Coastal rain showers and snow will be a major hindrance to travel in the West, while drenching rain could slow people down in parts of the South and East into Christmas Day.
Most areas from western and central Texas to the northern Plains and the Upper Midwest will catch a break during Christmas Eve and into Christmas Day ahead of a major storm for the weekend.
JUMP TO: Wintry weather to grip much of western US through Christmas | Rain, thunderstorms to accompany springlike warmth in the East on Christmas Eve | More springlike rain, thunderstorms to ramp up over Mississippi Valley on Christmas Day
The last storm in a long train of systems from the Pacific Ocean will drop southward along the Pacific coast, while spreading precipitation inland to end this week.
According to AccuWeather Senior Meteorologist Ken Clark, "The storm will put plenty of fresh powder down in the Sierra Nevada, as a Christmas present for skiers and boarders, but the storm will bring its share of problems for holiday travelers."
The southward-tracking storm will pull cold air with it and result in low snow levels from Washington to Southern California, as well as areas well inland over the West.
"Cold weather will have much of the West in its grasp with areas of snow into Christmas Day," Clark said.
Snowflakes can mix in with rain showers around Seattle and Portland, Oregon, on Christmas Eve and Christmas Day. While a great deal of snow is not expected with the storm in the Cascades, snow levels will be low enough for slippery roads to be a concern for motorists over Snoqualmie Pass.
Meanwhile, rain can be heavy at times and could cause substantial travel delays in San Francisco and Sacramento, California, on Christmas Eve.
During much of Christmas Eve, the storm will unload heavy snow on the Coast Ranges in southern Oregon and northern California, as well as the southern Cascades. Motorists should be prepared for snow-covered roads along Interstate 5 from Grant's Pass to Siskiyou Summit, Oregon, and Shasta Summit, California. This area could receive 6 inches or more of snow.
Similarly, snow levels will dip to 1,500 feet or so in the northern Sierra Nevada. The storm will deliver 1-2 feet of snow on the Sierra. Travel will be difficult over I-80 through Donner Pass, California.
In Southern California, rain showers will dot the Los Angeles Basin and the San Diego area on Christmas Eve into Christmas Day.
"There will be snow showers with a chance for slippery conditions over Cajon and Tehon passes during Thursday night into Christmas Day," Clark said.
Farther inland, areas of snow will extend from northern Nevada to Idaho, eastern Washington and western Montana on Christmas Eve.
Wet snowflakes could mix with rain showers around Las Vegas Thursday night. Salt Lake City may receive a fresh covering of snow Thursday night into Christmas Day.
"During Christmas Day, the heaviest snow will focus on parts of the Wasatch Range in Utah and the Rockies in western and central Colorado," Clark said.
Snow will also extend into the mountains of northern Arizona and could bring a small accumulation to Denver on Christmas Day.
By Friday evening, snow may break out east of the Rockies. People heading home for the holiday activities may get caught in a developing snowstorm from parts of South Dakota and northwestern Nebraska to Minnesota.
Christmas Eve will be nothing short of springlike and a record warm day for many locations in the eastern third of the nation.
Snow and widespread fog will be absent from the scene by Christmas Eve. Much of the steady rain will have departed as well.
However, sporadic showers and thunderstorms can be heavy enough to be more than a nuisance for motorists and airline passengers.
Locally gusty winds and a low cloud ceiling in the vicinity of thunderstorms could prompt delays at times in major airports such as Atlanta, Charlotte, North Carolina, Pittsburgh, Washington, D.C., Baltimore, Philadelphia, New York City and Boston.
Downpours can suddenly reduce the visibility and cause water to collect in poor drainage areas on the highways.
Major highways in the East that could be impacted by the downpours include I-10, I-20, I-40, I-77, I-80, I-81, I-85, I-90 and I-95.
On Christmas Day, a push of cooler air will have chased away the rain and warmth from the lower Great Lakes to New England.
However, April-like heat and sunshine will hold in the Deep South.
Where the warm and cool air meet, from the lower Mississippi Valley to the central Appalachians, rain will ramp up on Christmas Day.
Enough rain can fall in the swath from northeastern Texas to parts of Pennsylvania, West Virginia and Maryland to cause flash and urban flooding problems.
Long portions of the I-30, I-40, I-64 and I-70 corridors could be a slow ride.
Some secondary roads that wind along small streams in the region could become inundated.
Despite the risk of flooding rain and thunderstorms, violent storms are not likely in this area on Christmas Day.