Weather across America

(NATIONAL) Hazardous weather is expected across the country this upcoming week.

Snow over the northern Rockies is forecast to expand into the northern Plains to the Great Lakes and down into the central Rockies for the next couple of days, there will be heavy snow along the Cascades, and there's a risk of heavy rain, flash flooding and severe thunderstorms from the southern Plains to Tennessee Valleys.

An upper-level trough dipping across the western U.S. will interact with an outbreak of arctic air from Canada to spawn an energetic low pressure system which will bring a variety of impactful weather across the mid-section of the country during the next few days.  

The leading edge of the arctic air currently dipping further south into the northern Rockies is expanding the coverage of snow across the northern High Plains along with sharply falling temperatures and gusty winds from the north. The snow is forecast to spread eastward across the northern Plains Sunday night and into Monday before reaching the Great Lakes on Tuesday.  

Meanwhile, a low pressure system is forecast to develop along the arctic front in the central High Plains on Monday as the arctic air mass continues its southward plunge through the northern Plains. This will gradually shift the snow southward from the northern Rockies to reach the central Rockies later on Monday and into Tuesday.  

In the mean time, the low pressure system over the central Plains is forecast to track northeastward along the arctic front and reach the Midwest later on Tuesday. A swath of sleet and freezing rain is expected to develop and expand eastward across the upper Midwest and into the central Great Lakes on Tuesday.  

Farther north, periods of snow are forecast to continue across the central Minnesota through the upper Great Lakes on Tuesday, where more than a foot of snow can be expected by Tuesday evening. 

In addition, winds are expected to remain strong and gusty across the entire northern tier of the U.S. and down into the central Plains through Tuesday as the low pressure system intensifies further. 

To the south of the low pressure system, moisture from the Gulf of Mexico will stream northward and support an emerging threat of heavy rain, flash flooding and severe thunderstorms to gradually expand from the southern Plains to Tennessee Valley during the next couple of days. 

Weak onshore flow and upper-level energy will produce coastal rain and higher elevation snow over the Pacific Northwest. The snow will be heavy along the Cascades through Monday night before tapering off. 

The arctic air settling across the northern Plains will slowly filter westward across the northern Rockies and into the Pacific Northwest with temperatures falling well below normal by Tuesday behind the arctic front. A trend toward colder conditions is also expected for the Southwest as a cold upper trough dips through the area during the next couple of days.  

Higher elevation snow and lower elevation rain are forecast to work their way southward later on Monday and into Tuesday as a low pressure system develops across the Desert Southwest. 

Elsewhere, fire risk is forecast to reach critical levels over the southern High Plains through Monday night as the developing low pressure system over the central Plains brings gusty winds and dry air across the area.