[Updated at 8:04 p.m. ET] Nearly 3,000 flights have now been canceled in anticipation of the inclement weather, most of which is expected late Friday into Saturday.
Amtrak also has canceled many trips in the Northeast corridor. The rail transit company said on its website that northbound service from New York's Penn Station would be suspended after 1 p.m Friday.
[Updated at 6:51 p.m. ET] Connecticut Gov. Dannel Malloy says utility companies there are bringing additional crews from out of state to deal with potential power outages. Metro-North rail lines could also be closed at any time should winds exceed 40 mph.FULL STORY
People in the Mississippi River Valley could be in for some dangerous weather Tuesday, the National Weather Service's Storm Prediction Center warns.
Very cold air surging southeastward will clash with warm, moist air coming up from the Gulf of Mexico; a line of severe thunderstorms is expected to erupt along the cold front that separates the two air masses, CNN meteorologist Sean Morris said.
"This could be a particularly dangerous and deadly event due to the rapid movement of the storms and the tornado threat increasing during the overnight hours, causing people in the storms' paths to be caught unaware," Morris said.
A few of these storms could produce tornadoes across parts of Arkansas, Tennessee, Mississippi and Louisiana.
Editor's note: A devastating storm system moved across the United States on Friday, spawning a slew of tornadoes that contributed to at least 28 fatalities in Indiana, Kentucky and Ohio.
Friday's storms come days after a separate tornado outbreak that left 13 dead across Kansas, Missouri, Illinois and Tennessee and battered parts of Kentucky as well.
[Updated at 11:41 p.m. ET] the death toll from Friday's storms has risen to at least 28, authorities say. The deaths were reported in Indiana, Kentucky and Ohio.
[Updated at 6:42 p.m. ET] A second person has died in Clark County, Indiana, as a result of apparent tornadoes that swept through the area Friday, the county's emergency management director told CNN.
That brings the death toll for the state to five - two in Clark County and three in Jefferson County - according to state and county officials.
[Updated at 6:14 p.m. ET] At least four people have been killed in Indiana after powerful tornadoes swept through the state Friday, according to state and local officials. Three of the deaths are in Jefferson County and one is in Clark County.
[Updated at 4:02 p.m. ET] Between 40 to 50 homes in Hamilton County, Tennessee, have "significant damage that we know about," the county's Chief of Emergency Management Bill Tittle told CNN on Friday. He said that there are 24 reported injuries and, while none of those appear to be life-threatening, he acknowledged that "we have not reached all the homes."
[Updated at 3:01 p.m. ET] Trained weather spotters reported a tornado at 1:43 p.m. CT (2:43 p.m. ET) in Posey County, Indiana, according to the National Weather Service. It is the third tornado the weather agency has reported on Friday.
[Updated at 2:35 p.m. ET] Severe weather injured at least six people Friday and caused damage near Chattanooga, Tennessee, said Amy Maxwell, a spokeswoman for the Hamilton County Office of Emergency Management.
[Updated at 11:44 a.m. ET] At least 17,000 customers were without power Friday near Huntsville, Alabama, amid reports of a tornado or tornadoes in the area, the Madison County Emergency Management Agency said. Huntsville is in Madison County, which is in far northern Alabama.
[Updated at 11:26 a.m. ET] The National Weather Service issued a tornado emergency for Madison County, Alabama, on Friday morning after saying a large and extremely dangerous tornado caused widespread damage near Meridianville, Alabama.
[Updated at 11:20 a.m. ET] At least one apparent tornado damaged or destroyed several homes Friday morning in Limestone County, Alabama, just west of Huntsville in far northern Alabama, said Cindy Adams of the Limestone County Sheriff's Office.
Touchdowns were reported in the communities of Tanner and East Limestone, she said. One apparent tornado touched down at least once before authorities could sound a warning siren, she said.
[Initial post, 10:55 a.m. ET] An apparent tornado touched down Friday morning near Huntsville, Alabama, authorities said. Officials have reports of houses damaged in Madison County, said Paige Colburn, an emergency management official.FULL STORY
Editor's note: The following is advice from CNN Meteorologist Sean Morris on steps you can take when a tornado watch or a tornado warning is issued in your area.
A tornado watch means that tornadoes, high winds, and hail are possible in the watch area.
When a watch is issued in your area, keep abreast of the latest information by monitoring television, radio, and NOAA weather radio. A NOAA weather radio is a must, especially for storms that may occur overnight, when you may not be monitoring television or radio. Know the name of the county or parish in which you live and keep road maps handy to assist in tracking the storms.
Tornado warnings mean that a tornado has been spotted, or that radar has indicated that one exists. When a warning is issued in your area:
Material from a Sunday solar eruption hit the Earth on Tuesday, helping to create the planet's strongest solar radiation storm in more than eight years, NOAA's Space Weather Prediction Center said.
The eruption also has caused a minor geomagnetic storm, expected to continue at least through Tuesday. Together, the storms could affect GPS systems, other satellite systems and radio communications near the poles, the SWPC and NASA said.
