...Much cooler air will cross the Western US setting the stage for a
significant late season snowstorm across parts of the Intermountain West to the central Rockies through the weekend...
...An increasing threat of severe weather and possible tornadoes will
occur across the nations midsection on Sunday into Monday...
...Showers and thundershowers will continue across the Gulf Coast and be scattered out ahead of a front crossing the Ohio Valley and Northeast early in the forecast...
A deepening upper trough over the Western states will spread cooler air across much of the West by early Sunday.
A strong cold front will lie over the middle of the country on Sunday morning with rain changing to snow and only snow at the highest elevations across western Montana, central Idaho, Wyoming, Utah and Colorado.
By Sunday evening, heavy snow with accumulations likely to be greater than a foot in places will impact large portions of Wyoming, Colorado and the mountains of Utah.
Some of the hardest hit regions could occur in central and southern Wyoming, much of the Colorado Front Range, including Denver, and the Wasatch/Uinta ranges in Utah.
This storm system will also be associated with a strong cold front
separating the unseasonable chill over the West from very warm, humid conditions moving northward from the Gulf of Mexico.
Therefore, there will also be a significant threat of severe weather over parts of the Southern and Central Plains into the mid Mississippi Valley on Sunday and extend from the Gulf Coast northward across the Mississippi Valley into the lower Great Lakes on Monday.
In addition to the threat of severe thunderstorms and tornadoes, flash flooding will also be a threat due to heavy thunderstorms, especially over the lower Mississippi Valley on Monday.
A weak front will continue to push eastward across the Ohio Valley into
the Northeast on Saturday.
Scattered showers and thundershowers will precede the front before it pushes offshore on Sunday.
Meanwhile, a very moist flow off the Gulf of Mexico will continue to produce additional showers and thunderstorms along the Gulf Coast, adding to the threat of flash flooding due to recent heavy rainfall.
The front will dissipate as southwesterly flow begins to cover much of the central to eastern United States with very warm and humid conditions expanding in coverage from the Southern Plains and Southeast on Sunday to much of the eastern US on Monday.