Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
251 am PDT Tuesday Jul 7 2015
a slow moving low pressure system off the California coast will
move inland through central and Southern California Thursday
bringing stronger onshore flow and dry southwest flow aloft with
inland cooling and gusty west winds in the mountains and deserts
at times. The marine layer will deepen with areas of night and
morning low clouds with patchy fog and drizzle extending onto the
Lower Mountain slopes. There will continue to be slow or limited
clearing near some beaches each afternoon. The trough of low
pressure will weaken for Friday through early next week with
warming to near seasonal levels for early next week along with a
gradually shallower marine layer.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
A slow moving low pressure system off the California coast will
move inland through central and Southern California Thursday.
This will bring stronger onshore flow and dry southwest flow
aloft with inland cooling...gusty west winds in the mountains and
deserts at times...and a deeper marine layer. This is an
anomalously deep low pressure system for Southern California for
July with 500 mb heights over Southern California on Thursday
around four Standard deviations below average.
The marine layer will slowly deepen from around 3000 feet this
morning to around 4500 feet on Thursday and Friday mornings.
Night and morning coastal low clouds with patchy fog and drizzle
will extend onto the lower coastal mountain slopes. There will
continue to be slow or little clearing near some beaches each
Inland high temperatures will continue to cool into Thursday with
Thursday high temperatures for some mountain and inland valley
areas 15 to 20 degrees below average.
For Friday through early next week...the trough of low pressure
will weaken with warming to near seasonal levels for early next
week along with a gradually shallower marine layer.
070900z...coast/valleys...stratus...with bases from
1500-2300 feet mean sea level and tops to 2600 feet mean sea level...has developed over the
coast...and will continue to push into the valleys overnight. An
aircraft sounding from ksan at 07/0600z showed a marine layer
inversion of 9 degree c. Visible of 2-4 sm br will be possible where
stratus nears higher terrain. -Dz is possible near sunrise. Low
clouds will slowly erode over the valleys late this morning...but
will likely linger over the coast throughout the day. Low clouds
will push back into the valleys again this evening...with slightly
higher tops and bases. Forecaster confidence in stratus timing and
depth is moderate to high.
Mtns/deserts...few/sct cumulus clouds over the mountains/high deserts in
the afternoon. Local west surface winds 15-25 knots gusts to 35 knots late
afternoon/evening through San Gorgonio Pass and on Desert Mountain slopes.
Otherwise...mostly clear with unrestricted visible through Wednesday morning.
200 am...no hazardous marine weather is expected through
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.