Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 231600
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
900 AM PDT Tue May 23 2017

.SYNOPSIS...
Today will be another hot day in the valleys and deserts, while
the coastal areas will be cooler due to a shallow marine layer.
A weak trough will bring minor cooling Wednesday, with greater
cooling and gusty west winds in the mountains and deserts Thursday
and Friday. Marine layer clouds will spread farther inland each day,
and there may be areas of light rain along and west of the mountains
Thursday night into Friday morning. High pressure will rebuild over
the West Coast this weekend for warmer weather and a shallower
marine layer.

&&

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

The marine layer depth was 800 feet this morning, about the same as
yesterday morning. Low clouds pushed 10 miles inland last night and
retreated quickly back to the coast by 830 this morning. A thick
stratus shield was just offshore.

Today will be another very hot day in the Inland Empire and the
deserts. Valley highs will be in the 90s. The high deserts
will be in the upper 90s, and the lower deserts will top out
around 110. The record highs of 114 at Thermal and Palm Springs are
probably not reachable, nor is the record high of 112 at Borrego.
These three records were set in 2001.

No changes to current forecast. The ridge axis over California
will drift east tonight and be over the western AZ Wednesday
morning. Increasing onshore flow and a slowly deepening marine layer
will bring cooling into the valleys and deserts Wednesday.

*From Previous Discussion*

For Thursday and Friday...low pressure over the western states
will bring stronger onshore flow with cooling to around 10
degrees below average for inland areas...with Friday expected to
be the coolest day. There will be periods of strong gusty
southwest to west winds in the mountains and deserts. Greater
deepening of the marine layer will take coastal low clouds
into the inland valleys on Thursday morning...and onto the
coastal mountain slopes for late Thursday night into Friday
morning with a slight chance of light showers along and west of
the mountains. Any precipitation is expected to be light.

For the holiday weekend...high pressure aloft near the West Coast
will bring a warming trend with high temperatures for inland area
warming to near average on Sunday and a little above average on
Memorial Day. The marine layer and weak onshore flow will keep
coastal areas cooler with areas of night and morning low clouds
and fog.

&&

.AVIATION...
231500Z...A solid deck of low clouds had spread about 15 miles
inland early this morning. Bases are around 800 feet msl and tops to
1400 feet. Clearing has begun inland and clouds should clear to the
coast by 17Z. Vis has been reduced to 1-3sm or lower where clouds
and terrain intersect. Low clouds will move ashore again this
evening after 04Z. These clouds will be based at around 1000 feet
msl and spread farther inland overnight. Otherwise, mostly clear
skies except for a few high clouds and afternoon cumulus over the
mountains.

&&

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

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

PUBLIC...Moede
AVIATION/MARINE...PG



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