Cold high pressure over West-Central Canada and upper-level energy will aid in producing heavy snow over parts of the Northern Rockies into the Northern Plains.
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Further, the cold air associated with the high will be 20 to 35 degrees below average over parts of the Northern Rockies to the Northern High Plains.
In addition, the snow and cold will produce a long-duration winter storm that will continue from the Northern Rockies to the Northern Plains.
Another round of snow is expected on Thursday before ending on Friday.
Further, periods of heavy snow exceeding 1 inch per hour in the Northern Rockies and High Plains through Friday morning may lead to difficult travel conditions due to snow-covered or icy roads and poor visibility in areas of blowing snow.
Moreover, there is a high chance greater than 70 percent probability of an additional 8 inches of snowfall over northwest Wyoming and much of southwestern to northeastern North Dakota.
Additionally, temperatures will be well below normal by 20-30 degrees across the Northern High Plains and Northern Plains through the weekend.
Low temperatures in the teens and single digits will be common over much of Montana into the northern Plains.
Wind chills may dip below zero at times.
Furthermore, weak onshore flow will produce scattered rain and higher-elevation snow over parts of the Pacific Northwest and Northern/Central California that will wind down by Thursday morning.
Meanwhile, favorable upper-level flow and moisture streaming northward over the Plains from the Western Gulf of Mexico will create showers and thunderstorms with heavy rain over the Central/Southern Plains.
Therefore, the WPC has issued a Moderate Risk of excessive rainfall with these thunderstorms over parts of the Central/Southern Plains through Thursday morning.
The associated heavy rain will create numerous areas of flash flooding.
Furthermore, many streams may flood, potentially affecting larger rivers.
On Thursday, a front over the Upper Great Lakes to the Central High Plains will have moisture pooling along the boundary, producing showers and thunderstorms with heavy rain.
Therefore, the WPC has issued a Slight Risk of excessive rainfall over parts of the Upper Mississippi Valley/Upper Great Lakes from Thursday into Friday morning.
Additionally, on Thursday, favorable upper-level flow and moisture streaming northward over the Plains will create showers and thunderstorms with heavy rain.
Therefore, the WPC has issued a Slight Risk of excessive rainfall with these thunderstorms over the Southern Plains.
The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable.
On Friday, a front extending from the Upper Great Lakes to the Central Plains will move to the Great Lakes to the Southern Plains by Friday evening.
The boundary will trigger showers and thunderstorms from the Great Lakes to the Southern Plains on Friday.
Elsewhere, easterly flow off the Atlantic will create showers and thunderstorms over parts of Florida through Friday. ■