Weather across America

(NATIONAL) A winter storm will bring snow to the interior Mid-Atlantic and Northeast, a reinforcing surge of frigid air will bring dangerously cold conditions to much of the nation, a rare, significant winter storm across the South, and a Critical Risk of Fire Weather returns for Southern California.

A low-pressure system currently developing and beginning to exit the Mid-Atlantic states will continue to bring the latest round of wintry weather from the interior sections of the eastern U.S. up across New England through Sunday night into Monday morning. The heaviest snow will likely stay to the north and west of the I-95 corridor. Milder air from the nearby Atlantic kept the precipitation in the form of rain/drizzle Sunday afternoon for the eastern portion of the Mid-Atlantic states before colder air in the wake of the intensifying low-pressure system changed the rain to a period of snow Sunday evening.

As the intensifying cyclone tracks just off the New England coast Sunday night, a swath of snow is forecast to overspread southern New England into coastal Maine where 3-6 inches of accumulation with locally higher amounts can be expected. 

Meanwhile, rain is expected near the Cape Cod area and the east end of Long Island before changing to a period of snow as the deepening storm begins to move away later Sunday night. Partly sunny skies will return on Monday for much of the East Coast. Blustery northwesterly winds behind the storm will usher in the coldest arctic air this season, bringing tumbling wind chills and below-freezing temperatures all the way down to the Gulf Coast, Florida Panhandle, and northern Florida by Monday morning behind an arctic front.  

This expansive frigid air mass will continue to trigger the latest round of heavy lake-effect snow along the Snow Belt of the Great Lakes with cold northwesterly flow firmly in place. Sub-zero temperatures will be common across the northern U.S. through the next couple of mornings with readings approaching -30 degrees near International Falls. Cold Weather Watches/Warnings and Freeze Warnings are in effect all the way down to the Gulf Coast including southern Texas and northern Florida.  

Over the central/southern Rockies and adjacent High Plains, some snow showers will return on Monday as a shortwave dips into the region in the presence of post-frontal upslope flow. This shortwave will be instrumental in producing a very rare winter weather event across the Deep South beginning Monday night, and even down along the Gulf Coast on Tuesday. As the shortwave begins to interact with the arctic front lifting north across the Gulf of Mexico, a low-pressure system will intensify and track eastward and dump Gulf moisture into the cold air for the Gulf Coast states. 

This will result in very rare and significant snowfall accumulations with preliminary estimates upwards of 5 inches just inland from southeastern Texas across southern Louisiana on Tuesday. A few inches of snow are also possible near the New Orleans metropolitan area by Tuesday evening. In addition, a period of ice is possible near the immediate coast of Texas into Louisiana. Given the rarity of this winter storm, major traffic and travel disruptions are likely through mid-week. 

Some of the arctic airmass will reach portions of the Great Basin/Interior West as well, with highs by Tuesday only recovering into the 20s and 30s for most locations. Forecast highs are generally milder and around average along the West Coast, with the 40s for the Pacific Northwest, the 50s and 60s for California, and the 60s to low 70s for the Desert Southwest. Unfortunately, these mild conditions along with gusty winds and very low humidity have prompted the Storm Prediction Center to issue a Critical to Extreme Risk of Fire Weather for southern California at the beginning of the week.