Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
841 am PDT Sat Apr 18 2015
Synopsis... quiet weather with near average high temperatures
and light winds will continue through Monday...with the inland
extent of night and morning low clouds/patchy fog increasing each
day. Temperatures will cool after Monday...with below average
temperatures likely to end the week. Periods of rain and high
elevation snow showers will also be possible Wednesday through
Discussion...for extreme southwestern California including
Orange... San Diego...western Riverside and southwestern San
At 930 am...a intense 500 mb trough was centered over eastern Colorado
with weak ridging off the West Coast. Southern California was caught
between these two features with weak northwest flow at 500 mb. As a
result...clear skies and light winds prevail across the region this
Today and tonight...it will be a quiet day weather wise...with no
significant weather systems impacting the region. High
temperatures will be near seasonal averages along the
coast...while the inland Empire and deserts will see highs 3-6
degrees above seasonal averages. Light winds will continue for
most areas...although the desert slopes and eastern portions of
the San Gorgonio Pass may see wind gusts of 20 to 25 miles per hour this
evening. Low clouds and patchy fog will return to the immediate
coast late this evening.
Sunday and Monday...a weak disturbance embedded within the ridge
along the West Coast will keep temperatures near seasonal averages
during this time period. A return to onshore flow will allow night
and morning low clouds and patchy fog to push further inland each
Tuesday through the end of the week...the deterministic models
continue to advertise the development of a deep late season
trough along the West Coast for this time period. The northerly
origin of the system will keep precipitable water values low...resulting in
precipitation chances that are heavily dependent on dynamics.
Given that multiple embedded shortwaves are likely to rotate
around the parent trough...ample forcing should be present for at
least periods of scattered showers Wednesday through Friday.
Timing of the individual shortwaves within the parent trough is
still relatively uncertain...making it difficult to pinpoint the
most likely periods for showers at this time.
181530z...coastal areas...patchy low clouds with bases below 1000 feet
mean sea level and widespread visible 5sm or less developing this afternoon and
evening over the coastal waters...possibly impacting coastal taf
sites after 03z sun. Low clouds and fog could spread up to 8 Michigan inland
late tonight. Confidence in timing of onset is low.
Elsewhere...mostly clear with unrestricted visible through sun.
830 am...a few patches of dense fog with visible 1 nm or less may
develop over the coastal waters late this afternoon into Sunday
morning. Otherwise...no hazardous marine weather is expected Sunday
afternoon through Wednesday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.