Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 280404
Area Forecast Discussion
National Weather Service San Diego CA
904 PM PDT TUE SEP 27 2016
A low pressure will continue to move north over the area through
Thursday, bringing variable mid and high clouds and a chance of
scattered showers and isolated thunderstorms. The best chance of
precipitation will be on Wednesday. Gradual cooling through the
end of the week as onshore flow strengthens and the marine layer
slowly returns. Much cooler by the weekend with gusty westerly
winds over the mountains and deserts.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Scattered mid and high clouds continue to move in from the
northeast this evening as the upper level low centered over the
southern Colorado River Valley continues to drift north. Virga and
light showers were observed this afternoon, with a few mountain
locations picking up one-hundredth of an inch of rain. Shower
activity has since diminished, and have scaled back overnight
precip to just the highest mountain peaks. Surface pressure
gradients are nearly neutral to the Mojave Desert, and weakly
onshore to the Imperial Valley. As a result, temperatures are
running around 3 to as much as 15 degrees lower compared to this
Mid-level moisture over the area is still on the rise, now up to
1.32 in of precipitable water on the 00Z KNKX sounding. Wednesday
still looks like the best chance for showers and isolated thunderstorms,
mainly over the mountains, high desert, and inland valleys as
moisture and instability peak. The cooling trend will continue as
the upper low moves overhead and onshore flow increases. Some
drying will occur on Thursday as the low begins to lift to the
northeast, though enough moisture will remain for a slight chance
of showers and thunderstorms over the higher peaks of the
mountains. By Friday, dry and fair weather will prevail as
moisture decreases further. High temperatures will remain near to
slightly above average through Friday.
For Saturday through early next week, a longwave trough amplifying
along the West Coast will bring more considerable cooling with
temperatures dipping below normal. Marine stratus will return this
weekend, extending further inland each night as the marine layer
deepens. Gusty onshore winds will develop at times in the
mountains and deserts, mainly during the afternoons and evenings.
280245Z...SCT-BKN clouds AOA 8,000 ft MSL, unrestricted visibility
and light winds will prevail through Wednesday evening. There is a
slight chance of showers and thunderstorms over the mountains,
deserts, and Inland Empire Wednesday afternoon. Any storms that form
will produce local visibility restrictions and moderate to strong
No hazardous marine weather is expected through Sunday night.
A 2-3 ft south swell at 170-190 degrees will filter into the SoCal
bight Thursday and linger through the weekend. Given the swell
period of 14-18 seconds, 3 to 6 foot surf will be possible late
Thursday through at least Sunday at local beaches. The highest sets
should arrive along southwest facing beaches in OC and Northern SD
counties Friday and Saturday. Increased rip current frequency and
strength will accompany the elevated surf.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.