706
FXUS66 KSGX 261921
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1221 PM PDT Fri Jul 26 2024

.SYNOPSIS...
The heat wave will end after Friday due to a weather disturbance
that will move through northern California today and bring cooler
and breezier weather for mountains and deserts across southern
California into Saturday. Strongest wind conditions for Saturday
afternoon and evening. Dry air has moved in from the north and will
continue to spread southward resulting in lower humidity and has
ended the monsoon. Greater coverage of morning low clouds is expected
for coastal areas over the weekend with the low clouds becoming
patchier again next week. Also for next week, there will be a gradual
warming trend along with a slow increase in humidity. There is
uncertainty when the next threat for thunderstorms occurs but
slight chance for late next week.

&&

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

Almost cloud free along beaches with small patches left and
also clear inland with the air mass drying from north to south
with precipitable water values decreasing further. There was an
outflow that moved into the Coachella Valley early this morning
and raised dewpoints but convection is not expected today though
cumulus will form especially San Diego mountain desert slopes
closer to the remaining monsoon moisture of 1.4 inch values.
Notably stronger drier of under 1 inch precipitable water air mass
now over San Gabriel and San Bernardino mountains per Storm
Prediction analysis. Today is nearly as hot as yesterday for
inland areas with air mass of 25-26C on the coast but up to 31 to
32C for inland deserts, so we still have moderate heatrisk in the
Inland Empire and areas of major in the lower deserts. 109F at
Palm Springs as of noon and same as yesterday.

We finally have cooling of air mass for Saturday (22-28C at 850 mb
level), in the wake of the disturbance that tracks across
northern California. There is also a better push of more organized
low clouds and marine air into the valleys. Fire weather
conditions deteriorate because of drier air and increasing
onshore flow for all deserts and the mountains with the peak of
the westerly winds on Saturday. The coolest day for most areas
will be Sunday.

Weather pattern warms next week but still considerable uncertainty
as potential upper level wave arrives during midweek from Mexico
on the backside of the heat dome rebuilding over the Great Basin
and 4-corners region. This could bring back monsoon moisture as
well for late week.

&&

.AVIATION...
261930...Coast...Low clouds with more uniform coverage will move
ashore around 04-05Z and eventually cover coastal areas and western
valleys overnight. Bases will be around 800-1200 feet MSL and local
vis reduced 1-5SM on higher coastal terrain and western valleys.
Scatter out Saturday by 15-18Z.

Mountains/Deserts...Westerly winds gusting 25-35 kt gradually
tapering off overnight through mountain passes into adjacent
deserts. MOD up/downdrafts in lee of mountains.

&&

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

&&

.FIRE WEATHER...
Elevated fire weather conditions Friday and Saturday afternoons
due to the drier air, lower humidity, and increase afternoon
and evening onshore west winds for the mountains and all deserts,
especially the High Desert.

&&

.CLIMATE...
4th time this year Palm Springs has hit 120F. The record is 5 set
in 2020 and 2021.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 8 PM PDT this evening for Coachella
     Valley-San Diego County Deserts-San Gorgonio Pass Near
     Banning.

PZ...None.

&&

$$

PUBLIC...Tardy
AVIATION/MARINE...MM