Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 290348
Area Forecast Discussion
National Weather Service San Diego CA
848 PM PDT WED SEP 28 2016
The upper level low will move northeast of the region Thursday
through Friday, followed by a longwave trough moving in from the
west this weekend into early next week. Residual moisture will
continue the threat of showers and thunderstorms over the
mountains on Thursday. Cooling and drying is expected for Friday
through early next as onshore flow strengthens and the marine
layer slowly returns. Gusty winds will develop over the mountains
and deserts, strongest on Sunday and Monday.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Evening radar imagery indicates showers and thunderstorms have
dissipated over the forecast area. Any lingering light showers to
the west and northeast are slowly dissipating as well. The center
of the upper low is currently near Las Vegas and will continue to
lift northeast overnight. Weak easterly flow near 700 mb will help
maintain some mid-level moisture for Thursday, so a slight chance
of showers and thunderstorms remains in the forecast for the
mountains tomorrow afternoon.
A large long wave trough amplifies along the West Coast on Friday,
bringing drier southwest flow aloft. Some marine stratus may
return to the beaches as early as Friday morning as onshore flow
strengthens. The trough then digs and slowly progresses inland
Saturday through Monday, which will help deepen the marine layer
for more widespread night and morning low clouds and bring
considerable cooling. Gusty onshore winds will develop in the
mountains and deserts, strongest on Sunday and Monday as the main
trough axis moves through. High temperatures will be near to
slightly below normal on Saturday, and around 5 to 15 degrees
below normal Sunday and Monday. Temperatures star to rebound on
Tuesday as the trough moves off to the east and weak offshore flow
290200Z...Scattered clouds at or above 10K FT, otherwise clear with
unrestricted vis through Thu. There will be a chance for isolated
showers and thunderstorms in the mountains again Tue afternoon but
activity should be more isolated than today.
No hazardous marine weather is expected through Friday. Northwest
winds will increase over the outer waters Saturday afternoon as a
trough deepens along the West Coast. The strongest winds will arrive
on Sunday and Monday when Small Craft Advisories may be needed over
the Outer Waters.
A building south swell tonight will bring elevated surf of 3-5 feet
Thursday and Friday. Sets to 6 feet are possible in Orange County.
The south swell decreases slightly over the weekend, but above
average surf of 2-5 ft will continue, highest in Orange County.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.