Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 222135

Area Forecast Discussion
National Weather Service Boise ID
235 PM MST Sun Jan 22 2017

.SHORT TERM...Tonight through Tuesday...Widespread precip today is
snow at most locations and a rain/snow mix in the Snake River
Valley. Gusty winds have been observed today, but most locations
continue to see speeds below wind advisory levels. A few
locations could see brief periods of gusts 40-50 mph through this
evening. This is all courtesy of an upper low off the PACNW coast
that will impact the area through tomorrow night. The advisory
that was in place for Baker Malehur and Harney Counties will be
cancelled early as snowfall is rapidly ending in those locations.
A cold front is moving eastward and as of 230 PM MST is in Harney
County Oregon. This will progress through and bring a brief break
in precip late this evening into tonight for most locations,
excluding central Idaho including the Magic Valley. It will also
set up an all snow event for tomorrow. By Monday, the upper low
will slowly move south and rotate through a shortwave from
southwest to northeast that effectively broadens the trough, then
moves eastward. This will produce a band of precip that will move
north into the CWA then pivot out and east, and the location of
this pivot will dictate the location of the most snowfall. The
forecast challenge is where this band of precip will set up, but
current guidance keeps most of the activity in the southern half
of the CWA. A shift of 50 miles could make a huge difference in
snow amounts and models haven`t had much consistency. Nonetheless,
confidence is relatively high that the Owyhees and Southwest
Highlands and areas south to the Nevada border look to be impacted
enough to warrant a Winter Weather Advisory for snowfall of 2 to
4 inches tomorrow. Conditions are expected to dry out on Tuesday
as a cold northerly flow sets up with a ridge along the Pacific

.LONG TERM...Tuesday night through Sunday...Area will remain under
the influence of a broad upper trough centered over the Upper
Midwest. Northerly flow will solidify a cold air mass over the
region, keeping temperatures well below normal. While this colder
airmass will be dry, northerly flow and weak instability is enough
to keep mention of a slight chance of showers in the mountains on
Wednesday. A weak upper low remains progged to track into the
interior West on Thursday, and while its path remains uncertain, its
within bounds to mention a slight chance across southeast Oregon
zones on Thursday. Given the weak dynamics and dry air mass,
precipitation amounts would be light. An upper ridge builds over the
Intermountain NW Friday, kicking off an inversion.

Friday night through Sunday...The upper level ridge remains in place
through the extended. Temperatures will be well below normal for all
locations throughout this time.


.AVIATION...A broad area of IFR in snow across east-central Oregon
and mountains of southwest Idaho through early evening. VFR to MVFR
in the Snake Plain VFR in a rain or a rain/snow mix through late
this afternoon, with improving conditions after 00Z. Gusty easterly
surface winds 10-20 kts with gusts to 35 kts through 03Z (locally
higher in the vicinity of KTWF). Southerly winds aloft of 30-50 kts
through 10k feet MSL. IFR in snow redevelops south of a KBNO-KBOI-
KJER line on Monday with northwest winds surface and aloft.


ID...Winter Weather Advisory from 2 AM to 11 PM MST Monday IDZ015-029.



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