Discussion
Northeast winds Friday night through Saturday will create choppy conditions on area lakes.
A cutoff low pressure system brings widespread rain, with snow above 6,000 feet Saturday night through Monday morning.
Showers and thunderstorms will continue over western MT through noon, these showers are powered by Jet Stream energy aloft. Afternoon showers will continue but mainly in the mountains east of US-93, orographic uplift will become the main instigator.
Friday evening an easterly gradient develops over the region and winds slowly turn east northeasterly. Generally, gusts up to 30 mph in the gaps should be the strongest winds. For boaters going out early Saturday prepare for choppy conditions on area lakes.
This is a cooler air mass, Thursday was the warmest day with both Friday and Saturday 8 to 12 degrees cooler. Then as the closed low moves over the region Sunday, under the core of low pressure temperatures may cool an additional 10 to 15 degrees. Snow levels that are 8000-9000 feet on Saturday, will lower to around 7000 feet on Sunday. Historically under the core of low pressure snow levels are an additional 1000 feet lower, to around 6000 feet on Sunday evening, due to dynamic cooling processes. Still it is September and the main message for snow is the same for rain. Sunday into Monday in the back country will be wet and raw, unprepared outdoor enthusiasts may encounter hypothermia inducing conditions.
The models have continued a northward trend in the core of best precipitation, still I-90 and northward including all of Idaho and Clearwater Counties ID, have a 80 to 90% chance of widespread 0.25 or more precipitation. South and west to Butte, that chance lowers to 30 to 40%. Closed lows are notorious for wobbling at the last minute, so if total precipitation is important to your activities stay abreast of future forecasts. Up to 1 inch in the highest terrain of Idaho and Clearwater Counties is still possible, along with the Mission and Seeley Swan Mountains.