Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
784 FXUS65 KGGW 102215 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 315 PM MST Wed Dec 10 2025 .DISCUSSION... KEY MESSAGES: - Significant ice accumulation from freezing rain is expected along and near the Hi-Line now through Thursday. - A strong winter storm with snow accumulation is possible Thursday evening through Saturday morning. - Bitter cold temperatures are expected Thursday night through Saturday night. WEATHER PATTERN OVERVIEW: The prevailing upper-level flow is directing favorable precipitation up and over the quasi-stationary or waffling front draped across northeast Montana. The associated temperature profile supports a wintry mix of precipitation. Combining periods of expected freezing rain into one group of 24 to 30 hours shows about a quarter of an inch of ice is expected to accumulate through a swath of NE Montana. Having not seen this strong of a signal for accumulating ice for many years, we felt it was wise to upgrade the general winter weather advisory to a winter storm warning for ice for the selected zones along and near the Hi-Line. The most impactful period for ice will be later tonight through Thursday morning. On the heels of that winter hazard, will be another winter storm set to bring accumulating snow to most locations. To help emphasize more the ice impacts today and tomorrow, we chose to delay the upgrading the watch for snow until later tomorrow after the freezing rain has ended. But, to help decision makers plan for a busy travel weekend, it may be prudent to consider upgrading sooner if confidence increases in timing and snow amounts. Also connected to this accumulating snow storm on Friday and Saturday, is a push of arctic air from the north, which will combine with gusty north winds to create wind chill values of -25 to -35 degrees, which will likely require a cold weather advisory for wind chills through the remainder of the weekend. Late Saturday and into Sunday, the colder arctic air moves into the Great Lakes region and the northern Rockies and northern High Plains see a push of warm air and quiet weather, followed by a chinooking pattern off the Rocky Mountains. This would bring multiple days of melting to begin next week. FORECAST CONFIDENCE & DEVIATIONS: Average to high confidence on the mixed precipitation occurring today, tonight and Thursday, along with fluctuating temperature boundaries. Average confidence in ice accumulation up to a quarter of an inch. Average to high confidence on the accumulating heavy snow in the SW half of the forecast area between from Thursday through Saturday with lower confidence in the specific snow amounts for the NE corner zones. High confidence on the bitter cold temperatures Thursday night through Saturday night. && .AVIATION... LAST UPDATED: 2215Z, Wednesday afternoon 12/10 FLIGHT CAT: LIFR to borderline VLIFR. Expect airport minimums. DISCUSSION: Overrunning precipitation and a vertical temperature profile has led to conditions favorable to the formation of a wintry mix of precipitation - including freezing rain. Today`s push of freezing rain was a small taste of what to expect late tonight through Thursday. Any outdoor exposed airport equipment could see a quarter of an inch of ice accumulation, especially for KGGW and KOLF. KSDY may see around one tenth of an inch of ice and KGDV will likely only get a trace of ice. WIND: A persistent SE wind has kept speeds stronger than expected for KGGW, funneling up the Milk River Valley. This afternoon, from the SE around 15 to 20 kts. This evening and tonight, light and variable if not calm. Thursday, from the NW around 5 kts. Thursday afternoon and evening, from the north at 20 kts. && .GGW WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until 8 PM MST Thursday for Central and Southeast Phillips-Central and Southern Valley-McCone-Northern Phillips-Richland-Western Roosevelt. Winter Storm Watch from Thursday evening through Saturday morning for Central and Southeast Phillips-Central and Southern Valley-Dawson-Garfield-McCone-Northern Phillips-Petroleum- Prairie-Southwest Phillips. Winter Weather Advisory until 8 PM MST Thursday for Daniels- Dawson-Eastern Roosevelt-Garfield-Northern Valley-Petroleum- Prairie-Sheridan-Southwest Phillips-Wibaux. && $$ weather.gov/glasgow