Scientific Forecaster Discussion
fxus66 ksgx 190532
Area forecast discussion
National Weather Service San Diego California
932 PM PST Sat Nov 18 2017
clear skies will bring strong radiational cooling to the region
tonight. This will result in freezing temperatures across the
Mojave Desert, the coldest night of the season thus far in big
bear, and patchy radiational fog along the coast. Temperatures
will warm quickly tomorrow and be a few degrees above average by
early afternoon. A warming trend will build through the
abbreviated workweek, with the highest temperatures in the
contiguous 48 likely occurring in Southern California over the
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
At 915 PM...the region was under the influence of a broad low
amplitude subtropical ridge with very dry air above 850 mb
evident on the 00z nkx sounding. Skies were mostly clear apart
from a few patches of low clouds/fog along the San Diego County
coast. Winds were light and variable across the entire region with
very dry air at the surface in the mountains and deserts leading
to strong radiational cooling. Temperatures in the big bear area
were hovering between 26 f and 34 f, with several stations in the
Victorville area reporting temperatures in the upper 30s.
Strong radiation cooling will continue through sunrise Sunday.
This will help temperatures continue to tumble. The first
widespread occurrence of freezing temperatures is likely in
Victorville, Lucerne Valley, Apple Valley, and Hesperia, while Big
Bear Lake will shiver with the coldest temperatures of the season
thus far (some parts of the city bottoming out in the upper
teens). A frost advisory is in effect for the upper deserts, where
it would be a good idea to cover sensitive vegetation. Lows will
be cool, but not as cold west of the mountains, with areas of low
clouds and patchy radiational fog possible along the coast.
Temperatures should warm quickly Sunday at the ridge of high
pressure maintains control over the southwest U.S. Afternoon
highs will be a pleasant 3-7 degrees above average, with high
clouds increasing through the day. There is a strong possibility
of another photogenic sunset, the streak continues.
The subtropical ridge will slowly strengthen as we move through
the upcoming week, and maintain a firm grip on the region into the
Thanksgiving weekend. Models have trended a little stronger over
the last 24 hours and are now proging a 594 dm ridge over socal
by Wednesday. This along with forecast 850 mb temperatures near 22
c and light offshore flow, should bring warmth sufficient to
threaten daily record highs Wednesday through at least
Thanksgiving. The warmest temperatures in the Continental U.S. Could
potentially occur west of the mountains on Thanksgiving.
190350z...coast/valleys...few low clouds currently over the coastal
waters. 06z to 16z, patches of low clouds with bases 200-400 ft mean sea level
and tops 500-800 ft msl, along with local vis 1/4sm or less could
develop within 5-10 sm of the coast. Impacts to ksan, kcrq and ksna
are possible, but timing is uncertain and confidence is low.
Elsewhere, p6sm vis and mostly sky clear.
Mountains/deserts...sct-bkn clouds at or above 12000 ft mean sea level with
unrestricted vis through Sunday.
no hazardous marine conditions are expected through Thursday.
Skywarn activation will not be needed this week.
California...frost advisory from midnight tonight to 8 am PST Sunday for
apple and Lucerne valleys.