Scientific Forecaster Discussion
fxus66 ksgx 290424 aaa
Area forecast discussion
National Weather Service San Diego California
922 PM PDT sun may 28 2017
Coastal stratus has already developed this evening and is already
beginning to push into the western valleys. The 00z Miramar sounding
shows that the marine inversion is still pretty shallow but has
grown stronger over the last day. Monday will be another warm day
inland, but near the beaches clouds may linger into the afternoon
keeping things on the cool side. The forecast database remains on
track this evening and no changes were made.
weak high pressure aloft will bring warmer weather inland through
Tuesday, while the marine layer keeps the coast seasonal with areas
of night and morning low clouds and patchy fog. Cooler, with a
deeper marine layer and more extensive marine clouds midweek as a
low pressure trough develops over the West Coast. Modest warming
returns by next weekend under weak ridging aloft.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Patchy low clouds were observed over the coastal waters at midday,
but had cleared the beaches, otherwise the sky was clear across
socal. Marine clouds were extensive west of the islands.
Temperatures were running higher than yesterday inland, especially
at some of the higher elevations. At noon PST...Julian and Descanso
RAWS sites were 18 degrees f higher than yesterday, Anza was up 15
degrees as well. Surface pressure gradients were flat ksan to SW NV,
and about 6 mbs onshore to the lower deserts. Peak wind gusts were
below 25 miles per hour at noon PST.
Very little change is forecast to the synoptic pattern through Mon,
except for perhaps a weaker offshore sfc gradient from the NE. This
could result in better coastal marine stratus coverage Mon/Tue
mornings, especially given that it is climatologically favored, but
High latitude ridging over the west will maintain a split flow in
the atmosphere through midweek. The weaker southern branch will
support weak ridging over socal and warmer weather through Memorial
Day, then transition again to cooler conditions as a weak upper
trough develops and amplifies the marine layer. The global models
show the pattern repeating again next weekend into the following
week. Weak ridging aloft will lead to warming into the weekend,
followed by low pressure aloft and cooler conditions early next week.
Aside from the fluctuations in daytime temperatures, the pattern
looks seasonal, with onshore flow, locally gusty winds over the
mts/deserts at times, and nocturnal marine clouds varying in extent
and coverage over the coastal basin.
290400z...coast/valleys...bkn/ovc stratus will continue to spread
overnight, extending from San Diego County within 15-20 miles of the
coast through Orange County by 08z. Bases will be 1000-1500 ft mean sea level
with tops to 2000 ft mean sea level with local vis 3-5 miles and some terrain
obscurations. Most of the inland Empire will remain clear overnight.
Clearing at most coastal airports will occur 16z-19z Mon, except
local broken cigs could occur Mon afternoon near the beaches. Stratus
will redevelop Mon evening.
Mountains/deserts...mostly clear with unrestricted vis through
no hazardous marine weather is expected through Friday.
Skywarn activation is not requested.