This is our first official full week of the spring season, and it will be a great week to be here in Montana. The upper-level flow is beginning to turn northwesterly as pacific-driven moisture is riding over a large ridge beginning to settle over the northwestern part of the United States.
A small part of that moisture is approaching the Continental Divide early on this Monday morning, but there won't be much accumulation, or moisture making it over the Divide due to a lack of total moisture as well as a lack of lift needed to substantiate bands of precipitation across the Divide. Accumulation today will be limited to high peaks in northwest Montana like the Cabinet, Mission, and Swan ranges, with around 6" of snow being the maximum.
Tomorrow, the large ridge will move farther inland and its center will plant itself directly over the Pacific Northwest. This ridge will begin moving east as the week progresses, and due to this eastward movement; Montana will see a significant warming trend throughout the week.
By Wednesday areas of Montana will see temperatures in the 60s, along with plenty of sunshine. By Wednesday afternoon it isn't out of the realm of possibility for Helena, Great Falls, or both to possibly top 70º.
Thursday will be the first chance of precipitation we see during our work week. As the ridge moves east, the upper-level flow will flatten behind it. This will allow a quick-moving shortwave trough to develop. However, the shortwave trough will stay hugging the Canadian border, bringing rain chances along the Hi-Line.
Mild sustained wind with strong gusts are likely this week as atmospheric high pressure settles over the state.
It appears that after the small and fairly isolated rain chance on Thursday, Montana will head into a decently-prolonged period of warmer/drier weather; which will be further intensified by a number of ridges that will settle over the west coast of the United States.