Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 191100
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
300 AM PST Fri Jan 19 2018

.SYNOPSIS...
Through Saturday...a low pressure system will move inland through
California and into Arizona bringing stronger onshore flow with
cooling...strong gusty west winds in the mountains and
deserts...and scattered mostly light showers along and west of the
mountains for this afternoon into Saturday morning. Dry with a
warming trend for Sunday through Wednesday. Another low pressure
system could move quickly through California around Thursday of
next week bringing cooling...strong gusty west winds in the
mountains and deserts...and mostly light precipitation along and
west of the mountains. High surf will continue at the beaches
through Saturday.

&&

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

A low pressure system off the West Coast will move inland through
California through tonight...then into Arizona Saturday. It will
bring stronger onshore flow with areas of strong gusty southwest
to west winds in the mountains and deserts...and west to
northwest winds across the coastal waters for this afternoon into
Saturday. Cooling will begin for coastal and valley areas today
with greater cooling for all areas tonight and Saturday.

Scattered mostly light showers will spread southward across the
area during the afternoon and early evening...then end from the
northwest late tonight into Saturday morning. Rainfall is expected
to range from less than one tenth inch near the coast to one tenth
to one quarter inch in the mountains with local amounts to around
one half inch. Snow levels above 7000 feet will lower to around
5500 to 6000 feet during the late afternoon...to around 4500 feet
during the evening...and around 3500 feet by Saturday morning with
a few inches of snowfall...mostly above 4500 feet.

Dry weather will follow for Sunday through Wednesday with slow
warming on Sunday and greater warming for Monday through Wednesday
with high temperatures returning to near to a little above average
for Tuesday and Wednesday.

Another low pressure system could move quickly through California
around Thursday of next week bringing cooling...strong gusty west
winds in the mountains and deserts...and mostly light
precipitation along and west of the mountains. The current
forecast leans towards the faster timing of the ECMWF for late
Wednesday through Thursday which is supported by the Canadian
model and the GFS ensemble mean with the 00Z and 06Z runs of the
GFS a little slower.

&&

.AVIATION...
191020Z...COAST/VALLEYS...Marine stratus with bases 015-020 and tops
025-030 expanding inland through 18Z. from 18Z through 06Z expect
variable CIGS with layers to FL100 and isold rain showers or drizzle
at times. VIS mostly P6SM, but 3-5SM at times along the higher
coastal terrain and inland foothills due to scattered pcpn and
briefly lower CIGS.

Mountains/Deserts...Variable clouds AOA FL150 with unrestricted VIS
through 18Z. After 18Z clouds will increase over the mts obscuring
the terrain at times with light pcpn after 00Z. SW-W winds 20-30KT
with gusts 50KT at times developing after 20Z over the ridges and
along the desert slopes, producing mdt-strong up/downdrafts and LLWS
over and east of the mtns.

&&

.MARINE...
A weak cold front will pass over the coastal waters today, with
increasing westerly winds in its wake. Wind gusts to gale force are
expected at times later this afternoon through Saturday evening. A
large long-period northwest swell and shorter-period wind swell will
combine to create hazardous small craft conditions. Please refer to
LAXMWWSGX for details on the Small Craft Advisory and Gale Warning
now in effect.

&&

.BEACHES...
a large, long-period northwest swell will increase surf into
Saturday. A High Surf Warning is in effect. Please refer to
LAXCFWSGX for details.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Weather Advisory from 4 PM this afternoon to 6 AM PST
     Saturday for Riverside County Mountains-San Diego County
     Mountains.

     Winter Weather Advisory from 2 PM this afternoon to 6 AM PST
     Saturday for San Bernardino County Mountains.

     High Surf Advisory until 8 PM PST Saturday for Orange County
     Coastal Areas-San Diego County Coastal Areas.

PZ...Gale Warning from 2 PM this afternoon to 10 PM PST Saturday 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.

     Small Craft Advisory for hazardous seas until 2 PM PST this
     afternoon for Waters from San Mateo point to the Mexican
     Border Extending 30 to 60 nm out including San Clemente
     Island.

&&

$$

PUBLIC...17
AVIATION/MARINE/BEACHES...JAD



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