Frost, ice or snow coated the ground Friday morning across most of the eastern United States, a typical February morning.
But an unusual springlike surge of warmer, wetter weather from Friday night into Sunday morning is raising concerns that parts of the region will spend the weekend facing flooding rains, severe storms, freezing rain and, in the far north, deep snow.
The type of flash flooding that forecasters are expecting, especially in Tennessee and Kentucky, is unusual for this time of year, Alex Lamers, a meteorologist with the Weather Prediction Center, said early Friday morning. By next week, more typical February weather is expected to return.
Here are the hazards to watch out for.
Flooding rain: From northeastern Arkansas to southwestern West Virginia, there is a moderate risk of excessive rainfall that could cause rivers to rise to their brim or could lead to flash flooding.
Severe storms: In the Deep South, primarily in northern Louisiana and Mississippi, an outbreak of severe storms that could include tornadoes and damaging winds is possible from Saturday afternoon into the evening. That’s fairly typical for this time of year in this region.
Heavy snow: Depending on what track the storm takes, six to 10 inches of new snow could fall across the upper Midwest on Friday night, followed by the Great Lakes into southern Canada and New England this weekend.
Wintry mix: New York and other cities along the Northeast coast will see snow first on Saturday afternoon, before the warm air moves in, turning the precipitation to a mess of sleet, freezing rain and then rain. Some areas, especially close to the coast, will transition quickly from snow to rain. Some sleet and ice will fall as far south as the Central Appalachians.
The rainfall is the rarity of this mid-February storm.
The region most at risk of flooding — including Tennessee and Kentucky — is already sopping wet, with some rivers near or at flood stage after having seen weeks of recent rainfall. This rare amount of moisture surging north is more intense than the rain that has already fallen. And some places, like Lexington, Ky., where three to five inches of rain is forecast, could break their February record for daily rainfall. (Over three inches of rain was measured there on Feb. 13, 1989.)
Forecasters like Mr. Lamers have remained confident that heavy rain and flash flooding will occur across the region Saturday into Saturday night. However, as of Friday morning, they were unsure where exactly the worst of the it would fall during the storm.