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Area forecast discussion
National Weather Service San Diego California
930 am PDT Mon Apr 24 2017

Synopsis...
a low pressure system will continue moving by to the north today and
bring cool weather west of the mountains and very slow clearing of
the low clouds. Windy conditions will occur in the mountains and
deserts through tonight. The low pressure trough will be focused
more on the interior western United States from Tuesday through next
weekend as high pressure aloft prevails over the east Pacific. This
will bring warmer weather Tuesday and Wednesday and less extensive
coastal low clouds. Slight cooling and increasing winds could occur
late in the week as the inland trough deepens and expands.

&&

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

Nkx sounding showed the marine inversion base around 3000 feet with
about 6.5 deg c strength, so the stratus from the mountain slopes
west to the coastal waters will be slow to clear today. Mslp
gradients are increasing with about +8 mb from San Diego to thermal
and Imperial, and NAM shows gradients of up to +15 mb from San Diego
to Las Vegas this afternoon. This will help result in moderately
strong winds in the mountains and deserts the rest of today and
tonight. Stable layer will be around 7000-8000 feet mean sea level with will
mean that mountain waves will mainly strengthen the winds on the
east slopes of the San Diego County mountains and adjacent deserts
and result in strong gap winds through San Gorgonio Pass, though
local WRF shows some locally strong winds into the southern
Coachella Valley and well, plus the apple/Lucerne valleys. Some wind
gusts over 50 miles per hour will occur in windy locations, with very local
gusts around 65 miles per hour through windiest locations, such as San Gorgonio
Pass. Temps will mostly just be in the 65-75 deg f range west of the
mountains today.

Broad low pressure trough covers the West Coast and in the interior
west with a fast wave moving through northern California today. The
trough will deepen but shift east Tue/Wed and result in a warming
trend. There should be one last night of a deep marine layer west of
the mountains, with a weaking inversion, though enough of an
inversion could linger in San Diego County for widespread stratus
then and possible local drizzle. The marine layer should be more
shallow by mid-week though. Wednesday should be the warmest day as
the effects of the upper high off the coast will be greatest on so-
cal. A low-amplitude, fast-moving wave associated with a strong west-northwest-
to-east-southeast jet stream moving through northern Oregon could broaden the
trough a bit farther west late in the week and bring slight cooling
and increasing winds in the mountains/deserts. Weak offshore flow
could occur next weekend as the flow aloft becomes more northerly
due to amplification of the ridge and trough. Other than the small
chance of drizzle tonight, no precipitation is expected through
early next week.

&&

Aviation...
241600z...coast/valleys/coastal mountains slopes...low clouds with
bases near 2,000 ft msl should continue to break up through 20z,
leaving sky clear-few for this afternoon. Southerly surface winds
currently impacting coastal areas will transition to westerly near
10 kt through 22z. The low cloud deck will return this evening, with
low clouds and visibility restrictions developing along the coastal
slopes of the San Diego and Riverside County mountains after 03z
Tuesday. Broken ceilings near 2,500 ft msl are possible at ksan and
kcrq between 05z and 18z Tuesday. Ceilings are not anticipated at
kont or ksna between 20z Monday and 18z Tuesday.



Mountains/deserts...westerly winds will produce strong up/downdrafts
and low level wind shear over and near the deserts slopes of the mountains through
15z Tuesday. Areas of blowing dust and sand will also be possible,
and may reduce local visibility to 3 sm or less over portions of the
Coachella Valley and San Diego County deserts.

&&

Marine...
northwest winds will increase today and continue through Tuesday
evening with gusts reaching 20-30 knots. Winds will be accompanied
by a building short period northwest swell and lingering southerly
swell. This will result in short period combined seas of 10-12 near
and south of San Clemente Island. Inside of 30 nm, 5-8 ft combined
seas are anticipated. A Small Craft Advisory remains in effect
through Tuesday evening. Winds and seas will taper down some
Wednesday, before breezy northwest winds and choppy seas return
Thursday and Friday.

&&

Beaches...
a mix of northwesterly and southerly swells will continue to produce
3-6 ft surf at area beaches through this evening. Periodic sets to 7
ft are possible south of del Mar along west facing beaches. A beach
hazards statement is in effect for elevated surf and strong rips.

&&

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

&&

Sgx watches/warnings/advisories...
California...Wind Advisory from 2 PM this afternoon to 3 am PDT Tuesday 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.

Beach hazards statement through this evening for Orange County
coastal areas-San Diego County coastal areas.

Pz...Small Craft Advisory from 5 PM this afternoon to 10 PM PDT
Tuesday for waters from San Mateo Point to the Mexican
border extending 30 to 60 nm out including San Clemente
Island.

&&

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