Area Forecast Discussion
Issued by NWS San Diego, CA

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821
FXUS66 KSGX 091722
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
920 AM PST Fri Dec 9 2016

.SYNOPSIS...
Fair weather today with variable high clouds. A trough passing by to
the north will bring stronger onshore flow and a deeper marine layer
Saturday, and perhaps generate light showers Saturday night and
Sunday. Fair and seasonal weather Monday through Wednesday, followed
a stronger storm that could bring showers late next week.

&&

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

The 12Z NKX sounding showed low level moisture below 2000 feet, a
dry layer between 2-25kft, and a deep layer of high level moisture
above 25kft. Zonal flow over the lower 48 extends westward over the
Pacific all the way to the International Date Line High. This zonal
pattern will be in place through early next week with embedded
shortwaves over the Pacific passing by to the north from time to
time. One of these waves will move inland across California this
weekend and deepen the marine layer to 5000 feet by Sunday morning.
This may generate a few light showers west of the mountains Saturday
night into Sunday. The lifting mechanism is weak so the precip
amounts in most areas will be light, with trace amounts to a few
hundredths of an inch in most areas, with locally higher amounts of
0.10-0.20". The precipitation will end Sunday afternoon as drier air
moves into the lower layers. Mild Monday and Tuesday with scattered
to broken high clouds in prevailing moist zonal flow aloft.

Long Range...Model differences have surfaced with the 12Z run of the
GFS. It is now faster and weaker with the first shortwave arriving
on Wednesday instead of Thursday. This is followed by a much
stronger and deeper upper air pattern over the weekend with a closed
upper low stalled over northern California. Will not make any
changes to the long range forecast today with too much uncertainty
in the model solutions at this time.

&&

.AVIATION...
091537Z...Coast/Valleys...Through 10/0000 UTC...FEW-SCT clouds 1500-
2500 ft msl and BKN clouds AOA 20000 ft msl. Areas of haze producing
vis 3-5 sm gradually becoming P6SM through the late morning into the
afternoon. 10/0000-1500 UTC...OVC-BKN stratus quickly developing and
filling the coast and valleys with bases 1000-2000 ft msl, tops
around 2500 ft msl, and areas of vis 3-5 sm in the valleys. Forecast
confidence is moderate.

Mountains/Deserts...Unrestricted vis and BKN clouds AOA 20000 ft msl
continuing through Saturday morning.

&&

.MARINE...
No hazardous marine weather is expected through Tuesday.


&&

.MARINE...
No hazardous marine weather is expected through Tuesday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC...Moede
AVIATION/MARINE...Harrison



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