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000 
FXUS66 KSTO 300400
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
900 PM PDT Wed Mar 29 2017

.Synopsis...

An approaching upper level disturbance will bring light rain for the 
valley and light snow for elevations higher than 4000 feet.  Gusty 
north winds are likely Thursday and Friday. Seasonably dry 
weather anticipated for Saturday with chances for light rain in 
the Sierra Sunday.

&&

.Discussion...
A weak weather system is moving into parts of Northern California
this evening. Some scattered light showers exist at this time
north of about Chico. The low will deepen over the area late
tonight and by 8 am the trough axis will be over the Sierra
Nevada. Only some light showers will persist after then over the
western slopes but will continue to diminish throughout the day.
Snow levels start to drop late tonight and Thursday morning. A 
couple of inches of snow may accumulation near major pass levels 
with up to about 4 inches over the peaks. Rainfall amounts within 
the valley will be under a tenth of an inch and some areas may not
see any rainfall.

Northerly winds will increase behind the front during the morning
hours in the valley. Winds will increase to mainly between 15 and
25 mph with gusts between 25 to 35 mph. Locally there could be
some stronger winds. By evening the showers will have moved out of
the forecast area and winds will start to decrease but will likely
remain breezy into the evening hours.
.Previous Discussion (Today through Saturday)...

The upper level ridge over the eastern Pacific is beginning to break 
down as an upper level trough approaches from the northwest. 
Satellite and radar imagery shows increasing clouds and some areas 
of precipitation moving into the region across the northern 
mountains and northern Sacramento Valley.

Forecast concerns this period include some light rain for the valley 
and foothills with light snow for elevations higher than 4000 feet 
starting tonight through Thursday night/Friday morning, and gusty 
north winds on Friday.  Model forecasts are in good agreement and 
indicate the shortwave trough quickly moving through northern 
California, which will start late tonight and last through Friday. 
Little impacts are expected from the precipitation with only 1 to 2 
inches of snow for the mountains and some wet roadways.  A stronger 
mid to lower level jet will be present across the area Friday, which 
could translate to gusty north winds between 30 and 35 mph for the 
valley and upwards of 45 mph for the higher terrain.  Gusts will 
start to diminish Friday evening.  

Another upper level ridge will begin to build across the region and 
will allow for dry seasonal weather to return with temperatures 
between 5 and 10 degrees above normal. 

&&
.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)


The extended period will be somewhat unsettled with a couple
weather systems expected to move through the area. A shortwave
will deepen as it moves over the northwest US on Sunday, bringing
light precipitation to the NorCal mountains Sunday evening 
through the overnight hours. Temperatures will lower slightly by
Monday, and we could see a gusty northern wind event behind the
trough. Ridging builds again for the early part of the week with
temperatures remaining around 5 degrees warmer than normal. A 
larger upper level trough looks to approach the Pacific northwest 
by the end of the extended period, bringing a wetter storm system 
into the area beginning Wednesday evening.

HEC
&&

.AVIATION...


Mainly VFR conditions. A brief weather system will bring scattered
-SHRA through tomorrow morning and possible MVFR conditions to 
TAF sites after 11Z tomorrow. Winds increasing to sustained 
greater than 10-15 kt by 12Z with gusts up to 20-25 kt by 18Z.

HEC
&&

.STO WATCHES/WARNINGS/ADVISORIES...

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