Heavy Snow in Idaho, February 3 to 4, 2017

Area Forecast Discussion
National Weather Service Pocatello ID
316 AM MST Fri Feb 3 2017

.SHORT TERM...Today through Sunday. We return to an active weather
pattern heading into this weekend. Precipitation picks up this
morning especially across portions of the central mountains
northeast into the Island Park area. Other pockets of light snow
will persist as well. During the afternoon, we will see
things pick up in the mountains especially in the Sawtooths and
eastern highlands. These locations will see almost non-stop
moisture falling especially above the valley floors until later
Sunday. With several "waves" of rain and snow moving through,
other locations may see more breaks or overall lower totals. We
are converting all of our watches to warnings for today and
Saturday. For the Sawtooths and Wood River Valley: we are looking
for 6-12" from south of Hailey through Ketchum and 1-2ft for the
the mountains and also through the Stanley Basin. For the eastern
highlands: Areas above 6000ft should see 6-12" with higher
amounts above 7000ft along the Wyoming border from near Alpine to
south of Targhee Pass. For the Lost River/Pahsimeroi Ranges: Up to
8" is possible above 7000ft with much lighter amounts below that.
We are adding these areas to the advisory, especially when you
factor in the wind. Winds will be an issue also for warning areas.
For the rest of eastern Idaho, a mix of rain and snow will limit
amounts to under 3" through tomorrow afternoon as snow levels by
afternoon will be between 5000-6500ft. In fact, many areas across
the Snake Plain and for the southern valleys will go to rain and
likely stay there. This is due to inversion FINALLY breaking
and/or downslope keeping temperatures in the 30s and 40s even at
night. These areas are still looking for some decent rainfall,
although highest amounts may not be as widespread as previously
thought. (For more information, you can read all about in the
hydrology section farther down.)

Rain and snow continues through Sunday, although lower elevations
should see less precipitation. The mountains will still see some
decent snowfall especially in the Sawtooths. Wind and warm
temperatures will remain. Snow levels drop a bit but not too much.
Keyes

.LONG TERM...Sunday night through Friday.

Extended period continues to look wet and relatively warm. Expect a
round of precipitation on Sunday night continuing into Monday night.
Bulk of the precipitation will fall on Monday. Snow levels for this
event will sit around 5500 feet with snow levels falling Monday
night. Like many others, this event looks wet with advisories or
warnings possible. Expect a brief break before another round arrives
late Tuesday afternoon and persists through Wednesday. Snow levels
will start low Tuesday night, around valley floors before climbing
to 5500-6000 feet Wednesday afternoon. This event looks wet as well
with heavy snow possible. Models now showing another system arriving
by Friday and continuing into Saturday, possibly wet and heavy as
well. This system looks relatively warm though with snow levels
possibly over 7000 feet.

Valle

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.AVIATION...Rain/Snow will move into the area Today. KSUN will see
biggest impacts as the precipitation will arrive this morning,
possibly reducing vis or ceilings below airfield mins. Rain/snow
will spread east and arrive at other sites during the afternoon.
Think widespread mvfr conditions are possible along with pockets of
ifr by this evening. Expect brisk conditions to develop late this
afternoon or this evening across parts of the area.

Valle

&&

.HYDROLOGY...Looking at the NOHRSC web site we have roughly 1 to 6
inches of snow water equivalent moisture available to melt in
various locations within the lower elevations of SE Idaho
(Pocatello to Burley). Warming temperatures through the weekend
along with breezy winds will aid in the process of preparing the
snow for a rapid melt sometime this weekend or early next week.
Right now, many of these areas will see up 0.25 inches with
some areas seeing between 0.25-0.50 inches through Saturday
evening. The models are still wavering on where these heavier
pockets will fall, but the trend still exists for some decent rain
on snow across the Magic Valley, Lower Snake Plain and valleys
south toward the Utah border. We may see some downslope limit
rainfall from Pocatello to Burley, but the downslope wind and warm
air will make up for that and continue the melting process. Expect
rapidly increasing flood risk due to rain on snow and/or snowmelt.
The next period of elevated rainfall over snow looks to occur
Monday/ Tuesday, extending the area of impact further east to
around Pocatello and lower valleys south toward the Utah border.
Huston/Keyes

&&

.AIR STAGNATION...We should finally high pressure and inversions
give way in the next 24 hours. Air quality should beginning
improving over the weekend.  Keyes

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 6 AM this morning to 5 PM MST
Saturday for IDZ032.

Winter Storm Warning from 3 PM this afternoon to 5 PM MST
Saturday for IDZ019-023-025.

Winter Storm Warning from 6 AM this morning to 5 PM MST Saturday
for IDZ018-031.

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