Discussion: A dynamic, spring storm is set to impact central Montana Thursday night and throughout Friday. Prior to that, a weak disturbance will bring showers and isolated thunderstorms to areas south and east of Great Falls on Wednesday afternoon and evening. Mainly for locations along and north of I-90. The disturbance moves into northeastern Montana later Wednesday night before clearing the state by Thursday morning.
The next storm system begins to move into southwestern Montana by Thursday afternoon. Rain showers begin to overspread central Montana after dinnertime and throughout the overnight hours. Rain could be moderate to heavy at times through Friday afternoon causing ponding on the roadways in some locations. An easterly, downslope wind may limit rainfall totals in parts of Meagher and Broadwater counties as well as into the Helena Valley. The heaviest rainfall looks to be somewhere around the Route 200 corridor, particularly areas west and south of Great Falls.
This storm system is much warmer than the last two, meaning lower elevations will see primarily rainfall. However, snow may mix in if the precipitation becomes heavy enough and drags down cooler air from higher up in the atmosphere. Accumulations should stay limited to elevations above 5000 feet. There could be over 6" of accumulations for mountain passes. Roads will be snow-covered traveling over these passes Thursday night through Saturday morning.
Wednesday: Partly to mostly cloudy. Showers and isolated thunderstorms develop during the afternoon south and east of Great Falls. Thunderstorms should remain non-severe. High temperatures in the upper 50s. Skies clear tonight as temperatures fall into the lower 30s.
Thursday: Increasing clouds. Rain showers begin to develop after dinnertime. High temperatures in the upper 50s to around 60. Overnight low temperatures in the mid 30s.
Friday: Rain showers. Showers will be more scattered in nature for the Hi-Line. High temperatures in the lower 40s. Showers diminish overnight as temperatures fall into the low 30s.
Saturday: Clearing out with partly cloudy skies expected. High temperatures in the low to mid 50s. Overnight lows in the low to mid 30s.
Sunday: Partly cloudy. Showers possible, especially in the mountains. Highs in the mid 50s. Overnight lows in the mid 30s.
Monday: Scattered showers. High temperatures in the mid 50s, overnight low temperatures in the mid 30s.
Tuesday: Showers taper, partly cloudy skies. Highs in the mid 50s.