The National Weather Service has issued a flood advisory for the Fox River at Montgomery, affecting Kane and Kendall counties.

The flood advisory went into effect at 9:51 a.m. Wednesday, May 14, and was expected to be over late Wednesday night or early Thursday morning.

“Recent heavy rains have caused rises along the Fox River basin,” the advisory said, and advised drivers who encounter a flooded roadway to turn around and find an alternative route.

The action stage is 12.5 feet — the level recorded at 9:15 a.m. Wednesday. The flood stage is 13 feet.

Rain is expected Wednesday, but the river-level forecast is that the water level will stay at 12.5 feet, the NWS said.

Additonal FAQ Info, Courtesy of the National Weather Service

Where can I get detailed river information including current stages and forecast stages?
Detailed river information is available from our Advanced Hydrologic Prediction Service page.

I have seen the river forecasts change occasionally…Why the change?
Hydrologists use computer models to produce a river forecast. One important input to the models is rainfall. Each new model run incorporates the latest new rainfall in the last 24 hours. If additional heavy rain has fallen since the previous forecast, the new river forecast will likely change to reflect the new data. In addition to actual rainfall, river forecasts also use the amount of future or forecast rainfall expected during the next 24 hours. This can change greatly and can have a major impact on the river forecast. In addition, the forecasts may be adjusted based on actual flow measurements taken during the event by U.S. Geological Survey (USGS) hydrologic technicians.

How do you measure the current water levels?
The National Weather Service relies heavily on a network of river gages operated by the U.S. Geological Survey(USGS). Data is received from these river gages either by phone telemetry or satellite. In addition, during times of flooding, USGS technicians are out taking flow measurements and relaying that back to the NWS and other agencies which provides vital information for our river flood warning and forecast program. Learn more about the USGS streamgage network. The NWS also uses gages on the Illinois  Waterway operated by the Rock Island US Army Corps of Engineers.

What is a river stage?
A river stage represents the level of the water surface of a river or stream above an established datum at a given location. Learn more.

Can I get text message alerts for river gage locations?
Yes, the U.S. Geological Survey (USGS) provides a program…WaterAlert that allows you to receive email or text alerts for user defined thresholds such as river gage height.  Learn more.