A blast of frigid wintertime chill descending over the eastern half of the nation will help serve up the season’s first Northeast snowstorm, giving parts of interior New England potentially plowable snow to start the season. In its wake, the departing system will facilitate the arrival of a more significant — and widespread — plunge of cold air across the Lower 48. Temperatures 15 degrees or more below average could reach all the way to the Gulf of Mexico.

Round 1 of cold

The first batch of cold is already consolidating over Saskatchewan and Manitoba. It has nudged a pocket of gentle cooling over Upstate New York and northern New England. But the real cold shot begins tracking southeast Wednesday into Thursday, heralded by a strong cold front that will march through the Tennessee and Lower Mississippi valleys Thursday evening.

Along the front, heavy rains are possible over eastern Oklahoma, Arkansas and the Ozark Plateau. Lighter showers may accompany the front from the Appalachians to the gulf.

Kansas City will enjoy a Wednesday near 60 degrees. On Wednesday night, a touch of snow is possible. Thursday’s high temperature may not escape the 30s. Atlanta could go from a high of 70 Wednesday to a Saturday morning low of 35.

That cold will spill to the gulf by Saturday, bringing below-average temperatures everywhere but the Florida Peninsula. In Biloxi, Miss., Saturday morning could start in the lower 40s. “Sea smoke” is possible where the chilled breeze passes over the much warmer ocean waters. It could be just as cold in Mobile, Ala., while New Orleans could bottom out in the “balmy” mid-40s.

The storm

Guiding the cold front will be a developing low in the Northeast — one that could bring a dash of decorative snow to central and western New England.

It’s by no means a blockbuster, and it could be a welcome atmospheric offering for ski resorts looking to jump-start their season. It’s also right in line with when the first flakes usually fly for northern New England.

A strip of low pressure will begin form just east of the Interstate 95 corridor overnight Thursday, developing as it heads northeast into the Gulf of Maine. It’s winding up too late to give most spots anything more than a few inches, with warm mid-level air encroaching near the coast keeping most spots in the lower elevations wet, rather than white. Moreover, a westward shift in the storm’s forecast track further enhances coastal warmth, dwindling the odds of snow there.

Precipitation amounts will be light, with a quarter of an inch, give or take, of rain south of the Massachusetts Turnpike. North of there, it will still be all rain for southern New Hampshire, Vermont and Maine. In the higher elevations, however, cold air banked up behind the stalled front will foster all snow, with three to five inches possible in the mountains. A few spots could get half a foot.

Less snow is in the cards for northern Maine, which will be further removed from the best moisture and dynamics.

Overall, this system is not overly powerful, and wind/coastal issues are of no concern.

The cold: Round 2

In the wake of the departing low, a wedge of exceptionally frigid air will scream south, enveloping areas from the Plains eastward in its icy throes.

Temperatures over the Northern Tier and Upper Midwest could fall to more than 20 degrees below average, the polar deep freeze meandering east thereafter. Veterans Day could feature highs in the teens from the Dakotas to the Twin Cities. Chicago is likely to spend Monday in the 20s.

While the specifics have yet to be ironed out, the stage is set for a long-duration period of chilly weather east of the Mississippi. On the opposite side of the nation, a stagnant ridge of high pressure will bake the West. Highs there could range 10 or 15 degrees above average.