Weather across America

(NATIONAL) There is a Moderate Risk of excessive rainfall over parts of the Southern Plains/Lower Mississippi Valley, a Slight Risk of severe thunderstorms over parts of the Great Lakes through the Southern Plains, and temperatures will be 10 to 30 degrees below average over parts of the Upper Midwest.

A strong storm over the Southwestern Ontario, Canada, will northeastward farther into Canada through Tuesday evening. The associated front will destabilize the atmosphere from the Great Lakes to the Southern Plains. Therefore, the SPC has issued a Slight Risk of severe thunderstorms over parts of the Great Lakes/Western Ohio Valley, and two smaller regions over the Southern Plains through Monday morning. 

The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. However, there is an increased risk for large hail, two inches or greater over parts of southwestern Texas.  

The showers and thunderstorms will produce heavy rain along the associated front on Sunday. Therefore, the WPC has issued a Moderate Risk of excessive rainfall with these thunderstorms along the front through Monday morning over parts of the Southern Plains and Lower Mississippi Valley.

The associated heavy rain will create numerous areas of flash flooding. Furthermore, many streams may flood, potentially affecting larger rivers.  

In contrast, the low and high pressure in Canada will funnel cold air over the Upper Midwest producing temperatures 10 to 30 degrees below average. The temperatures will begin to moderate late Monday into Tuesday. Along with the cold, snow will continue over parts of the Upper Midwest through Monday morning. Then, light snow lingers over parts of the Upper Mississippi Valley/Upper Great Lakes through Tuesday evening.  

On Monday, the showers and thunderstorms will move eastward from the Lower Great Lakes to the Southern Plains and Western/Central Gulf Coast, as the severe thunderstorm threat decreases to a Marginal Rick along the front. In addition, the excessive rainfall threat reduces to a Marginal Risk over parts of eastern/southern Texas into the Lower Mississippi Valley.  

Meanwhile, upper-level energy moving over the Central/Southern Rockies will produce snow over parts of the Central/Southern Rockies through Monday afternoon.  

Furthermore, a front will move onshore over the Pacific Northwest overnight Sunday and move inland to the Northern Rockies/Great Basin by Tuesday afternoon. The system will produce rain and the highest elevation snow over parts of the Northwest, with rain extending into the Northern Rockies for Monday into Tuesday.