Scientific Forecaster Discussion
fxus66 ksgx 081146
Area forecast discussion
National Weather Service San Diego California
335 am PST sun Dec 8 2019
moist southwest flow aloft will bring periods of light rain and high
elevation snowfall today. Showers will end late tonight after a cold
front moves south across the region. Weak high pressure aloft will
bring dry weather Monday and Tuesday. Another ridge of high pressure
will bring even warmer days Thursday and Friday.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Six-hour rain totals ending at 3 am today ranged from the low end of
0.01"-0.05" in the coastal and valley zones to the higher values of
0.10"-0.25" on the west and southwest facing mountain slopes. This
pattern will continue through the morning with a steady stream of
tropical moisture moving in from the southwest.
This afternoon the pwats that were near 1.45" early this morning
will fall to around 1.00" as the tropical moisture plume is forced
south by a longwave trough moving in from the north. The
precipitation will become more convective in nature as shortwaves
round the base of the trough this afternoon/evening. Cold air aloft
and positive vorticity advection will destabilize the atmosphere with scattered light to
moderate showers possible just about anywhere. Southwest onshore
winds ahead of the trough will be a little stronger this
afternoon/evening which should continue to enhance precipitation
amounts on the west/southwest facing mountain slopes.
Showers will taper off tonight as the trough axis moves east. Snow
levels near 7,500 feet this morning will steadily fall during the
day to around 6000 feet tonight with a few inches of snow in the
Monday through Friday...a ridge building over the West Coast Tuesday
gets flattened Wednesday by a weak shortwave, but the ridge then
morphs into an elongated east-west oriented 592 dm high over the
eastern Pacific. This pattern will bring dry, warmer weather
Thursday and Friday. Ensemble blends show the ridge weakening for
minor cooling Saturday and Sunday but temperatures will still be at
or above normal.
081010z...coasts/valleys...bkn-ovc cigs with bases 1500-2500 ft msl,
locally 600-800 ft mean sea level at times, through 20z. After 20z broken-overcast cigs
2500-4000 ft msl, locally lower in areas of -ra. Periods of
-ra through Sun night, with greatest coverage 15z-23z sun. Reduced
vis 2-5 miles possible in areas of -ra.
Mountains...-ra will continue at times through sun evening with some
-sn above 7000 feet mean sea level Sunday and 6000 feet mean sea level Sunday evening.
Widespread terrain obscurations in -ra/-sn/fg will occur. West winds
with gusts to 35 kt over the mountains will bring weak-moderate
up/downdrafts and low level wind shear over and east of the mtns 12z sun-06z Mon.
Deserts...isolated -ra possible through sun with broken-overcast cigs 4000-
7000 ft mean sea level. Local vis 3-5 miles will be possible in -ra through
sun. Mid-high level clouds expected to clear by sun evening.
scattered rain showers at times through Sunday night. Combined seas
of 6 to 8 ft are expected through Sunday evening.
a high surf advisory remains in effect through 4 am Monday for long-
period west to northwest swells of 10 to 14 seconds. Swells will
peak this morning, and subside by Monday morning. Surf of 5-8 ft
will continue in San Diego County with 4-7 ft surf on beaches prone
to west-northwest swells in Orange County.
California...high surf advisory until 4 am PST Monday for Orange County
coastal areas-San Diego County coastal areas.