Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
408 am PDT Thursday Oct 30 2014
mild weather today...then a major winter-like storm push into the
West Coast during the day Friday with cooler temperatures and
increasing cloudiness as a trough of low pressure deepens down
the West Coast. This storm will bring stronger onshore flow...a
deeper marine layer...and rain and high elevation snow showers to
much of the region. The storm will drift east Sunday and be
followed by increasing high pressure for warmer days and weak to
moderate offshore flow early next week.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
..precipitation likely with the first storm of the season late
Friday night into Saturday morning for much of the area...
High pressure ridge is pushing off to the east early this morning.
Abundant high cloudiness is steaming out ahead of a southern
stream small upper low over the eastern Pacific...about 700 miles
west-southwest of San Diego. This upper low will pass over Southern
California today and continue to bring a shield of high clouds for
much of the day but not much of any other impacts as it will
remain mild for most locations...and with only weak onshore
gradients later today the marine layer will continue to make only a
Onshore flow will begin to pick up tonight and bring a cooler
airmass through the coastal valleys. A major east Pacific trough
will become negatively tilted as it approaches first northern
California during the day Friday...then dig down the coast towards
San Diego by Friday night. This trough will kick a rather
robust cold front across our region late Friday night and
Saturday morning. There is good run to run consistency in the
models with this system although the timing has been pushed back
maybe 6 hours so that the brunt of the precipitation is expected
after midnight Friday and into Saturday morning. Trick or
treaters have a high probability of remaining dry if they can get
back home not long after dark.
As mentioned the brunt of precipitation will come after midnight
Friday night and with some Post frontal showers still likely to
continue Saturday morning particularly over the mountains. The
heaviest precipitation will be focused in the San Bernardino and
Riverside Mountains...although around one-tenth of an inch of
total rainfall is forecast for San Diego proper with higher
amounts possible to the north and east of the city.
The colder air wrapping into the system will arrive late Friday
night and will turn the rain to snow above about 6500 feet through
Saturday morning. There could be a period of moderate snow during
that timeframe. Total snowfall amounts of two to four inches with
up to six inches in the highest mountains of San Bernardino and
Riverside counties will be possible.
Strong southwest to west winds will also be likely Friday night
into Saturday morning with the highest gusts up to 60 miles per hour in the
mountains. A Wind Advisory will likely be needed later today for
Light precipitation is forecast for the high deserts with little
or no precipitation for the lower deserts.
Secondary trough passage through Saturday night will keep a slight
chance for rain and snow showers.
Broad upper level high pressure ridging will then ensue for early
into middle next week. Great Basin surface high will become
established early next week which could bring light to moderate
offshore flow to our region. This will likely bring unseasonably
warm temperatures along with gusty offshore winds and very low
relative humidity possible.
300930z...patchy low clouds will develop and dissipate randomly
along the coast this morning through 15z. When/where ceilings
occur...bases will be around 600 feet mean sea level with local visible 3-5sm.
Meanwhile variable high clouds at or above 15000 feet mean sea level will spread across
the entire region today. More widespread low clouds based at around
1500 feet mean sea level are expected to develop at coastal airports from
02-06z this evening and head into lower valleys overnight.
230 am...no hazardous marine weather is expected through Friday.
A cold front moving through Southern California will bring strong
winds and steep waves to the coastal waters on Saturday...which
would be hazardous for small craft in the outer coastal waters.
Conditions will improve early Sunday.
Skywarn activation will not be needed today.