MINNEAPOLIS (WCCO) — The National Weather Service said Monday parts of Minnesota will likely see “extreme flooding” this spring.

But how they calculate the expected amount of flooding is a year-round process. The National Weather Service has dozens of water gauges lined along and on the bottom of rivers and lakes all over Minnesota.

All of those transmit water level information back to the National Weather Service office in Chanhassen, where meteorologists can analyze it and assess the risk for flooding in a particular area. They then translate all of that information onto a coded map where we can see what areas are at risk, the least amount being a green pinpoint meaning no flooding to the most dangerous in red, major flooding.

“It’s very involved. It can be time consuming, you know this time of year we have hydrologists that are working 24-7 trying to update the forecast as it comes in so it is very involved this time of year,” said Chris Franks with the National Weather Service.

Communities in the Red River Valley, like Moorhead and Fargo, are already bracing for major flooding. Over the past week, volunteers have filled nearly two million sandbags. They’ll be distributed to different neighborhoods this week.

Communities along the southern part of the Mississippi River near Winona could also be in danger of flooding this year. The most recent models predict rivers won’t crest here in Minnesota, for another week or so.