Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 141035

Area Forecast Discussion
National Weather Service Pocatello ID
335 AM MST Wed Feb 14 2018

.SHORT TERM...Today through Friday. We are seeing a couple of
areas where stratus has developed overnight, from around Lone Pine
to Island Park and around Bear Lake. There COULD be some very
light snow fall out of that but nothing of consequence. The threat
of fog is also low at the moment. All eyes turn to this afternoon
and tonight, as a quick moving storm trucks across the state.
Light snow moves into the central mountains and Upper Snake
Highlands (especially along the Montana border) this afternoon. It
also looks like some light snow forms across the peaks in the
southern highlands. We also expect some very light rain and snow
to develop across the western Magic Valley. Strong winds should
shadow the I-86 corridor and much of the Snake Plain. For this
evening, precipitation quickly shifts into southern and eastern
highlands. It looks like with warmer air and strong winds
continuing, the chances of appreciable rain or snow across the
Plain is low although we could see a dusting in some spots. There
is a little better chance of rain or snow west of Burley and
Shoshone. For the central mountains, lingering light snow is
forecast. By sunrise Thursday, pockets of snow persist across
portions of the central mountains and eastern highlands.
Confidence isn`t high YET but all signs toward a convergence band
developing across the far Upper Snake Plain and Highlands. The
current trend keeps it north of a Mud Lake to Driggs line early,
then shifting southwest to near Pocatello to Craters of the Moon
by afternoon. We are should see the eastern end settle into the
Teton Valley, Swan Valley and adjacent highlands. Snowfall amounts
through 5am Thursday seem pretty solid at anywhere from a dusting
to 3" in highlands areas. We could see some localized amounts
over that in the Sawtooths, the Big Holes near Driggs and along
the Wyoming border. Again, not much if anything for the Plain. For
Thursday, the only concern for snowfall would be with that
convergence band. Initial forecasts (with low confidence) show up
to 2" along and east of I-15 and US-20 from Ashton to Pocatello.
Locally higher amounts could fall around Pine Creek Pass and
Blackfoot Reservoir. Blowing/drifting snow will become an issue as
winds increase today at higher elevations, perhaps even above
pass level initially. While it will be an impact, we are not
expecting widespread travel issues from that. There could be some
blowing of light snowfall at lower elevations but again, big or
long- lasting impacts aren`t anticipated. At the moment, we are
not issuing any winter weather or wind-related headlines as
nothing stands out or is long enough to warrant anything.

Northwest flow keeps some snow possible Friday across the central
mountains and from Island Park to near Wayan. We can`t rule out
some light precipitation in other areas, but the chances of that
are pretty darn low.  Keyes

.LONG TERM...Friday night through Wednesday. Leading shortwave
drives through the region Friday night for showers mainly in higher
elevations. Stronger shortwave driving into the PacNW by late
Saturday spreads precip across the region, mainly into Saturday
night. There are some differences among the models. The operational
GFS and ECMWF are sharper with the trough and stronger with warming
ahead of it than the ensembles. Heaviest snowfall should occur
Sunday into Monday, tapering Monday night as trough axis shifts
further east.  The ensembles remain significantly less amplified
than the operational models even into early in the week. Thus,
heading into Tuesday, the operational model guidance has trended
significantly lower, though there is quite a bit of spread in
solutions. Gave a healthy nudge to the numerical guidance, going
quite a bit colder for Tuesday. Region remains under the influence
of cool northwest flow, and another shortwave dropping through BC
Canada toward Idaho during the day Wednesday. GFS a little faster
than ECMWF with this feature. Either way, temperatures remain cool
moving into mid week. DMH


.AVIATION...Stratus in place across northern borders of the region,
and over higher elevations in the southeast corner. These ceilings
likely MVFR or IFR. There is a possibility of keeping low confidence
shift to lower ceilings and vis for a few of the terminals this
morning around sunrise. Precipitation spreads across the region
mainly this evening, though could be mid afternoon for KSUN. Expect
lowering ceilings and vis, with precipitation expected to be snow at
all locations. DMH



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