Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
800 PM PST Monday Dec 9 2013
strong high pressure over the Great Basin will continue gusty east
to northeast winds through and below passes and canyons through
Tuesday morning. The cold...dry air mass will bring areas of near
freezing temperatures in wind sheltered parts of the valleys...
deserts...and even near the coast. There will be a warming trend
through Wednesday...along with periods of high cirrus clouds at
times to decorate sunrises and sunsets. The weather will remain dry
through at least next weekend.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Strong NE-east winds continue to funnel through the passes and canyons
this evening as cold...dry...dense air piles up against our Desert
Mountain slopes due to strong high pressure over the Great Basin. At
7 PM PST...winds were still gusting over 40 miles per hour over portions of the
San Diego County mountains...the Santa Ana Mountains....and west of
Banning. Strong offshore pressure gradient trends were observed from
Nevada. At 7 PM PST...it was 12 mbs from Tonopah. Earlier today...winds
peaked at 86 miles per hour at Fremont Canyon in Orange County. See our web
Page at www.Wrh.NOAA.Gov/sgx for a link to the strongest observed
wind gusts today. A High Wind Warning and wind advisories are still
in effect below the Cajon Pass and in the coastal foothill areas of
the mountains. Please see laxnpwsgx for details.
Infrared satellite imagery this evening shows a large area of clouds
spinning well off the socal coast. High clouds associated with this
cut-off low are drifting east and thinning as they drift over the
County Warning Area. Thicker clouds are to the south and well offshore.
The highly amplified flow aloft with a ridge along 140w...and a
deep north.A. Trough to the east of California...will gradually flatten through
midweek. A cut-off low beneath the ridge...about 500 nm SW of San
Diego...will send patchy high cirrus clouds our way through Thursday as
it slowly drifts east. The low is forecast to pass to our south on
Thursday and get absorbed into the westerlies by the end of the week. The
low will have little if any weather effects over socal except for
the high clouds...but it will retard height/thickness recovery over
the region and support weakened offshore gradients.
With the cut-off out of the picture later this week...heights/
thickness will rebound and bring temperatures over socal back above normal
by the weekend under dry...northwest flow aloft. Another cut-off may
approach the coast early next week...but there is too much spread in
model solutions at this time to determine if it will affect socal at
Winds will increase again overnight near the foothills...but should
otherwise drop off in the valleys. With the cirrus clouds expected
to remain thin...and the dewpoints very low...minimum temperatures
will take a nose dive where winds do not stir. Where winds remain
active...it will be warmer...so expect a lot of variability in temperatures
overnight. Many areas will fall below freezing by morning...but rise
quickly Tuesday morning. A frost advisory is in effect for the lower
deserts...and west of the mountains except o... more wind is expected
100330z...sct-bkn clouds at or above 15000 feet mean sea level and unrestricted visible
through Tuesday night. Areas of NE to east winds 15-25 kts gusting to
45 kts below favored passes/canyons with moderate-strong uddfs/low level wind shear over the
mountains and adjacent coastal foothills through Tuesday morning...weakening
a few hours of critical or near critical fire weather conditions
occurred today in mountain areas and below canyons...such as Fremont
Canyon due to surface northeast winds of 25 miles per hour with gusts over 35
miles per hour and relative humidity of 10-15 percent simultaneously. These conditions will
subside slightly overnight...albeit with poor relative humidity recovery to
around 30 percent...then winds will increase again Tuesday morning...but
weaker than today. Recent rains in some areas and temperatures in
the 50s to lower 60s will limit the wildfire threat.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
Wind Advisory until 10 am PST Tuesday for the Coachella Valley...
Riverside County mountains.
High Wind Warning until 10 am PST Tuesday for the Orange County
coastal areas...San Bernardino County mountains...San Bernardino and
Riverside County valleys-the inland Empire...San Diego County
mountains...San Diego County valleys...Santa Ana Mountains and
Frost advisory from 9 PM this evening to 9 am PST Tuesday for
the Coachella Valley...San Bernardino and Riverside County
valleys-the inland Empire...San Diego County coastal
areas...San Diego County deserts...San Diego County valleys.