A storm pounding California's Sierra Nevada mountains with snow Tuesday was taking aim at the Colorado Rockies and could roll east and slam the Appalachians on Thanksgiving Day, bringing unsettling travel weather to millions of Americans hitting the skies ...

"Heavy coastal and mountain rain may lead to instances of flash flooding, particularly over the windward foothills of the southern Sierra Nevada below 8,000 feet, where excessive rainfall may cause land/rock/mudslides," the NWS said in a forecast Tuesday morning.

A weather system is traveling for the Thanksgiving holiday too, bringing snow and stormy weather from the West into the Midwest, South and Northeast this week. Time it out here.

That's because of "another atmospheric river event" that will bring copious rainfall to coastal and valley locations and 3 to 4 feet of snow to the Sierra, forecasters said. The storm will move into the Rockies by midweek: "One tricky travel area will be in and around the Denver area as snow spreads across the area on Wednesday,

Two separate storm systems carrying heavy rain are expected to impact the busy Thanksgiving holiday travel in New York City, and the second one could even bring some snow to parts of the Tri-State area.

Tens of millions will travel during the holiday period, and weather could interrupt plans for some. Here's a look at the forecast.

This storm will bring the first snow accumulation to parts of southern and central New England. Taking into account the time of year, ocean temperatures, and storm track, the best chance of accumulating snowfall will be in the higher elevations. This is fairly typical for late November storms.