Area Forecast Discussion
Issued by NWS San Diego, CA

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231
FXUS66 KSGX 192036
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
136 PM PDT Tue Mar 19 2019

.SYNOPSIS...
Marine layer low clouds continue along the coast this afternoon.
Expect the marine layer to deepen and clouds spread farther inland
tonight as a low pressure system approaches from the west. Cloudy
and cooler, with unsettled weather for Wednesday through Thursday.
Periods of showers and mountain snow are likely Wednesday morning
through Thursday, with a slight chance of thunderstorms for Wednesday
afternoon and early evening. Fair and a little warmer on Friday.
The next low pressure system will bring a chance of mostly light
showers on Saturday. Sunday and Monday will be dry with a warming
trend.

&&

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

This afternoon...temperatures west of the mountains are generally
lower than at this time yesterday as the marine layer continues
to deepen with low clouds and fog along the coast. In some coastal
areas, temperatures are 10-14 degrees lower. Onshore flow is
increasing and will spread low clouds and fog farther inland
overnight.

From previous discussion...
A low pressure system currently at about 125 west longitude will
move through SoCal Wednesday and Thursday. It will bring lower
temperatures, increasing clouds, gusty westerly winds and periods
of showers Wed through Thu. Showers will move in from the west on
Wednesday morning. Most of the precip will fall between early Wed
morning and Wed evening, decreasing thereafter. Isolated to
scattered showers will continue through Thursday. Cold air
advection aloft and increasing instability will bring a chance of
thunderstorms Wed afternoon and evening. Current rainfall
estimates are for 0.15-0.25 inch near the coast, 0.30-0.75 inch
in the mtns and less than 0.25 inch in the deserts.

Snow levels will be 5500-6500 feet Wed morning and early
afternoon, lowering to 5000-5500 feet for Wed night into Thu
morning. Snowfall amounts of 2-4 inches are expected above 5000
feet and up to 6 inches above 6000 feet.

Winds will strengthen from the west early Wed morning, peak Wed
evening and weaken Thu morning. Wind gusts of up to 45 mph will be
possible on the desert slopes of San Diego County and the
Coachella Valley.

A cooling trend will begin today and continue through Thursday
which will be the coolest day, with daytime temperatures in the
50s to low 60s at lower elevations west of the mtns.

Fair and warmer on Friday as a dynamic upper-level ridge moves in
from the west. Daytime temperatures will be mostly in the mid 60s
at lower elevations west of the mtns. Another low pressure system
moving inland to the north on Sat will bring cooler and unsettled
weather. This will be a relatively fast-moving system so precip is
expected to begin Sat morning and end by Sat evening. SoCal will
be on the southern periphery of this system so only small amounts
of precip is expected.

After this system moves inland to the northeast, a building ridge
of high pressure over the western U.S. will bring dry weather and
a warming trend. Daytime temperatures are expected to return to
near seasonal averages by early next week.

&&

.AVIATION...
192000Z...Coast/Valleys...Patchy low clouds with bases near 1000 FT
MSL with brief periods of BKN cigs will continue through the day on
the immediate coast, affecting KSAN/KCRQ/KSNA. Low clouds will
redevelop and extend well into inland valleys after 20/01Z, with
bases near 1000-1500 FT. Elevated coastal terrain will be obscured
in FG/BR with vis locally below 1 mi, though confidence is low in
significant vis restrictions at TAF sites. -SHRA likely as early as
20/14Z at KSNA, and a few hours later at the other TAF sites.
Isolated TSRA will be possible Wednesday, particularly near the
coast.

Mountains/Deserts...BKN-OVC skies will obscure mountain slopes after
20/15Z, with -SHRA expected through the day Wednesday. Vis 2-5 mi is
likely in higher terrain obscured by clouds and during heavier
showers. West SFC winds 15-20 kts gusting to 35 kts over the
mountain crests, with MOD UDDFTS likely over and east of the mtns.

&&

.MARINE...
A weak storm will bring stronger winds and higher seas, along with
showers Wednesday through Thursday. An isolated thunderstorm is
possible Wednesday. Otherwise, no hazardous marine weather is
forecast through Saturday.

&&

.BEACHES...
High surf of 3-8 feet is expected Wednesday afternoon through Friday
morning, highest in southern San Diego County. Swell and surf will
subside on Friday.

&&

.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 5 PM Wednesday to 8 PM PDT Thursday
     for Riverside County Mountains-San Bernardino County
     Mountains.

     High Surf Advisory from 1 PM Wednesday to 1 PM PDT Friday for
     Orange County Coastal Areas-San Diego County Coastal Areas.

PZ...NONE.

&&

$$

PUBLIC...PG
AVIATION/MARINE/BEACHES...Rodriguez



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