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Area forecast discussion 
National Weather Service San Diego California
145 PM PST sun Dec 28 2014

Synopsis...
high pressure aloft combined weak surface high pressure over Nevada
and Utah will allow mainly high clouds to stream over the area at
times through Monday morning. A Gulf of Alaska storm is expected to
move through Canada...then south into our area Tuesday and
Wednesday. Unseasonably cold conditions are expected...along with
showers...possible thunderstorms...gusty winds...and unusually low
snow levels by Tuesday afternoon...and extending into Wednesday.
Travel impacts are expected Tuesday afternoon into Wednesday. Skies
should clear by late Thursday into Friday under gusty north to
northwest flow. Temperatures remaining a little below seasonal
normals...but significantly below normal nights and mornings.

&&

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

Mostly clear today as the airmass begins to warm a bit and push
somewhat back toward normal. Thin high clouds only so far. Cool
again tonight...but limited patches of frost in the prone areas is
the expectation. The BUFKIT soundings and local WRF indicate some
increase in low level moisture for Monday morning...but the most
significant onshore push is Monday night into Tuesday morning.

A storm originating in the Gulf of Alaska...the main concern...will
be moving south through western Canada...then dropping into the
western states. It should develop further as it moves over Southern
California. The GFS ensemble puts the general location of the low
over the upper deserts Wednesday...similar to the deterministic
runs.

There has been some issues with timing and strength of the
storm...but as we get closer the models have been able to converge
on a believable solution...a very unseasonably cold...snowy one for
many areas.

The system should have all the moisture it needs to generate decent
rains across our region. Above about 2000 feet mean sea level...including the
higher portions of the inland valley areas...most areas should see
some snow. Below some passes the snow level should be locally lower
than that...with snow pellets falling below 2000 feet where
convection occurs. Accumulating small hail or graupel could occur
with the slow steering currents associated with the low being nearly
overhead... even west of the mountains. Especially under the nearly
stationary convective cells. We may even need a Snow Advisory for
some of the higher inland valley locations during the peak of the
storm.

With the new years Holiday...we could see some significant impacts
to travel through the region from Tuesday night through Wednesday
night. In addition...gusty winds will generate very low wind chills
in the mountains...possibly below zero wind chill values at times.
Winter weather headlines may be needed later today or by Monday for
this storm event.

Behind the storm late Thursday...cool northerly flow will persist...
keeping our region in below normal temperatures. Could have some
frost and freeze activity by then. A warming trend by next Sunday
with dry weather is the current thinking.

&&

Aviation...
282130z...sct-bkn cirrus clouds at or above fl200-fl250 with
unrestricted visible through 291000z.

West of the mts...scattered clouds at or below 2000 feet are possible after 291000z
as marine air starts to return...but VFR conditions should
prevail.

&&

Marine...
100 PM...no marine concerns through Monday. A winter storm will
approach later Tuesday through Wednesday bringing stronger onshore
winds... showers...and a chance of thunderstorms.

&&

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

&&

Sgx watches/warnings/advisories...
California...Winter Storm Watch from Tuesday afternoon through Wednesday
afternoon for the apple and Lucerne valleys...Riverside
County mountains...San Bernardino County mountains...San
Diego County mountains.
Pz...none.

&&

$$

Public...small
aviation/marine...Pierce

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