Area Forecast Discussion
Issued by NWS Boise, ID

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585
FXUS65 KBOI 231711
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1011 AM MST Thu Feb 23 2017

.DISCUSSION...Snow is continuing to fall over southeast Idaho,
with light snow showers elsewhere as a slow moving upper low spins
north and east bringing wrap-around moisture to the region.
Threat of snow will generally end by early this afternoon except
across the eastern Boise mountains, Camas Prairie, and Snake Plain
(east of Mountain Home) to the ID/NV border. Looking for an
additional 1 to 4 inches in these areas, with the highest peaks
expected to get up to 5 inches. Southwest Highlands are still
under a Winter Weather Advisory through the early afternoon and
areas of the Magic Valley south to the Nevada border are under a
Winter Storm Warning through this evening. Will monitor these
areas closely. Snow will slowly taper off tonight into Friday as
the upper low moves into eastern Idaho and northwest Wyoming.
Gusty northwest winds today behind the exiting upper low. Most
areas will see winds at 15 to 25 MPH with gusts to 35 MPH, except
in the Upper Treasure Valley south and east of Boise where a Wind
Advisory is now in effect through this evening. Winds there will
see winds at 25 to 35 MPH with gusts up to 50 MPH. Winds are
expected to generally diminish tonight. Higher elevations across
southwest Idaho may also see stronger winds. Forecast was updated
this morning to reflect the stronger winds seen across the region.
Otherwise, forecast is on track.


&&

.AVIATION...VFR with periods of MVFR in light snow. Periods of
snowfall will be found across the area, with the heavies snow
expected to impact KTWF and KJER through much of the TAF period with
periods IFR to LIFR conditions expected. Mountains will remain
obscured. This system will also bring strong wind across many
terminals, especially those in Baker, Treasure and Magic Valley.
Surface winds generally W-NW 15-25 kt with gusts up to 40 kts across
the central valleys. Wind is expected to weaken through the
overnight hours. Winds aloft at 10kft MSL: NW-NE 20-35kt.


&&

.PREV DISCUSSION...
SHORT TERM...Today through Friday...A slow moving upper low
positioned over s-central Idaho this morning will keep snow over
central Idaho into Friday. Focus of the heaviest snow will be
across the eastern Boise mountains, Camas Prairie, Snake Plain
(east of Mountain Home) to the ID/NV border where an additional 1
to 4 inches is expected. To the west of this band, expect light
snow showers today as an upper level weakness tracks through
southeast Oregon. Accumulations from this activity will be less
than an inch and only on grassy surfaces across lower elevations.
Drier air moves in from the west tonight, cutting off snow showers
for all but central ID zones where moisture continues to wrap
around the low over s-central ID. This feature does eventually
lift into southwest MT during the day Friday bringing an end to
the snow for all but the central ID mountains. Surface low over
eastern ID will sustain gusty northwest winds across much of the
region today into tonight. Strongest winds will channel from the
Baker Valley through the Snake Plain where gusts of 30-40 MPH are
likely. Winds will weaken late tonight into Friday as the surface
low fills and lifts to the northeast. With a broad upper trough
over the area temperatures will remain about 10 degrees below
normal through Friday.

For the current suite of products. Flow on the Malheur at Vale is
continuing to drop and will likely be enough below flood stage to
cancel the warning this morning. Feel winter highlights are
adequate for the expected additional accumulations and
accompanying impacts. Areas from Glenns Ferry and Bruneau south
and east will see the most accumulating snow through this evening,
though accumulations on paved surfaces will likely be diminished
after 18Z. Did extend timing on Southwest Highlands zone by 3
hours to cover snowfall into early afternoon.


LONG TERM...Friday night through Wednesday...Cold active weather
pattern will continue through Tuesday with the passage of two upper
level troughs. Models remain consistent in keeping the first trough
on Friday night into Saturday well off the west coast with the
forecast area remaining largely unaffected. Showers could develop
over the higher terrain Saturday afternoon but snow accumulations
will be little if any. This trough weakens as it shifts southeast
across California Saturday night. A second stronger and more
moisture trough moves along the coast Sunday before shifting inland
late Monday into Tuesday. Models still don`t have a great handle on
this system and differ with how far south the trough drops Monday
before moving inland. This mainly has implications with the extent
of shower coverage Sunday afternoon through Monday. Northwesterly flow
will continue the changes for snow showers on Tuesday. Snow amounts
will be light with a few inches in the mountains to little if any
accumulations in the valley as the ground and surface temperatures
remain at or above freezing Sunday through Monday. Upper level ridge
begins to build along the west coast Wednesday and remaining through
the weekend. It`s not particularly strong but it will keep the area
dry with temperatures climbing back to seasonal normals by Thursday.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory until 8 PM MST this evening IDZ014.
     Winter Storm Warning until 11 PM MST this evening IDZ016-030.
     Winter Weather Advisory until 2 PM MST this afternoon IDZ015.
OR...None.

&&

$$

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DISCUSSION...AB
AVIATION.....KB
PREV SHORT TERM...DG
PREV LONG TERM....JS



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