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Area forecast discussion 
National Weather Service San Diego California
128 PM PST Friday Feb 12 2016

Synopsis...
fair and very warm weather again today...with temperatures lowering
a few degrees on Saturday as the ridge of high pressure weakens.
Another warm-up expected Sunday through Tuesday as the ridge aloft
re-builds and stronger offshore flow moves in. Locally strong and
gusty northeast to east winds possible in the passes...canyons and
coastal foothills Sunday through Tuesday...with strongest winds on
Monday. By next Wednesday...the ridge will weaken and onshore flow
returns...resulting in decreasing temperatures. A low pressure
trough will continue to cooling trend and may bring some showers to
the region on Thursday.

&&

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

Afternoon visible satellite shows a large area of fog over the
offshore waters near San Clemente Island...with thin high clouds to
the northwest. Looking at the 12z Miramar sounding and comparing to
yesterdays 12z sounding...the atmosphere has cooled slightly up
through 600 mb. Meanwhile...offshore pressure gradients continue to
weaken...with gradients of 7.0 mb from San Diego to Tonopah and 7.9
mb from San Diego to Salt Lake City...whereas the gradients were
12.9 mb and 14.4 mb respectively at this time yesterday. As a
result...northeast to east wind gusts are only in the 15-20 miles per hour
range in the passes/canyons and coastal foothills. The weaker
offshore flow is allowing for a sea breeze to bring minor cooling to
the coast today...with San Diego only showing a temperature of 77
right now...whereas it was 82 at 1 PM yesterday. However...highs
elsewhere will still be 10-20 degrees...and locally 25
degrees...above normal. In the inland coastal areas...valleys and
lower deserts...expect highs in the middle-to-upper 80s...mid-to-upper
70s at the beaches and high deserts...70s at the Lower Mountain
slopes...and the low 60s at the high elevations. We may have a few
stations reaching record highs again today.

Water vapor imagery indicates an upper level ridge over Southern
California slowly being nudged east...with a trough far to the west.
With offshore flow continuing to weaken tonight...it may allow for
some dense fog to reach the coastal areas up to a few miles inland
late tonight into Saturday morning. In fact...the 19z hrrr seems to
have initialized the area of fog offshore pretty well...and has
dense fog moving into the coast by mid-evening. A trough moving
inland over the Pacific northwest Saturday will create some cooling
for Saturday...but temperatures will still be well above normal.

Sunday into Tuesday...ridging to the west will build back over the
region. This...in addition to strengthening offshore flow resulting
from strong surface high pressure over the Great Basin...will create
another warm-up...with highs once again reaching 10-20 degrees...and
locally 25 degrees...above normal. Monday and Tuesday look like the
warmest days...with daily high temperature records at a few to
several stations possibly getting broken. Models indicate that the
offshore pressure gradients from San Diego to Tonopah strengthen to
about 7-10 mb Sunday...and then 11-16 mb Monday. Meanwhile...upper
support increases as well...with 850 mb winds out of the northeast
reaching about 10-20 knots on Sunday...and then 15-30 knots on Monday.
Thus...look for weak to locally moderate Santa Ana winds on
Sunday...with northeast to east wind gusts of 25-40 miles per hour in the
passes/canyons and coastal foothills...and then winds strengthening
further Monday...with northeast to east wind gusts reaching 40-50
miles per hour and locally 60 miles per hour in the passes/canyons and coastal foothills.
Offshore flow weakens a little on Tuesday.

The ridge starts to weaken and we turn back onshore during the day
Wednesday as a trough approaches the West Coast...creating cooler
conditions. The long-range models are still in a fair amount of
disagreement regarding how deep and strong the trough will be as it
moves inland on Thursday. The 12z GFS is pretty similar to the 06z
run...showing a weak trough and associated precipitation moving by
to our north...leaving US mostly dry. However...the 12z European model (ecmwf) is
much stronger...wetter and slower for Southern California. The 12z
Canadian seems to show compromise between the European model (ecmwf) and GFS.
Considering that 2 of the 3 long range models consistently show
precipitation for Thursday...have increased the probability of precipitation a bit. At the very
least...expect the cooling trend to continue into Thursday.

&&

Aviation...
122100z...few-sct clouds at or above 20000 feet mean sea level and unrestricted visible
through Saturday. There is a chance of low clouds and fog with visible
2sm or less just reaching the coast late tonight into Saturday
morning...possibly vicinity ksan/kcrq/ksna. Confidence is slightly
higher at this time for fog occurrence due to new hi-res model
guidance. Will stick with vcfg for coastal taf sites for now
though...but maybe a few more low clouds.

&&

Marine...
100 PM...fog with visibility 1sm or less is likely over the coastal
waters and approaching the coast tonight through Saturday morning.
Otherwise no hazardous marine weather is expected Saturday afternoon
through Tuesday.

&&

Beaches...
100 PM...a long-period swell from 290 degrees will build
today...peaking Saturday at 9 feet/18 second. This will generate high
surf of 4 to 8 feet today through Sunday with highest sets north of
Newport Beach and south of del Mar. A high surf advisory remains in
effect from 10 am today through 8 PM Sunday. Swell and surf will
subside Monday.

&&

Fire weather...
light offshore winds will continue through Saturday...then offshore
winds strengthen a little Sunday...with northeast to east gusts 25-
40 miles per hour in the passes/canyons and coastal foothills...and then
strengthen further on Monday...with northeast to east gusts 40-50
miles per hour and locally 60 miles per hour in the passes/canyons and coastal foothills.
The offshore flow will combine with very warm conditions and minimum
relative humidities in the single digits to teens to create elevated
to possibly critical fire weather concerns on Monday. Overnight
humidity recoveries look to be poor to locally moderate.

Humidity will start to increase Wednesday as onshore flow returns
and a trough approaches from the Pacific. This trough could produce
wetting rains next Thursday.

&&

Skywarn...
Skywarn activation will not be needed today.

&&

Sgx watches/warnings/advisories...
California...high surf advisory until 8 PM PST Sunday for Orange County
coastal areas-San Diego County coastal areas.

Pz...none.
&&

$$

Public/fire weather...Harrison
aviation/marine/beaches...ts

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