San Diego Forecast Discussion
000
FXUS66 KSGX 282138
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
138 PM PST Tue Nov 28 2023
.SYNOPSIS...
A series of mostly weak low pressure systems will bring cooling
for Wednesday through Friday, chances for showers, and gusty west
winds for the mountains and deserts. Then dry with warming for the
weekend into the middle of next week.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
The high clouds from this morning have cleared out to the east
this afternoon, leaving us with mostly clear skies. Temperatures
this afternoon are overall running right around where they were
yesterday. Offshore winds have gradually started turning onshore
inland this afternoon.
With the return of onshore flow brings the return of the marine
layer. The marine layer cloud forecast tonight is a bit tricky, as
it usually is when we transition from offshore to onshore flow.
Low clouds should develop along the coast overnight, but it will
likely be pretty late in the overnight hours, and coverage will be
patchy at best until later on Wednesday morning.
A low pressure system currently situated just off the coast of
northern California will begin to progress southeast along the
coast on Wednesday. This will strengthen onshore flow and spread
cooling inland. Highs on Wednesday are expected to be 5 to 10
degrees cooler than Tuesday for all areas, with continued cooling
into Thursday. In addition to the cooler temperatures, winds will
increase across the mountains and deserts and through the passes
Wednesday afternoon and evening, with peak gusts 45 to 50 mph.
This system looks to be pretty moisture starved, with
rather unimpressive PWAT values in the ensemble solutions. Almost all
the ensembles are wet though, so expect some precipitation later
on Wednesday into Thursday, but it won`t be much. The storm is on
track to bring the highest precipitation totals to southern San
Diego County, with very little for areas north of San Diego
County Wednesday evening into Thursday.
This wave will race east on Thursday, with another system on it`s
heels for later Thursday into Friday. Guidance has further trended
this storm more to our north, so our rainfall forecast has trended
even lower from the previous forecast. The highest rainfall
amounts look to occur on the coastal mountain slopes of the San
Diego County mountains, with very little accumulation expected
north of San Diego County.
Forecast rainfall totals Wednesday through Friday:
Orange County and Inland Empire: 0.00 to 0.10 inch
San Diego coast and valleys: 0.15 to 0.30 inch
San Bernardino mountains: 0.00 to 0.10 inch
Riverside mountains: 0.00 to 0.10 inch
San Diego mountains: 0.15 to 0.45 inch
Deserts: 0.00 to 0.05 inch
Snow levels will be above 6000 feet Wednesday and Thursday, then
drop to around 5500 feet on Friday. Some snow accumulation will be
possible on Friday in the mountains, but it`s not looking like
much, perhaps up to an inch above 6000 feet.
So overall after today, expect cooler conditions, more cloud
cover, stronger onshore winds, and periods of showers. The
precipitation won`t amount to much, but we will take anything we
can get during the typical peak of our fire season.
Ensembles are pretty set on a ridge of high pressure building in
after the low departs to the east this weekend. This will bring us
dry and warmer conditions through at least the first half of next
week.
&&
.AVIATION...
282100Z...Coast/Valleys...FEW-SCT high clouds AOA 20000 feet this
afternoon. Patchy low cloud coverage with bases near 1500-3000
feet MSL starting 12-15Z Wed. Local vis reduced 3-5SM along inland
extent of clouds in valleys. Low confidence in onset time of low
cloud coverage. -SHRA possible after 21Z Wed, most likely in San
Diego county. Vis down to 2SM and cigs locally near 1000 ft MSL in
SHRA.
Mountains/Deserts...Westerly winds with gusts 35 to 45 kt over the
mountains, through passes, and into the deserts after 18Z Wed-06Z
Thu.
&&
.MARINE...
Northwest wind gusts near 20 kt over the outer waters Thursday night
through Friday night. During that same time, an incoming northwest
swell of 6-7 ft and 8 seconds from 280 degrees is expected. Choppy
seas and hazardous boating conditions are likely in the outer
coastal waters.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&
$$
PUBLIC...Connolly
AVIATION/MARINE...CO
NWS SGX Office Area Forecast Discussion
