Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 416 PM EDT Wed Oct 10 2018 Valid 00Z Thu Oct 11 2018 - 00Z Sun Oct 14 2018 Day 1... ...Eastern Dakotas/Minnesota... Surface low pressure associated with a negatively-tilted upper level shortwave over the upper Mississippi valley will continue to deepen and track northeast overnight across the upper Great Lakes. Light to moderate precipitation within the comma-head centered over the eastern Dakotas and northwest Minnesota this afternoon will lift out to the northeast along with the departing low -- producing some additional light accumulations across northern Minnesota, with WPC probabilities indicating a Slight Risk for additional snow amounts of 4-inches or more after 00 UTC Thu. While widespread significant ice accumulations (quarter inch or more) are not expected, thermal profiles supporting a wintry mix may result in some light ice amounts centered across the Arrowhead region. ...Northern and Central Rockies... Increasing lift ahead of an amplifying shortwave dropping south out of western Canada will support snow showers with the potential for localized significant amounts across the higher peaks of the southwestern Montana and northwestern Wyoming ranges tonight. On Thursday, guidance continues to show energy digging south, with a positively-tilted upper trough developing over the western U.S. Low level warm air and moisture advection ahead of the trough along with modest frontogenesis is expected to support snow showers developing further south across the Utah and western to central Colorado ranges, with WPC probabilities indicating the potential for localized significant accumulations across some of the higher terrain. The probability of significant icing (quarter inch or more) is less than 10 percent. Day 2... ...Central Rockies... Snows developing on Thursday may continue into the evening hours, producing some additional, mainly light accumulations across the Colorado ranges before dissipating overnight. The probability of significant icing (quarter inch or more) is less than 10 percent. Day 3... ...Northern Rockies... Increasing low to mid level frontogenesis and upslope flow developing ahead of another shortwave digging southeast will support another round of mountain snows along the northern Rockies. This may produce some significant accumulations across the higher terrain within Glacier National Park and further south across the southwest Montana and northwest Wyoming ranges, including portions of Yellowstone National Park. The probability of significant icing (quarter inch or more) is less than 10 percent. Pereira