Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
935 am PDT Monday Jul 28 2014
the increased possibility of thunderstorms continues today as
sufficient monsoonal moisture remains in place. Drier air moving
into the region will limit thunderstorm chances to the mountains
on Tuesday and Wednesday...then diminish chances for the remainder
of the week. Near normal temperatures will continue through middle-
week...then increase to slightly above normal through the weekend.
High pressure aloft will continue a patchy...shallow marine layer.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
At 9 am PDT...water vapor satellite imagery displayed an upper-
level ridge parked over the Texas/New Mexico border...and a weak
disturbance moving north over SW California. Composite radar imagery
showed an isolated light shower moving north over northern Orange
County. The 28/1200 UTC knkx sounding displayed a more stable
atmosphere...compared to yesterday mornings sounding...and also
calculated 1.65 in of precipitable water throughout the column.
The possibility of isolated to scattered showers and thunderstorms
will continue this morning as the aforementioned disturbance
moves north across the region. Shower activity has mainly been
restricted to over the coastal waters and coastal Orange County.
However...additional showers could develop along the coast and
valleys over the next few hours with upper-level instability and
sufficient moisture present. Thunderstorm activity is forecast to
be restricted to the far inland valleys...mountains and deserts
this afternoon and evening as surface heating continues. Although
there is plenty of monsoonal moisture across the area...widespread
storm activity is not expected at this time from subsidence
trailing behind the disturbance. Storms that do develop could
generate heavy rain...localized flash flooding...gusty winds and
The aforementioned upper-level high pressure will shift southward
Tuesday...shifting the upper-level flow from southeast to SW. This will
help transport some middle and upper-level moisture to the area from
Tropical Storm Hernan. Clouds and virga are expected from the SW
flow. However...isolated thunderstorms will be possible Tuesday
and Wednesday afternoon...mainly over mountain peaks.
The high will then build west over SW California Thursday through the
weekend...which will help to dry out the atmosphere...remove the
possibility of thunderstorms and slightly increase high
temperatures to a few degrees above normal. The marine layer will
remain fairly shallow and patchy due to the various middle and high
clouds...and the building ridge aloft. Low clouds and fog will be
restricted mainly to the coast and coastal valleys.
281530z...coasts/valleys...vcsh over coastal airports through
28/1800z. However...most of this activity will be high based...with
bases at or above 10000 feet mean sea level. A few/scattered stratus cloud deck with bases near
1000 feet mean sea level and tops 1400 feet mean sea level will be affecting portions of the
immediate coastline throughout this afternoon and evening. A more
pronounced scattered/broken low cloud deck with similar base and tops should
develop over the coastal waters tonight and move 5-10 sm inland after
28/0900z. This would affect ksan...kcrq...and ksna. Confidence of a
broken layer occurring at these airports is low to moderate.
Mountains/deserts...isolated showers this morning. Scattered
mountain thunderstorms and isolated desert thunderstorms developing after 28/1800z
with bases 6000-8000 feet mean sea level and tops to 35000 feet mean sea level. Showers and
thunderstorms diminishing this evening. Otherwise multiple scattered-broken
cloud layers at or above 8000 feet mean sea level.
845 am PDT...scattered showers and isolated thunderstorms will
continue through this late this morning. Thunderstorms may produce
cloud-to-water lightning...brief heavy rain...and gusty winds. No
hazardous marine weather expected tonight through Friday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.