Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 232050
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
150 PM PDT Sat Mar 23 2024

.SYNOPSIS...
Periods of precipitation, gusty winds, and cool conditions are on
tap for this weekend. Conditions will slowly dry into early next
week, but periods of light precipitation and gusty west winds are
again possible Monday into Tuesday and potentially Thursday. A
gradual warming is expected for Monday-Wednesday, with cooling
conditions expected Thursday into the weekend. Periods of clouds,
both high and low are expected through the week. Unsettled weather
looks likely for next weekend, with low confidence in details.

&&

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

Radar imagery at 1 PM was showing the front moving through eastern
portions of the Inland Empire and through much of San Diego
County. Winds along the coast in Orange County, behind the front,
have transitioned to west winds. As of 1 PM rainfall totals have
been 0.25-0.50 inch for Orange County; 0.05-0.15 inches in the
Inland Empire, Riverside mountains, and San Bernardino mountains,
locally up to 0.50 inches in the San Bernardino mountains; and
0.05-0.20 inches across San Diego County. A rainfall summary has
been headlined on our weather.gov/sandiego homepage. A series of
shortwaves passing through the mean flow of the trough will bring
periods of enhanced precipitation and even thunderstorms tonight
into Sunday. This is a cold system, with mountain snow expected
down to 4500-5000 ft by tonight, staying there through Sunday.
More details on this weekend`s rain and mountains snow can be
found in the Hydrology section below.

Gusty westerly winds are expected in the mountains, deserts, and at
the coast through Sunday night. Winds in the mountains and deserts
will peak this evening and overnight with gusts 50 to 65 mph,
locally upwards of 70 mph on the favored desert slopes and canyons.
Winds weaken slightly for the mountains and deserts on Sunday. Winds
along the coast will increase this evening and overnight into early
Sunday morning with peak gusts around 35 mph. Winds are expected to
be enhanced Sunday afternoon and evening with gusts 25-35 mph,
locally as high as 40 mph at the beaches.

Much cooler weather is expected on Sunday with high temperatures 15
to 20 degrees below normal, with the greatest departure from normal
in the mountains. Conditions will gradually warm early to mid-week
as the trough departs. Highs on Monday will be around 5-10 degrees
higher than Sunday, but still around 5-10 degrees below normal. A
few additional degrees of warming are expected on Tuesday. By
Wednesday, an upper level ridge briefly moves over the area bringing
additional warming. Highs will climb back to just below seasonal
normals.

For early next week, a passing shortwave will keep breezier westerly
winds in the mountains, locally into the deserts. Peak gusts Monday
and Tuesday afternoon and evening are expected to be around 40-50
mph. The periodic disturbances make it difficult to completely rule
out light showers as they move through the mean flow, especially
with a deep marine layer. It`s possible drizzle or light showers may
develop, mostly across San Diego County. Most ensemble members of
the global models are showing at least trace amounts of
precipitation. Current forecast has slight chances (15-20%) of rain,
mainly along the mountain slopes Monday night into Tuesday.

Another massive low moves east on Thursday and stalls off the Pac NW
coast. One short wave moves through on Thursday, though there is
still uncertainty in the timing and depth of this trough, and not
all ensembles are on board with bringing precipitation this far
south. Current forecast follows NBM and keeps chances of
precipitation under 10 percent for Thursday. Friday looks a little
cooler but mostly dry. Another wave dropping out of the Gulf of
Alaska is forecast to develop into a closed low before moving
towards SoCal next weekend, bringing more rain, mountain snow, and
gusty winds. There is still substantial spread in the track and
timing of this low, so it`s too early to discuss the details.

&&

.HYDROLOGY...
At 1 PM, showers were moving from west to southeast across the
area. Maximum observed rain rates have been 0.10 to 0.20 inches
per hour. High resolution model guidance is indicating rain rates
will become enhanced this evening, up to 0.30 inches per hour.
Scattered showers with periodically dry conditions are expected
this afternoon through the day Sunday. The track of the trough on
Sunday continues to favor San Diego County for precipitation, with
lower chances/amounts to the north. Thunderstorm chances increase
overnight with a slight (10-20%) chance of thunderstorms, with
the greatest chances in San Diego County. Colder air aloft on
Sunday will lead to greater instability and thunderstorm chances
(15-25%), especially Sunday afternoon during peak heating. Rain
rates will increase to around 0.30-0.50 inch/hour on Sunday
afternoon with any convection that occurs. Showers taper off from
north to south late Sunday night.

