Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus66 ksgx 140512 

Area forecast discussion
National Weather Service San Diego California
912 PM PST Wed Nov 13 2019

an upper level trough of low pressure will bring cooler weather
and a deeper marine layer Thursday and Friday. Offshore flow will
return for the weekend bringing warmer and drier conditions.
Onshore flow returns early next week bringing cooler weather to
the area through midweek.


Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino

low clouds have already begun to spread back into the coastal
areas. The marine layer is quite a bit deeper than last night, so
clouds should spread further into the valleys, including far west
portions of the inland Empire. Dense fog will also be less
widespread. Otherwise scattered high clouds continue to move over
the area ahead of the upper low off the central California coast. No
major changes to the forecast this evening.

Previous discussion...
a weak upper level trough will move slowly move through Thursday
and Friday. This pattern change will spark a cooling trend through
Friday. The shift to stronger onshore flow will also help extend
the marine layer into the western valleys each night through
Friday. Upper- level southwest flow ahead of the trough will bring
areas of high clouds to Southern California during this time
period as well.

The trough will begin to move east during the day Friday leaving an
area of high pressure over the West Coast this weekend. This will
bring areas of weak offshore flow Saturday night into Sunday. East
to northeast winds will set up over the coastal mountain slopes and
could make it into the valleys. Wind gusts are expected to reach up
to 35 mph, locally higher in wind prone locations. The offshore flow
will help boost high temperatures this weekend 10 to 15 degrees
above average.

Early next week, the ridge will break down and another trough
pattern will set up. This will bring cooler weather and the return
of night and morning low clouds along the coast. Towards the middle
of next week, Southern California will see its first chance of rain
in a while. There is still a large spread in global ensemble members
at this time so confidence on timing and amounts are still low.


140500z...coast/valleys...bkn/ovc stratus will continue to develop
between 05z and 09z in coastal areas and into some valleys,
including far west and south parts of the inland Empire. Bases will
be higher than previous nights, generally 800-1200 ft mean sea level with tops
to 1400 ft mean sea level. Areas of vis 1-3 miles will occur in the valleys and
some higher coastal terrain, mainly 08z-16z Thu. Most areas will
clear 16z-18z Thu, with stratus returning early Thu evening.
Otherwise, scattered-broken high clouds at/above 20000 ft mean sea level will prevail
through Thu evening.

Mountains/deserts...sct-bkn high clouds at/above 20000 ft mean sea level and
unrestricted vis will prevail through Thu evening.


no hazardous marine conditions through Monday.


Fire weather...
onshore flow will strengthen into Friday, spreading
cooler weather and higher humidity inland. Winds will turn
offshore Saturday morning, strengthening Sunday and gradually
weakening Monday. Sustained winds on the coastal mountain slopes
and through passes on Sunday will be around 15-20 mph, with gusts
up to 35 mph. Locally higher wind gusts possible in wind prone
areas. Minimum humidity Sunday and Monday will be 10-15 percent,
before recovering with the return of onshore Tuesday.

While confidence on timing and amounts are still low, the first
chance of rain is expected towards the middle of next week.


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


Sgx watches/warnings/advisories...

National Weather Service Glossary of Abbreviations