Weather across America

(NATIONAL) Heavy snow over the Cascades and Sierra Nevada Mountains, snow, rain, and freezing rain over parts of the Upper Midwest into the Northeast, a Moderate Risk of severe thunderstorms over parts of the Southern Plains and a Slight Risk over the Ohio Valley plus High Wind Warnings and High Wind Advisories from the Southern Rockies and High Plains to the Ohio and Tennessee Valleys and Central and Southern Appalachians. 

A storm over the Central/Southern High Plains will move eastward off the Eastern Seaboard by Monday morning. The system will produce showers and severe thunderstorms over the  Central and Southern Plains. Therefore, the Storm Prediction Center (SPC) has issued a Moderate Risk of severe thunderstorms over parts of the Southern Plains through Monday morning. 

The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. In addition, there is a higher threat of wind gusts of 65 knots or greater, two-inch or greater hail, and EF2-EF5 over parts of the Southern Plains into the Middle Mississippi Valley. In addition, there is a marginal Risk of excessive rainfall over parts of the Central Plains into the Upper/Middle Mississippi Valley through Monday morning. The associated heavy rain will create localized areas of flash flooding, affecting areas that experience rapid runoff with heavy rain. 

Moisture streaming northward over the Plain/Mississippi Valley will create rain and light to moderate snow over parts of the Upper West overnight Sunday into Monday morning. Along the rain/snow line, there will be areas of light to moderate rain/freezing rain. On Monday, the rain and snow will move into the Great Lakes into parts of the Northeast. Likewise, light to moderate rain/freezing rain will also develop over the region on Monday. 

Overnight Monday, the snow will move into parts of New England, while areas of rain/freezing rain will come to an end over parts of the Great Lakes and Central Appalachians. The snow will continue over parts of the Northeast on Tuesday. The combination of snow and ice will result in reduced visibility and hazardous driving conditions. 

In the meantime, the threat of severe storms reduces slightly on Monday. Therefore, the SPC has issued a Slight Risk of severe thunderstorms over parts of the Ohio Valley from Monday into Tuesday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, a few tornadoes, and a minimal threat of hail. 

There will also be a Marginal Risk of excessive rainfall over parts of the Ohio Valley on Monday into Tuesday morning. However, the threat of severe thunderstorms ends on Tuesday.

A front over the Eastern Pacific Northwest and the associated deep upper-level trough will move onshore over the Pacific Northwest overnight Sunday. A second front over Southern California will move eastward to the Southern High Plains by Monday evening. The systems will produce coastal rain and higher elevation snow over parts of the Northwest and California overnight Sunday into the Northern/Central Rockies through Tuesday. 

The storm systems moving southeast across the Pacific Northwest through midweek will produce heavy snow in the Cascades, Coastal Ranges, and Sierra Nevada. Northern and Central California mountains, including the Sierra Nevada, will see heavy snow rates in excess of 2 inches per hour. Combined with high winds, which would cause blizzard conditions, dangerous to even impossible travel is expected. If you plan to travel by road at elevations above 2,000 feet through West Coast states, be prepared for rapidly changing conditions and have winter driving supplies.

Elsewhere, the strong pressure gradient associated with the low moving across the Southern Rockies to the Appalachians will produce high winds over the region through Monday. Therefore, the pressure gradient has prompted High Wind Warnings and High Wind Advisories from the Southern Rockies and High Plains to the Ohio and Tennessee Valleys and the Central and Southern Appalachians.

Additionally, upper-level energy will create snow over parts of the Northeast from Sunday evening into Monday.