Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service San Diego California
140 PM PST Sat Dec 20 2014

a dirty ridge of high pressure will build along the West Coast
through Tuesday...bringing periods of high clouds as well as a
gradual warming trend to Southern California. Gusty northeast will
also develop for Sunday through Tuesday...with moderate to locally
strong winds possible on Monday night and Tuesday morning. A trough
of low pressure will bring some cooler conditions by Christmas day
as well as some gusty west winds to the mountains and deserts.
However...some minor warming and offshore winds will be possible
again for the remainder of the Holiday weekend.


Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino

Water vapor imagery shows high pressure beginning to build over the
eastern Pacific this afternoon...with an extremely moist
northwesterly flow sending plenty of high clouds across California.
There are a few more breaks in these high clouds than there were
this morning...but the cirrus shield is still thick. As a
result...temperatures are running 3 to 5 degrees cooler this
afternoon than yesterday. This will make for a very mild evening
across the region.

High pressure will continue to rebuild along the West Coast for
Sunday through Tuesday...with a gradual warming trend and periods of
offshore winds developing. There will also be enough upper level
moisture moving around this ridge that periods of high clouds will
be least through Monday. At this time...the offshore
winds will be relatively weak for Sunday...but increase for Monday
and Tuesday...with moderate to strong winds possible for Monday
night and Tuesday morning. Our local WRF shows 850 mb winds
increasing to between 45 and 55 kts late Monday night...with the San
Diego to Daggett gradient increasing to 9 mbs on Tuesday morning.
If this comes to pass...the favored passes and canyons would likely
see some gusts in the 65 to 75 miles per hour range.

A trough of low pressure will then flatten the ridge on Wednesday
and Christmas...moving inland to our north and across the Great
Basin. The models still vary quite a bit with the handling of this
system...even though the latest 12z runs are looking a little more
similar. The GFS is still the most consistent of the
models...keeping all the moisture well to our north and east. The
12z European model (ecmwf) is still trying to bring some moisture this far
south...but is now timing for late in the day on Christmas and into
Thursday night. At this time...think the drier solutions are the
ones to believe...but cooler conditions will develop these days.
Onshore flow will return as well...and may persist into the weak troughing lingers over the region.


202130z...sct/bkn high clouds through tonight. Patchy stratus...with
bases around 2500 feet mean sea level and tops near 3000 feet mean sea level...may develop
over portions of the coast and valleys this afternoon through
tonight. However...high clouds moving over the region will likely
inhibit widespread low cloud development. Forecaster confidence in
low clouds developing over coastal and valley aerodromes tonight is
low to moderate.


130 PM...combined seas to 9 feet is possible over portions of the
outer coastal waters late tonight into Sunday morning. Otherwise no
hazardous marine weather is expected through Wednesday.


130 PM...a large...long period west-northwest swell will build today
and create elevated surf and stronger rip currents late today
through early Sunday. In addition...morning high tides around 7 feet
could contribute to minor tidal overflow through Tuesday. See the
beach hazard statement for details...laxcfwsgx.


Fire weather...
offshore flow and drier conditions will develop across Southern
California for Sunday through Tuesday. Although the offshore
gradients will be relatively weak on Sunday and Monday...locally
gusty north to northeast winds will be possible. These north to
northeast winds will likely increase on Monday evening though...with
moderate to strong winds possible late Monday night and into
Tuesday. The favored passes and canyons as well as coastal slopes
may see gusts ranging between 65 and 75 miles per hour. Humidity values will
gradually lower these days as well...falling to between 10 and 20
percent by Tuesday. However...increased fuel moisture due to recent
rains will limit the potential fire danger.


Skywarn activation will not be needed today.


Sgx watches/warnings/advisories...
California...beach hazards statement through Tuesday morning for the beaches
in the Orange County coastal areas...San Diego County
coastal areas.




Public/fire weather...Palmer

National Weather Service Glossary of Abbreviations