Scientific Forecaster Discussion
fxus66 ksgx 280544
Area forecast discussion
National Weather Service San Diego California
944 PM PST Mon Feb 27 2017
moderate to locally heavy rain will continue across San Diego
County and southeast portions of the inland Empire this evening as
a low pressure trough pulls a deep moist layer inland. Some snow
will fall on the higher mountain peaks to the north as well.
Precipitation will taper off tonight, ending by Tuesday morning.
Slightly warmer Tuesday, then dry with a warming trend for
Wednesday through Friday with periods of weak offshore flow. A
little cooler next weekend.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Update...moderate to heavy rainfall is ongoing over portions of
San Diego County through the late evening. Rainfall rates across
portions of the County are on the order of one-third to one-half
inch per hour. Further north rates are generally one-tenth inch
per hour or less. Expect heavy rain to continue through about 11
PM, then start to decrease as an upper level trough pushes the
deep moisture to the southeast. Showers will end by Tuesday
morning. Additional rainfall totals of one-quarter to one-half
inch are possible in San Diego County, locally up to 1 inch along
the southwest facing mountain slopes. Elsewhere accumulations will
be less than one-quarter inch.Given the ongoing precipitation, the
Flash Flood Watch has been extended through 2 am for San Diego
Moderate flooding is now forecast for the San Diego River tonight
and large flows are likely in other rivers and streams across the
County as well. Of particular concern is the tijuana River Valley
where low-lying areas will likley have flooding. Flood waters will
begin to rapidly recede late tonight into Tuesday morning.
From previous discussion...
The large upper-level trough responsible for drawing in the Pacific
moisture today will move east of the area tonight. Atmospheric
heights/thickness will gradually rise as low level winds turn
offshore. It will be fair and slightly warmer on Tuesday, then much
warmer and dry Wednesday through Friday with clear, cool nights.
Another trough will develop over the pacnw next weekend and suppress
heights across socal while allowing sfc wind to turn back onshore.
This will allow relative humidity to increase and perhaps bring back some low
clouds and fog to coastal areas by Sunday morning.
280515z...rains will gradually decrease 07z-10z over San Diego
County and western Riverside County. Areas of cigs in these areas
will continue to be 700-1700 ft mean sea level with local vis 2-4 mi through
around 09z, including vcnty ksan, kcrq, kmyf, krnm as well as kpsp,
ktrm. Higher terrain, including mountains, will be obscured
in clouds. Otherwise, cigs will be mostly 1500-3000 ft mean sea level with a
chance of fog with vis 2-4 mi in the valleys late. Fog will be
possible 10z-16z Tue vcnty kpsp and ktrm with a possible cig below
1000 ft mean sea level. VFR conditions will prevail in most areas after 16z
Local westerly surface winds 20-30 kt with gusts 35-45 kt will
continue along mountain crests, desert slopes and near passes
through 18z Tue along with low level wind shear and strong up/downdrafts.
winds have shifted to the west-northwest and will increase slightly
overnight to mostly 15-20 knots with gusts to 25 knots, especially
in the outer waters. A Small Craft Advisory remains in effect
through 9 am Tuesday.
Skywarn activation is requested through 12 am. Skywarn activation
will not be needed Tuesday.
California...Flash Flood Watch until 2 am PST Tuesday for San Diego County
coastal areas-San Diego County mountains-San Diego County
Pz...Small Craft Advisory for winds until 9 am PST Tuesday for waters
from San Mateo Point to the Mexican border extending 30 to
60 nm out including San Clemente Island.
Small Craft Advisory until 9 am PST Tuesday for coastal waters
from San Mateo Point to the Mexican border and out to 30 nm.