Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 301023 CCA
AREA FORECAST DISCUSSION
National Weather Service San Diego CA
318 AM PDT THU JUN 30 2016
High pressure aloft will weaken and result in a cooling trend the
rest of this week and for the upcoming holiday weekend. There is a
small chance of showers and storms over the mountains this afternoon
and early evening, and again Friday afternoon and early evening. Dry
conditions prevailing by the weekend. Areas of night and morning
coastal low clouds and fog will expand slightly through the end of
the week, along with gusty west to southwest winds over the
mountains and deserts. The high pressure ridge will rebuild early
next week and bring slight warming.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
The marine layer is a touch deeper this morning with low stratus
decks already moving into the western valleys. Expect some stratus
will reach portions of the inland empire around Ontario by
daybreak as well. Substantial cooling has taken place aloft and
temperatures will be noticeably "not quite as hot" for inland
locations, beginning today. Inland Temperatures should be about 5
degrees cooler, to as much as 10 degrees cooler compared to
yesterday in some spots.
Slightly deeper marine layer will bring the low stratus decks
relatively far inland for late tonight into early Friday morning,
with clouds filling much of the valleys during that timeframe,
which patchy fog along the coast and where low clouds intersect
with hilly terrain.
Weak instability and weak residual moisture over the mountains,
coupled with some weak PVA should be sufficient to generate a few
showers and storms over the higher mountains this afternoon and
again Friday afternoon and early evening.
Continued slight cooling will take place Friday and Saturday as
well as a weak low forms off the Central California Coast and
helps to usher in a more pronounced onshore flow and drier NW flow
aloft for our region. Shortwave trough will exit the San Joaquin
Valley by Sunday and introduce a more pronounced zonal flow to the
The latest medium range models continue to have some
disagreements, mainly regarding the strength and placement of
next weeks high pres ridge, with the EC now favoring a position
around or to the south of the border through much of next week,
which would keep any subtropical moisture "return flow" from
reaching Socal. The GFS has been consistently showing a more
southerly placement, also it is trending a bit stronger with the
PacNW troughing through the end of next week, which could support
the further south position of the ridge south of the border
better. The ensembles also are having trouble nudging the ridge
much to the north of Socal, with the PacNW trough showing some
southward expansion. Therefore, it seems like more of a
persistence forecast is the way to go for the forecast towards mid
to late next week, but with some slight warmup away from the coast
due to the persistent ridge likely to be near or just to the south
for much of mid to late next week. Will also not add any mention
of precipitation for the time being due to the ridge position.
301000Z...Coast/Valleys...BKN-OVC low clouds with bases from 800-
1400 feet MSL and tops 1200-1700 feet MSL will continue to build
through 14z over the coast and western valleys. Local visibilities
of 2 SM or less will occur in fog and haze over the coastal mesas
and higher terrain of the western valleys. Low clouds will pull back
to the immediate coast and become patchy after 15z. Light westerly
sea breezes are expected after 17z...with low clouds rebuilding over
the coastal TAF sites after 03z Thursday.
Mountains and Deserts...SKC and unrestricted visibility will prevail
through Thursday night.
300 am...No hazardous marine weather is expected through Monday.
300 am...A long period southerly swell from 200 degrees will
continue to impact local beaches through at least Friday. The swell
will peak Thursday at 3-4 ft with a period of 17-19 sec. This will
produce 3-6 ft surf with local sets to 7 ft along southwest facing
beaches through Friday. Strong rip and longshore currents are also
expected. Please see the Beach Hazard Statement for additional
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
CA...Beach Hazards Statement through Friday evening for Orange County
Coastal Areas-San Diego County Coastal Areas.