Editor's Note: Our updated forecast and weather story for Thursday can be found here. Our original story continues below.
A winter storm watch was upgraded to a winter weather advisory that has expanded to numerous Chicago-area counties ahead of a system that's expected to bring the potential for accumulating snow and dangerous travel Thursday and Friday.
The advisories begin Thursday afternoon and evening for several northern and northwestern counties, bringing the potential for hazardous commutes both Thursday evening and Friday morning.
Here's what you need to know.
Winter weather advisories
They include:
McHenry County: In effect from 3 p.m. Thursday to 7 a.m. Friday. The alert warns of "accumulating wet snow" with totals between 4 and 7 inches expected.
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Lake County (IL): In effect from 6 p.m. Thursday to 10 a.m. Friday. The alert warns of "accumulating wet snow" with totals between 4 and 7 inches expected.
DeKalb and Kane Counties: In effect from 3 p.m. Thursday to 7 a.m. Friday. The alert warns of "accumulating wet snow" with totals between 2 and 5 inches expected.
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DuPage County and Northern and Central Cook County: From 6 p.m. Thursday to 10 a.m. Friday. Warns of "accumulating wet snow" with totals between 2 and 5 inches expected.
Biggest threats
According to the alerts, travel could be hazardous during the storm.
"Snow rates are likely to peak near 1 inch per hour early Thursday evening," the alerts state, urging drivers to "slow down and use caution."
Earlier, a winter storm watch was issued for McHenry and Lake counties.
The watch also says shoveling could be difficult due to the "expected heavy, wet nature of the snow."
How much snow is expected?
The National Weather Service predicts the storm system will bring both snow and rain to the Chicago area Thursday afternoon through Friday morning, though accumulations will vary across the area.
The system is still developing and much could change in the hours ahead, particularly as even the smallest shifts in the storm's path could alter snow projections.
As of Wednesday morning, the NBC 5 Storm Team said locations north of Chicago could see accumulations in excess of 4 inches, while other parts of the region could see between 1 and 3 inches. The NWS agrees, saying the biggest impacts will be along the Illinois-Wisconsin border, though it could extend as far as south as Interstate 80.
Areas south and in northwest Indiana are more likely to see rain than snow with this system as of now, however.
Timing of the storm
The precipitation is expected to begin as early as Thursday evening, continuing into Friday morning before gradually coming to an end.
But the biggest timing threat will depend on where you live.
McHenry County: Thursday evening's commute is expected to be most impacted.
Lake County (IL): Friday morning's commute is expected to be most impacted.
DeKalb and Kane Counties: Thursday evening's commute is expected to be most impacted
DuPage County and Northern and Central Cook County: Friday morning's commute is expected to be most impacted.
