High Surf Advisory 2, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
844 AM PST Fri Jan 5 2024

.SYNOPSIS...
Passing high clouds today, will give way to fair skies and mild days
through Saturday. It will be cold again tonight, with frost in the
valleys. For Saturday night and Sunday, strong and gusty westerly
winds will develop, along with a few passing, light rain and snow
showers. It will be fair and colder Sunday into Monday as winds turn
offshore from the north and become locally gusty. Another weather
system from the northwest will bring a chance for more showers
Thursday and Friday.

&&

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

Satellite imagery showed a large area of high clouds moving over
Southern California this morning. The clouds moved in late last
night, so there was plenty of time for radiational cooling, which
allowed temperatures to fall into the 30s in many valleys. At 8 AM
PST, surface pressure gradients across the region were weak, and
winds were light. Our 12Z sounding had a sfc-based inversion, and
indicated 3-6C of warming below 16K FT. As clouds thin, the warmer
atmosphere should set us up for a mild afternoon. No forecast
updates planned this morning.

From previous discussion...

Skies are mostly clear with scattered thin high clouds drifting
overhead. Those clouds aren't doing much to insulate the surface,
so heat is radiating skyward rather efficiently this morning.
Temperatures are in the 30s over many valleys and low-lying
coastal areas (and the mountains and high desert, of course). The
Frost Advisory for the Inland Empire continues this morning, but
less widespread/patches of frost will be felt in the valleys of
San Diego County. Light offshore flow will keep dry and cold
continental air prevailing over the region, so very similar temps
are expected for tonight into Saturday, and the IE will be under
another Frost Advisory. Fair and cool weather today will feature
high temps a few degrees below normal. A robust, powerful low
pressure system will move through northern CA and drop into AZ, a
sort of inside slider. True to form, this system will bring much
more wind than precipitation to our region. Winds will become
strong Saturday afternoon through much of Sunday particularly for
the ocean, the coast, the mountains and deserts. Top gusts should
reach 50-70 mph over mountain ridges, 25-35 mph along the coast,
and 35-50 mph across much of the deserts. Showers begin to move
in from northwest to southeast Saturday night, favoring San Diego
County, and move out by late Sunday morning. Total precip amounts
will be meager, around 0.04-0.20 inch, and probably nothing or
next to nothing in Orange County, the northern IE and the deserts.
It will be a cold system, dropping snow levels to about 4000
feet, but it won't really matter as less than 1 inch is expected
in the mountains. If you think Saturday was cool, wait till Sunday
and Monday. Cold continental air will come out of the north and
spread across the region. High temps Sunday and Monday should be
in the 50s to lower 60s and lower elevations, 5-10 degrees below
normal, 20s and 30s in the mountains, 10-20 degrees below normal,
and highs in the 40s for the high desert, about 10 degrees below
normal. Northwest winds Sunday will weaken but shift to northeast
Sunday night through Monday morning. Clouds will decrease Sunday,
leaving mostly clear skies for Monday into Wednesday. Days will
continue cool, a few degrees below average, while nights will be
downright cold, with areas of frost inland. The high desert will
have to get comfortable with 20s Monday and Tuesday mornings. The
jet stream begins to buckle again Wednesday, taking advantage of
some Pacific moisture and sending it our way. It could be enough
for showers Wednesday night and Thursday, with a second, stronger
wave bringing more precip Friday. This is all very fuzzy as the
range of outcomes provided by deterministic models and ensembles
are all over, with solutions ranging from dry to very wet. You
know the drill: we wait for better consensus and a narrowing of
the range of outcomes, which will come into better focus a little
each day.

&&

.AVIATION...
051630Z...All Areas...FEW-SCT clouds at or abv 15000 feet MSL with
unrestricted VIS through tonight.

21Z today to 15Z Saturday...N-NE winds gusting 25-40 kts will occur
over the mountains and locally into portions of the Inland Empire.
Moderate up/downdrafts are possible over and just south of the San
Bernardino mountains.

&&

.MARINE...
Weaker onshore flow will prevail into Saturday. Northwest winds
gusting to 40 kts and combined seas of 10-13 ft are expected
Saturday evening through Sunday night. The winds will weaken and
turn offshore Monday, with strengthening onshore winds again for the
middle of next week.

&&

.BEACHES...
Increasing west swell from 280-290 degrees this weekend will created
elevated surf. Confidence on exact heights remain low at this time,
with current forecasts indicating that the highest surf will be on
Sunday. Highest surf will likely be on exposed west-facing beaches
in southern San Diego County.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory until 9 AM PST this morning for San Bernardino
     and Riverside County Valleys-The Inland Empire.

     Frost Advisory from 2 AM to 9 AM PST Saturday for San Bernardino
     and Riverside County Valleys-The Inland Empire.

PZ...Gale Watch from Saturday evening through late Sunday night for
     Coastal Waters from San Mateo Point to the Mexican Border
     and out to 30 nm-Waters from San Mateo Point to the Mexican
     Border Extending 30 to 60 nm out including San Clemente
     Island.

&&

PUBLIC...MM
AVIATION/MARINE/BEACHES...APR