Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
130 PM PST Tuesday Nov 24 2015
Synopsis... a winter storm over the Pacific northwest will bring
colder weather and periods of mostly light showers to Southern
California tonight through the weekend. Gusty west winds will impact
the mountains tonight through Wednesday morning.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
A deep...cold upper low over the Oregon/California border will move
south tonight...stall over the Great Basin Wednesday through
Sunday...and bring an extended period of cool weather that will
persist through the weekend. A series of shortwaves rotating around
the base of the trough will move across Southern California and
bring scattered light showers at times. The first shortwave over
central California this afternoon will bring showers to socal
tonight as it moves across the region. The lack of strong dynamic
forcing will keep the precipitation amts fairly light in most areas...but
the lifting along the surface cold front should produce scattered
showers just about anywhere from the mountains to the coast. Freezing
levels start out around 7000 feet this evening...then lower to 5000-
6000 feet Wednesday morning when some light accumulation is possible
in the San Bernardino and San Jacinto Mountains much colder Wednesday
behind the cold front.
The storm is already bringing strong winds to the mountains and high
deserts where 20-30 miles per hour winds were gusting to 45 miles per hour. Pressure
gradients have done a complete reversal the past 24 hours with the
gradient san-tph going from -2.2 mb at 20z yesterday to +8.6 mb at
20z today. This is also helping to deepen the marine layer and
increase coastal zone dewpoints by 15 to 25 degrees over the past 24
hours. Still very dry in the mountains though with dewpoints only in
A quasi-stationary amplified weather pattern will persist through
the end of the week with a closed low stalled over the Great Basin.
Weak impulses rotating around the backside of the closed upper low
are will track close to socal. Moisture will be limited...but these
impulses could trigger episodes of light showers Thursday through
Forecast precipitation amounts have not changed. Rainfall amounts
through Thursday will range from one tenth inch or less near the
coast to one quarter to locally one half inch in the mountains. For
San Diego County...rainfall amounts will range from around one
quarter inch near the coast to locally two thirds of an inch in the
mountains. A few inches of snow may accumulate in the mountains
above 5000 feet.
Early next week the closed low is finally ejected eastward by a
trough moving in from the eastern Pacific. Weak ridging over socal
will bring minor warming Monday.
Aviation... 242100z...coast/valleys...sct low clouds along the
coast... increasing this afternoon with bases 1800 feet
mean sea level...otherwise few middle/high clouds above 10000 feet mean sea level. Broken-overcast
conditions developing after 25/0600z with bases 2000-2500 feet along the
coast then spreading into the valleys this evening...reaching the
lower coastal slopes of the mountains tonight. Light rain showers
reducing visible to 5sm in spots...in Orange County and the inland
Empire after 25/0000z...then spreading southward to San Diego County
after 25/0600z. Remaining overcast tonight with scattered showers. Cloud
bases 2500-3500 feet mean sea level and tops ranging from 4000-6000 feet mean sea level.
Westerly winds increasing after 24/0600z 10-15 knots along the
immediate coast...affecting the coastal sites. Continued gusty
Mountains/deserts...scattered middle and high clouds with unrestricted visible
through this evening. -Shra developing along and west of the mountains
and over the high deserts after 25/0600z this evening with -shra
continuing through the day on Wednesday. Coastal slopes of the mountains
will be obscured in clouds/precip.
Areas of west surface winds 20-30 knots with gusts 35-45 knots will occur this
afternoon through Wednesday morning on the Desert Mountain slopes and
through San Gorgonio Pass...with locally strong up/downdrafts and
low level wind shear. Expect gusty conditions as well in the upper desserts.
Marine... 100 PM...a trough moving through the region will bring west-
northwest winds 20-25 knots with combined seas of 5-8 feet late tonight into
Wednesday night....creating hazardous conditions for small craft. A
few showers will occur this evening through early Thursday morning
as well. Conditions will improve Thursday.
Beaches... 100 PM...astronomical high tides will reach at least 7
feet each morning through Friday. Predicted highest tides along the
open coast of San Diego and Orange counties will be:
Wednesday: 7.6 feet at 751 am PST
thursday: 7.5 feet at 831 am PST
friday: 7.3 feet at 912 am PST
There is a threat of minor coastal flooding through Friday
during morning high tides. Elevated surf of 3 to 4 feet could add to
the flooding threat...especially Wednesday morning. Strong rip
currents will likely develop with the elevated surf Wednesday and
during the transition from high to low tide each morning. Conditions
will improve late this week.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...Wind Advisory from 6 PM this evening to 10 am PST Wednesday for
Riverside County mountains-San Diego County mountains-San
Gorgonio Pass near Banning.
Wind Advisory until 10 am PST Wednesday for San
Bernardino County mountains.
Coastal Flood Advisory until noon PST Friday for Orange County
coastal areas-San Diego County coastal areas.
Pz...Small Craft Advisory from 3 am Wednesday to 3 am PST Thursday
for coastal waters from San Mateo Point to the Mexican
border and out to 30 nm-waters from San Mateo Point to the
Mexican border extending 30 to 60 nm out including San