Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 181721

Area Forecast Discussion
National Weather Service Boise ID
1021 AM MST Wed Jan 18 2017

.DISCUSSION...A mixed bag of wintry precip is falling around the
CWA this morning. Freezing rain was noted in southeast Oregon, and
snow pellets (sleet) and snow have been reported across most of
the area. We expect the sleet to diminish as most of the
precipitation turns over to snow for the afternoon for all but
southern Malheur and southern Harney counties. Winds have been
strong enough (20-30 mph) to result in blowing snow in parts of
Baker County, near Jerome, and near Mountain Home. High elevation
sites are also reporting strong winds. Latest indications are that
precip will remain snow well into the evening in the Upper
Treasure and western Magic Valleys. This will significantly change
the expected snow totals for these areas. We are releasing a
special weather sounding shortly, and these data will be used to
help modify the current forecast for the afternoon package.
Freezing rain is still possible in valleys, especially the lower
Treasure Valley, through tomorrow morning. No update at this


.AVIATION...MVFR/IFR, isolated LIFR in heaviest showers today.
Isolated areas of sleet this morning with most precip falling as
snow. Expecting snow to be the predominant precip type today
through around midnight, then switching over. Heaviest amounts
expected this afternoon. Will see more of a wintery mix towards
the Magic Valley. Surface winds generally southeast 10-20 kts.
Gusts to 30 kts in Baker County. Northeast winds 30 kts near KJER.
BLSN in these areas. Winds aloft southwesterly 35 to 45 kts at 10
kft MSL.


.HYDROLOGY...Model trends indicate lesser amounts of precipitation
falling as rain across the Treasure Valley through the duration of
the storm. Surface temperatures are expected to rise above freezing
but not a dramatic warmup, so melting of the snowpack in the valley
shouldn`t be excessive. Feeling is that the threat of minor flooding
due to rain and snowmelt is pretty small. Impacts are more likely to
occur on Thursday an be limited to standing water along some city
streets and highways where snow and ice may be clogging gutters and
storm drains.

Ice jams on the Snake River around Ontario and Payette downstream to
near Weiser remain a concern. Folks in low-lying areas near the
Snake River, especially around Ontario and Payette should continue
to monitor river conditions and be prepared for fluctuating river
levels and possible lowland flooding due to ice jams.


SHORT TERM...Today through Thursday...Freezing rain occurred for
a few hours in Baker City and Burns before changing over to snow
or a mix of freezing rain and snow. The forecast for the winter
storm remains complicated, with a mixture of snow, freezing rain
and rain in SE Oregon and SW Idaho through Thursday. The challenge
will be locations for the freezing rain and mix of weather
elements. Latest model temperatures have trended slightly lower in
the lower valleys today, likely due to the colder air mass already
in place this morning. New model runs suggest that the valley
inversion will mix out a little later this evening in the Boise
area than previously forecast. Biggest change will be lower snow
amounts near the Nevada border where temperatures this afternoon
will be above freezing and should remain above freezing for most
of tonight. Heaviest snow amounts are still on track for areas
generally north of a Burns-Ontario-Jerome line, with totals
widely variable in valley locations that receive snow mixed with
freezing rain and/or rain. Due to the complexity of the situation
and low confidence for temperatures and location of freezing rain,
will leave the winter weather headlines intact but with future
modifications as conditions warrant.

LONG TERM...Thursday night through Tuesday...Models in good
agreement through the period. They show brief clearing Thursday
night before the next Pacific storm comes into Oregon Friday with
more snow. Storm will make only gradual eastward progress Friday
but eventually it will bring several inches of new snow to all
areas through Saturday morning. Dry and milder Saturday afternoon
and night under narrow but relatively strong upper ridge, but the
next Pacific cold front will quickly follow in with snow showers
and cooler temps Sunday. Associated upper trough will come inland
Monday and Tuesday with more snow showers. Models then hint at a
pattern change to milder wx as an upper ridge develops along the
coast Tuesday.


ID...Winter Storm Warning until 5 PM MST Thursday IDZ016.
     Winter Storm Warning until 11 AM MST Thursday IDZ011-012-033.
     Winter Weather Advisory until 5 PM MST Thursday IDZ015-028-030.
     Winter Weather Advisory until 11 AM MST Thursday IDZ013-014-029.
OR...Winter Storm Warning until 11 AM MST /10 AM PST/ Thursday
     Winter Weather Advisory until 4 AM PST Thursday ORZ061.



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