Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service San Diego California
125 PM PDT Sat Apr 19 2014

Synopsis...
weak ridging will build over Southern California through early next
week...bringing warmer and drier conditions to the region.
However...a few lingering buildups and a stray shower may be
possible over the mountains through this evening. A trough of low
pressure will then move inland across the west on Tuesday and
Wednesday...bringing cooler conditions to the Southland as well as a
deeper marine layer and strong west winds to the mountains and
deserts. A transitory ridge will bring some modest warming for
Thursday and Friday. However...another stronger trough will bring
more cooling and strong and gusty winds for next weekend.

&&

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

Water vapor imagery shows a weak disturbance moving through the
building ridge over Southern California this afternoon...bringing
some thin high clouds to the region. There is also enough lingering
middle level moisture that some cumulus build ups are developing over
the mountains. That being said...the build ups are not that
impressive...and with the ridge nosing into the region...am doubtful
we will get more than a stray shower a best. Currently...the only
radar returns are east of the Salton Sea and near the Colorado River
Basin. Otherwise...skies are mostly sunny today...with most
locations running a few degrees warmer than this time yesterday.

The local WRF shows that the marine layer will return quickly this
evening to the San Diego County coast. This trend may hold
true...but visible imagery also shows a back edge to the marine
layer...associated with the passing disturbance. Therefore...think
that the marine layer will probably push inland...but then at least
partially dissipate...before reforming along the immediate coast.
As it does...it will likely be more patchy in nature and more
shallow...with the marine inversion falling to between 1500 and 2000
feet tonight.

Weak ridging will dominate our weather through Easter Sunday and
into the first part of the work week...with even warmer conditions
developing. Temperatures across the inland areas will likely be 5
to 10 degrees warmer than average...which coastal areas continue to
be more moderated by the shallow and patchy marine layer. The
marine layer will also reduce in depth again Sunday night and Monday
morning...with some patchy...and potentially dense...fog possible
for the Monday morning commute.

A trough of low pressure will then move inland across the West Coast
for Tuesday and Wednesday...bringing more cooling to the region as
well as increasing the onshore flow once again. The marine layer
will deepen as well...pushing back into the inland valleys and
becoming more widespread by Tuesday night. That being said...it
appears that all the moisture with this system will stay well to our
north. Therefore...the main story with this trough though will be
the cooler temperatures and the winds. In fact...it appears that
strong and west west winds will likely develop in the mountains and
deserts these days...with blowing dust or sand a possible issue in
the deserts.

As this trough shifts east...a transitory ridge will build back
across Southern California for Thursday and Friday...with some
modest warming possible. However...models are hinting at another
and potentially stronger trough digging along the West Coast for the
weekend. For this reason...expect cooler conditions to develop once
again...along with a deeper marine layer and strong and gusty west
winds. At this time...there are still some timing and strength
issues with the trough for next weekend...but it appears that this
trough may tap into some subtropical moisture. For now...it is
still a question as to whether or not this moisture plume will make
it this far south? Unfortunately...the 12z runs have backed off the
threat of precipitation this far south...limiting any chances of
precipitation to just marine layer drizzle...but at least it appears
that northern and central California could see another decent
soaking before this Spring ends.

&&

Aviation...
192022z...coast/valleys...unrestricted visible and few clouds 1500-3000 feet
mean sea level through 20/0000 UTC. 20/0000-1500 UTC...patchy stratus gradually
forming within 15-20 sm of the coast with bases 800-1200 feet mean sea level and
tops 1200-1600 feet mean sea level. Timing of stratus occurrence for ksan...kcrq
and ksna is low confidence due to the patchy nature of the stratus.
Expect local visible 3-5sm br. Clearing of stratus 20/1600-1800 UTC.

Mtns/deserts...few-sct clouds at or above 12000 feet mean sea level through Sunday morning.
Visible will be mostly unrestricted...except there is a slight chance of
showers/virga for the mountains through 2300 UTC which may bring local
visible at or below 5sm...in addition to locally gusty surface winds to 35 knots.

&&

Marine...
west to northwest winds will strengthen Tuesday as a trough of low
pressure moves over California. The winds will peak Tuesday night
with gusts of 25-30 knots over the outer coastal waters...and gusts in
the inner waters of 20 to locally 25 knots. These winds will combine
with a 7-9 foot short-period swell to likely bring hazardous
conditions for small craft over the outer waters. Confidence is
moderate to high in hazardous conditions for small craft for the
outer waters...and low to moderate confidence for the inner waters.

&&

Skywarn...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

Sgx watches/warnings/advisories...none.

&&

$$

Public...Palmer
aviation/marine...Harrison