Gale Watch 3, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
120 PM PST Sat Feb 17 2018

.SYNOPSIS...
Increasing onshore flow will bring marine clouds and possible fog
to coastal areas overnight, then noticeably cooler weather on
Sunday. A cold low pressure system will be moving into the Great
Basin Sunday and Monday. Strong westerly winds will develop over the
mountains and deserts, and some light rain and snow showers may
break out, creating wintery conditions over the mountains Sunday
night through Monday night. Dry and a little warmer midweek, then
cooler again next weekend with another chance for light
precipitation as another cold trough moves south along the Coast.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

Skies were sunny midday across SoCal, with scattered high clouds
drifting NE. The sfc pressure gradient had relaxed from SW NV-KSAN
and was about neutral. Winds were generally light with a few wind-
prone areas still reporting easterly gusts at Noon over 20 MPH.
Surface dewpoints were still in the teens and 20s F, even some
coastal stations.

Our string of exceptional winter weather is about to come to an end
as the atmosphere undergoes an adjustment favoring troughing over
the West. Monday could be the coolest day over a good chunk of the
CWA since last winter. A large, cold, low pressure trough will drop
into the Great Basin through Monday. It will drop sfc pressure over
the interior west, and force strong onshore flow across SoCal. Winds
will be strongest over the mts. deserts, and coastal waters. Wind
and winter weather products may be needed for the mts/deserts as
well as the coastal waters for the Sunday afternoon through Monday
evening period.

Some light precip will break out over and west of the mts as well,
and even though amounts will be limited, low snow-levels may create
an impact to travelers through the mtn passes and at resort levels,
especially later Mon/Mon night when the snow level will fall below
3000 FT in some areas. Up to a few inches of snow could accumulate
in some spots above 4500 FT by Tue morning, but the main impact will
be low windchills.

It will be much cooler through Tuesday. Maximum daytime temperatures
on Monday may not get out of the 50s west of the mts, 30s at mtn
resorts, and 40s over the high deserts. This equates to widespread
maximum daytime temps of from 8 to 15 degrees below average.

Some moderation in temperatures will occur during the midweek
period, but continued troughing over the West will keep them below
average for this time of year. Generally, the ECMWF model has
handled the transition to lower heights/thickness over the West
better than the GFS operational runs. If we follow the latest 12Z
run into next weekend, it looks like another cold trough could drop
south over the West with another chance of light precip and well
below average temps.

&&

.AVIATION...
172100Z...FEW-SCT clouds at or abv 20000 ft MSL and unrestricted VIS
through this evening. Low clouds and fog will develop along the
coast aft 06Z Sunday, with bases around 500 feet MSL and areas of
VIS below 1 mile. KCRQ and KSNA have the best chance of fog by early
Sunday morning, although timing is uncertain. Bases will lift as the
low clouds spread inland overnight into Sunday morning. Low clouds
could reach the coastal mtn slopes Sunday afternoon, but cigs will
likely be 3000 ft MSL or higher by then.

&&

.MARINE...
No hazardous weather is expected through Sunday. West-northwest
winds gusting around 30 kt, and combined seas of 7-11 ft with steep
waves are likely Sunday night through early Tuesday. These
conditions will be hazardous to small craft. Conditions will improve
by Tuesday afternoon.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory from 10 PM Sunday to 6 AM PST Tuesday for
     Coastal Waters from San Mateo Point to the Mexican Border
     and out to 30 nm-Waters from San Mateo point to the Mexican
     Border Extending 30 to 60 nm out including San Clemente
     Island.

&&

PUBLIC...jad
AVIATION/MARINE...PG