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A school bus travels Interstate 59 in near white-out conditions on Thursday, Jan. 17, 2013. (Joe Songer/jsonger@al.com)

Updated at 8:35 a.m.: Jackson and DeKalb county school systems have announced they will be closed today.

With the threat of wintry weather across parts of north Alabama on Wednesday morning, weather experts are cautioning that travel may be treacherous.

As a result, school systems have started announcing delays for classes Wednesday, according to AL.com and news partner WHNT-Channel 19.

Madison County: 3-hour delay.

Madison Academy: 3-hour delay.

Athens Bible School: Delayed until 11 a.m.

Jackson County: Closed.

Athens State University: Opening at 9:30.

Lawrence County: 2-hour delay.

Limestone County: 2-hour delay.

Marshall County: 3-hour delay.

DeKalb County: Closed.

Decatur Heritage: Upper school will begin at 8:45, lower school at 9.

Morgan County: 2-hour delay.

Decatur City: Elementary schools opening at 8:45 a.m., middle and high schools opening at 9:30 a.m

Randolph School: Will operate on typical "late-start Wednesday with faculty/staff scheduled to report at 7:30.

Mars Hill Bible: Delayed until 10.

Lauderdale County: Delayed until 10.

Oakwood Adventist Academy: 3-hour delay.

The National Weather Service forecast office in Huntsville has issued a winter weather advisory for Wednesday from 3 a.m. until noon. A wintry mix of light snow, sleet and freezing rain is expected before the precipitation transitions to all rain in the afternoon.

Accumulations of one-half inch to 1 inch are expected.