Chino Hills, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

232
FXUS66 KSGX 122102
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
202 PM PDT Wed Mar 12 2025

.SYNOPSIS...
Cool, wet, and windy weather is expected through the end of the
week. A round of widespread precipitation is expected late tonight
into early Thursday morning, with additional scattered, locally
heavy rain continuing through Thursday afternoon. Widespread gusty
winds expected through Thursday from the coast to the deserts.
Additional rounds of light rain and snow will continue Friday,
with gusty winds for the mountains and deserts. Dry conditions are
expected over the weekend. There is the potential for another
system to impact the region early next week.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

Visible satellite at 2 PM was showing mostly cloudy skies from the
coast to the deserts. Radar imagery was showing areas of scattered,
light rain in the valleys and on the coastal slopes of the
mountains. Over the past 3 hours a tenth of an inch or less of rain
has accumulated in the coastal basin. Southwesterly winds will
increase through the evening ahead of an approaching upper level
trough, especially for the mountains and deserts.

A period of widespread, heavy precipitation is expected to start
late Wednesday night near the Orange/San Bernardino/Los Angeles
County lines, with precipitation moving southeast across the area.
Heavy precipitation is expected to make it to San Diego County just
before sunrise Thursday morning. This system is expected to be quite
cold aloft which increases the chances of thunderstorms across the
area, leading to an increased threat of flooding especially with the
main band of precipitation in the early morning hours. High
resolution guidance is indicating rainfall rates of 0.50 to 0.75"
per hour, with the potential for local amounts up to 1" per hour
where thunderstorms develop and in the mountains below the snow
level. Once the main band of precipitation passes, scattered showers
are expected to linger through the afternoon. There are additional
chances of thunderstorms Thursday afternoon, but the threat will be
much more isolated. Locally heavy rain, locally strong winds, and
graupel/small hail are possible where thunderstorms develop.
Through Thursday night, rainfall and liquid-equivalent above the
snow level is expected to range from around one inch near the
coast to 2 to 3 inches in the mountains with local amounts to
around 5 inches on the coastal slopes of the San Bernardino County
mountains. For the Apple and Lucerne Valleys, one-half to one
inch is expected with one- quarter to one-half inch for the lower
deserts.

A snow level around 6000-6500 feet through tonight, will lower to
4000 feet by Thursday afternoon and 3500 feet by late Thursday
evening. Snowfall of 1 to 5 inches is expected at 4000-5000 feet, 6
to 12 inches at 5500-6500 ft, and 12 to 24 inches above 6500 feet.

Gusty southerly winds this evening and overnight will become
westerly on Thursday. For the coast and valleys, there will be a
round of gusty southerly winds with the front passage/main band of
precipitation late Wednesday into Thursday morning with additional
gusty westerly winds Thursday afternoon. Gusts Thursday afternoon of
30 to 40 mph for the coast and valleys with the stronger gusts along
the desert slopes of the mountains to 50 to 60 mph with isolated
gusts to 65 mph on the desert mountain slopes.

A weaker weather system moving inland to the north is expected to
bring another round of showers for Friday afternoon and evening but
with less totals, around one-tenth inch near the coast to one-
quarter to one-half inch in the mountains. There will also likely be
additional winds in the mountains and deserts. Dry with warmer
conditions expected for the weekend with Sunday high temperatures
warming to near average. For late Monday into Tuesday, another
Pacific low pressure system could bring additional precipitation.

