Weather across America

(NATIONAL) Lake-effect snow downwind from the eastern Great Lakes, temperatures 10 to 25 degrees below average across the North and Northwest, another fast-moving storm with developing wintry mix stretching from the Ozarks through the Southern Mid-Atlantic, and heavy rainfall and localized flash flooding may be possible across the Lower Mississippi and northern Deep South.  

A surface low pressure is deepening southeast of New England with last vestiges of snow tapering off Sunday evening; however, in its wake, the Lake Ontario lake effect belt will remain active through Sunday night and into early Tuesday, likely to produce locally up to a foot of snow before another very weak clipper-like system presses through on Tuesday.

Lake Erie will be much less active, but 1-3" is possible downstream in N PA/W NY. Another Arctic high pressure and associated cold front is starting to drop into the Northern High Plains Sunday and will usher in well below temperatures across the region Monday at nearly 20-30 degrees below normal before moderating a bit and spreading out across the rest of the northern, central Plains and into the Southern High Plains by Tuesday. This cold air will leak through the Pacific Northwest, as well and with 15-20 degrees below average may reach a few potential low records, particularly on Tuesday.   

As the cold front drops south with larger scale upper-level trough developing across the Rockies and connecting with southern stream across the Great Basin/Four Corners region; return moisture and warm air will emerge from the Western Gulf of Mexico and tighten the frontal zone across the Southern Plains all the way east to the Carolinas by Tuesday.  

Along and south of the front, showers and thunderstorms will break out Tuesday night across N LA, MS, AL into the southern foothills/plateaus of the Southern Appalachians. The above average moisture and favorable steering currents for the cells may result in excessive rainfall capable of localized flash flooding. As such, the Weather Prediction Center has issued a Slight Risk (Level 2 of 4).

Along the north-side of the front, the cold air dumping in will allow for the development of wintry weather conditions with snows across the eastern Central Plains through northern Kentucky, western Virginia on Tuesday. There may be some wintry mix along/just north of the front west of the Appalachians; however, eastward, cold air damned in from prior front leaving will allow for broader area of freezing rain/sleet along the NC/VA border with heavy snow fall rates across Virginia. A tight gradient is expected and may vary north and south over the next few days as the pieces move into place.