


Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
197 FXUS65 KMSO 180901 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 301 AM MDT Wed Jun 18 2025 .DISCUSSION... KEY MESSAGES: - Warm, dry and breezy conditions today. - Strong thunderstorms, with isolated severe threat, Thursday into Friday across west-central and southwest Montana. - Widespread precipitation Friday night into the weekend, with cooler temperatures, and high elevation snow. A weak ridge of high pressure will remain across the Northern Rockies through today, with above-normal temperatures, and plentiful sunshine. Deep atmospheric mixing will lead to breezy winds this afternoon, with gusts of 15-25 mph in the valleys and 25-35 mph across the higher terrain. Showers and thunderstorms will return Thursday across southwest Montana, focusing across Ravalli, Granite, Deer Lodge, and Silver Bow Counties and in Lemhi County, ID as southwesterly flow transports Pacific moisture and instability into the region. Forecast soundings suggest inverted-V profiles, along with modest shear and instability, supporting the development of strong to isolated severe thunderstorms (5% probability), with strong outflow winds being the primary concern. The risk for strong to isolated severe thunderstorms expands into west-central Montana and along the divide in northwest Montana Friday. A cut-off low will move inland across the Pacific Northwest, with south-southwest flow bringing increased moisture and instability, while the low provides synoptic ascent. Forecast models suggest isolated thunderstorms will form early in the morning, with storm coverage expanding by the early afternoon, spreading south to north from Lemhi County, Idaho and southwest Montana into west-central Montana and along the divide in northwest Montana. The environment will support storms capable of producing small hail, gusty winds, and periods of heavy rain. An isolated storm or two will be capable of producing large hail and strong to potentially damaging winds, with the greatest threat focused along the divide in southwest Montana, north of where a surface low will deepen in the afternoon. The aforementioned closed low will move eastward across the Northern Rockies late Friday into the weekend, with widespread precipitation, cooler temperatures, and high elevation snow impacting the region. Guidance has trended the lows track further south over the last 24-hrs, with ensemble means placing the mid- level circulation moreso along the USA-Canada border, while previous runs moved the low into southern Alberta. This trend has lead to higher precipitation amounts in the forecast, with probabilities for >0.50 inches of rain increasing above 80% north of I-90, with 40-60% south of I-90. Flathead and Lincoln Counties are favored to receive the highest precipitation amounts with a 70 and 50% chance for an inch or more of precipitation, respectively. Those with plans in the backcountry and/or high elevations should begin preparing for cold temperatures, accumulating snow, and raw conditions, including Glacier Park. Speaking of Glacier Park, snow amounts have trended higher, with models indicating 3-12 inches of snow, with the highest accumulations above 7,000 feet. Of particular note is Logan Pass, where there`s a 50% chance for 4 inches or more and a 15% chance of a foot or more. The low will begin to exit the area Sunday, with scattered showers continuing with a northwesterly flow pattern. && .AVIATION...VFR conditions will continue today, with plenty of sunshine. Deep mixing will promote gusty winds after 18/1900Z, with 20-25kt gusts. Shower and thunderstorm activity returns Thursday across southwest Montana and Lemhi County, ID. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$