The storms prompted some airlines to divert planes from routes near the north pole, where radio communications may be affected and passengers at high altitudes may be at "a higher than normal radiation risk," the SWPC said.FULL STORY
Tropical Storm Don has developed over the southern Gulf of Mexico with maximum sustained winds of 40 mph, the National Hurricane Center said Wednesday.
If it continues on its current path, it should approach the coast of the northwestern Gulf of Mexico on Friday.
As of 5 p.m. ET Wednesday, the storm was located 190 kilometers (118 miles) north of Cozumel, Mexico, and about 1,220 kilometers (758 miles) east southeast of Corpus Christi, Texas, the center said. It was moving to the west northwest near 19 kilometers per hour (12 mph).FULL STORY
As Tropical Storm Arlene steadily chugged toward the east-central coast of Mexico Wednesday, Mexican authorities issued a hurricane watch that stretches from the country's eastern municipality of Tuxpan northward to La Cruz, the National Hurricane Center reported.
Arlene - the first named storm of the 2011 Atlantic hurricane season - is moving at about 8 mph, packing sustained winds of 50 mph.
It is expected to make landfall early Thursday very near hurricane strength.
Arlene is also expected to produce 4- to 8-inches of rain in some areas. Meteorologists say isolated rainfall amounts of 15 inches over mountainous terrain could cause life-threatening flash floods and mud slides.FULL STORY
A confirmed tornado is approaching the town of Romance, Arkansas, the National Weather Service said.
The weather service urged residents of Romance to take cover immediately.
Week after week, the U.S. has been pummeled by severe winter weather since December – and this week will be no exception.
Some of the coldest air of the season will plummet southward and combine with another storm developing over the southern Plains. An intense surface low will develop over north Texas and pull abundant warm, moist air from the Gulf of Mexico into the frigid Arctic air diving southward into the Plains.
The result: blizzard conditions, heavy snow, ice storms and tornadoes. This storm appears to be another one for the record books.
Very heavy snow will fall from Oklahoma northeastward through Kansas, Missouri and Illinois. Snow accumulations here will be measured in feet, not in inches.READ MORE ABOUT COMING STORM
[Updated at 6:07 p.m.] The National Weather Service issued a tornado warning for central Florida's Orlando area, set to expire at 7 p.m. ET Tuesday.
The Walt Disney World Resort is within the warning area. Radar indicated a storm capable of producing a tornado near Windermere moving north-northeast at 45 mph at 5:51 p.m., the weather service said.
Earlier, the service issued a tornado warning for Florida's Tampa/St. Petersburg area. That warning, which was to expire at 5:45 p.m., came after radar indicated a possible tornado near Lealman, just north of St. Petersburg, at 5:08 p.m., moving east at 45 mph.
The warnings came as a line of severe storms capable of producing damaging winds and isolated tornadoes was moving through Florida's Tampa and Orlando areas late Tuesday afternoon and early Tuesday evening.
Damaging thunderstorm winds gusting to 60 mph and quarter-sized hail is possible with this line of storms. A tornado watch was in effect for northern and central Florida until 9 p.m.
Don't focus on the skinny line. That's the advice often given by meteorologists as a tropical storm or hurricane approaches the coast line.
When looking at the forecast track of a particular tropical storm or hurricane you will notice a shaded area that falls to the left and right of the forecast track. This shaded area is called the "cone of uncertainty" and is the average error in the forecast tracks of tropical cyclones issued by the National Hurricane Center. As a hurricane approaches, the track could shift to the left or right within the shaded area. So it is important to monitor the forecasts of tropical cyclones until you fall outside of the cone.
Tropical cyclones (the all-encompassing term for tropical depressions, tropical storms and hurricanes) can have far-reaching effects far away from the forecast track. For example, Earl's tropical storm force winds extend outward from the center by up to 200 miles. The entire system is now the size of the state of California. If the storm is moving at an average speed of 20 miles per hour, you can do the math: tropical storm force winds could arrive in your location up to 10 hours in advance of the hurricane!
Severe thunderstorms will develop later this morning and continue through the overnight hours across portions of the mid- and lower- Mississippi River Valley.
The Storm Prediction Center is forecasting a few strong tornadoes across the lower Mississippi River Valley this afternoon and tonight.
iReport: See severe weather in your area?S end photos and video (But please stay safe and take caution if you do.)
Severe weather threatens much of the country Tuesday with storm systems bringing rains, flooding, high wind, extreme hot weather and winter warnings to varying parts of the country.
A late season winter storm will slam the Rockies and the central Plains beginning today. A winter storm warning is in effect for Denver through midnight tonight. The western suburbs could see up to a foot of snow.
A large area of high pressure will bring near-record high temperatures to the Dakotas today and Friday. The warm temperatures are expected to rapidly melt up to 6 inches of snow across the Red River Basin. This is equivalent to receiving 6 inches of rain across the entire Red River Basin in a day.