Balboa, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

255
FXUS66 KSGX 181735
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
935 AM PST Sat Jan 18 2025

.SYNOPSIS...
Onshore flow will continue to bring cooler weather and partly
cloudy skies west of the mountains during the nights and mornings
into Monday. Offshore flow will develop late Monday with Santa
Ana Winds late Monday through Tuesday, and possibly again
Thursday.

&&

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

.SHORT TERM...

Update: The inversion is continuing to break with most of the low
clouds lifting and dissipating within the inland valleys, and
only a more predominant cloud bank still hugging a portion of the
coastal region in Orange County, south of Santa Ana. Clear skies
are expected to persist through the afternoon hours. Latestmodel
data still looks for the onset of moderate Santa Ana conditions
to begin on Monday afternoon, with the strongest winds occurring
on Tuesday during the morning hours. Through tomorrow, winds will
be mostly diurnally influenced with weak onshore flow during the
day, and light offshore flow at night. Analyzing high res
guidance, the inversion near the surface will establish itself
again by later this evening, and there could be low clouds and fog
developing again west of the mtns overnight and through tomorrow
morning.

Previous discussion (329 AM)

Weakening onshore sfc pressure gradients will result in a diurnal
wind pattern through Sunday, with downsloping winds at night and
a sea breeze in the afternoons. This will continue low clouds for
the coastal areas and valleys tonight and again Sunday night.
Daytime temperatures will remain somewhat below seasonal averages
for the lower elevations west of the mtns through Sunday.
Overnight low temps will remain below seasonal averages west of
the mountains through Sunday night, and some low-lying areas of
the inland valleys could experience frost.

Sfc high pressure moving into the Great basin and setting up
strong offshore pressure gradients, along with a shortwave trough
moving south out of Canada in the mean flow aloft will likely
produce another Santa Ana wind event early next week. With the
shortwave trough providing upper level support, the northeast to
east winds will likely peak Monday night/Tue morning with gusts
locally reaching 60-65 mph in the windiest locations. As we would
expect, humidities will drop into the single-digit range by Tue
afternoon for all areas inland of the immediate coast. After that
shortwave passes to the east, the winds will weaken as upper
support is lost and offshore sfc pressure gradients weaken.
Daytime high temperatures will rise but remain near or slightly
below seasonal averages due to the cold air advection opposing the
compression warming as the air flows downhill out of the Great
Basin.

A second shortwave trough will follow later in the week but will
likely take a more inland track which would be less effective at
lending upper support so that the next surge of offshore winds for
Thu/Fri will likely not be as strong as the Mon/Tue event.
Humidities will remain low for inland areas through Friday.

Onshore flow with lower temperatures, increasing humidity and a
return of marine layer low clouds could return for next Saturday.

&&

.AVIATION...
181630Z...Stratus based at 3500ft MSL lingers this morning. Coverage
is SCT-BKN over the northern half of Orange County and in parts of
the Inland Empire, but clouds have generally cleared off of the
coast. Stratus should fully clear the region by 19z.

Low clouds redevelop and move inland after 04-06z this evening with
lower bases and a more typical full coverage marine layer. Bases
will be around 1000-1500ft MSL, slightly lowering through the night,
and conditions may be IFR by 10-12z along the coast. VIS
restrictions 3-6SM possible along the coasts with locally lower VIS
within valleys and on coastal higher terrain down to 1/2SM.
Confidence for KSAN is 80-90% for MVFR CIGs and VIS around 6SM
overnight, and a 25-35% for IFR CIGs after 10z. Any low clouds
and/or FG should clear to the coasts by 16z with full clearing by 18-
19z.

NWS San Diego is aware of limited communications of observations
from KTRM since January 8th. We are working with the FAA to address
this issue.

&&

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

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Fire Weather Watch from Monday morning through Tuesday evening
     for Orange County Inland Areas-Riverside County Mountains-
     Including The San Jacinto Ranger District Of The San
     Bernardino National Forest-San Bernardino County Mountains-
     Including The Mountain Top And Front Country Ranger
     Districts Of The San Bernardino National Forest-San
     Bernardino and Riverside County Valleys  -The Inland Empire-
     San Diego County Inland Valleys-San Diego County Mountains-
     Including The Palomar And Descanso Ranger Districts of the
     Cleveland National Forest-San Gorgonio Pass Near Banning-
     Santa Ana Mountains-Including The Trabuco Ranger District
     of the Cleveland National Forest.

PZ...None.

&&

$$

UPDATE...Stewey
PUBLIC...PG
AVIATION/MARINE...Zuber