Area forecast discussion
National Weather Service San Diego California
902 PM PDT Sat may 18 2013
Synopsis...
high pressure over the east Pacific will expand over California
through Tuesday bringing drier and warmer conditions...and a
shallower marine layer. A period of gusty offshore winds is possible
Monday morning along the coastal foothills...helping to push daytime
temperatures back above normal. Cooler by Wednesday and for the
remainder of the week as an upper-level low deepens south along the
West Coast and onshore flow increases. The marine layer and
associated low clouds will become more extensive through Friday...
and gusty westerly winds will affect the mountains and deserts.
&&
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
counties...
Other than scattered clouds over the coastal waters...skies were
clear across the region early this evening. Surface pressure
gradients were running 4-8 mbs onshore with 25-30 miles per hour and locally
stronger wind gusts in the windier mountain and desert spots. The
00z Miramar sounding had a weak inversion based near 3k feet.
High pressure over the eastpac and low pressure over the Great Basin
will continue a dry...northwest flow over California through Tuesday. Heights/thickness
will slowly build over socal...while the marine layer decreases...
limiting nocturnal low clouds/fog to coastal and western valleys
areas. A short-wave trough sliding southeast in that flow toward northwest Arizona by
Monday morning will temporarily build surface pressure over Nevada and force an
offshore flow over inland portions of the County Warning Area. Winds will weaken and
turn back onshore later in the day and remain onshore for the
balance of the week as an upper-level low pressure trough deepens
south along the West Coast and the marine layer deepens. Seasonally
gusty westerly winds will redevelop Wednesday through Friday through the
mountains and into the deserts each evening. Warmest days will be
Monday and Tuesday...with a cooling trend bringing temperatures back to near
normal for the remainder of the week.
One potential issue will surface on Monday morning when it appears some
gusty offshore winds could develop below the passes and canyons. At
the same time...dew points will be falling and temperatures rising sharply.
This would increase the threat of wildfire. Later in the day...the
winds will weaken and turn back onshore...but it will continue quite
warm and dry far inland into Tuesday. The local wrfems indicates the
offshore will have little effect over coastal areas with the marine
layer remaining intact.
Medium range guidance suggests general troughing should hold over
the west through next weekend with a moderate marine layer and temperatures
close to average.
&&
Aviation...
190330z...coast/valleys...few low clouds with bases 1200-1500 feet mean sea level
and tops to 1800 feet mean sea level are currently increasing over the coastal
waters. The clouds will spread inland overnight...impacting ksan and
kcrq with broken-overcast ceilings 1000-1200 feet mean sea level after 05z...and impacting ksna
with broken-overcast ceilings around 1200 feet mean sea level after 07z. By 12z...low clouds
and fog could reach 10-15 miles inland. Low clouds are not likely to
reach kont...although visible may lower to 3-5sm by 12z. Expect clearing
to the coast between 16z and 18z.
Mtns/deserts...unrestricted visible and sky clear through Sunday morning. West to
northwest winds with gusts of 25-35 knots will continue to create moderate-strong
uddfs and low level wind shear over the mountains and adjacent desert slopes through
tonight.
&&
Marine...
a long-period southwest swell from the South Pacific will arrive
tomorrow and continue through Wednesday...bringing elevated surf and
strong rip currents to south and southwest facing beaches.
&&
Fire weather...
much warmer and drier conditions will develop over the Southland on
Sunday and Monday...with daytime temperatures rising 5 to 15 degrees
above normal by Monday. Daytime relative humidity values will also
fall into the lower teens and single digits on Monday...following
moderate to locally poor overnight recoveries.
There is also the potential for some moderate and gusty northeast
winds to develop over the coastal foothills of the San Bernardino
Mountains...the Santa Ana Mountains...and the Riverside County
mountains late Sunday night into Monday morning. Although
widespread gusts appear to remain around 30 miles per hour at this time...some
of the favored windy spots through and below the canyons and passes
may see local gusts up to 40 miles per hour. The duration of these northeast
winds will be relatively short lived...so no highlights are
anticipated at this time. However...these gusty winds will combine
with the very warm and dry conditions on Monday to elevate the
wildfire danger across portions of San Bernardino...Orange...and
Riverside counties.
&&
Sgx watches/warnings/advisories...none.
&&
$$
Public...jad
aviation/marine...pg
fire weather...Palmer
