Illinois (ECWd) –
The big picture: An upper level trough is coming onshore in the Pacific Northwest right now. When that crosses the Great Plains tomorrow night, surface low pressure will develop. That low will lift northeast across Missouri and into Illinois on Saturday, with accumulating snow spreading across the region ahead of it.
Snow Amounts: Area-wide snow is expected by early Saturday morning, with a burst of heavier snow occurring along a warm front lifting through central/southeast IL mid morning-mid afternoon. By Saturday evening, the north-south position of that front is uncertain, with some models placing it as far north as roughly I-80, and others positioning farther south, near I-70. For areas overtaken by the warm front, precipitation may change to a rain/snow mix, and snow that has already fallen will compact – reducing snow accumulations considerably. These locations may see up to 9 inches of snowfall, but snow depth will generally stay under 5 inches due to compaction and melting. Areas north of the front will not warm enough for a rain/snow mix or experience as much in the way of compaction. These locations will see the heaviest snow accumulations, ranging generally from 5 to 10 inches (locally higher).
Timing: Snow may start as early as late evening Friday west of the IL River, but will spread across most of central IL by daybreak Saturday. Heaviest snow will occur mid morning into the afternoon, when it may change to a rain/snow mix along and south of the warm front.
Impacts: The combination of moderate to briefly heavy snow and southeast winds gusting to 30 mph will result in visibilities less than a half-mile at times. The wind will cause minor to moderate drifting, resulting in patches of drifted snow across even recently-plowed roadways. The heavy, wet “character” of the snow will increase the cardiovascular risk from overexertion among those shoveling snow.
For the latest on the weekend winter weather, see our Decision Support Packet, which you can access from the upper right on our home page, weather.gov/ilx.
Stay safe,
John Bumgardner
NWS Lincoln WRN Team
