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Area forecast discussion
National Weather Service San Diego California
230 PM PDT sun Oct 13 2019

Synopsis...
an upper-level trough will bring cooling through Monday, along with
areas of night and morning coastal low clouds and patchy fog. It
will be much warmer midweek under high pressure aloft. A series of
Pacific troughs will force additional cooling and gusty mountain
and desert winds for the latter half of the week. Other than
periods of low clouds and morning fog, skies will be fair this
week and it will stay dry. A Santa Ana wind event could begin next
Sunday, but strength is unknown at this time.

&&

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

Highlights...

* temps below normal thru Mon, warmer Tue-Wed, cooler late week
* locally gusty offshore winds Tue, lower humidity inland
* gusty west winds over the mountains/deserts Thu into Fri
* Santa Ana winds Oct. 20-22 (low confidence on strength)

An upper level trough off our coast will move east with its axis
moving across socal Monday evening. Weak upper ridging will follow
behind.

The marine layer will deepen ahead of the trough tonight-Monday,
cloud bases at or above 2000 feet msl, with patchy fog limited to
elevated terrain over the inland valleys. The marine layer will
become shallower Tue-Wed as winds turn offshore. Max wind gusts to
30 mph are forecast Tuesday morning over the inland Empire across
areas below the San Gorgonio Pass as well as along the Riverside
and San Diego County coastal mountain slopes/foothills. The
offshore winds will weaken Wednesday as temps rise.

Another upper trough will move in from the northwest on Thursday.
Winds will turn onshore and strengthen with gusty winds forecast
from the Mountain Ridge tops to the desert slopes and onto parts
of the desert floor, particularly below the San Gorgonio Pass and
the San Diego County deserts. West wind gusts in these areas
are forecast to reach 30-40. Winds will weaken Fri-Sat as
temperatures cool under cyclonic upper flow.

There continues to be indication of a potential Santa Ana wind
event beginning Sunday, October 20th. Strength will depend on the
trajectory and amplification of a shortwave, which is shown by
model ensembles moving southeastward into the intermountain west
early next week. High confidence on offshore winds, warming, and
lowering humidity as this has been a signal for some time now.
However, low confidence on Santa Ana strength, I.E. Just how
strong the winds will be and how low the humidity will get. This
will be something we will continue to monitor closely in the days
ahead.

&&

Aviation...
132100z...coast/valleys...patchy low clouds are lingering at the
immediate coast this afternoon, with bases 2000-2500 ft mean sea level and tops
around 3000 ft mean sea level. Broken/overcast cigs will spread inland tonight, with
onset 04z-08z at coastal taf sites. Expect bases 2000-2500 ft mean sea level
and tops to 3000 ft mean sea level. Higher terrain will be locally obscured
after 08z, though most vis will remain 5+ miles below the clouds.
Cigs could reach kont and ksbd around 11z. Most areas will clear 15z-
18z.

Mountains/deserts...clear with unrestricted vis through Monday.

Marine...
no hazardous marine conditions are expected through Thursday.

&&

Fire weather...
through Monday...weak onshore flow will bring higher relative humidity and cooler
days inland through Monday.

Tuesday and Wednesday...winds turn offshore with gusts to 30 mph
over the inland Empire in areas below the San Gorgonio Pass and
along the coastal mountain slopes of Riverside and San Diego counties.
This will once again elevate fire weather conditions, but minimum
relative humidity levels and winds are expected to remain below
critical thresholds.

Thursday through Saturday...conditions cool with recovering
relative humidities. Gusty west winds will impact the deserts
mountain slopes and deserts with peak gust to 40 mph in favored
locales.

Sunday-Wednesday, October 20-22...potential Santa Ana conditions,
but strength is unknown at this time. We are confident that
conditions will warm on offshore wind flow, just not certain of
the strength of the event and this will be monitored closely in
the days ahead.

&&

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



&&

Sgx watches/warnings/advisories...
California...none.
Pz...none.
&&

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