National Weather Service Forecast Discussion

Dicussion provided by the National Weather Service Forecast Office located in San Diego, California

000
FXUS66 KSGX 301629
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
929 AM PDT Wed Sep 30 2020

.SYNOPSIS...
High pressure aloft will bring hot and very dry conditions through
Friday with the the heat extending almost to the coast today. The
return of onshore flow and weakening of high pressure aloft will
bring a cooling trend, beginning in the coastal areas on Friday
then spreading inland through early next week. Although
temperatures are expected to remain above average. Patchy night
and morning coastal low clouds and fog will return during the
weekend with greater coverage and inland spread for early next
week.

&&

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

Sunny and warm this morning with weak offshore flow and a
conspicuously absent marine layer. Temperatures are generally
higher than at this time yesterday, especially near the coast and
in the Santa Ana mountains where temperatures are as much as 24
degrees warmer than at this time yesterday. The offshore flow is
however producing light easterly winds in the western valleys and
the inland coastal areas.

Today through Friday...Warming will continue today, with the heat
peaking for most areas as high temperatures reach 10 to locally
15 degrees above average for the mountains and deserts, and 15 to
20 degrees above average for the coast and valleys. There will be
east to northeast winds locally gusting to less than 25 mph near
the coastal slopes of the mountains this morning and again
Thursday morning. The return of weak onshore flow will bring slight
cooling to the coast and western portions of the inland valleys
for Thursday and Friday.

Saturday through Wednesday... High pressure aloft will weaken
in response to a weak low pressure system off the California
coast moving inland into California. This will bring a return of
onshore flow and spread cooler marine air inland, with high
temperatures Tuesday around 5 degrees above average.

That weak low pressure system will bring a few mid and high clouds
for Sunday into early next week. Patchy night and morning coastal
low clouds and fog will also return during the weekend with
greater coverage and inland spread for early next week.

&&

.AVIATION...
301510Z...Clear with unrestricted VIS through tonight.

&&

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

&&

.BEACHES...
Above average surf of 3 to 5 feet through Thursday will produce a
high rip current risk.

&&

.FIRE WEATHER...
Hot and dry conditions will continue for inland areas this week.
Through Thursday, lowest daytime humidity in the mountains,
deserts, and inland valleys will fall to between 8 and 12
percent. There will be locally gusty east to northeast winds less
than 25 mph near the coastal foothills of the mountains this
morning and again Thursday morning with westerly sea breeze winds
to 15 mph spreading inland each afternoon.

The return of onshore flow and weakening of high pressure aloft
will spread cooling and higher humidity inland for Saturday
through early next week.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 8 PM PDT Friday for San Bernardino and
     Riverside County Valleys-The Inland Empire-San Diego County
     Valleys.

     Heat Advisory until 8 PM PDT Thursday for Orange County Coastal
     Areas-Orange County Inland Areas-San Diego County Coastal
     Areas.

PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...PG
AVIATION/MARINE...CO

NWS SGX Office Area Forecast Discussion