Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 041657
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
957 AM MST Sun Dec 4 2016

.DISCUSSION...No updates this morning. Snow currently
accumulating over the mountains in Baker County and over the West
Central and Boise Mtns. Models still indicating snowfall totals
which prompted today`s Winter Weather Advisory for the West
Central and Boise Mtns, scheduled to expire at 8 PM MST. Snow
levels currently around 4000-4500 FT MSL and rising ahead of the
cold frontal passage. Cold front to traverse southeast Oregon
this afternoon and southwest Idaho this evening. As the cold front
passes through the Treasure and Magic Valley, precipitation will
briefly switch over to a rain/snow mix before tapering off rapidly
in its wake. No snow accumulation expected in the valley with
frontal passage. Looking for this to occur around 5-7 PM MST in
Boise and around 8-10 PM MST in Twin Falls. Much cooler
temperatures will follow for Monday`s high and low temperatures.
Patchy fog in sheltered mountain valleys expected to develop in
the morning.


&&

.AVIATION...IFR and widespread mountain obscuration across mountains
of east-central Oregon and west-central Idaho today due to snow and
low ceilings. Snow levels of 4-5k feet with low VFR and local MVFR
at sites below 4k feet. Surface winds south to east at 10-20 kts
through this afternoon. Cold front will bring wind shift late this
afternoon across southeast Oregon and early this evening for
southwest Idaho. VFR most sites tonight into Monday with sheltered
mountain valleys seeing fog development early Monday morning. West
winds aloft of 30-50 kts up through 10k feet MSL.


&&

.PREV DISCUSSION...
SHORT TERM...Today through Monday...A potent winter-like storm is
entering the CWA this morning, bringing snow and rain to the
region. The Winter Weather Advisory has been altered to remove the
Upper Weiser River Basin. Although precipitation will likely
start as snow there, it will quickly turn to rain and travel
problems, if any, will be short-lived. The only other change in
the advisory was to bring the end time from 11 pm MST to 8 pm MST.
The mountains will see plenty of snow with this system, even as
warm air advection moves in today. We still expect 4-8 inches
between 5000 and 7000 feet, with 9-15 inches above. In the lower
elevations, precip may begin as snow or a rain/snow mix before
changing over to rain. A strong cold front will move through
tonight, changing any lingering precipitation back to snow before
ending. The front is expected to move into the northwestern part
of the CWA and be aligned roughly from Burns to McCall late this
afternoon. It will then race through the region this evening,
clearing the western Magic Valley by midnight. Winds this
afternoon and evening will gust to around 40 mph above 7000 feet,
but in the lower elevations winds are only expected to exceed 20
mph in southeast Oregon. After the front moves through,
precipitation is expected to taper off rapidly. After a dry late
night and first part of Monday, another colder system will move in
from the northwest. This will spread light snow to much of the
area Monday afternoon, generally north and west of a line from
Rome, Oregon to Ontario to Banner Summit. Temperatures will start
out relatively mild this morning, but struggle to warm up where
rain or snow occur. The far southern portion of the CWA, roughly
from Rome, Oregon to Jerome, will see temps warm up roughly 10
degrees from morning lows. Elsewhere, the warm up will be roughly
5 degrees. Tonight, after the front moves through, we will see
temps drop into the single digits in the mountains and at
elevations above roughly 5000 feet, with teens common in southeast
Oregon and lower 20s in the Treasure Valley. Monday, highs will
reach the 30s in the lower elevations with teens and 20s in the
mountains.

LONG TERM...Monday night through Saturday...A cold northwest flow
aloft will keep temperatures below freezing Monday night through
Wednesday. Monday night and Tuesday an upper-level trough, which
originated over Alaska, will cross southeast Oregon and southwest
Idaho, leaving 1 or 2 inches of snow in the valleys and 2 to 4
inches in the mountains. Wednesday morning the combination of
light winds, partial clearing, and snow cover will result in the
coldest temperatures since early January, with lows in the 10 to
20 degree range in the Snake River Valley and single digits above
and below zero in the mountains. We will be between storms Tuesday
night and Wednesday, but Wednesday night through Thursday night a
Pacific weather system will spread snow across our area. By Friday
morning we can expect 3 to 5 inches of new snow at lower
elevations and 5 to 8 inches in the mountains. A moist westerly
flow will continue the chance of snow showers Friday through the
weekend, as milder Pacific air warms temperatures to near normal.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory until 8 PM MST this evening IDZ011-013.
OR...None.

&&

$$

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DISCUSSION...AB
AVIATION.....DG
PREV SHORT TERM...SP
PREV LONG TERM....JT


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