San Ysidro, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

077
FXUS66 KSGX 311624
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
924 AM PDT Sat May 31 2025

.SYNOPSIS...
An area of low pressure to the south will bring cloudier conditions
and a chance for showers and thunderstorms this weekend. Slightly
cooler today, with further cooling tomorrow into early next week.
High pressure over the Pacific will move closer to the region
later in the week, leading to warmer weather across SoCal.

&&

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

.Morning Update...

High clouds continue to increase over SE California into San Diego
County this morning. As stated below, clouds may thicken enough to
bring light shower and sprinkles to southern areas later this
afternoon. As the low pressure system to the south pushes inland,
expect a better chance of showers overnight into Sunday. Models
slightly differ on exact placement of the low as it pushes inland
on Sunday. If the low stays further west, it will bring a better
chance of showers and storms across inland areas; not so much if
it pushes further east into the desert. No forecast changes this
morning as this degree of uncertainty continues. High temperatures
today will continue to be warm, but would not be surprised to see
them turn out a few degrees cooler in southern areas due to
increased high cloud coverage this morning.

.Previous Discussion (312 AM Saturday)...

A cut-off upper level low was meandering over the Pacific Waters
at roughly 300 miles southwest of San Diego. Clouds will continue
to lift and thicken, with some light rain showers becoming
possible by later in the day due to the influence of this U/L low,
especially over the mountains of San Diego County. The lower
heights over the region due to the upper level low, as well as mid
to upper level clouds moving overhead, will result in
temperatures being slightly cooler today, ranging from the low to
mid 70s at the coast, to upper 80s in the inland areas of San
Diego and Orange counties, to mid to upper 90s for most areas
within the IE. For the mountains and deserts, temperatures will
still be on the mild side, and slightly above the seasonal average
for this time of year. Given how high based any precipitable
clouds will be, it is more likely that most of these showers will
be in the form of virga (precip evaporating before reaching the
surface).

The latest models are in relatively good agreement with the
transition of this U/L low, which looks to remain nearly quasi-
stationary through the early morning hours on Sunday, until it
finally begins to propagate northeastward after getting "kicked" out
of position by another deepening low in the split flow of the
longwave trough over the region. Simultaneously, there is also going
to be the remnants of a tropical system (currently Tropical Storm
Alvin), feeding moisture into the U/L low from the south. A
general consensus of the models puts its position roughly to the
southeast of San Diego by the early morning on Sunday. This puts a
lot of the region more on the convergent quadrant of the U/L low,
and precipitation might be more sparse due to this.

By later in the afternoon on Sunday, and especially with some
increased instability with further moisture streaming up from the
remnants of Alvin, that there will be a better chance of more
widely scattered showers and possibly even a few thunderstorms
over the mountains and east-facing slopes of the high deserts in
San Diego County. The chance of precip will diminish going north
and west. There could be a few cells dropping locally heavier
amounts for portions of the mountains and deserts with the
developing showers and thunderstorms by later in the afternoon,
otherwise most areas will struggle to receive a tenth of an inch
or more before it is all said and done. There will be some
stronger and gusty winds, although not anything strong enough to
warrant the issuance of any wind advisories. It will also be
cooler on Sunday, and even further cooler on Monday, with highs
being slightly below the seasonal average for most locations.

Tuesday through early next weekend...

There will be a gradual warmup for the region beginning Tuesday, and
on through into the early part of the following weekend. Given that
there will continue to be an overall area of troughing remaining in
place over the western states, it will continue to be closer to the
seasonal average with pleasant conditions in place throughout this
period in the forecast with high pressure conditions in control.

&&

.AVIATION...
311530Z...Coasts/Valleys...Low clouds based 700-1100ft MSL with tops
to 1700ft MSL extend down the coast and up to 5-10 miles inland and
SCT high clouds around 20,000ft. Low clouds are already beginning to
clear and will continue through 17-18z. Isolated showers are
possible starting later this morning/this afternoon, mainly in San
Diego Co, with a 10-20% chance for SHRA at coastal and valley sites.
Greater chances for SHRA overnight through Sunday morning. Low
clouds may redevelop tonight, with lesser inland extent and only a
20-40% chance for a CIG at KSAN or other coastal sites, with the
best chance being between 12-16z Sunday. Iso TSRA will possible for
the far eastern valleys and foothills, primarily after 18z Sunday.

Deserts/Mountains...SCT-BKN high clouds at 10,000-20,000ft MSL
through the day. -SHRA possible starting this afternoon with higher
chances tonight and Sunday morning, especially in San Diego County
mtns. Brief outflow gusts over 25 kts possible with any developing
SHRA. Iso-Sct TSRA possible generally after 18z Sunday with the
highest confidence being in the mountains/higher terrain. Near zero
VIS in any storm with heavy rain, along with erratic and gusty
winds.

&&

.MARINE...
No hazardous marine conditions are expected through Wednesday.
Chance of showers (20-35%) tonight into Sunday across the coastal
waters.

&&

.BEACHES...
A long period south swell will build into the region Sunday, leading
to elevated surf for south and southwest facing beaches of 4 to 6
feet with sets to 7 or 8 feet possible. This will result in higher
rip current risk and locally hazardous swimming conditions. Surf
peaks Monday and gradually diminishes Tuesday through Thursday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

UPDATE...APR
PUBLIC...Stewey
AVIATION/MARINE...Zuber