Rancho Cucamonga, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

434
FXUS66 KSGX 111600
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
900 AM PDT Fri Apr 11 2025

.SYNOPSIS...
Warm weather will continue today with a subtle cooling trend
through the weekend. Dense fog will continue along the coast
through mid morning. The marine layer depth increases slightly
through the weekend with the focus of dense fog shifting onto the
coastal mesas. Cooling trend continues through next week with
breezy onshore flow in the mountains and deserts each afternoon.

&&

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

..UPDATE...

No significant changes from the previous forecast. Patchy dense fog
is quickly moving offshore this morning and dissipating, and the
Dense Fog Advisory has been allowed to drop off. Low clouds and fog
will continue to develop each morning, but set up further inland
each day as the base of the marine layer rises. Otherwise,
temperatures cool slightly through the weekend and into next week
with gusty westerly winds developing in the mountains and deserts
each afternoon. Models attempt some precipitation for Southern
California next week, both Monday into Tuesday and Thursday into
Friday, although models have yet to align on the upper level
pattern for either system to warrant confidence greater than 10%
at this time.

...PREVIOUS DISCUSSION FROM 310 AM FRIDAY...

Areas of fog have developed over the coastal waters and up to a
few miles inland in San Diego County, but skies remain clear for
much of Orange County. Satellite imagery shows the fog bank
beginning to spread north off the Orange County coast and the HREF
is insistent on cloud/fog development there later this morning.
For that reason, went ahead and issued a Dense Fog Advisory for
both the San Diego and Orange County coastal areas through 9 AM.
Elsewhere skies are clear and winds are light outside of a couple
gusts around 25-30 mph through the San Gorgonio Pass. The upper
level ridge progresses slightly eastward and begins to weaken
today, though this will result in little to no change in high
temperatures today. NBM probabilities of high temperatures of 100
degrees are more are still upwards of 90% in the lower deserts,
and changes of 90 degrees or more are around 70-90 percent across
the Inland Empire. In general highs will be around 15-20 degrees
above normal inland, and around 5-10 degrees above normal closer
to the coast.

Through the weekend, an upper level trough essentially splitting
into three waves will move inland across the Pac NW, Central
California, and digging south well off the coast of Baja
California. This will bring cooling with highs lowering to around
5-10 degrees above normal by Sunday. Onshore surface pressure
gradients will strengthen for breezy southwest to west winds in
the mountains and deserts each afternoon with most gusts below 35
mph. The marine layer remains very shallow tonight into Saturday
morning, continuing the threat of dense fog along the coast. It
then deepens for Saturday night to Sunday morning, shifting the
focus of dense fog onto the coastal mesas and far western valleys.

The split flow pattern remains somewhat messy through the week,
though no matter the outcome the weather looks to remain
relatively benign. The low off the Baja coast becomes negatively
tilted as it moves into So Cal on Monday, but with no associated
moisture will only act to continue the cooling trend. Another low
drops down behind it, closing off to our SW before slowly
meandering towards the region by midweek and remaining nearby into
late week. To no one`s surprise, there is quite a bit of spread
amongst the ensemble members with respect to the timing and track
of this feature, resulting in more spread in temperature
forecasts. At some point later in the week the marine layer could
deepen enough for light precipitation from the coasts to the
mountain foothills, though at this time precipitation chances
remain below 10%. Overall expect cooling trend to continue through
the latter half of the week with breezy onshore winds in the
mountains and deserts.


&&

.AVIATION...
111530Z...Coast...FG has retreated to the beaches in Orange
County and within a few miles of the San Diego County coastline
with bases 200-300 ft MSL and VIS improving to 1-2SM. Fog will
continue to retreat to the SD County beaches 16-17z, with
intermittent clearing through the afternoon. Low clouds with
slightly higher bases developing and moving up to 10 miles inland
after 05Z Sat. Bases rising over 500 feet MSL may allow for
improving visibility at the coast by early Saturday morning.

Elsewhere...Mostly clear skies tonight and Friday with VFR
conditions.

&&

.MARINE...
Areas of fog with visibility 1 NM or less are expected through
this morning. Otherwise, no hazardous marine conditions are
expected through Monday.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Dense Fog Advisory until 9 AM PDT this morning for Orange County
     Coastal Areas-San Diego County Coastal Areas.

PZ...None.

&&

$$

PUBLIC...Zuber
AVIATION/MARINE...Westerink