Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 240927
Area Forecast Discussion
National Weather Service San Diego CA
227 AM PDT Mon Oct 24 2016
Scattered showers and isolated thunderstorms will continue through
this afternoon as a weak low pressure trough moves across the
region. Fair and warmer midweek as high pressure rebuilds aloft.
Another low pressure trough will bring more clouds...cooling...and
a chance of precipitation late in the week.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Showers and thunderstorms continue to move north-northeast across
the region this morning, mainly over Orange, Riverside, and San
Bernardino Counties. The main band of precipitation has begun to
shift east slightly with shower activity increasing over portions
of San Diego County. This eastward trend will continue through the
afternoon as a short-wave trough rotating around the base of the
upper low off the coast lifts northeast and weakens. Both the NAM,
and to a lesser extent, the GFS, show increasing elevated
instability and a 110 kt jet streak nosing into the area this
afternoon. This will maintain the chance of showers and
thunderstorms through the day, with precipitation gradually
tapering off from west to east by late afternoon as drier air
filters into Southern California.
Marine layer low clouds and fog may develop west of the mountains
tonight, though given the weak marine inversion expect coverage to
be patchy. Warmer and drier conditions will prevail Tuesday and
Wednesday as an upper level ridge builds over the Desert
Southwest. Night and morning low clouds and fog will prevail in
the coastal areas and western valleys. Highs west of the mountains
will be near to slightly below normal, and around 3-5 degrees
above normal in the mountains and deserts.
Some cooling takes place Thursday as the ridge shifts east and an
upper level trough begins to push into Central and Southern
California. Latest guidance from the GFS and EC have slowed down
the progression of this system, keeping any precip out of the area
until early Friday. It still appears that some subtropical
moisture may be entrained into Southern California ahead of the
upper low, however, the low rapidly weakens as it lifts northeast
across Central California, keeping the bulk of the precipitation
to the northwest of the forecast area. There is chance of
light precipitation on Friday into early Saturday, with the best
chances in Orange County and western portions of San Bernardino
and Riverside Counties. Minor warming over the weekend as the
ridge rebuilds to the southeast.
240900Z...Scattered showers and a slight chance of tstorms will
continue today. Cloud bases will be as low as 5000 feet msl in
showers, but mostly in variable layers above 10000 feet. Vis locally
reduced 3-5sm in heavier showers. Precip chance ends after 00Z and
skies will gradually thin of clouds this evening.
Slight chance of tstorms today, but mainly this morning. The biggest
threat would be cloud-to-water lightning. The Marine Weather
Statement highlights this threat through midday. Otherwise, no
hazardous marine weather is expected through Friday.
Slight chance of tstorms, but mainly this morning. Isolated
lightning strikes on the beaches are possible. A beach hazards
statement would be issued if/when lightning strikes are imminent.
Skywarn activation is not requested at this time. However weather
spotters are encouraged to report significant weather conditions.