631
FXUS66 KSGX 260430 CCA
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
930 PM PDT Sat May 25 2019

.SYNOPSIS...
An upper level low from the north will bring occasional showers late
tonight through Monday morning, along with strong gusty winds in the
mountains and deserts and cooler weather. Some snow could fall in
the higher mountains. Monday afternoon through Wednesday will be
drier with a warming trend as the upper low moves east, though upper
level low pressure will likely strengthen again over the West Coast
the second half of next week for renewed cooling and possibly a few
showers.

&&

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

Mostly cloudy conditions prevailed this evening, with greatest cloud
cover in the mountains and inland valleys. The upper low will
continue to approach from the northwest with spotty showers
developing overnight, then a front from the west around sunrise
Sunday will spread more organized, albeit mostly light, precip onto
land. There will be orographics at times over the south and
southwest facing slopes due to winds around 850 MB of 25-45 knots
and saturation up to 8000 to locally 14000 feet above sea level.
After the initial front Sunday morning, the precip should weaken at
lower elevations but not weaken much in the mountains due to the
orographics, but then the main upper low will track over the Mojave
Desert Sunday evening, and a wave associated with the low will
enhance the precipitation. Instability will be insufficient for
thunderstorms, but some brief moderate to heavy rain could occur in
the mountains with maximum rates up to 0.30 or 0.40 inches in an
hour. Overall precipitation totals appear to average around 1/4 inch
at lower elevations and 1/2 to 1 inch in the mountains, with the
potential of local 2 inch amounts on the south slopes in San
Bernardino County. Snow levels should mostly be 6500-7000 feet
Sunday but should fall to 5500-6000 feet Sunday night, with the
potential of a few inches of snow, mainly close to the low in San
Bernardino County. With the pressure height gradients aloft
producing winds up to 45 knots at 850 MB and 60 knots at 700 MB,
there will be strong winds in the mountains and deserts, especially
in the usual locations from the mountain crests through the desert
slopes and through San Gorgonio Pass. Local gusts could reach 65 MPH
Sunday afternoon and evening. Of course, with an unseasonably strong
upper low for late May, maximum temperatures will be 15-25 degrees
below normal Sunday.

Models indicate some lingering showers Monday, mostly early in the
day, with Monday still being unseasonably cool but generally 5-10
degrees warmer than Sunday. Almost all GFS ensemble runs show deep
troughing continuing just inland from the West Coast Monday through
Wednesday, but at least with increasing heights, temperatures should
increase though not quite to normal levels. Some sort of upper low
could dive south along the West Coast the second half of next week
and bring more cooling, a deep but possibly disorganized marine
layer and perhaps a few showers, though moisture will be limited.

&&

.AVIATION...
260300Z...Coast/Valleys...Low clouds off the coast will be moving
ashore sometime around 05Z Sunday with BKN-OVC cigs 1500-2500 ft
MSL. These low clouds will push into most inland valley locations
and obscure coastal slopes and higher terrain. Isolated -SHRA
possible after 26/08Z spreading in coverage from west to east. Bases
1500-2000 ft MSL and local vis 3-5 miles possible during showers.
These cigs and showers will prevail through much of the day on
Sunday.

Mountains/Deserts...SCT-BKN cigs this evening, becoming BKN-OVC.
Coastal mountain slopes becoming obscured in clouds/fog/-SHRA after
26/08Z. SW to W winds beginning to pick up this evening with gusts
25-35 kts. Winds peaking afternoon Sunday with sfc gusts 35-45 kt
along the mountain crests/desert mountain slopes and below the
passes. MOD-STG UDDFS and LLWS expected over and NE/E of the
mountains.

&&

.MARINE...
No hazardous marine weather is expected through Thursday.


&&

.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 noon Sunday to midnight PDT Sunday
     night for Riverside County Mountains-San Bernardino County
     Mountains.

     Wind Advisory from 6 AM Sunday to 2 AM PDT Monday 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 Banning.

PZ...NONE.
&&

$$

PUBLIC...Maxwell
AVIATION/MARINE...APR




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