Canyon Crest, California Weather Forecast Discussion

885
FXUS66 KSGX 051542
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
842 AM PDT Sun Oct 5 2025
.SYNOPSIS...
Below normal temperatures through Monday, with a gradual warming
trend into the latter part of the week. Areas of night and morning
low clouds and fog will continue along the coasts and parts of
the valleys through midweek. Mid and high level tropical moisture
moving into the region will bring a slight chance of showers late
Thursday through Saturday.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
The expected coastal eddy circulation finally developed early this
morning, pushing patchy low clouds inland into western San Diego
County valleys and localized parts of Orange County. These will
hang out in areas through 10-11 AM before clearing to offshore.
Zooming out, a large scale positively tilted trough is over much
of the north-central and western U.S. A shortwave can be seen
developing on the west side of the trough off the northern
California coast currently. This will develop into a little closed
low late today into Monday morning as it moves down to the south-
central California coast, as the weak ridge over the southern U.S.
moves to cover Southern California. This will result in a gradual
warm up for areas inland from the immediate coast through Tuesday,
starting with inland high temperatures today that will be 2-5
degrees warmer than yesterday`s. Temperatures will still be a
couple of degrees below the daily average today, despite this
mild warm up. A few degrees of warming each day through Tuesday
will bring temperatures closer to normal.
Our weak inversion will strengthen tonight, leading to more
widespread low cloud coverage overnight. Clouds that develop this
evening will still initially be quite patchy, and could remain
patchy to a certain extent overnight, but will be much more
uniform than previous days and make it further inland, even
possibly into parts of the western and southern Inland Empire.
Similar story for the next few nights.
The low lifts north and opens up late Tuesday into early
Wednesday, with little change to the local area. A very large low
pressure system will drop south from the Gulf of Alaska mid- to
late-week, though models have come to more of a consensus that
this will remain pretty well to our north/northwest.
PREVIOUS DISCUSSION...310 AM PDT Sun Oct 5 2025...
Main story this week remains the potential for tropical moisture
from what is now Tropical Storm Priscilla being drawn into the
region late Thursday through Saturday. Ensemble mean Precipitable
Water from both the EC and GEFS are around 1.5", which isn`t bad
for early October. However, it looks like most of this moisture
will be above the 700 mb level.
The real question is how much forcing we`ll have to work with.
Instability remains weak with MUCAPE less than 100 J/kg, so
thunderstorm probabilities are less than 10%. While there is less
spread amongst the ensembles with respect to the position of the
large upper low off the coast during this period, enough spread
remains that uncertainty in forcing and therefore rainfall amounts
remain. With the low further west, placing us more under the
influence of the ridge to the east, accumulating precipitation
will be harder to come by. A further west track of the low would
provide a little more lift and precipitation.
Given the lack of strong dynamics either way, this generally
looks like a case where rainfall rates will remain on the low end
absent any thunderstorms developing, really limiting the flooding
threat. NBM 10th/90th percentile 48 hr rainfall accumulations
range from zero to around an inch for late Thu-late Sat, though
the 90th percentile is definitely skewed by a couple of very wet
ensemble members. NBM mean is closer to 0.2-0.3". Ensemble PW
falls off a cliff on Sunday as the upper trough passes, pushing
tropical moisture out of the area. Highs will remain near normal
through Friday, then a cooling trend follows for Saturday and
Sunday as the trough moves through.
&&
.AVIATION...
051530Z....Coasts/Valleys...Patchy low clouds 1200-1800 ft MSL at
the coast, most widespread in San Diego County. Low clouds should
clear inland areas by 19Z, but may linger at the immediate coastline
this afternoon. Clouds with bases 1200-1800 ft MSL will start to
move inland after 00z Mon, spreading into the valleys and portions
of the Inland Empire. There is a 40% chance of low clouds reaching
KONT by 12Z Mon.
Mountains/Deserts...VFR conditions will prevail into Mon morning.
&&
.MARINE...
No hazardous marine conditions are expected through Thursday
morning.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
PUBLIC...CSP/SS
AVIATION/MARINE...CO

NWS SGX Office Area Forecast Discussion