Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus66 ksgx 141723 

Area forecast discussion
National Weather Service San Diego California
920 am PST Sat Dec 14 2019

a trough will bring cool weather today and tonight along with
scattered light showers west of the mountains. Gusty west winds will
impact the mountains, deserts, and the coastal waters. Dry weather
will follow on Sunday behind the departing trough. A dry Santa Ana
pattern Monday and Tuesday will bring generally clear skies. It will
also bring gusty northeast winds to the mountains, foothills and
inland valleys. A weak trough will bring a chance for more light
showers late Wednesday into Thursday.


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

A 4,000 foot deep marine layer is in place this morning with low
clouds extending from the coast to the mountain foothills. The top
of the Cajon Pass (~4,000 ft) was shrouded in clouds and dense fog
at 8 am. The deep marine layer also produced spotty light rain and
drizzle this morning. Chino Hills picked up 0.04" overnight,
Fallbrook 0.02", and Yorba Linda 0.01".

Winds were picking up in the mountains and deserts with gusts of 59
mph at Toro Peak in the Santa Rosa Mountains, 50 mph at Harrison
Park in the San Diego County mountains, and 48 mph at White Water
near to top of the San Gorgonio Pass above I-10.

No changes to the forecast today. It'll stay generally cloudy west
of the mountains ahead of a weak shortwave that will race across
socal tonight. This feature will trigger a few passing showers over
and west of the mountains through tonight. The strengthening onshore
gradients will result in gusty mountain and desert winds where a
Wind Advisory is in effect through 10 am Sunday. Winds over the
coastal waters will gust as high as 30 kt, and a Small Craft
Advisory is in effect until 4 PM Sunday. Big surf will pound the
shoreline with waves from 5-10 feet. A high surf advisory is in

*From previous discussion*

Behind the wave, a transient ridge will build a strong sfc high into
the Great Basin early next week (1040+ mbs), forcing the winds to
turn offshore across socal. Moderate to locally strong east-NE winds
are possible through the passes and on the wind-prone coastal
slopes, but upper support is weak to nil. This will mean dry and
warmer weather for Monday and Tuesday, with the warmest weather
along the coast, setting up a couple of nice beach days.

Another shortwave follows the ridge for the midweek period and may
generate some light rain or showers late Wednesday or Thursday but
chances appear to be dwindling here as it becomes overwhelmed by the
abundance of dry, Continental air. A shallow, transient ridge floats
by toward the end of next week, again with some warming west of the
mountains. A longwave trough appears over the eastpac next weekend
and poses a potential for more substantial precipitation then, but
this is near the end of the forecast period with low confidence.


141715z...coast and valleys...bkn-ovc010-020 tops 040 through 20z
today with areas of lower ceilings from 005-010 and vis from 1-3 miles
in fg/-ra/-dz. After 20z...bkn-ovc015-025 tops 050 through 12z
Sunday with scattered -shra.

Mountains/deserts...west facing mountain slopes obscured in clouds
and fog through 12z Sunday with scattered -shra. Ridgetops and
eastern slopes...mostly clear with unrestricted vis through tonight.
Gusty west winds in the mountains/passes and over the desert slopes
with gusts to 50 kt and strong up/downdrafts and low level wind shear.


a large, long period west-northwest swell of 15-17 seconds will
combine with a fresh 7-9 second swell to produce combined seas of 9
to 12 ft through Sunday. West northwest winds will increase over the
outer coastal waters, peaking tonight into Sunday morning with gusts
25 to 30 knots, and locally to 35 knots near San Clemente Island. A
Small Craft Advisory is in effect for all of the coastal waters
through 4 PM Sunday.


high surf advisory in effect through Sunday afternoon for 5-10 ft
surf, highest in San Diego County. The pounding surf will contribute
to local beach erosion during the 6 ft+ morning high tides.


Skywarn activation will not be needed today.


Sgx watches/warnings/advisories...
California...Wind Advisory from 1 PM today to 10 am PST 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

High surf advisory until 4 PM PST Sunday for Orange County
coastal areas-San Diego County coastal areas.

Pz...Small Craft Advisory until 4 PM PST 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.


National Weather Service Glossary of Abbreviations