For Orange, southwestern San Bernardino, and western Riverside
Counties, rainfall is expected to range from 0.20 to 0.40 inch for
the coast and valleys to 1.50 to 2 inches in the mountains. For San
Diego County, rainfall is expected to range from 0.25 to 0.50 inch
along the coast, 0.75 to 1.25 inches in the valleys, and 1.5 to 2.50
inches, locally up to 3 inches, in the mountains.

A snow level of around 7000 feet this morning will fall to around
4500 feet for early Sunday morning, then fluctuate between 4500 and
5000 feet for Sunday afternoon and evening. For the San Bernardino
and Riverside County Mountains, total snow accumulations of 1 to 3
inches from 5000 to 5500 feet, 3 to 8 inches from 5500 to 6500 feet,
8 to 12 inches from 6500 to 7500 ft, and 12 to 18 inches above 7500
feet. A trace to an inch of snow possible from 4500 to 5000 feet.
For the San Diego County Mountains, total snow accumulations 2 to 6
inches from 5000 to 5500 ft and 6 to 12 inches above 5500 ft. A
trace of snow possible down to 4500 ft.

&&

.AVIATION...
231935Z...Coasts/Valleys...Multiple cloud layers with SCT 800-1500
FT MSL, BKN 2500-5000 FT MSL and BKN-OVC AOA 12,000 FT MSL. Terrain
obscurations along the foothills of the mtn ranges through tonight.
SHRA are moving toward the SE this afternoon. CIGS to 1000-1500 FT
MSL and VIS to 1-2 SM during SHRA. S-SW winds early this afternoon
turning to the W-NW behind a cold front. Diminishing SHRA from NW-SE
into this evening, with SHRA/TSRA redeveloping after 04z Sun, with
the highest chances in San Diego Co.

Mountains...BKN-OVC AOA 12,000 FT MSL today, and mtns below 4,000 FT
MSL obscured by clouds/FG through tonight. SHRA/SHSN continuing
through around 02z Sun across northern mtns with a brief break
through around 06z Sun, and continuing through San Diego Co through
Sun. Lower cigs/FG in SHRA. Breezy S-W winds developing this
afternoon continuing through Sun with peak gusts of 40-55 kt,
strongest over ridgelines, below passes and through wind-prone
canyons. Strong up/downdrafts and LLWS over/E of mtns.

Deserts...Inc clouds AOA 10,000 FT MSL today/tonight. Breezy W winds
continuing through Sun with peak gusts of 40-50 kt. Strong
up/downdrafts and LLWS along desert slopes.

&&

.MARINE...
Strong northwest winds will generate hazardous conditions this
afternoon through Monday. A Small Craft Advisory is in effect for
this afternoon through Sunday morning and a Gale Watch continues for
Sunday afternoon through Sunday night. The strongest winds, gusting
30-40 kts, and combined seas of 9-17 feet are expected. Another
period of gusty northwest winds will be possible Monday afternoon
and night. Conditions will improve on Tuesday.

&&

.BEACHES...
Large short-period swell from the west-northwest will arrive early
Sunday, peak Sunday night, and subside Monday. This storm swell will
likely produce breaking waves 4 to 7 feet, with sets up to 8-10 feet
Sunday night, highest in southern San Diego County. A Beach Hazards
Statement is in effect for Orange County and a High Surf Advisory
has been issued for San Diego County.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 5 PM this afternoon to 8 PM PDT Sunday for
     Orange County Coastal Areas-San Diego County Coastal Areas.

     High Surf Advisory from 9 AM Sunday to noon PDT Monday for San
     Diego County Coastal Areas.

     Wind Advisory until 11 PM PDT Sunday for Apple and Lucerne
     Valleys-Coachella Valley-Riverside County Mountains-San
     Bernardino County Mountains-San Diego County Deserts-San
     Diego County Mountains-San Gorgonio Pass Near Banning.

     Winter Storm Warning until 11 PM PDT Sunday for Riverside County
     Mountains-San Bernardino County Mountains.

     Winter Storm Warning from midnight tonight to 11 PM PDT Sunday
     for San Diego County Mountains.

     Beach Hazards Statement from Sunday morning through Monday
     morning for Orange County Coastal Areas.

PZ...Small Craft Advisory until 2 PM PDT Sunday 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.

     Gale Watch from Sunday afternoon 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/HYDROLOGY...CO
AVIATION/MARINE/BEACHES...EA


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