Eastern US: Upcoming rainstorm to bring flooding, fog and ice risks
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A gathering storm over the south-central United States will bring heavy rain and the risk of urban flooding to parts of the Midwest, Appalachians and Atlantic Seaboard from this weekend to early this week. AccuWeather meteorologists also warn that just enough cold air will be around on the front end of the storm to produce a glaze of ice in some areas.
Soon after one storm triggered severe weather and downpours over parts of the South Central states Friday, a second storm sprung up Saturday and will roll northeastward toward the Great Lakes on Sunday while tapping into a stream of Gulf of Mexico moisture this weekend.
Rain will arrive again over the South Central states and expand from the lower Mississippi Valley to the Tennessee and Ohio valleys, southern and central Appalachians and the Great Lakes region from into Sunday. From 1-2 inches of rain will fall over much of this zone, but there will also be a substantial area where 2-4 inches will fall, especially on the southeastern slopes of the Appalachians, with locally higher amounts between 6 and 8 inches.
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Much of that rain may fall during a four-to-eight-hour period, enough to push small streams out of their banks. At the very least, significant and rapid runoff onto streets and along secondary rural roads will lead to flooding. In mountainous areas, there can be some debris that gets washed onto the roads.
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The heavy rain can be especially troublesome in southern Appalachian areas ravaged by Helene in late September. Much of the infrastructure still needs permanent repair, and some people are still living in temporary or makeshift shelters. Stream beds and storm drains that are filled with rocks and debris can flood easily.
Gusty winds will accompany the rain as it swings northeastward. The combination of rain and wind will make for true stormy and nasty wintertime conditions despite the absence of snow.
As the storm continues to move along, the ribbon of moisture containing the heavy rain will pivot from the Appalachians on Sunday to New England by Monday. The heaviest rain along much of the I-95 mid-Atlantic is likely to be Sunday night. During this time, poor visibility, downpours and urban flooding will lead to substantial travel delays. Shifting travel time to well before or after the storm leaves may be a better option when possible.
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Just enough cold air will linger in the lower part of the atmosphere, along with some cold surfaces, to raise the risk of patchy ice over the interior Northeast as the main storm arrives.
From Saturday night to Sunday morning, an icy zone may extend from the northeastern corner of New York to the northern parts of Vermont, New Hampshire and much of Maine.
Milder air with plain rain will reach all the way to the Canadian border. That means that, aside from some icy conditions for a time, the snow on the ski slopes over the northern Appalachians will tend to get soft and slushy in many cases.
Even a thin glaze of ice that is patchy and not widespread can be dangerous for motorists and pedestrians. Surfaces may appear wet but can have a thin sheet of clear ice instead. Ice of this nature can form even where air temperatures are a bit above the freezing mark, 32 F.
Long nights and moist air are the perfect ingredients for fog in the wintertime. The fog can be especially dense as a storm is moving in over snowcover or even just cold ground.
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Full length man wearing sports clothing and red headphones running on the road in foggy weather condition. |
As the storm pivots, two types of fog can occur. One will be low-level fog near the ground, and the other will be associated with low clouds that can obscure the ridges and make for poor visibility for motorists on the highways and aircraft as they attempt landings and takeoffs. Substantial delays due to the dangerous conditions can occur.
The intensity of the storm will be great enough to produce severe thunderstorms and tornadoes from the central Gulf Coast to the Tennessee Valley on Saturday and then the southern Atlantic Seaboard on Sunday.
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The strongest storms have already produced tornadoes and widespread wind damage across the central Gulf coast states into Saturday night. On Sunday, the most widespread threats will be strong wind gusts and flash flooding.
Soon after the big rainstorm leaves the region, a trailing storm could tap into just enough cold air to bring accumulating snow to part of the interior Northeast from Tuesday to New Year's Day.
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At this time, the storm is likely to deliver rain to the coast, including the major I-95 cities of the Northeast, with the potential for snow farther inland. However, a shift in the storm track could change which areas get rain and which areas are blanketed by snow.
A potential third storm could have colder air to work with near the coast. From late next week to the first weekend of 2025, a portion of I-95 and some interior locations will be watched for wintry trouble.
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