La Mesa, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

458
FXUS66 KSGX 281024
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
224 AM PST Sat Dec 28 2024

.SYNOPSIS...
An upper ridge will build from the southwest over the weekend,
bringing mild temperatures and a shallow marine layer with the
potential for dense fog in the coastal areas. Offshore flow will
likely develop Tuesday through Thursday bringing gradual warming
and much drier weather. Cooler Friday and Saturday as a trough
approaches the West Coast.

&&

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

Plenty of high clouds are around again early this morning in
northwest flow aloft. Below this, areas of low clouds continue
across the coastal areas and western valleys, though the marine
layer remains deep enough to limit any dense fog concerns. Low
clouds should clear back to the coast this afternoon, though high
clouds will stick around for much of the day. Otherwise warmer
today with highs 7-12 degrees above normal inland as an upper
level ridge of high pressure to our southwest shifts eastward
towards Baja.

With the building high, the marine layer will become much more
shallow tonight into Sunday morning with an increased risk of
dense fog in the coastal areas. A weak short wave trough moves
inland to the north late in the day Sunday, bringing an increase
in onshore flow for breezy west winds in the mountains and
deserts Sunday afternoon and evening with peak gusts near 30 mph.
Otherwise minor warming in the deserts with little change in
temperatures elsewhere on Sunday. The marine layer remains shallow
Sunday night into Monday, likely resulting in another night of
dense fog for the coastal areas.

Cold air setting into the Great Basin behind this wave will
generate weak offshore flow by Monday morning. Another slightly
more amplified wave moves through the Great Basin on Tuesday,
causing pressure gradients to increase further. There is still a
lot of spread in the ensembles regarding the strength of the event
and whether it will peak on Tuesday or Wednesday. The models have
trended away from the more amplified trough solution, so the
chances of a moderate event have lowered to around 15-20%. While
wind speeds are still highly uncertain, one thing we do know is
that this will bring warmer weather, especially west of the
mountains, and much drier conditions across the region. Whether or
not the marine layer and pesky dense fog go away during this
period will also depend on the strength of the offshore flow. By
Thursday, when the upper high amplifies and weak offshore flow
continues, high temperatures in the valleys could be in the upper
70s to low 80s.

Onshore flow returns for Friday and Saturday as an upper level
trough moves inland across the West Coast, bringing cooling and
increasing humidity. Sadly it looks like moisture remains to our
north yet again with this trough, leaving us without any
precipitation.

&&

.AVIATION...
281030Z...Coast/Valleys...Despite BKN high cirrus clouds
obscuring satellite, surface observations show low clouds along
the coasts and up to 10-15 miles inland. Bases are generally
900-1200ft MSL, but should settle closer to 800-1000ft MSL as the
morning progresses. Most locations will have VIS of 5+ miles
though 1-3 miles is possible at times for coastal mesas and higher
elevations inland. Clearing expected around 16-19z Saturday.

Clouds look to redevelop and move back ashore around 01-03z Sunday
evening, but bases should be a few hundred feet lower than this
morning, around 400-700ft MSL. More VIS restrictions anticipated,
including the coasts which could fall below 2 miles at times.

Mountains/Deserts...SCT-BKN high cirrus clouds with unrestricted VIS
will prevail through early Sunday morning..

&&

.MARINE...
Long period west-northwesterly swells will continue through Sunday.
Seas will be 5-8 feet in the outer coastal waters (30-60 NM from the
coast) and 3-5 feet in the inner waters (within 30 NM). Otherwise,
no marine weather hazards are expected through Wednesday.

&&

.BEACHES...
The long period (15 to 17 seconds) northwesterly (280-290 degree)
swell of 3-5 feet will continue through Sunday, decreasing Monday.
Elevated surf of 4-7 feet will continue through Monday at San Diego
County beaches with local sets to 8 feet on west-northwest facing
beaches. Minor coastal flooding8 is possible in vulnerable areas
during morning high tides as tides will increase this weekend
(peaking on 12/31), coinciding with the elevated surf. See the Beach
Hazards Statement for more information.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Sunday afternoon for San Diego
     County Coastal Areas.

PZ...None.

&&

$$

PUBLIC...SS
AVIATION/MARINE/BEACHES...Munyan