Oncoming rain brings a risk of flooding, fog and ice

An intensifying storm across the south-central United States will bring heavy rain and the risk of urban flooding to parts of the Midwest, Appalachians and the Atlantic coast from this weekend into early next week. AccuWeather Meteorologists also warn that there will be just enough cold air at the front of the storm to produce a glaze of ice in some areas.

Soon after, a storm breaks out severe weather and showers across parts of the south central states into Friday, another storm will spring up and roll northeast as it taps into a stream of Gulf of Mexico moisture beginning this weekend.

Rain will arrive again across the south central states and expand from the lower Mississippi Valley into the Tennessee and Ohio Valleys, the southern and central Appalachians and the Great Lakes region from Saturday into Sunday. From 1-2 inches of rain will fall across much of this zone, but there will also be a significant area where 2-4 inches will fall, with locally higher amounts between 6 and 8 inches.

Much of that rain can fall in a four- to eight-hour period, enough to push small streams to full width and potentially trigger small stream flooding. At the very least, significant and rapid runoff onto streets and along secondary country roads will lead to flooding. In mountainous areas, there may be some debris washed onto the roads.

As the storm continues to move, the band of moisture containing the heavy rain will swing from the Appalachians to the mid- and south Atlantic coast and New England from Sunday afternoon into early Monday. The heaviest rain along much of I-95 will likely be from Sunday afternoon through Sunday evening. During this time, poor visibility, downpours and urban flooding will lead to significant travel delays. Moving the travel time to well before or after the storm leaves may be a better option when possible.

Just enough cold air will linger in the lower atmosphere, along with some cold surfaces, to increase the risk of patchy ice over the interior Northeast when the main storm arrives.

“Similar to Thursday morning over the higher elevations of the central Appalachians, a more expansive zone of freezing rain will extend from western Maryland through parts of western, central and northern Pennsylvania and part of southern New York and last until Friday morning,” said AccuWeather meteorologist Brandon Buckingham.

“A more extensive zone where icing of ice may occur is likely from Friday night into Saturday morning from western Maryland to northern and northeastern Pennsylvania, northwestern New Jersey, upstate eastern New York, inland Connecticut, western and central Massachusetts and southern and central parts of Vermont and New Hampshire,” added AccuWeather Senior Meteorologist Dave Dombek.

From Saturday night into Sunday morning, the icy zone may extend from the northeastern corner of New York to northern parts of Vermont, New Hampshire and much of Maine.

Milder air with normal rain will reach all the way to the Canadian border. This means that apart from some icy conditions for a period of time, the snow on the ski slopes across the northern Appalachians will tend to be soft and slushy in many cases.

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Even a thin glaze of ice that is patchy and not widespread can be dangerous for drivers and pedestrians. Surfaces may appear wet, but may instead have a thin sheet of clear ice. Ice of this kind can form even where air temperatures are slightly above freezing, 32 F.

Long nights and humid air are the perfect ingredients for fog in winter. The fog can be especially dense when a storm moves in over snow cover or even just cold ground.

As the storm rolls around, two types of fog can occur. One will be low-lying fog near the ground, and the other will be associated with low clouds that can obscure the ridges and provide poor visibility for highway drivers and airplanes as they attempt to land and take off. Significant delays may occur due to the hazardous conditions.

The intensity of the storm will be great enough to produce showers and locally strong thunderstorms central Gulf Coast to Tennessee Valley on Saturday and then the South Atlantic coast on Sunday.

A few tornadoes may occur in the strongest storms, with the most widespread threats being strong winds and flash flooding.

Shortly after the big rainstorm leaves the region, a trailing storm could bring in just enough cold air to bring snow accumulation to part of the Inland Northeast from next Tuesday through New Year’s Day.

At this point, the storm is likely to deliver rain to the coast, including the major I-95 cities in the Northeast, with the potential for snow further inland. However, a shift in the storm track can change which areas get rain and which areas are covered in snow.

A potential third storm could have colder air to work with near the coast. From the end of next week through the first weekend of 2025, part of I-95 and some interior locations will be watched for wintry issues.

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