Scientific Forecaster Discussion
fxus66 ksgx 181047
Area forecast discussion
National Weather Service San Diego California
347 am PDT Fri Oct 18 2019
lower level flow will be onshore through Saturday night except
weak northerly near the San Bernardino County mountains for this
morning and Saturday morning with locally gusty north winds. Weak
offshore flow will develop on Sunday and become a little stronger
for late Sunday night into Monday morning with gusty northeast
winds to 35 mph near the coastal slopes of the mountains. Weaker
northeast winds of 25 mph or less will then continue into Tuesday
morning. High temperatures will warm for Sunday through Tuesday,
then cool for Wednesday and Thursday as the return of onshore
flow spreads cooling inland.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Short term (today through sunday)...
generally northwest flow aloft will prevail through Sunday with
high pressure aloft off the West Coast and a trough of low
pressure over The Rockies. Lower level flow will be onshore,
except weak northerly this morning for inland areas and again
for late tonight into Saturday morning. There will be gusty north
winds, mostly 35 mph or less, this morning near the coastal slopes
of the San Bernardino County mountains and the Santa Ana Mountains
and below the Cajon Pass with weaker and more localized winds for
late tonight into Saturday morning.
Areas of low clouds in the far inland valleys onto the coastal
slopes of the mountains will be eroded by the northerly lower
level flow this morning. High temperatures today and Saturday will
be similar to those of yesterday, around average.
The lower level flow on Sunday will become weakly offshore with
gusty northeast winds in the mountains, mostly less than 35 mph.
High temperatures for the mountains and deserts will warm slightly
on Sunday with high temperatures around 5 degrees warmer for the
valleys and inland coastal areas.
Long term (monday through thursday)...
the trend for the offshore low for early next week continues to
be weaker. High pressure aloft over the eastern Pacific will
extend across Southern California. Offshore lower level flow on
Monday will become weaker on Tuesday and become weak onshore for
Wednesday and Thursday.
For late Sunday night into Monday morning therw will be gusty
northeast winds to 35 mph near the coastal slopes of the
mountains. Weaker northeast winds of 25 mph or less will then
continue into Tuesday morning.
High temperatures will warm on Monday and continue to warm for
inland areas on Tuesday with slight cooling near the coast on
Tuesday. Weak onshore will spread cooling inland on Wednesday and
Thursday with high temperatures on Thursday closer to average.
180900z...coast/valleys...areas of stratus with bases 2000-3000 ft
mean sea level and tops to 5000 ft mean sea level over the coasts and valleys. Most
airports varying between scattered and broken clouds, with all areas clearing
by 17z. After 17z, mostly clear. Patchy low clouds with bases below
1000 ft mean sea level and fog may develop late tonight into early Sat morning
along the immediate coast, but confidence in ceilings and vis
restrictions at the coastal airports is low.
Mountains/deserts...local terrain obscurations in clouds below 5000
ft mean sea level on the west/South Mountain slopes this morning, clearing by
16z. After 16z, mostly clear with unrestricted vis through Sat
West to northwest sfc winds with gusts 25 to 35 kt will continue
through mountain passes and on desert slopes through 12z, weakening
and becoming northerly during the late morning.
a northwest swell from 290 degrees will produce seas of 6-8 feet
through late this morning in the outer waters south of San Clemente
Island. A short period will generate steep waves that could be
hazardous to small craft. Seas will lower this afternoon.
the trend for offshore winds for Sunday into early next week
continues to be weaker. Weak offshore flow will develop on Sunday
and become a little stronger for late Sunday nigbt into Monday
morning with gusty northeast winds to 35 mph near the coastal
slopes of the mountains. Weaker northeast winds of 25 mph or less
will then continue into Tuesday morning.
Lowest daytime humidity for inland areas will fall to around 10
percent on Monday and Tuesday with elevated to locally critical
fire weather conditions for the mountains and inland valleys on
Monday and elevated conditions for those areas on Tuesday. Weak
onshore flow on Wednesday and Thursday will spread cooling and
higher coastal humidity inland.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.