&&

.AVIATION...
122030Z...Mostly cloudy conditions will prevail today and tonight.
-SHRA this afternoon increasing in coverage into tonight. Cloud
bases will vary between 1200-3500 feet MSL, and vis reduced to 3-5SM
in SHRA. Intermittent higher terrain obscurations. Cloud bases in
the deserts mostly 4000-10000 feet MSL. Gusty south to west winds
will remain elevated tonight in the San Bernardino County mountains
and deserts, which will continue to gust 25-45 kt. Gusts 20-35 kt
expected in other mountain/desert locations. Areas of strong
up/downdrafts will occur in lee of mountain ridges into deserts.
Winds decrease slightly for the coastal basin this evening before
picking up again ahead of the cold frontal passage between 6-10Z for
Orange County/ Inland Empire and 9-14Z for San Diego County. +RA
with a slight chance of TS with the cold front Thursday morning.
Winds in the afternoon remain elevated in the coastal basin with
gusts 25-30 kts, especially at the immediate coast, with gusts 30-35
kts. Slight chance of an isolated TS through Thursday afternoon.

&&

.MARINE...
Strong south winds will develop late tonight, then turn west to
northwest Thursday morning with winds approaching gale force. These
winds will produce hazardous boating conditions late tonight through
Thursday night. A Small Craft Advisory has the details. There is a
slight chance of thunderstorms Thursday; a Marine Weather Statement
has been issued and contains more details. Hazardous conditions will
diminish Friday, but brisk northwest winds return Friday night.
Conditions will rapidly improve Saturday and continue Sunday.

&&

.BEACHES...
Surf will increase Thursday, reaching 3 to 6 feet, with sets to 7
feet in San Diego County in the afternoon and evening. There is also
a slight chance of thunderstorms and lightning strikes Thursday.

&&

.HYDROLOGY...
The San Diego and Santa Margarita rivers are forecast to reach
monitor/action stage on Thursday. The San Diego River at Fashion
Valley will reach Monitor Stage at 7.5 around 11 AM Thursday the
13th, peaking in the afternoon around 8.5 ft. The river is forecast
to fall to below monitor stage by Friday morning. The Santa
Margarita River will reach Monitor Stage at 8.2 ft by Thursday
afternoon. The river is expected to peak at 9.3 ft by Thursday
evening. The river is expected to fall back below monitor stage by
Friday morning.

Additionally, areas of urban flooding are possible Thursday morning,
with a band of rainfall moving northwest to southeast across the
area producing rainfall rates of mainly 0.50 to 0.75" per hour,
locally up to 1" in the mountains. Additional chances of more
localized flooding are possible Thursday afternoon.

Stay informed on the latest forecast and conditions. Do not drive
through flooded areas or around barricades.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Flood Watch from 10 PM PDT this evening through Thursday
     afternoon for Orange County Coastal Areas-Orange County
     Inland Areas-Riverside County Mountains-San Bernardino
     County Mountains-San Bernardino and Riverside County
     Valleys-The Inland Empire-San Diego County Coastal Areas-
     San Diego County Mountains-San Diego County Valleys-Santa
     Ana Mountains and Foothills.

     Wind Advisory from noon to 8 PM PDT Thursday for Orange County
     Coastal Areas-Orange County Inland Areas-San Bernardino and
     Riverside County Valleys-The Inland Empire-San Diego County
     Coastal Areas-San Diego County Valleys-Santa Ana Mountains
     and Foothills.

     Winter Storm Warning until 11 PM PDT Thursday for Riverside
     County Mountains-San Bernardino County Mountains.

     Winter Weather Advisory from 6 AM to 11 PM PDT Thursday for San
     Diego County Mountains.

     Wind Advisory from 5 PM this afternoon to 5 AM PDT Friday for
     Apple and Lucerne Valleys.

     Wind Advisory from 7 PM this evening to 11 PM PDT Thursday for
     San Diego County Deserts.

     Wind Advisory from 7 PM this evening to 5 AM PDT Friday for San
     Gorgonio Pass near Banning.

PZ...Small Craft Advisory from 10 PM this evening to 2 AM PDT Friday
     for Coastal Waters from San Mateo Point to the Mexican
     Border and out to 30 nm-Waters from San Mateo Point to the
     Mexican Border Extending 30 to 60 nm out including San
     Clemente Island.


&&

$$

PUBLIC...CO
AVIATION/MARINE/BEACHES...Westerink