Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 162017

Area Forecast Discussion
National Weather Service Pocatello ID
217 PM MDT Fri Mar 16 2018

.SHORT TERM...Tonight through Sunday. The big low continues to
spin along the Washington/Oregon coast this afternoon. This storm
is still on track to move inland and over Idaho through the
weekend. It will split into 2 main lows, one moving right over the
state and the other dropping toward the Four Corners. We`ve seen
some light precipitation moving into the Upper Snake Highlands and
also across portions of the central mountains mainly from Hailey
to near Lone Pine. We`ve had a couple of showers try to form over
the Snake Plain but nothing really yet. The focus through tonight
for heavier snowfall (perhaps a little bit of rain early on) will
be from Island Park south and west in the mountains to the Wood
River Valley. The combination of moisture, a slow moving boundary,
and upslope will lead to some decent amounts especially late
evening onward. We will see some lighter rain and snow along the
southern extension of the band into the Snake Plain/Magic Valley
and southern highlands. Other showers are expected to develop
farther south and east. Those areas will see generally light
amounts as well, with the expectation areas from American Falls to
Ashton, and the Teton Valley seeing downslope and really limiting
things. On Saturday, the bulk of the snow continues in upslope
areas from the Wood River Valley to Island Park. As the low begins
slide east and the front along with it, showers will increase
across the rest of eastern Idaho. By late afternoon, the focus
will be in the highlands with decreasing showers across the Plain.
Snow amounts in WINTER STORM WARNING area are forecast to be 5-12
inches with locally higher amounts. Once you get into the
Challis, snow will be limited due to warmer temperatures and
downslope. For the WINTER WEATHER ADVISORY locations, look for 3-8
inches and locally higher in the mountains.There is some concern
we could be a little light on amounts, especially if upslope is
stronger or we see thunderstorms. The rest of eastern Idaho, snow
amounts will vary greatly. At lower elevations it could be
anywhere from a dusting to maybe 3 inches. For mountains spots,
some places higher up could see 3-6 inches. There will be some
wind for some blowing and drifting snow, but widespread impacts
from that aren`t anticipated even in areas that have headlines.
Showers continue across the Upper Snake Highlands and central
mountains Saturday night, which may lend itself to extending those
headlines but won`t make the call right now. As the low moves
over Sunday, showers are forecast over the entire area. Additional
snowfall will be spotty and on the light side of the scale. Keyes

.LONG TERM...Monday through Friday. Lingering effects from the
weekend storm continue on Monday near the Idaho Montana border into
the Island Park region as a final piece of energy swings past. Over
the rest of the area clearing skies and warming temperatures can be
anticipated as a ridge of high pressure temporarily builds.  Models
both agree on a strong low pressure system developing off the west
coast. This will place central and eastern Idaho in strong warming
pattern into mid-week.  As the low begins to move inland widespread
valley rain and heavy snow likely across all our mountains.  Initial
indication is this could be a very impactful storm with even
thunderstorms in the area depending on the orientation of the low
and upper jet stream along with a prolonged wet period extending
towards next weekend. VP


.AVIATION...Scattered valley rain showers and mountain snow showers
expected this afternoon with even a chance for some isolated
thunderstorms through 7 pm.  As the initial storm energy moves in
this evening  expect the Magic Valley into the central Idaho
mountains to deteriorate to MVFR and even some IFR conditions by 12z
tomorrow morning.  KPIH and KIDA will only see isolated rain showers
with brief periods of mvfr due to ceilings through the overnight
hours with larger impacted anticipated through the day tomorrow with
snow developed and periods of ifr possible.  KDIJ will be in a
similar situation but anticipate snow only for this location. VP


Winter Storm Warning from 6 PM this evening to 6 PM MDT Saturday
for IDZ018-031-032.

Winter Weather Advisory from midnight tonight to 6 PM MDT
Saturday for IDZ019.


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