Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 040352
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
852 PM MST Sat Dec 3 2016

.DISCUSSION...No updates at this time. Latest model runs are
similar to previous ones and are in step with the latest forecast
and winter weather headlines for Sunday. Snow will start in the
north, possibly by midnight across the higher elevations of Baker
County and the Boise/West Central Mtns of SW Idaho. The snow
intensity will increase by early Sunday morning which matches the
start time of the Winter Weather Advisories. The snow levels will
begin at around 3000 feet before rising ahead of a cold front
Sunday afternoon, so a rain/snow mix is possible in portions of
the Treasure Valley in the morning. However, snow accumulations
are not expected - except for possibly light amounts on the
benches. The cold front will move through late Sunday afternoon
through evening, with precip tapering off rapidly behind the
front, followed by much colder temperatures on Monday.

&&

.AVIATION...Deteriorating conditions tonight as snow spreads over
the area. Light snow will being across Baker County and the
Central Mountains of Idaho after 06Z with the heavier amounts
after 12Z. Surface winds variable 12 knots or less. Winds aloft
northwesterly 30-40 knots up through 10K feet MSL.

Sunday: Showers will spread to the rest of the forecast area
after 17Z with rain at lower elevations and snow above 3,000-3,500
feet MSL. Mountains will become obscured along with widespread IFR
conditions in snow. Lower elevations with rain may see local MVFR
conditions in low clouds and fog. Surface winds south to southwest
10-20 knots with gusts of 20-25 knots by Sunday afternoon with
higher gusts across Harney County Oregon. Winds aloft westerly
40-50 knots up through 10K feet MSL.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Monday...Mid to upper level cloud
coverage will increase tonight from the northwest as a strong
upper level system approaches the region. Ahead of this system,
a northwest flow aloft will allow for a continuation of light
snow accumulations this evening over the mountains. Upper level
flow will combine with a deep moisture plume overnight, bringing
more significant snow accumulations to the mountains in the early
morning hours through the day Sunday. Light precipitation expected
elsewhere with snow levels around 3500-4500 FT MSL. A Winter
Weather Advisory is now in affect for the Weiser River Valley from
5 AM MST and 5 PM MST and the West Central and Boise Mountain from
5 AM MST and 11 PM MST Sunday. Light snow showers will continue
for a few hours after the advisory ends. The Boise metro may see a
brief period of light snow Sunday morning as precipitation first
begins and again Monday morning as the cold front transitions
through the area, just in time for the morning commute. As the
cold front exits the region Monday morning, a dry and cold air
mass will move into the region. Monday`s high temperatures will
be about 8-12 degrees lower than Sunday`s for temps in the lower
30s in the lowest valleys. The next system will approach the
region Monday and begin to enter the region from the northwest
late Monday evening. All precipitation is expected to fall as
snow, though snowfall will be light.

LONG TERM...Monday night through Saturday...The cold air mass is
reinforced as an upper low tracks south out of British Columbia on
Tuesday. This will bring a chance of light snow to the region as
snow levels are down to valley floors. The low center tracks through
southwest Oregon to the ID/NV border, which will be the focus of
higher snow amounts. Wednesday is dry and cold under northwest flow
aloft. Though slight timing differences remain between the GFS and
ECMWF, there is good agreement that by late Thursday moist westerly
flow will bring another round of precipitation to the interior
northwest. With cold air trapped at the lowest levels precipitation
could start as snow at all elevations before changing to rain late
Thursday or possibly Friday. The pattern remains cold and unsettled
into the weekend. Temperatures will be 5 to 10 degrees below normal
through Thursday, warming back towards normal for the weekend.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory from 5 AM to 5 PM MST Sunday IDZ033.
     Winter Weather Advisory from 5 AM to 11 PM MST Sunday IDZ011-013.
OR...None.

&&

$$

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DISCUSSION...BW
AVIATION.....JA
PREV SHORT TERM...AB
PREV LONG TERM....DG/WH



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