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fxus66 ksgx 161139 
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Area forecast discussion 
National Weather Service San Diego California 
339 am PST Sat Feb 16 2019 


Synopsis... 
a weak low pressure trough may generate a few showers over and 
west of the mountains through this evening. A stronger, colder 
trough on Sunday will bring widespread showers with snow in the 
mountains down to 3000 feet. Monday through Wednesday will be dry 
and cold. Another cold storm will bring a chance for more precipitation 
Thursday. 


&& 


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


An exceptionally cold and windy weekend is ahead with periods of 
rain and mountain snow giving it a wintry feel. A long wave trough 
will deepen over the west as shortwaves drive progressively colder 
air into the southwest through Monday. A shortwave that brought 
rain and mountain snow last night is moving east this morning. A 
precip summary is headlined on our webpage. 


The second wave is weaker but still has enough moisture for 
isolated showers today and tonight. The precip will primarily 
fall over the mountains and foothills, but a few showers west of 
the mountains can't be ruled out. 


On Sunday a stronger shortwave will bring rain and mountain snow 
from midday through the evening. Ingredients are coming together 
to make this a moderate to high impact winter storm. Sunday will 
be a cold, windy day in all areas. Strong positive vorticity advection aloft and surface 
forcing along and ahead of the cold front will interact with a 
modest moisture surge from the west (pw of 0.65") to generate 
showers and mountains snow squalls at times. 700mb temps fall to 
-11c, and 850 mb temps fall to -2c which will lower snow levels 
to between 3,000 and 3,500 feet. Snow accumulations in the 
mountains above 4,000 feet will range from 4-8" with as much as 
12" at the higher elevations. The highest amounts are mostly 
likely in Riverside and San Diego counties where strong westerly 
onshore flow will maximize the orographic potential. The Winter 
Weather Advisory may need to be upgraded to a Winter Storm Warning 
Sunday. 


The storm clears the area Sunday night. Monday and Tuesday will 
be dry with cool days and cold nights. Overnight lows will fall 
below freezing in the inland valleys and low lying coastal areas. 
Frost or freeze products may be needed. 


Clouds increase Wednesday ahead of another strong shortwave in the 
cold northerly flow aloft. This systems lacks the deep moisture, but 
it's another very cold system that will wring out convective showers 
Thursday. Snow levels will once again be very low. 


Friday through sunday: a pattern change may be forthcoming as the 
00z GFS and European model (ecmwf) show a transition from a high amplitude 
ridge/trough wave pattern to more zonal westerly flow over the 
weekend. If this were to materialize we would see temperatures 
moderating back to near normal for the last days of February. 


&& 


Aviation... 
161015z...a band of showers will continue to move southeast over 
San Diego County through 12z, with isolated showers behind this 
band tapering off by 15z. Ceilings mainly 3500-4500 ft mean sea level with tops 
to 6500 ft msl, locally down to 2500 ft mean sea level in showers. Terrain 
will be obscured at times. Rain showers developing again after 17/00z with 
areas of ceilings 2000-3000 ft msl, mainly in eastern portions of the 
inland Empire and San Diego County. 


Strong west winds with sfc gusts 30-45 kt near the mountain 
ridges and desert slopes through 15z this morning and again this 
evening into early Sunday. Uddfs and areas of low level wind shear likely over and 
east of the mountains through Sunday. 


&& 


Marine... 
gusty west-northwest winds will continue through Monday morning, 
with strongest gusts around 30 kt this evening and Sunday evening. 
A combination of steep wind waves and a mix of westerly swells 
will result in choppy seas. A Small Craft Advisory is in effect 
through 10 am Monday. Winds and waves will lower through the day 
Monday. 


&& 


Beaches... 
a new west-northwest swell of around 10-12 feet/8-9 sec from 290 
degrees will generate elevated surf through Sunday, mainly in 
southern San Diego County where sets of around 8 feet are possible. 
A beach hazards statement remains in effect for elevated surf and 
strong rip currents through Sunday afternoon. 


&& 


Skywarn... 
Skywarn activation may be requested on Sunday for rain and snow 
amounts. A big "thank you" for all or your reports during the 
Thursday record breaking rain event! 


&& 


Sgx watches/warnings/advisories... 
California...Winter Weather Advisory until 2 am PST Monday for Riverside 
County mountains-San Bernardino County mountains-San Diego 
County mountains. 


Beach hazards statement through Sunday afternoon for Orange 
County coastal areas-San Diego County coastal areas. 


Pz...Small Craft Advisory until 10 am PST Monday 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. 


&& 






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