818
FXUS66 KSGX 190941
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
241 AM PDT Sat Apr 19 2025

.SYNOPSIS...
Dry and warmer through early next week with high temperatures
near to around 5 degrees above normal inland by Monday. Gradual
cooling follows Tuesday through Saturday. Areas of night and
morning low clouds and fog continuing through next week, becoming
more widespread towards the middle of the week as the marine layer
deepens.

&&

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

Water vapor imagery shows the upper level low has moved into
Central Arizona with dry northwesterly flow in its wake. Surface
pressure gradients are trending very weakly offshore to the Great
Basin but remain onshore to the local deserts. Offshore flow will
strengthen later this morning with breezy north to northeasterly
winds developing along the coastal slopes of the mountains and
below the Cajon Pass into the Inland Empire. Wind gusts will
generally be around 25-35 mph, locally up to 40 mph in the wind-
prone canyons and slopes. These winds will also help clear out any
lingering low clouds, which are generally confined to the
valleys and foothills now.

Not much weather-wise over the next week or so. Gradual warming
across the region through Sunday as the upper low lifts out and we
are left under weakly cyclonic flow with the jet well to our
north. Minor cooling occurs west of the mountains on Monday as a
weak short wave progresses inland to the north and onshore flow
strengthens, with minor warming across the mountains and deserts.
Highs will be around 5-7 degrees above normal inland on Monday but
near normal at the coast. The marine layer will be much more
shallow with low clouds and patchy fog limited to the coastal
areas and far western valleys Sunday and Monday mornings.

Ensembles are in generally good agreement through Thursday with a
weak trough along the west coast slightly amplifying. This will
bring gradual cooling and a deepening of the marine layer. As we
head into the latter part of the week, ensembles begin to diverge
on the evolution of another upper low off the Pac NW coast and
eventually moving inland somewhere along the West Coast, though
the position of the center of the low ranges anywhere from OR to
central CA, with some timing differences too. This will affect how
much cooling will occur and when, the depth of the marine layer,
and the strength of onshore winds. If the trough digs far enough
south we could see some precip next weekend, though any ensembles
members with measurable rain are few and far between and amounts
are all light. Precipitation chances remain below 10% for next
weekend. Only other hope for precipitation is for patchy drizzle
from a deepening marine layer. Otherwise expect more widespread
night and morning low clouds and fog for the latter half of the
week and breezy west winds across the mountains and deserts each
afternoon and evening.

&&

.AVIATION...
180930Z....Coasts/Valleys/Foothills...Low clouds have mostly cleared
out with the exception of the mountain foothills and portions of the
Inland Empire. The clouds that do remain at this hour are based near
2500-3500ft MSL but should continue to gradually scatter out over
the next few hours. Mostly clear conditions follow through this
afternoon with FEW-SCT clouds around 1000ft MSL possible near
the coast late Saturday night.

Higher Mountains/Deserts...Strong winds have largely diminished in
the deserts with elevated winds still across the higher mountains.
Winds shifting NE by 12z with gusts near 30kts at times along
coastal slopes of Orange / SBD Counties until 21z this afternoon.

&&

.MARINE...
No hazardous marine conditions are expected through Wednesday.

&&

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


&&

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

&&

$$

PUBLIC...SS
AVIATION/MARINE...Munyan