLAX indicate a 3200 foot
deep marine layer depth in place. Clouds should continue to fill
in across the Southland as the trough position should promote
low-level moisture to increase.

A cooler air mass and unsettled air mass will remain in place for
the next couple of days as the trough center slowly drifts
southeast across the area, coming ashore in Orange County on
Friday morning. Shower chances linger in the forecast into Friday.
It should be noted that the trough position is favorable for
wrap-around shower activity across the interior areas into Friday.
PoPs have been extended into Friday for this reason. A breezy
afternoon looks on tap for Friday as the surface pattern tightens
some. It appears to be marginal for any wind advisories, but a
wind advisory cannot ruled out across southern Santa Barbara
County on Friday evening.

A drying and warming trend should begin on Saturday as high
pressure aloft starts to build into the region. Some low clouds
and fog could remain across the region, but less low cloud
coverage should be expected into the weekend.

.LONG TERM (SUN-WED)...19/456 AM.

High pressure aloft will build into the region for early next
week and bring a warming trend. The latest temperature forecast
breaks away from NBM values for Sunday and Monday when high
pressure and onshore flow weaken. Potentially, weak offshore flow
could develop across the region and make temperatures several
degrees warmer than indicated. EPS cloud cover means indicate
minimal clouds for early next week during the night through
morning period, thus marine layer induced low clouds and fog
coverage could be less in coverage for Sunday and Monday than what
the current forecast alludes to.

Some cooling should develop for the latter half of next week as
another trough will attempt to dig south. This trough is not
expected to be as strong as the current one and will only increase
onshore flow and make the low cloud field a bit more expansive.
There is quite a spread in the forecast ensembles for late week as
there are plenty of solutions offering warmer solutions. The
forecast trends the way of the majority of the cooler solutions
with more low clouds and fog.

&&

.AVIATION...19/1304Z.

At 12Z at KLAX, there was a 5000 ft deep moist layer and no
inversion.

Good confidence in TAFs for KPMD and KWJF.

Low confidence in the remainder of the TAFs. Cig heights will
vary frequently due to presence of upper level low moving over the
region. There is a 20-30% chance of TSTMs with brief +RA and
gusty and erratic winds. Timing of flight cat and VCSH/VCTS
changes could be off by +/- 3 hours.

For KPRB, TSTM (30% chc) and rain shower chances diminish after
06Z Fri.

For KSMX, KSBP, and KSBA -DZ is possible through the
morning. Very low confidence in KSMX and KSBP conds through 15Z as
LIFR conds are possible, but MVFR conds are mainly expected. Then
there is a 20% chance of TSTMs 17Z Thurs-10Z Fri.

For Ventura and Los Angeles County TAFs (except desert TAFs),
cigs will vary between MVFR and VFR through 17Z, then lift to
VFR. -DZ is possible at all sites through the morning due to the
marine layer rapidly deepening. There is a 10-20% chance of
isolated TSTMs at KOXR and KCMA after 00Z Fri, and after 06Z Fri
for LA County sites. There is a 20% chance of MVFR cigs at L.A.
sites after 04Z Fri.

KLAX...Low to moderate confidence in TAF. Cigs may vary between
BKN015-035 frequently through 17Z as upper level clouds move
overhead. -DZ is possible through 17Z Thurs. There is a 20%
chance of BKN025-030 cigs after 04Z Fri. There is a 20% chance of
TSTMs after 06Z Fri. No significant east wind component is
expected.

KBUR...Low to moderate confidence in TAF. There is a 20% chance
of BKN022-030 conds through 15Z Thurs and after 04Z Fri. There is
a 20% chance of TSTMs after 06Z Fri.

&&

.MARINE...19/348 AM.

Low confidence in the current forecast for the period. Higher
confidence exists in the forecast for seas. Lower confidence in
the current forecast for winds and thunderstorms.

Isolated to scattered thunderstorms will be possible across all
of the coastal waters this afternoon through at least this evening
as an upper-level low pressure system drops from Northern
California to near Pt. Conception by the afternoon. The trough
will move southeastward across the southern California bight
tonight and onshore over southern California through Friday. A
Marine Weather Statement is in effect to communicate the hazards
from thunderstorms to the marine community.

Winds and seas will likely remain below Small Craft Advisory (SCA)
levels through the majority of the period. However, for the
waters from Point Conception south to San Nicolas Island, in the
vicinity of the Channel Islands, and across the western portion of
the Santa Barbara Channel, there is a 30 percent chance of SCA
level wind gusts this afternoon/evening, and a 40 percent chance
Friday afternoon/evening.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Flood Watch in effect through this evening for zones
      38-344-345-377. (See LAXFFALOX).
PZ...NONE.

&&

$$

PUBLIC...Hall
AVIATION...Lund
MARINE...Lund/Hall
SYNOPSIS...Hall

weather.gov/losangeles

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