Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 061713
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
913 AM PST Tue Dec 6 2016

.SYNOPSIS...
A low pressure system moving from the Pacific Northwest into the
Great Basin will bring stronger onshore flow across Southern
California through tonight with more clouds and with gusty west
winds in the mountains and deserts. Weak offshore flow will follow
for Wednesday into Thursday bringing warming on Thursday and gusty
northeast winds below the Cajon Pass and for the coastal foothills
of the Santa Ana Mountains Wednesday. A little cooler into
Saturday...then a little warmer into early next week with periods
of high clouds at times.

&&

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

...Update...

Coastal stratus is bumping all the way up against the coastal
mountain slopes this morning as the marine layer has deepened. Web
cam images show the depth to about 5k FT. WRF hi-res run shows
some light precip along the coastal mountain slopes and portions
of the Inland Empire late this afternoon/evening. Any rainfall
will that occurs will be light (few hundredths of an inch) as
moisture is limited. PW on the San Diego sounding this morning is
at 0.71 inches. No significant changes will be made to the
forecast this morning. See previous discussion below for further
forecast details.

...Previous Discussion (Issued at 430 AM PST Tue Dec 6 2016)...

.SHORT TERM (Today through Thursday)...
A low pressure system moving from the Pacific Northwest into the
Great Basin will bring stronger onshore flow across Southern
California with periods of stronger and gusty west winds for the
mountains and deserts from late this morning through late tonight.
It will also bring deepening of the marine layer with low clouds
extending on the coastal mountain slopes. There could be a few
sprinkles or light showers...mainly late this afternoon through
this evening...near the coastal mountain slopes into adjacent
portions of the Inland Empire.

Offshore flow will follow for Wednesday...with weaker offshore
flow for Wednesday night into Thursday. Winds could be near
advisory strength below the Cajon Pass and into the coastal
foothills of the Santa Ana Mountains for Wednesday morning into
early Wednesday afternoon. High temperatures will be near to
around 5 degrees below average for today and Wednesday...warming
to near to around 5 degrees above average for Thursday.

Besides the coastal low clouds that will continue into Wednesday
morning...there will continue to be high clouds at times through
Thursday.

&&

.LONG TERM (Friday through Monday)...
Generally zonal flow will continue into next week across the
eastern Pacific into the western states with the subtropical jet
axis remaining to the north of Southern California. A weak
shortwave moving inland through the Great Basin on Saturday will
bring stronger onshore flow with gusty west winds in the
mountains and deserts...cooling to slightly below average...and a
return of the marine layer with night and morning coastal low
clouds and fog. Warming for Sunday and Monday with weaker onshore
flow. With Southern California remaining just south of the
subtropical jet axis...there will continue to be periods of high
clouds.

&&

.AVIATION...
061630Z...Coast/Valleys...Low clouds in the coastal basin will only
partially clear today, with bases mostly 2500-4000 ft MSL with
tops locally to 5500 ft MSL. Most of the airports will have SCT-BKN
conditions. Variable cloudiness will occur tonight with slightly
lower cigs, mostly 2000-3000 ft MSL, with clearing between 12Z and
17Z Wed, with earlier clearing vcnty KONT and KSNA and later
clearing vcnty KSAN and KCRQ.

Mountains/deserts...Areas of strong westerly winds 20-30 knots with
local gusts to 50 knots will occur this afternoon/evening causing
moderate/strong up/down drafts and local LLWS. Areas of terrain
below 5500 ft MSL on the coastal slopes will be obscured in clouds
and fog through 21Z. Otherwise, variable clouds at/above 15000 ft
MSL will continue through Wednesday with unrestricted vis above the
terrain obscurations.

&&

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


&&

.FIRE WEATHER...
Offshore flow will develop on Wednesday bringing gusty northeast
winds and lower humidities below the Cajon Pass and for the
coastal foothills of the Santa Ana Mountains with elevated fire
weather conditions from mid morning through early afternoon
Wednesday. Weaker winds winds with lower humidities for the
valleys on Thursday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 3 AM PST Wednesday for Apple and Lucerne
     Valleys-Riverside County Mountains-San Bernardino County
     Mountains-San Diego County Deserts-San Diego County
     Mountains-San Gorgonio Pass Near Banning.

PZ...None.
&&

$$

PUBLIC...Gregoria (Update)/17
AVIATION/MARINE...Maxwell



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