Wildfire in California, August 1 to 31, 2020

Area Forecast Discussion
National Weather Service San Diego CA
930 PM PDT Fri Jul 31 2020

.SYNOPSIS...
The heat wave will continue through Saturday, except near the coast,
followed by a gradual cooling trend for Sunday into the middle of
next week. More widespread coastal low clouds and fog will return
near the coast for Saturday night into Sunday morning, then spread
farther inland into the valleys toward the middle part of next week.

&&

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

Evening Update:

Several record hot temperatures were set today. Please see our posts
on social media, headlines on our website, and the record report
that was sent earlier this evening. The heat continues...unabated!
Saturday will be the last day for the extreme conditions, but
continued above normal temperatures will persist into early next
week. A few patches of fog and low clouds have been drifting near
the coast and will probably continue to be a risk of patchy low
clouds and fog overnight near the coast. The only forecast update
this evening was to add a bit of low clouds to the forecast along
the San Diego County coast. Otherwise no major updates to the
forecast this evening.

Previous Forecast Discussion from Friday Afternoon:

We're pouring on the heat today. Palm Springs had achieved 117 so
far at 1 pm today, good for first place in the heat race that hour.
Soupy air has been moving into the eastern Coachella Valley, the
higher moisture influencing the temperature rise, e.g., Thermal
was 110 with 13% humidity at 10 am and 105 with 28% humidity at 11
am. While that is interesting, it doesn't change the fact that
temps are still on trajectory for nearing records in all inland
areas this afternoon. That means hitting 120 in the lower deserts
and touching 110 in the Inland Empire and high desert. A few high
minimum temperature records could also fall if they survive
through midnight. Low clouds have become an afterthought as the
marine layer has shallowed. Subsidence and northwest winds have
eroded most of the cloud deck within the bight region. That's not
to say the coastal clouds and fog will go away completely as
patchy coastal fog remains in the forecast, but it could be
briefly dense when it returns. Some higher moisture continues to
stream into the region from the south, seen as some high clouds
and cumulus over the mountains today. That tap will run dry
Saturday. Subtract only about 0-4 degrees for Saturday's highs
with respect to today's. Still very hot and the hazards continue.
Next week the high pressure ridge aloft, responsible for this
heat, will weaken considerably but slowly. A weak trough of low
pressure to our north will gradually sag southward, providing
confidence in a gradual cooling trend next week. By Wednesday we
could even dip below normal in the temp department. Guidance has
consistently shown a coastal eddy to spin up starting Saturday and
strengthening Sunday into Monday. That will help rebuild the
marine layer and the low cloud deck. Initially some of that fog
could be dense Saturday night, but will quickly lift Sunday.
Coastal clouds should start infiltrating the valleys by Tuesday or
Wednesday morning. Thursday and beyond we settle into a rather
seasonal pattern with no meaningful monsoon push in sight.

&&

.AVIATION...
010345Z...Coast/Valleys...Very patchy low clouds with bases 500-800
ft MSL and vis 3 SM or less possible along the southern San Diego
County coast at times through 15Z. Low confidence in any clouds/fog
reaching KSAN tonight into Saturday morning. More widespread low
clouds with bases 500-1000 ft MSL developing along the coast and up
to a few miles inland Saturday night. Otherwise clear through
Saturday evening with areas of smoke VCTY KBUO due to ongoing
wildfire.

Mountains/Deserts...SCT cu with bases near 10000 ft MSL may develop
over the mountain crests again Saturday after 18Z, dissipating by
sunset. Otherwise clear with unrestricted vis through Saturday
evening.

&&

.MARINE...
Northwest wind gusts around 20 kts are expected over the outer
coastal waters near San Clemente Island this evening, weakening
overnight. Otherwise, no hazardous marine weather is expected
through Wednesday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 9 PM PDT Saturday for Apple and
     Lucerne Valleys-Coachella Valley-San Bernardino and
     Riverside County Valleys-The Inland Empire-San Diego County
     Deserts-San Gorgonio Pass Near Banning.

     Heat Advisory until 9 PM PDT Saturday for Orange County Inland
     Areas-Riverside County Mountains-San Bernardino County
     Mountains-San Diego County Mountains-San Diego County
     Valleys-Santa Ana Mountains and Foothills.

PZ...NONE.

&&

PUBLIC...MM/JMB
AVIATION/MARINE...SS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN DIEGO CA
1057 PM PDT FRI JUL 31 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0455 PM     WILDFIRE         4 NNE BEAUMONT          33.99N 116.96W
07/31/2020                   RIVERSIDE          CA   FIRE DEPT/RESCUE

            THE APPLE FIRE STARTED AROUND 4:55 PM IN
            CHERRY VALLEY. IT STARTED AS MULTIPLE SMALL
            FIRES ALONG OAK GLEN ROAD, AND IT HAS GROWN
            TO 900 ACRES AS OF 10:05 PM FRIDAY WITH 0%
            CONTAINMENT. EVACUATION ORDERS ARE IN PLACE
            FOR RESIDENTS SOUTH OF COUNTY LINE, NORTH OF
            DUTTON STREET, AND EAST OF OAK GLEN ROAD.
            HOT AND DRY CONDITIONS WERE PRESENT AT THE
            START OF THE FIRE. TEMPS IN THE MID 90S AND
            RH WAS AROUND 15-20%. AT LEAST 1 STRUCTURE
            HAS BEEN DAMAGED, ALONG WITH A CAR AND A
            BOAT. MANY STRUCTURES CONTINUE TO BE
            THREATENED.

&&

SC