505
FXUS66 KSGX 131937
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
1237 PM PDT Mon Jul 13 2026
.SYNOPSIS... A moisture surge will bring scattered showers and
thunderstorms to the mountains this afternoon and evening with a
slight chance of precipitation reaching into the lower elevations.
Building high pressure will bring above average temperatures for
midweek with highest temperatures on Wednesday. Widespread moderate
to major HeatRisk is expected. This will also subdue thunderstorm
coverage with only a slight chance of precipitation in the
mountains. The high pressure breaks down by Friday into the weekend
with temperatures returning to near normal, along with increasing
chances for monsoon storms once again. Coastal flooding will impact
beaches through Tuesday with evening high tides exceeding 7 feet.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Leftovers from last night`s monsoon dinner in Arizona and Sonora is
streaming overhead in the form of mid and high level clouds today.
Drying can be seen on satellite coming northward from Baja which
will aid in a better monsoonal storm development pattern for the day
as moisture and elevated instability is locked in place. To note,
this morning`s sounding shows notable PWAT values around 1.65
inches. Cumulus beginning to build over the mountain crest will
produce areas of showers and thunderstorms this afternoon into the
early evening. Latest radar imagery and hi-res guidance shows
mountains in the San Diego and Riverside mountains seeing the
greatest chance for storm activity, though chances reach all the way
north into eastern portions of the SBD mts into the high desert. Any
storm will be capable of producing bouts of heavy rain, cloud to
ground lightning and gusty winds.
Moisture decreases by Tuesday into Wednesday as seen in the latest
model guidance as high pressure expands over the region. This will
decrease chances for storms in the mountains, but increase high and
low temperatures. An Extreme Heat Warning is now in effect for all
mountains and western valleys, as well as a Heat Advisory for
coastal areas Wednesday through Thursday. Wednesday will be the
hottest day with highs well into the 90s for the mountains and
coastal valleys, triple digits for the Inland Empire and eastern San
Diego Co valleys. Low temperatures will also be in the 70s across
much of this region each night. This, along with increased humidity,
will give areas moderate (rating 3/5) to major (4/5) Heat Risk.
Vulnerable populations and those who are outside for long periods
will have a greater chance to see heat impacts and related
illnesses. Limited places will be available to cool off, including
the mountains, so please limit time outdoors.
The area of high pressure will stick around the central Rockies
later into the week, bringing monsoonal moisture around it into the
desert southwest. SoCal will be right on the periphery each day,
where a lower chance for storms will occur each day mainly along
the mountain crests from the Mexican border up to the Big Bear
Lake region. A slight increase is noted by Thursday and Friday
(25-35%). The area of high pressure becomes more focused away from
our region, resulting in temperatures sliding back to near normal
by Friday into the weekend with humidity remaining.
&&
.AVIATION...
141600Z....Coast/Valleys...Low clouds are currently 1,000-1,500ft
MSL along the coast and should scatter out within the next couple of
hours giving way to mid/upper level clouds AOA 20,000ft MSL.
Afternoon rain and thunderstorms should stick to mountain areas this
afternoon but there is a 10-15% chance they could spill into
adjacent valley areas. Patchy low clouds are expected to start
moving in over the coast after 01-03Z Tuesday, filling in after 06-
09Z. Cigs will be slightly higher with bases 900-1,500ft MSL and
will be intermittent at times. Low clouds clear after 16-17Z Tuesday.
Mountains/Deserts...Highest chances for thunderstorms will be over
mountain areas with chances in the 40-80% range this afternoon with
a 20-50% chance in the high deserts. Expect lightning, erratic gusty
winds, and brief heavy rain with any storm development. Areas with
the highest probabilities of convection will be in the vicinity of
the San Gorgonio and San Jacinto mountain areas. CB bases near
10,000 ft MSL with tops to 35,000 ft MSL. Otherwise variable mid and
high cloud cover AOA 20,000 ft MSL.
&&
.MARINE...
No hazardous marine conditions are expected through Saturday.
&&
.BEACHES...
Astronomical high tides peaking 7.0-7.5 ft each day through Tuesday.
High tides combine with a modest south swell (3 ft swell at 13-15
seconds from 190 degrees) to generate surf of 3-5 ft for south-
facing beaches and 2-4 ft elsewhere. This will produce areas of
coastal flooding in low lying areas, boardwalks, beach parking lots,
and beach adjacent streets during evening high tides. Highest tides
each evening will generally occur between 8 and 10 PM. A Beach
Hazards Statement remains in effect through Tuesday evening and
contains further details. There will be an increased risk of rip
currents through Wednesday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Tuesday evening for Orange
County Coastal Areas-San Diego County Coastal Areas.
Heat Advisory from 10 AM Wednesday to 8 PM PDT Thursday for
Orange County Coastal Areas-San Diego County Coastal Areas.
Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Thursday
for Orange County Inland Areas-Riverside County Mountains-
San Bernardino County Mountains-San Bernardino and
Riverside County Valleys-The Inland Empire-San Diego County
Mountains-San Diego County Valleys-San Gorgonio Pass near
Banning-Santa Ana Mountains and Foothills.
PZ...None.
&&
$$
PUBLIC...APR
AVIATION/MARINE...Villafane
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