Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 171657

Area Forecast Discussion
National Weather Service Boise ID
957 AM MST Tue Jan 17 2017

.DISCUSSION...Complex weather system moving in tonight through
Thursday with Watches, Warnings, and Advisories already in the
forecast. Latest models continue to evolve and alter where/when
warm air will move into the CWA. Highest confidence areas for
heavy snow and/or freezing rain are the lower Treasure Valley, nrn
Malheur, Baker, nern Harney, Washington, and Adams Counties. Still
assessing incoming data and new forecast with adjusted warnings
and advisories will be out mid-afternoon. Latest for the Boise
metro area indicates 1-3 inches of snow through mid-afternoon Wed,
then mixing with freezing rain, and finally changing to all rain
late afternoon or early evening. No changes at this time.


.AVIATION...Areas of MVFR/IFR conditions in valley fog and
stratus with conditions improving to VFR after 18Z. Increasing
clouds from the northwest after 18Z today with the incoming
Pacific system. Precip will begin over SE Oregon after 18/06Z and
southwest Idaho after 18/12Z. Precip will begin as snow but may
switch over Wednesday evening/night to a wintery mix. Widespread
IFR and areas of LIFR conditions in snow along with mountain
obscuration will spread over the region. Surface winds: mainly
east-southeast 5-15 kts, except 15-15 kts in KJER and KBKE. Winds
aloft near 10kft MSL: WSW 10-20 kts, increasing to 25-40 kts kts
after 18/03Z.


SHORT TERM...Today through Wednesday...
Incoming Pacific storm will bring significant amounts of snow,
freezing rain, and rain to our CWA late tonight through and
beyond Wednesday. Temperature and snow levels will rise
dramatically during the storm especially Wednesday afternoon,
but cold air will remain in wind-sheltered valleys resulting in
freezing rain there. Current winter storm watch will shortly be
converted to winter storm warnings for heavy snow, or winter
weather advisories for mixed precipitation with smaller
accumulations of snow but also some accumulation of ice.

LONG TERM...Wednesday night through Monday...A very moist Southwest
flow aloft ahead of an approaching upper trough will bring
significant precipitation to SE Oregon and SW Idaho Wednesday night
through Thursday. There should be enough wind to scour out the
inversion with snow levels rising above valley floors for portions
of the Treasure Valley, where a mix of rain and snow is expected.
The cold air may have a tougher time mixing out of the Lower
Treasure Valley around Ontario which could lead to higher snowfall
totals. The heaviest amounts will be in the higher elevations of
Baker County and the Boise/West Central Mountains. There will also
be freezing rain in some valley locations. The upper trough will
move through late Thursday sending snow levels back down to valley
floors, although the precip will taper off by then. Additional
(weaker) Pacific systems will move through the region for the
remainder of the extended period. Temperatures will be cold enough
for snow at all elevations.


ID...Winter Storm Warning from 8 AM Wednesday to 5 PM MST Thursday
     Winter Weather Advisory from 5 AM to 5 PM MST Wednesday
     Winter Storm Watch from Wednesday afternoon through Thursday
     afternoon IDZ015-016-030.
OR...Winter Weather Advisory from 11 PM MST /10 PM PST/ this evening
     to 5 AM MST /4 AM PST/ Thursday ORZ061-063.
     Winter Storm Warning from 4 AM Wednesday to 10 AM PST Thursday
     Winter Weather Advisory from 5 AM to 11 PM MST Wednesday ORZ064.



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