Flight delays and cancellations mount as severe weather impacts holiday travel across the U.S.

Storms across the southern and western portions of the United States continue to impact flight schedules on one of the busiest travel weekends of the year, causing delays and cancellations as people head back home from the holiday season.

As of 1 p.m. ET on Friday, more than 3,500 flights had been delayed and 96 had been canceled for travel within, into or out of the United States, according to FlightAware. On Thursday, 8,832 flights were delayed and 791 flights were canceled within, into or out of the U.S. in part thanks to strong storms that resulted in multiple tornadoes in Texas and Louisiana.

While the chances of severe weather will not be as great in the southern U.S. as on Thursday, the risk of hail, heavy rainfall and more tornadoes will increase again on Saturday.

"We do have an increasing concern that there are going to be a lot of storms with a severe weather threat there on Saturday," National Weather Service meteorologist Evan Bentley said. "With it being a pretty active time of year for holiday travel, we want to make sure anyone who's in that corridor or is traveling through that corridor is aware of the weather threat."

The states at highest risk of severe weather on Saturday will be Louisiana and Alabama, the National Weather Service said.

In a Friday bulletin from the NWS, the Weather Prediction Center said that the weekend will bring an "increasingly wet pattern developing from the Lower Mississippi Valley,

spreading northeast into the Tennessee Valley, Appalachians, Mid-Atlantic and Northeast.”

Storms will also continue to pound the Pacific Northwest, bringing “heavy lower elevation rain and higher elevation heavy snow” in states like Washington, Oregon and California.

The NWS has posted flood warnings for lower elevation portions of Oregon and Washington and winter storm warnings for some mountainous regions of California, Nevada, Colorado, Idaho, Oregon and Washington. Snowfall totals of between 6 and 18 inches are expected in some locations and wind gusts could top 70 mph.

Travel season

The potential increase in travel delays at the nation's airports comes during what is expected to be the busiest travel season in U.S. history.

"We expect to screen nearly 40M people from Dec. 19-Jan. 2, a 6.2% increase from last year," the Transportation Security Administration said in a message posted to social media, adding that Friday and Monday will be two of the three busiest travel days.

The vast majority of holiday travel, however, will be done not in the sky but on the nation’s roadways. According to AAA, 90% of the trips Americans will make this season will be done by car. For the next few days, most of the country will not see more snow and ice on the highway thanks to above-average temperatures.

“This much above average pattern will support the potential for record high morning low temperatures across the Central Plains into the Mid to Upper Mississippi Valley on today, across the Upper Mississippi Valley and Great Lakes region on Saturday, and the Mid-Atlantic and Northeast on Sunday,” the NWS bulletin said.

But with the possibility of more severe weather across much of the South, officials are warning travelers to pay attention to the changing weather conditions.

"As Texans and out-of-state visitors begin traveling after the Christmas holiday, it's crucial that everyone regularly monitor road conditions, make an emergency plan, and heed the guidance of state and local officials," Texas Gov. Greg Abbott said Thursday in a news release.