Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 180422

Area Forecast Discussion
National Weather Service San Diego CA
922 PM PDT Sat Mar 17 2018

A few light rain and snow showers remain possible through early
Sunday morning. Quiet, dry and slightly warmer weather is
anticipated Sunday into Tuesday. By the second half of the
workweek focus shifts toward the arrival of our next storm system
and a potentially strong atmospheric river in Southern California.
Though precise timing and rainfall amounts remain up in the air,
a period of heavy rainfall looks likely sometime between
Wednesday and Friday morning. Flooding appears possible with this



At 9 PM...Skies were mostly cloudy with the tail end of an upper
level trough just beginning to swing through the region. Widely
scattered light-moderate showers were showing up on radar. At the
surface, winds were light apart from the desert slopes, where a
few gusts into the 30s were still being reported.

Scattered light showers will continue overnight for the mountains
westward, instigated by the passage of the upper trough and a
shallow layer of instability below 700 mb. Parts of San Diego
County may see 0.10-0.25 inches of precipitation overnight,
otherwise totals will be limited to just a couple hundredths. Snow
showers remain possible above 4,000 ft, but any accumulations
should be limited to a couple inches at most.

The weather pattern will return to a docile state Sunday-Tuesday
as ridging develops over the Southwest. During this period
temperatures will trend upward and dry weather will prevail.

Conditions are expected to shift in a soggier direction during
the second half of the workweek as a storm system off the coast
drags a strong atmospheric river into the southern half of
California. Though timing differences of around 12-36 hours remain
between the global models, run to run model consistency in the
track/depth of moisture result in moderate-high forecaster
confidence in the occurrence of a significant precipitation event.
Best projections right now suggest moderate to heavy rain
developing north of L.A. as early as Tuesday evening, with the
heaviest precipitation pushing slowly south through San Diego by
early Friday. At this time there appears to be a potential for
rain rates in the 0.5-0.75 inch per hour range, urban flooding,
and debris flows near recent burn scars. Those with interests that
may be impacted should monitor the forecast closely over the
coming days. Though rain amounts may be significant during this
period, the warm nature of this system should limit the potential
for snow. Snow levels will likely remaining at or above 8,000 ft
for most of the storm.


180400Z...SHRA will continue overnight as a system moves across the
region. Low cloud bases will range from 1500-2500 ft MSL in showers,
and remain above 3000 ft MSL for other areas. Small hail is possible
in the heavier showers, along with reduced VIS to 2 SM. Mountains
will be obscured at times in the clouds. Westerly wind gusts of 35-
45 kt are possible along desert mountain slopes tonight. Conditions
will improve by early Sunday morning, with VFR conditions most areas.


West-northwest winds of 15-25 kt will continue through tonight as a
system moves across the area. A Small Craft Advisory remains in
effect from through 4 AM Sunday.

Showers will continue at times through Sunday morning.


Skywarn activation will not be needed today.


CA...Winter Weather Advisory until 3 AM PDT Sunday for Riverside
     County Mountains-San Bernardino County Mountains-San Diego
     County Mountains.

PZ...Small Craft Advisory until 4 AM PDT Sunday 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 Clemente Island.



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