902
FXUS66 KSGX 140429
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
929 PM PDT Fri Mar 13 2026
.SYNOPSIS...
The ridge of high pressure over the region will weaken some over the
weekend, where slight cooling will take place with a deeper marine
layer near the coast. The ridge of high pressure will reamplify by
next week, leading to a prolonged heat wave. This event will
encompass temperatures of 20 to potentially up to 30 degrees above
normal for this time of year, leading to moderate to high heat risk.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Update: At nearly 8 pm this evening, many portions of the inland
areas are still experiencing temperatures above 80 degrees. This is
only a segue into what is going to happen next week in terms of a
unprecedented heat wave for this time of year here in SoCal. With
only some relief from the heat for tomorrow as we begin to see a
better push of onshore flow, with many locations (especially
within the IE) being notably cooler tomorrow. With tomorrow being
the coolest day of the week, it will still be generally 10 to 15
degrees above the seasonal average, but will feel relatively
cooler in comparison to how temperatures were for today. From then
on, the ridge is going to continue to build in strong next week,
with high pressure heights aloft approaching 600 dm just south of
the region. This will translate into very hot temperatures, and
likely not only shattering daily records, but possibly monthly
records towards the end of next week. There could even be a few
localities flirting with all-time records, as temperatures look
to soar into the mid 100s for the IE, and over 110 within the
deserts, by next Thursday. Even higher elevations will experience
record warmth as well. The latest forecast for next Thursday calls
for Palomar Mountain to have a high of 89 next Thursday, which
would crush their previous daily record by 10 degrees, as an
example. It is especially important during this very warm period
to ensure that you are staying properly hydrated, especially if
outdoors, and to also check up on elderly/pets/children, and
anyone else sensitive to extreme heat. It is not only the strength
of the high that makes this a rare and unprecedented event, but
the duration of this remaining in place as well. Please continue
to monitor, and stay advised of any heat advisories/warnings for
your area.
Previous discussion submitted at 1229 pm:
A 588 dm high is maintaining its strength over the eastern Pacific.
This hot air mass will give another very warm day out there with
temperatures 15-20 degrees above normal. The places that will see
some better relief from the hottest temperatures will be at the
coast and higher elevations over 5,000 feet. The ridge will weaken
some by this weekend, along for greater onshore flow and the marine
layer to deepen slightly. This will give the chance for low clouds
and fog to form near the coast by early Saturday morning (around a
20% chance at San Diego). Saturday will be the coolest day over the
next week, though highs will still be near 10 to 15 degrees above
normal. As onshore flow takes hold, there is near a 50-50 chance to
see wind gusts over 30 MPH across mountain desert passes into the
high desert by Saturday afternoon. The marine layer will be its
deepest by Sunday morning with low clouds and patchy fog moving in
from the coast to about ten miles inland.
The high off the coast will begin reamplify on Sunday, where higher
pressure heights near 585mb move into the area. This will kickoff
a major heat wave for the region as we move into the upcoming week.
Sunday temperatures will warm another 5 to 10 degrees across inland
valleys west of the mountains, about the same from Saturday
everywhere else. Chances are low to moderate to see areas of the
northern Inland Empire go over 95 degrees on Sunday.
The center of the high slowly moves toward the region by Monday
through Wednesday, then moves slowly eastward into Arizona by later
in the week. This is a very hot air mass with temperatures at 850 mb
nearing 25C, which is about 15C above normal for this time of year,
very hot! Due to this prolonged heat event, an Extreme Heat Watch
has been issued for all areas west of the mountains Monday through
Friday. The greatest warming will begin in these areas by Monday and
Tuesday, with highs nearing 100 degrees by Tuesday for the valleys
of San Diego/Orange County into the Inland Empire. The coastal areas
will see a tougher forecast as cool westerly winds off the ocean
will have a large effect on the temperatures within a mile or so
from the coast, where some areas may stay much cooler than inland
regions. Please use this time to prepare for the incoming heat by
making sure you have enough water and products to keep cool.
The area of high pressure will continue to strengthen for the latter
half of next week. This will bring even hotter temperatures to the
area, where many of our climate sites will not only break daily
temperature records but also monthly record temperatures. Please see
the climate information section below for more details. The
temperature forecast for later next week is somewhat lower
confidence on the exact temperature details, but whatever you way
you slice it, it will be very hot for the middle of March. 850 mb
temperatures will peak near 25C during this period as the high
amplifies near 593-595 dm. Thursday and Friday look to be the
hottest days over all, with low to moderate chances of seeing highs
reach 105 degrees across the Inland Empire, as well as reaching 100
degrees and inland valleys east of the 5 and the 15 in Orange and
San Diego Counties. The most extreme heat will be across the
Coachella Valley during this time. NBM probabilities show a
a moderate to high chance of going over 110 degrees by late next
week as well. To put this in perspective, the highest temperature
recorded in March at Palm Springs and Indio is 104 degrees (both
sites of which have a period of record over 100 years old). Low
temperatures will cool off some into the 60s for many areas below
5,000 feet with lows staying in the 70s across the lower deserts.
Please make sure to check on family, friends, and neighbors this
coming week! Outdoor activities should be limited as the duration of
this early season heat wave will lead to increased risk of heat
illness. This includes the mountains, where highs will reach into
the 80s and 90s by the latter half of the upcoming week. The ridge
looks to slowly weaken by the following weekend, which will aid in a
cooling trend.
&&
.AVIATION...
140430Z...VFR conditions with increasing high clouds through
Saturday morning. Patchy low clouds and fog 300-500 ft MSL with vis
2-4 SM over the waters and isolated coastal areas 12-16Z Saturday.
Slight chance for cigs and reduced vis at coastal airports (10-20%
chance at KCRQ/KSNA), with a better chance (40%) for intermittent
cigs at KSAN during this period. Greater coverage of coastal clouds
500-900 ft MSL Sat evening after 15/02Z.
&&
.MARINE...No hazardous marine conditions are expected through
Wednesday.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Extreme Heat Watch from Monday morning through Friday evening
for Orange County Coastal Areas-Orange County Inland Areas-
San Bernardino and Riverside County Valleys-The Inland
Empire-San Diego County Coastal Areas-San Diego County
Valleys-Santa Ana Mountains and Foothills.
PZ...None.
&&
$$
PUBLIC...Stewey
AVIATION/MARINE...CSP
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