An active weather pattern is forecast to continue over the Pacific Northwest and into the Northern Rockies through Thursday as a series of upper level shortwaves move around the northern edge of a high pressure ridge over the Pacific. At the surface, these shortwaves will be in the form of frontal troughs that will serve as focusing mechanisms for rain and heavy mountain snow. Given a rather persistent westerly flow from the ocean, moist upslope flow will enhance precipitation amounts on windward mountain slopes.
Parts of the Cascades, Bitterroots, and mountainous regions of Wyoming may see at least 12 inches of snow by Wednesday evening. A short period of warm and pleasant weather is expected for the eastern third of the country through early Friday as southwesterly flow dominates. By Friday, a cold front is forecast to approach from the west and bring a return to conditions more typical of February as we head into the weekend.
Low pressure exiting the upper Great Lakes will contribute to areas of snowfall across the northern Green Mountains of Vermont and northern White Mountains. The surface wave is expected to track across southern Maine on Thursday, with additional snowfall generated across the northern half, with some 4+ inch amounts anticipated. Northwest flow aloft and emergence of a clipper system in the vicinity of eastern Montana will be the two primary winter weather features Thursday and Friday.
The jet-level winds direct intense orographic lift across isolated portions of the higher terrain will produce heavy snowfall, especially the Bitteroots, Teton Range, northern Wasatch, and Colorado Divide.
There is a slight risk of severe thunderstorms today for the Tennessee Valley and southern Appalachians.