207
FXUS66 KSGX 050429
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
930 PM PDT Sat May 4 2024

.SYNOPSIS...
A period of mostly light rain will move through the region
overnight followed by a mostly cloudy cool day Sunday and a chilly
night with fewer clouds Sunday night. Gusty winds will continue
especially in the mountains and deserts through Sunday evening. Dry
weather with gradual warming will prevail most of next week.

&&

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

Update...

Clouds covered the region this evening, with precipitation still
mostly over Ventura and Santa Barbara Counties where hourly rates
have been mostly around 1/10 inch or less, with 6-hourly totals with
the system being mostly around 1/10 inch but with local amounts
around 1/2 inch. That is mostly what we will expect when the system
and associated cold front move through overnight. The last few
hourly runs of the HRRR have slowed the precip (beginning and ending
by 1-2 hours) and have decreased rainfall totals slightly, so lower
elevations will, like areas to our northwest mentioned above,
receive mostly around 1/10 inch. The mountains and deserts will
continue to be windy through Sunday with the peak winds overnight
with local gusts to 70 MPH and a secondary peak Sunday
afternoon/evening. After the system passes to the east, there should
be an unseasonably chilly night Sunday night, with MOS guidance
suggesting upper 30s in coldest valley locations, such as Ramona or
along the 215 corridor in the Inland Empire. Gradual warming will
occur starting Monday with fair weather...see below for more...

From previous discussion...

Visible satellite imagery at 1 PM was showing the low cloud deck
slowly breaking up, with high clouds moving into Orange and San
Bernardino counties. High clouds will become more widespread through
the afternoon ahead of a low pressure system that will move inland
across northern California. This low will dig into the Great Basin
into Sunday, bringing cold and windy conditions with periods of
showers to Southern California.

Gusty southwest to west winds are expected over the mountains,
through passes, and into portions of the deserts. Winds will slowly
increase in strength through this afternoon and evening, peaking
late tonight into early Sunday morning. Winds will weaken slightly
through the day Sunday but remain elevated into Sunday night. Peak
wind gusts will be 50 to 65 mph with isolated gusts to 70 mph
possible through the San Gorgonio Pass and on the desert foothills
of the San Bernardino Mountains. Another round of weaker but still
gusty west winds will occur Monday afternoon and evening. Peak gusts
of 40 to 50 mph expected over the mountains and into portions of the
deserts. Winds will taper off into Tuesday morning, but periods of
enhanced winds in the mountains and deserts may continue in the
afternoons and evenings most days next week.

The trough axis of the low and associated cold front are expected to
quickly pass through Southern California tonight into early Sunday.
Periods of mostly light rainfall are expected for areas in and west
of the mountains as the front passes. As far as rainfall totals go
generally less than 0.15 inch expected for the coasts/valleys with
local amounts around 0.25 inch near the foothills. Orographics will
enhance precipitation along the coastal slopes of the mountains with
amounts of 0.25 to 0.50 inch, upwards of 0.75 inch on the
southwest facing slopes of the San Bernardino Mountains. Amounts
in the High Desert, if any, will be a couple hundredths of an
inch, with no precipitation expected in the low deserts.
Precipitation will come to an end by early Sunday afternoon. Snow
levels will begin near 7500-8000 ft tonight, falling to around
5500-6000 ft behind the cold front as precipitation tapers off.
Any snow accumulation will be limited to an inch or less.

High temperatures on Sunday will be 15-20 degrees below normal for
inland areas and 5-10 degrees below normal near the coast. Cool
conditions expected Monday morning before temperatures rebound
during the day. Low temperatures Monday morning will be quite
chilly, with lows in the mid to upper 30s for the High Desert,  mid-
20s to mid-30s for the mountains, and the low 40s for some valley
locations. Conditions are expected to gradually warm Tuesday into
much of next week, although there is some uncertainty in the
forecast for the middle to end of the week. By Wednesday, ensembles
are pretty much split half and half on warmer vs cooler scenarios.
By Thursday, the cooler scenario with the low retrograding much
further SW is the outlier containing only 7 percent of global
ensemble members. Given the large uncertainty the current forecast
follows NBM for temperatures which shows a very subtle warming trend
through the week.

&&

.AVIATION...
050330Z...Coasts/Valleys/Foothills...Low clouds are expected to
cover the region west of the mtns overnight, with bases in one layer
SCT-BKN 1500-2500 FT MSL, and another BKN-OVC 2500-4000 FT MSL. VIS
reduced to 1-3SM where low clouds and terrain intersect, obscuring
higher terrain. Scattered -SHRA beginning as early as 06z Sun at
the coast, but more likely between 06-09z for Orange County/Inland
Empire and 09-12z for San Diego County. Briefly lower CIGs and
slightly reduced VIS down to as low as 3 SM in -SHRA. Gradually
clearing then for Sunday after 18-20z.

Mountains/Deserts...Strong W-SW winds will continue through 07Z,
then decreasing through the rest of the night. Expect another round
of strong W-SW winds 20-35 kt with gusts of 45-60 kt after 18Z.
Areas of MOD-STG up/downdrafts and LLWS over/east of mtns.

&&

.MARINE...
Gusty northwest wind gusts of 25 to 30 knots will occur this evening
through Sunday evening, which will generate hazardous boating
conditions, especially in the outer waters. Northwest wind gusts up
to 20 knots will be possible over the outer waters each afternoon
and evening for Monday through the middle of next week.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 8 PM PDT Sunday for Apple and Lucerne
     Valleys-San Bernardino County Mountains-San Gorgonio Pass
     Near Banning.

     Wind Advisory until 8 PM PDT Sunday for Coachella Valley-
     Riverside County Mountains-San Diego County Deserts-San
     Diego County Mountains.

PZ...Small Craft Advisory from 3 AM to 10 PM PDT Sunday for Coastal
     Waters from San Mateo Point to the Mexican Border and out
     to 30 nm.

     Small Craft Advisory until 3 AM PDT Monday for Waters from
     San Mateo Point to the Mexican Border Extending 30 to 60 nm
     out including San Clemente Island.

&&

$$

PUBLIC...Maxwell (Update)/CO (Previous Discussion)
AVIATION/MARINE...Suk