Area forecast discussion
National Weather Service San Diego California
909 PM PDT sun may 19 2013
Synopsis...
a high pressure ridge aloft will drift over Southern California
through Tuesday bringing warmer days and locally gusty offshore
winds near the foothills. Closer to the coast...the marine layer
will continue to bring night and morning low clouds and fog...and
seasonal temperatures. The ridge will be replaced by a large low
pressure trough for the latter half of the week. The trough will
generate stronger onshore flow...cooling...and more extensive
marine clouds. Slightly warmer next weekend as the upper low
retreats farther north and the marine layer shrinks back toward
the coast.
&&
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
counties...
Skies were clear over the region this evening. Although stratus was
lurking south of our coastal waters at 9 PM PDT. Southerly flow was
observed along the coast indicating a weak eddy offshore. Surface
pressure gradients were weak offshore to Nevada...and moderate onshore
to the lower deserts. Strongest westerly wind gusts were mostly
under 25 miles per hour this evening. The 00z Miramar sounding had a 4 degree c
inversion base near 1900 feet.
With southerly flow along the coast and moderate onshore pressure
gradients to the east...expect the marine stratus will soon make a
move northward along the Baja California coast...or just form. Arrival may be
very late over Orange County...but by morning marine it is likely
that clouds will blanket the coast and western valleys...along with
patchy fog.
A strong ridge of high pressure remains over the eastpac along
130w...while a large trough covers the Great Plains and The Rockies.
California is caught between these blocky systems in northwest flow aloft. Changes
are in the works over the next several days as the ridge over the
Pacific flattens...and an unusually deep upper low drops south out
of the Canadian northwest territories toward the pacnw. This cold...cut-
off system will stall and spin along the West Coast much of the week
before weakening and lifting back to the north next weekend. The
result will be a brief warm-up Monday...then a pronounced cooling trend
through Thursday....followed by a modest warm-up next weekend.
Winds will briefly turn offshore on Monday morning...and may be locally
gusty below the Cajon and morongo passes...then go back onshore in
the afternoon. For the midweek period...westerly winds will increase
through the mountains and deserts...becoming strong and gusty in the
late afternoons and evenings. Advisory strength winds look possible
again Wednesday/Thursday as surface pressure falls sharply over Nevada.
Expect the marine stratus to eventually build back over coastal and
western valley areas overnight...and may take a bit longer to burn
off Monday morning with a coastal eddy and stronger marine inversion
expected. After the marine clouds burn away...expect mostly sunny
skies by midday and seasonal temperatures both Monday and Tuesday over
coastal areas. Much warmer inland Monday...with slight cooling Tuesday.
Then...cooler again Wednesday through Friday with maximum temperatures a few degrees
below normal.
Looking ahead to next week...models favor troughing along the West
Coast. This should maintain onshore flow...a moderate marine
layer...and seasonal to slightly below average temperatures through
at least the first half of the week.
&&
Aviation...
200330z...coast/valleys...skis are currently clear with unrestricted
visible. The timing is uncertain...but low clouds will return to the
coastal areas tonight. Possibly impacting ksan and kcrq as early as
06z. Ceilings will likely be around 1500 feet mean sea level and tops to near 2000 feet
mean sea level. Ceilings are expected to lower to around 1000 feet mean sea level by 12z with
low clouds extending 10-15 miles inland. However...low ceilings and fog
are not expected to reach kont. Low clouds and fog will clear to the
coast between 15z and 17z.
Mtns/deserts...unrestricted visible and sky clear through Monday.
&&
Marine...
a 3 foot long-period SW swell from the South Pacific will continue
through midweek...creating elevated surf and strong rip currents
along south and southwest facing beaches. Maximum sets will be around
6 feet.
6 to 8 foot short-period northwest swells will move into the outer
coastal waters Wednesday and Thursday...bringing choppy seas to
areas south and east of San Clemente Island. The increasing northwest
swells will also bring elevated surf to exposed west facing shores.
&&
Fire weather...
Monday will be the warmest day across the Southland...with daytime
temperatures ranging between 5 and 15 degrees above normal across
the inland areas. Daytime relative humidity values will also fall
to between 10 and 15 percent on Monday. These dry and warm
conditions will combine with a light to locally moderate north to
northeast wind to elevate the wildfire danger across the coastal
foothills of San Bernardino...Orange...and Riverside counties on
Monday. This wind event will be relatively short-lived...as the
winds turn back onshore by Monday afternoon.
&&
Sgx watches/warnings/advisories...none.
&&
$$
Public...jad
fire...Palmer
aviation/marine...pg
