FXUS66 KSGX 161630

Area Forecast Discussion
National Weather Service San Diego CA
930 AM PDT Sun May 16 2021

An area of low pressure will move into Southern California over
the next couple of days, maintaining cool conditions with gusty
onshore winds over the mountains and deserts, and a deep marine
layer over the coast and western valleys. Areas of drizzle and
light rain will continue from the coast to the coastal mountain
slopes through Monday night. A ridge will arrive Tuesday,
providing dry and warmer weather through Wednesday. Another cold,
upper level trough will develop over the state on Thursday,
setting up another round of cooling and widespread gusty onshore
winds across the region.




Areas of drizzle and light rain is occurring this morning from the
coast to the coastal mountain slopes. The maximum rainfall amounts
is Paivika Ridge along the San Bernardino County coastal mountain
slopes, coming in at 0.39 inches. Over the coast and valleys, most
locales have received a few hundredths of an inch, but localized

Clouds will hang tough west of the mountains throughout the day
today, but there will be some breaks in the cloudiness, especially
over the Inland Empire.

The deep marine layer will continue in place through Monday,
leading to continued abundant cloudiness along with areas of light
rain from the coast to the slopes. Meanwhile, over the higher
terrain and across the deserts, the sky will remain mostly clear.
Gusty west winds will prevail across these areas as well.

Previous Discussion (Issued at 508 AM PDT Sun May 16 2021):

.SHORT TERM...(Today through Tuesday)...
An area of low pressure currently spinning its way across central
California will continue its journey south today. This system
will bring continued cool weather, cloudy skies along and west of
the mountains, and windy conditions for the mountains and deserts.
Winds will continue to be gusty throughout the day, diminishing
by Monday morning. As the low dips south, this will provide a
deeper marine layer with increasing precipitable water values
close to an inch in some spots near the coast. Some spotty
drizzle and light showers are possible through early afternoon
from the coast to the coastal slopes. HRRR model points to another
increase in some precipitation Sunday night into Monday morning
as PWAT values increase. Rain totals near one tenth in some spots
for the coast and western valleys with some coastal slopes near
one half inch.

As the system pushes off to the east into Arizona on Monday, we
will still see some lingering moisture and a deep enough marine
layer to produce some areas of drizzle Monday night, primarily for
western San Diego County. Temperatures will slowly begin to rise
as a weak ridge enters the region, though temperatures will still
be a bit below average west of the mountains and a bit above
average across the deserts Monday and Tuesday.


.LONG TERM...(Wednesday through Saturday)...
The weak ridge will not last for long into Wednesday, which will
make it the warmest day of the week for many. Ensemble models are
in agreement of a large trough pushing into the western CONUS
during the middle of the week. As of now, the accordance in
strength on this feature is quite good, where it may protrude into
parts of the Great Basin. The presence of this stronger trough
would bring cooler weather and more widespread breezy conditions,
highest across the desert mountain slopes into the deserts. A
larger spread in model solutions starts to occur by the end of
the week, where some keep the trough locked in place and others
make it weaker and give it a more progressive push to the east.


161612Z...Coasts/Valleys/Coastal Mountain Slopes...Stratus layers
with bases 2000-4000 ft MSL and tops to 5500 ft MSL continuing along
the mountains westward through Monday morning. DZ/-RA possible at
times through Monday morning, with the greatest coverage today into
tonight. Local vis 3-5 SM and BKN-OVC clouds lowering to 1500 ft MSL
in heavier showers. Coastal mountain slopes obscured in clouds/fog.
Risk of BKN-OVC low clouds based 2000-3000 feet MSL at KSAN midday
into the evening is moderate to high, so confidence in TAF cloud
forecasts levels is moderate to high.

Desert Mountain Slopes/Deserts...West winds with sfc gusts 30-40 kt
with isolated gusts to 45 kt increasing this afternoon and evening.
Strongest winds on the east facing desert slopes and through the San
Gorgonio Pass. MOD-STG up/downdrafts, LLWS, and rotors possible over
and east of the mountains, including near KPSP.


No hazardous marine weather is expected through Thursday.


A long period south swell from 200 degrees at 3 ft/17 sec will
produce 3-6 ft surf on south-southwest facing beaches of Orange
County and far northern San Diego County today. Surf of 2-4 ft is
expected elsewhere. Strong rip and longshore currents are likely
today into Monday. Swell and surf lower Monday. Another south swell
arrives late Tuesday and peaks Wednesday for another round of
elevated surf and a high risk of rip currents.


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


CA...Wind Advisory until 8 AM PDT Monday for Riverside County
     Mountains-San Diego County Deserts-San Diego County
     Mountains-San Gorgonio Pass Near Banning.

     Wind Advisory until 7 PM PDT this evening for Apple and Lucerne
     Valleys-Coachella Valley.



PUBLIC...Gregoria (Update)/APR (Previous Discussion)

Chino Hills, Ca. Weather | www.ChinoHillsWeather.com