


Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
199 FXUS65 KMSO 202017 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 217 PM MDT Sun Apr 20 2025 .DISCUSSION... KEY MESSAGES: - Snow over mountain passes on Monday morning. - Unsettled spring-like weather will continue into the middle of next week with a warm-up later in the week. Some instability this afternoon is leading to isolated convective showers over western Montana. Some of these showers are producing lightning strikes. Although convection will wrap up early this evening, unsettled weather in the form of more widespread precipitation will continue. A trough of low pressure over western Canada will dig southward this evening into the Northern Rockies. This system, along with an associated cold front, will keep valley rain and mountain snow in the forecast through Monday. Snow levels will drop below about 4000 tonight. Motorists should expect a few inches of snow for Lookout, Lolo, Lost Trail, and Marias passes for the Monday morning commute. Moist northwesterly flow will bring continued mountain showers on Tuesday, especially for northwest Montana east of about Highway 93, the Idaho-Montana border, and the Clearwater range. The position of an upper level jet streak and an unstable atmosphere will be conducive to windy conditions during the day Monday as well. Those venturing to the higher terrain will experience ridgetop gusts of 30-40 mph. The forecast for late Wednesday is showing some uncertainty. Most solutions (about 75%) are showing a fast-moving open wave bringing scattered showers to southwest Montana and Lemhi County. The remaining 25% of solutions are showing a mid-level low pressure circulation over northwest Wyoming. This second solution would be capable of moderate winter travel impacts for Lemhi County and southwest Montana including Homestake Pass on Wednesday night and early Thursday morning. The current forecast is more reflective of the first, more probable, solution. As far as north-central Idaho, west-central Montana, and northwest Montana are concerned, Thursday and Friday are looking like the warmest days of the week and ensemble solutions are liking a brief period of high pressure. Another round of unsettled weather is the most probable solution for next weekend. However, timing and amplitude of a low pressure system moving onshore are still very much in question. && .AVIATION...Showers continue to increase in coverage across north-central Idaho and western Montana, as seen on satellite and radar imagery, with isolated thunderstorms also observed. High- resolution models indicate multiple rounds of showers from this evening through Monday morning as a trough approaches from the west and moves into the Northern Rockies. Snow levels are expected to lower to around 4,500 feet, with terrain becoming obscured in clouds and snow showers. Periods of reduced visibility, lowered ceilings, and gusts of 2025 knots are likely in the valleys, including near TAF sites. Showery conditions and increasing west winds are expected to persist on Monday as the trough moves overhead. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$