Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 142058

Area Forecast Discussion
National Weather Service Pocatello ID
158 PM MST Sat Jan 14 2017

.SHORT TERM...Tonight through Monday night. Dry northwesterly flow
to remain in place through Monday throughout the region without
much change in the airmass characteristics. This will mean a
forecast of persistence -- with more patchy freezing fog after
sunset tonight through the post-dawn hours in valley areas, and
again Sunday night/Monday morning. If traveling, be prepared for
rapid changes in visibility and reduce speeds due to low
visibility in spots and the potential for some ice buildup due to
patchy freezing fog. For temperatures, chose the coldest guidance
and manually adjusted the Arco Desert and Big/Little Lost River
and Pashimeroi valleys colder based on recent trends. Challis
recorded the coldest temperature in the lower 48 yesterday
morning, and came within 3 degrees of breaking their all-time
record low this morning with a low of -31. Expect lows here to dip
to near -30 again, as well as at Stanley and Copper Basin. With
temperatures this cold, very little wind will result in
dangerously low wind chills. Avoid prolonged exposure to
these conditions. Elsewhere, temperatures remain below seasonal
averages through Monday. AD/Valle

.LONG TERM...Tuesday through Saturday.

Big weather system arriving for midweek. Looks like it may slow down
a little and arrive Tuesday night or Wednesday. But expect another
warm moisture rich system to move into the area for Wednesday and
Thursday. Expect rain or rain/snow mix below 5500 feet with very
heavy snow above this level. Could see 10 to 15 inches of snow from
Hailey to Stanley with up to 2 feet likely on the surrounding
mountain ranges. The Snake Plain and Magic Valley will see much less
with most of the snow falling Thursday after the cold front passes.
From Blackfoot north, 3 to 5 inches is possible with a couple inches
possible south and west of there. The southern and eastern highlands
may see 4 to 8 inches. Potentially, the Magic Valley could see up to
0.75 inches of rain from this which could create or aggravate
existing flooding problems.

After this system exits the region, another weaker system will
arrive for Friday/Saturday. This looks like all snow, but with much
much lesser amounts.



.AVIATION...Some patchy fog is possible around IDA and BYI
tonight because of proximity to the Snake River. Fog and low
stratus is possible near PIH because of proximity to local
industry interacting with the temperature inversions in place.



.HYDROLOGY...An Areal Flood Advisory will remain in effect for
Cassia and southern Minidoka county through the weekend.
Floodwaters on roads has frozen over and several county roads
remain closed.

A Flood Warning continues at Antelope Creek in Darlington due to an ice
jam on this creek along with runoff from early-week rainfall and
snowmelt has resulted in some homes being flooded in Darlington.

The Flood Advisory for the Challis River Bridge south of Challis
will continue at the request of the BLM and local law enforcement.
Citizens are urged to avoid this area.

Below freezing temperatures continue in the forecast into early
week leading to risk for ice jam flood concerns on rivers and
small streams across Southeast Idaho. The area is not expected to
receive any additional precipitation through Monday night. A new
storm system will bring a new round of precipitation and warmer
temperatures to SE Idaho at the earliest late Tuesday lasting
through Thursday, with the potential for another storm system late
in the week into early next weekend. The first system is expected
to bring a mix with rain or a changeover to rain across the Snake
Plain and Southern Highland valleys Wednesday night into Thursday
which may cause renewed flooding concerns with rain falling on
existing snowpack and frozen ground. At this time, rainfall
amounts are expected to be slightly less than our previous system.



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