Wildfire in California, July 27 to 31, 2023

Area Forecast Discussion
National Weather Service San Diego CA
146 PM PDT Thu Jul 27 2023

.SYNOPSIS...
Above average temperatures expected into Saturday. Chances of
thunderstorms return for the weekend into early next week. Inland
areas are not expected to be as hot for the end of the weekend
into next week. A weak coastal eddy is expected through the end of
the week, slowly deepening the marine layer with night and
morning coastal low clouds and fog spreading a little farther
inland each night.

&&

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

*Well above average temperatures and hot conditions into Saturday.
*Increasing chances of thunderstorms for the weekend into early
 next week.
*Patchy dense fog near the coast Friday morning, especially near
 higher coastal terrain.

Areas of low clouds continue to stick along the coast this
afternoon, mainly in San Diego County. The coastal eddy will help
deepen the marine layer into Friday but areas of patchy dense fog
are expected near the coast Friday morning, especially near higher
coastal terrain. High temperatures will continue to be 5 to 10
degrees above average through Saturday.

A few thunderstorms have developed just south of the border as of
1 PM this afternoon. There is a slight chance thunderstorms might
spread into San Diego County this afternoon and again Friday
afternoon. Chances of thunderstorms will increase starting
Saturday, peaking Sunday and Monday. Global models are showing an
inverted trough developing over northern Mexico early Sunday with
the southeasterly monsoonal flow maintaining into Tuesday. This
will will help increase moisture over the area. Global ensemble
members are showing a spike in precipitable water, with values
increasing to over 1.5 inches in the lower deserts for Sunday and
Monday. There is still uncertainty surrounding the finer details
of the forecast. Most ensemble members from the GFS are showing
precipitation from the coast to the deserts during the
Sunday/Monday timeframe. In contrast to that, ensemble members of
the ECMWF are mostly dry for areas west of the mountains with
about half of the ensemble members showing a least some
precipitation for the mountains and about a quarter of the members
are showing precipitation for the deserts. There is also the
potential isolated showers and thunderstorms will occur overnight,
Sunday night into Monday. Current forecast has the highest
chances of thunderstorms in the mountains and deserts Sunday and
Monday afternoon. For places west of the mountains, the forecast
has at least slight chances for San Diego County and portions of
the Inland Empire for Sunday and Monday. Thunderstorm chances
begin to decrease on Tuesday, but 15-30 percent chances still
remain for the mountains and deserts.

The moisture influx will help knock high temperatures down for
inland areas. Highs are forecast to fall to near average by Sunday.
The models have drier southwest flow aloft returning around
Wednesday. Even with the return of drier air, conditions do not look
like they will get quite as hot as we have seen over the past few
weeks due to the more eastward placement of the high pressure system
over New Mexico and Texas.

&&

.AVIATION...
272000Z...Coast...Patches of low clouds lingering at the beaches
this afternoon. Bases are 500-800 ft MSL with tops to 1300 ft MSL.
Low clouds likely to begin increasing in coverage at the immediate
coast after 06Z Fri with similar bases and tops. Low clouds could
extend up to 5 miles inland with areas of fog reducing VIS to 1-3
miles on higher coastal terrain. 06Z-16Z Fri, there will be a 50-60
percent chance of CIG impacts at KSAN and 40-50 percent chance for
CIG impacts at KCRQ and KSNA. Expect clearing from inland to the
coast 15Z-17Z Friday.

Elsewhere, SCT clouds at or abv 15,000 ft MSL through Friday morning.

&&

.MARINE...
There is a slight (15-25%) chance of thunderstorms over the coastal
waters on both Sunday and Monday. Otherwise, no hazardous marine
conditions are expected through Monday.

&&

.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 Saturday for Riverside County
     Mountains-San Bernardino County Mountains-San Bernardino
     and Riverside County Valleys-The Inland Empire-San Diego
     County Mountains.

     Heat Advisory until 7 PM PDT Saturday for San Diego County
     Valleys.

     Excessive Heat Warning until 8 PM PDT Saturday for Coachella
     Valley-San Diego County Deserts-San Gorgonio Pass Near
     Banning.

PZ...None.

&&

PUBLIC...CO
AVIATION/MARINE...PG