Upland, California Weather Forecast Discussion

774
FXUS66 KSGX 191547
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
847 AM PDT Fri Sep 19 2025
.SYNOPSIS...
Southwest flow aloft will bring drying of tropical moisture
through Saturday with warming of high temperatures to within a few
degrees of average and a noticeable decrease in humidity for
inland areas on Saturday. For Sunday through Wednesday, low
pressure to the northwest and high pressure to the southeast may
direct tropical moisture into the vicinity of southwestern
California at times with chances of measurable rainfall for Sunday
and Monday of 30 to 40 percent from showers and for Tuesday and
Wednesday of 10 to 30 percent from showers along with a slight
chance of afternoon thunderstorms.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.UPDATE...
Models continue to run drier in regards to the rain chances for
this afternoon. Low level moisture will wane through the
afternoon and evening, and hi-res models show only a few
thunderstorms developing off the mountains today. Best chances
will be for the far northern portions of the San Bernardino
Mountains where storms look to develop and move northward into the
High Deserts. Any precipitation should end by sunset tonight, with
drier weather for Saturday. Heading into Sunday, moisture surging
from the south may be enough to produce some localized heavier
rain showers, however, the majority of the moisture will be in the
middle and upper elevations, so rain may struggle to reach the
ground on Sunday.
&&
.PREVIOUS FORECAST FROM 319 AM...
.SHORT TERM (Today through Sunday)...
Southwest flow aloft will bring drying of tropical moisture for
today and Saturday. There remains a 20 percent chance of
measurable rainfall for this afternoon for the mountains of San
Bernardino and Riverside Counties northward into the high desert
from isolated showers or thunderstorms with peak hourly rainfall
of one-quarter inch or less. High temperatures for inland areas
will warm, but still be a few degrees below average on Saturday.
It should be noticeably less humid for inland areas on Saturday.
By late Saturday night and Sunday, low pressure to the northwest
and high pressure to the southeast could begin to direct mid and
high level tropical moisture into southwestern California with
increasing clouds and a slight chance of showers. High
temperatures on Sunday will be around 5 degrees cooler than
Saturday with high temperatures ranging from the lower to mid 70s
near the coast to the lower to mid 80s for the Inland Empire with
the lower 90s for the lower deserts.
&&
.LONG TERM (Monday through Thursday)...
Low pressure to the northwest and high pressure to the southeast
will continue to direct tropical moisture into the vicinity of
southwest California at times with more clouds, with chances for
showers at times along with a slight chance of afternoon
thunderstorms. There is increasing spread in the details by
Tuesday and Wednesday.
&&
.AVIATION...
191530Z....Coast/Valleys...Ceilings begin to lift and scatter by 19z-
21z for this afternoon with low clouds returning along the coast
around 01z-02z for San Diego County and arriving at Orange County
coast around 04z-05z tonight into tomorrow morning. Minor vis
reductions will be possible along higher coastal terrain in the late
evening around 06z to the late morning hours around 10Z Saturday.
.Mountains/Deserts...VFR conditions expected through the TAF
period with some SCT-BKN mid level clouds based 5000-10000 ft MSL
lingering through the late afternoon around KONT. Otherwise SKC at
Inland sites. MVFR vis will be possible around 15z-18z around KONT
and KSBD Saturday.
&&
.MARINE...No hazardous marine conditions are expected through
Tuesday morning.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
PUBLIC...Zuber
AVIATION/MARINE...Villafane

NWS SGX Office Area Forecast Discussion