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Area forecast discussion 
National Weather Service San Diego California
420 am PDT Tuesday may 5 2015


Onshore flow will bring slow cooling through Wednesday with gusty
west winds in the mountains and deserts and a continued deeper
marine layer west of the mountains with areas of night and morning
low clouds and fog extending inland onto the lower coastal mountain
slopes. For Thursday and Friday...a cold low pressure system from
the north will bring additional inland cooling...stronger gusty west
winds in the mountains and deserts...and periods of showers along
and west of the mountains...mostly likely Thursday night. Dry with a
warming trend for Saturday through Monday under high pressure.


Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino

Very weak shortwave ridging behind the low pressure system that
moved inland through Southern California Monday will move east today
with another weak low pressure system moving inland through Southern
California and northern Baja California late tonight and Wednesday. This will
maintain stronger onshore flow and a deeper marine layer. This will
bring slow inland cooling through Wednesday with gusty west winds in
the mountains and deserts a little stronger on Wednesday.

For Thursday and Friday...a colder low pressure system from the
north will bring additional cooling...stronger onshore flow with
stronger gusty west winds in the mountains and deserts...and chances
for precipitation. Some lighter precipitation is possible along and
west of the mountains late Wednesday night into Thursday morning
with greater potential for somewhat greater coverage and amounts
along and west of the mountains for late Thursday through Thursday
night into early Friday. The models are in general agreement through
Thursday night with the inland track of the system limiting
available moisture and precipitation potential somewhat. With the
arrival of colder air aloft into the northern half of Southern
California...there is also a slight chance of thunderstorms for
Thursday night and Friday...more likely for Orange and Riverside
counties northward. Snow levels will lower to 6000 to 6500 feet for
late Thursday into Friday...possibility a little lower.

Less certain is the precipitation potential for Friday into Friday
evening. Other than the operational GFS...the models show a drying
trend for Friday into Friday night. The operational GFS continues to
bring one last shortwave into Southern California on Friday with a
greater overwater trajectory with slightly different tracks for the
00z and 06z runs. If this shortwave were to materialize...this would
increase the precipitation chances for Friday into Friday evening
with the possibility for greater amounts than for Thursday and
Thursday night. The current forecast continues to show a decreasing
trend for precipitation chances for Friday and Friday night.

For Saturday through Monday...high pressure will bring dry weather
with a warming trend with high temperatures returning to near
average for Sunday and Monday.



050930z...coast/valleys...widespread low clouds with overcast ceilings 2000-
3000 feet mean sea level with tops to 4000 feet mean sea level. Low clouds gradually clearing
between 17-20z. Expect low clouds with similar bases and tops to
return to coastal areas by 03z Wednesday...spreading inland to the coastal
slopes overnight. Forecast confidence moderate-to-high.

Mtns/deserts...coastal slopes above 3000 feet mean sea level expected to be
obscured by low clouds. Otherwise...unrestricted visible with scattered clouds
above 4500 feet. Northwest winds 20-25 knots with gusts to 35 knots will
produce moderate-strong uddfs/low level wind shear over and east of the mountains



230 hazardous marine weather is expected through Saturday.
However...breezy northwest wind gusts of around 20 knots are likely in
the afternoons and evenings Wednesday through Friday...mainly in the
outer waters near San Clemente Island. Also...a low pressure trough
will create a slight chance of showers Thursday and Friday.



230 am...south-southwest swells continue through today at about 4 feet
with a 17 second period. Widespread surf of 3 to 7 feet will
continue...with sets of 8 to 11 feet possible along south-facing
beaches. Strong rip and longshore currents...beach erosion and minor
tidal flooding of low-lying coastal areas during the evening high
tide is expected. A high surf advisory is in effect through this
evening. On Wednesday the swell is expected to decrease to less than
4 feet with decreasing surf. The swell will continue to fall
Thursday and Friday.


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


Sgx watches/warnings/advisories...
California...Wind Advisory from 4 PM Wednesday to 3 am PDT Friday for apple
and Lucerne valleys-San Diego County deserts-San Gorgonio
Pass near Banning.

High surf advisory until 11 PM PDT this evening for Orange
County coastal areas-San Diego County coastal areas.




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