Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 260412

Area Forecast Discussion
National Weather Service San Diego CA
912 PM PDT Fri May 25 2018

A low pressure system moving inland across California will continue
cooler than average weather through Saturday. The marine layer will
remain very deep with low clouds returning tonight and a chance for
early morning light rain or drizzle west of the mountains tomorrow.
From Sunday through Tuesday the weather will turn warmer and the
marine layer shallower as the trough moves east.



Cooling at the top of the marine layer inversion and some weak
dynamic forcing allowed for better mixing of the lower atmosphere
producing mostly sunny skies west of the mtns this afternoon. The
cooling aloft seems to have ended this evening and the low clouds
are beginning to slowly increase in coverage west of the mtns.
This trend is expected to continue overnight.

From previous discussion...
A low pressure system centered over the Bay Area this evening will
move inland tonight. Shortwave energy rounding the base of trough
will move across SoCal Saturday morning and that is when more
areas of light rain or drizzle are possible along and west of the
mountains. It will turn windy in the mtns and deserts with the
passages of the trough axis with gap winds gusting to 30-50 mph
through the San Gorgonio Pass and into some of the Lower Deserts.

The trough moves inland Sunday and higher pressure building over the
Southwest will bring a slow warming trend to the region along
with a shallower marine layer. This trend will become noticeable
early next week with further warming Monday through Wednesday.

On Thursday and Friday the long range progs forecast a trough to
deepen along the West Coast. The GFS deepens the trough for a
colder and windier solution here in SoCal, while the ECMWF is
weaker and farther north with this trough. Used a model blend in
the long range with minor cooling and some gusty mountain and
desert winds at times.


260415Z..Coast/Valleys/Coastal Mountain Slopes...SCT-BKN low clouds
will gradually become BKN-OVC overnight, with bases 1800-2500 ft MSL
and tops to 3500 ft MSL. Higher terrain will be obscured, though
most vis will be above 5 miles below the cloud bases. Patchy
drizzle will be possible late tonight and early Saturday. Most areas
will clear 17Z-20Z Sat, with stratus developing again Sat evening.

Mountain Crests/Desert Mountain Slopes/Deserts...Mostly clear skies
will continue through Saturday evening. West surface winds 15-25 kt
with gusts 25-35 kt will produce localized LLWS with moderate
up/downdrafts from the mountain crests to the desert mountain
slopes and through passes through Saturday evening.


West northwest winds with a few gusts exceeding 20 knots are
expected out near San Clemente Island through Saturday night,
especially Saturday evening. Otherwise, no hazardous marine
weather is expected Sunday through Wednesday.


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





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