From the Pocatello Forecast Office

...Winter storm system to bring several inches of snow to the
Idaho Central Mountains Tuesday night and Wednesday...

.A winter weather disturbance will bring snow to the mountains of
Idaho Tuesday night and Wednesday. Snow accumulations of 2 to
6 inches is expected with accumulations of 5 to 10 inches
possible above 8000 feet elevation. Travel through mountain
passes may become difficult.

Upper Snake Highlands-South Central Highlands-Caribou Highlands-
Wasatch Mountains/Idaho Portion-
Including the cities of St. Anthony, Ashton, Driggs, Victor,
Henry, Soda Springs, and Montpelier

...WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM 5 AM TO 11 PM
MST WEDNESDAY...

* WHAT...Snow expected. Plan on slippery road conditions,
  including during the evening commute on Wednesday. Total snow
  accumulations of 2 to 4 inches, with localized amounts up to
  10 inches, are expected.

* WHERE...Caribou Highlands and Wasatch Mountains/Idaho portion.
  Highway 30 from McCammon to Wyoming border, South Central
  Highlands, including Interstate 84 from Interstate 84/86
  junction south to Juniper. Upper Snake Highlands including the
  Highway 20 corridor from Ashton Hill north to Montana and Pine
  Creek Pass.

From the Riverton Forecast Office

810 PM MST Tue Dec 19 2017

...Snow moving into Northwest Wyoming tonight...

.Moderate to heavy snow is expected late tonight through early
Wednesday evening.

Yellowstone National Park-Teton and Gros Ventre Mountains-
Including the cities of Lake, Mammoth, and Old Faithful
810 PM MST Tue Dec 19 2017

...WINTER WEATHER ADVISORY IN EFFECT FROM 2 AM TO 8 PM MST
WEDNESDAY...

* WHAT...Snow expected. Plan on slippery road conditions,
  including during the morning commute on Wednesday. Total snow
  accumulations of 4 to 8 inches. Localized snow amounts up to 10
  inches in southwest portions of Yellowstone Park and the Tetons.

* WHERE...Yellowstone National Park and Teton and Gros Ventre
  Mountains.

* WHEN...2 AM to 8 PM Wednesday.

* ADDITIONAL DETAILS...Be prepared for reduced visibilities at
  times. Travel over Teton Pass could be hazardous at times.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Weather Advisory for snow means periods of snow will
cause primarily travel difficulties. Be prepared for snow covered
roads and limited visibilities, and use caution while driving.
The latest road conditions for the state you are calling from can
be obtained by calling 5 1 1.