Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
242 FXUS65 KGGW 182029 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 229 PM MDT Mon Aug 18 2025 .DISCUSSION... KEY MESSAGES: 1) Dangerously hot temperatures are expected over NE Montana for Tuesday and Wednesday with high temperatures between 95 and 100 degrees. 2) A cold front Wednesday night will increase shower and thunderstorm chances with cooler weather late week. WEATHER PATTERN OVERVIEW: Upper ridging extending over Montana will lead to very hot and dry conditions on Tuesday and Wednesday. Have nudged forecast highs to a range of 95 to 105 degrees, close to the NBM 75th percentile, to account for prefrontal warming ahead of the cold front Wednesday night. There is growing concern in the valley locations along the Yellowstone River for example near Terry and Glendive that excessive heat will be particularly dangerous where some places may see highs above 105. Future shifts will have to carefully weigh whether this merits an upgrade to Excessive Heat Warning, especially given that this is the first significant heat spell in some time. Expect increasing showers and thunderstorms Wednesday night into Thursday with a cold frontal passage. Markedly cooler temperatures are then expected to settle into the region later in the week. FORECAST CONFIDENCE & DEVIATIONS: NBM was used for much of the forecast cycle which is overall fairly quiet. That said, temperatures were nudged toward NBM75 for Tuesday and Wednesday high temperatures to account for pre-frontal compressional warming. There is particular concern in the Yellowstone River Valley Wednesday afternoon. Heat risk remains squarely at a 3 for much of the area, but given that this heat is of significant impact compered to recent conditions, effects could be somewhat amplified. && .AVIATION... LAST UPDATED: August 18, 2025 at 2030Z. FLIGHT CAT RANGE: VFR . DISCUSSION: Aside from a few mid and high level clouds, mainly dry weather conditions are expected. Very hot temperatures above 100 degrees for Tuesday and Wednesday afternoon could provide impacts to heat sensitive equipment. WIND: Light and variable overnight. && .GGW WATCHES/WARNINGS/ADVISORIES... Heat Advisory from 10 AM Tuesday to 8 PM MDT Wednesday for Central and Southeast Phillips-Central and Southern Valley- Daniels-Dawson-Eastern Roosevelt-Garfield-McCone-Northern Phillips-Northern Valley-Petroleum-Prairie-Richland-Sheridan- Southwest Phillips-Western Roosevelt-Wibaux. && $$ weather.gov/glasgow