From NWS Chicago – NOAA:
Rock, Fox, and Kankakee Basin emergency managers and stormwater contacts,
This is a heads up regarding the potential for rapid river ice formation today through the weekend which could lead to freeze-up ice jams. Some supplemental reports from our volunteer ice spotter network indicate that the very cold temperatures have already formed river ice in some areas. River gauges are not yet showing obvious signs of ice jams, but we are seeing some “ice bite,” indicating the simultaneous freeze-up of smaller creeks and tributaries which is causing the bigger rivers to fall abruptly.
The potential for ice jams will continue through the weekend. Ice jams are difficult to forecast and may occur with little warning. Warmer temperatures next week will reduce the risk of new river ice and ice jams, but if significant jamming occurs (such as seen in January) it may take several days to clear.
If confidence increases that ice jam flooding is imminent, or if we receive a report of ice jam flooding, watches/warnings/advisories may be issued. At this time we do not plan to send additional briefing emails, but if there are any questions or concerns, please call our operations line.
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