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Area forecast discussion 
National Weather Service San Diego California
902 PM PDT Fri Oct 21 2016

still very dry inland Saturday, but more noticeably cooler as the
highest temperatures in the inland valleys only reach the low
ninetys. The cooling trend continues and temperatures will
return to near seasonal averages by early next week. The
potential for showers and/or thunderstorms will arrive Sunday and
Monday over the entire region. Drier and warmer conditions are
expected during the middle next week, as attention turns towards
the next potential weather maker along the California coast late Thursday
into Saturday.


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

Clear with light winds this evening. Temperatures are generally
several degrees lower west of the mtns than this time yesterday.
The mtns and high deserts were generally a little warmer than at
the same time yesterday, likely due to an absence of cold air
advection from the northeast.

For the rest of tonight, continued low rh, clear skies and
cooling below 800 mb should help temperatures to lower
significantly this evening and overnight. No significant marine
layer fog or stratus is expected through Saturday morning. As
onshore flow becomes more established, the likelihood increases
that marine layer low clouds and fog could return to the coastal
areas Saturday night, before the arrival of higher clouds on

From previous discussion...
the ridge that dominated our weather for the past 3-4 days will
weaken and shift eastward over the weekend as a deep trough of low
pressure develops off the West Coast. As this occurs, moderate
southwest flow will develop and draw sub-tropical moisture
northward over socal by Sunday. Light showers or virga will be
possible Sunday for all areas, with light shower activity possible
Monday as the moist layer aloft increases in depth. Isentropic
lift and/or a weak shortwave may help produce a small amount of
elevated cape during this period, potentially resulting in a few
lightning strikes. However, widespread thunderstorm activity is
not expected at this time. Precipitation totals should be light
with this event, with most locations seeing only a trace to 0.15
inches, local amounts to 0.60 inches are possible in the mountains
where evaporation due to low level dry air should be less

An amplified ridge is expected to develop during the middle of
next week over The Four Corners. This will bring minor warming
Tuesday- Wednesday, but allow onshore flow to continue moderating
temperatures near the coast. After Wednesday, the forecast
becomes more uncertain with good continuity between the 12z European model (ecmwf)
and GFS deterministic runs contradicted by spread in their
respective ensembles. This makes it difficult to determine the
likely timing and impact of the next storm system along the West
Coast. At this point the only thing that can be said with any
confidence is that a significant plume of sub-tropical moisture
will impact the California coast between Thursday and Saturday of next


220315z...mostly clear with unrestricted visibilities, except
the risk of patchy dense fog within 5 sm of the coastline from 22/06z
this evening through 22/15z Saturday morning exists. Since the risk
is very low, the confidence in only sct low clouds and no dense fog in
the coastal tafs is moderate-high.


an upper level disturbance and surge of mid-level moisture will
create some showers and possibly some thunderstorms over the coastal
waters at times Sunday into Monday. Otherwise, no hazardous marine
weather is expected through Thursday.


there is a slight chance of thunderstorms Sunday evening through at
least Monday morning from an upper level disturbance, mainly for the
San Diego County beaches. Cloud-to-ground and cloud-to-water
lightning could occur, resulting in a danger to beach goers
and swimmers.


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


Sgx watches/warnings/advisories...



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