Royal Palms Beach Park, California Weather Forecast Discussion

096
FXUS66 KLOX 201022
AFDLOX
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
322 AM PDT Sat Sep 20 2025
.SYNOPSIS...20/156 AM.
A warming and drying trend will continue today. Isolated showers
cannot be ruled out over the mountains this afternoon, but drier
southwest flow should continue to stabilize the air mass. Monsoonal
moisture will begin to move north again on Sunday, and a return
of convective storms is possible as early as Sunday afternoon and
evening. Any shower activity for the coastal and valley areas
will likely delay until Tuesday.
&&
.SHORT TERM (TDY-MON)...20/320 AM.
The latest water vapor imagery indicates an upper-level ridge of
high pressure over the region this morning, while an upstream
cutoff trough sits off the California coast. The low cloud field
is pretty broken up due to a weak marine inversion in place, but
the most coverage of low clouds is along the Central Coast and
into the Santa Ynez Valley.
A drier southwest flow aloft will continue today across the
region. Marginal PoPs remain in the forecast over the western
portion of the Transverse Ranges due to just enough moisture in
place and some difluence with the weak trough offshore. High
resolution multi-model ensemble members favor shower chances over
the Santa Barbara and Ventura County mountains this afternoon and
evening. People planning to travel mountain roads and/or
participate in outdoor activities today should be prepared for
brief heavy downpours, gusty and erratic winds, and dangerous
lightning.
Ridging aloft in place will bring a warming trend through the
weekend. Weak onshore flow with less cloud coverage will allow for
a slight warming trend to develop for the valley, mountain, and
desert areas. Closer to the coast, the onshore flow should inhibit
the bulk of the warming.
The latest model solutions and forecast ensembles continue to
indicate a surge of monsoonal moisture moving north between Sunday
and Tuesday. The moisture, associated with a tropical disturbance
off the Baja California coast, will be transported northward as
the weak cutoff trough off the coast approaches the coastline. The
cyclonic flow pattern will entrain some tropical moisture. PoPs
could increase as soon as Sunday. High resolution multi-model
ensemble members give a likely (60-70 percent) chance of
precipitable water values exceeding 1 inch by Sunday across
southern Los Angeles County. This agrees well with AI integrated
EPS ensemble members which increase PWAT values around to 1.1
inches at KLAX by Sunday afternoon, but the bulk of the moisture
looks to remain to the south until late Monday night or early
Tuesday morning. The PoP forecast for coastal and valleys areas
goes with NBM values for Sunday, but PoPs were increased across
the mountains and desert to account for isolated showers that
could pop up.
.LONG TERM (TUE-FRI)...20/320 AM.
The latest forecast ensembles increase precipitable water value
means through Tuesday to near 1.50 inches as the weak cutoff
trough slowly approaches the California coast. This should bring a
return of showers and thunderstorms to the area between Monday
night and Tuesday night as the moisture interacts with the
instability provided by the trough. A similar approach was
applied to PoPs for Monday through Wednesday, allowing for the
forecast for coastal and valley areas to go with NBM values, but
PoPs were increased across the mountains and desert to account for
increased convection over the areas.
The trough should pass by to the east for late week and bring some
warming and drying.
&&
.AVIATION...20/0545Z.
At 0458Z at KLAX, the marine layer was around 600 feet deep. The
top of the inversion was 1300 feet with a temperature of 22 C.
High confidence in VFR TAFs for desert airfields (KWJF and KPMD).
Good confidence in VFR TAF for KPRB with only a 

NWS LOX Office Area Forecast Discussion