NWS hydrologist presents preliminary outlook
National Weather Service (NWS) hydrologist David Pearson said there is an above-normal risk for spring flooding this year. He presented preliminary 2020 flood outlook information during a meeting Tuesday at Christensen Field in Fremont.
The meeting primarily concerned the Platte and Elkhorn rivers, though Pearson also discussed the factors that led to last year's flooding around the state, including snowfall, rain, soil moisture and frozen ground. He gave an overview of where those factors stand so far in 2020. Pearson said the meeting was also to provide people information so they can be informed for the coming spring.
"One thing we heard in the last flood is, while we talked to a lot of people, there were people that didn't get information ahead of time that we feel would have been useful," he said.
Though Pearson said there is an above-average risk for spring flooding, he added there is still much to be determined when it comes to future weather, ground and river conditions.
"(The meeting) is not meant to be a final answer to the question of, 'Is it going to flood this spring?'" Pearson said. "We don't know everything yet, there's things that haven't happened yet."
One of the unknown factors is how much snow and precipitation is yet to fall across Nebraska, including the eastern part of the state. Pearson said there was little to no snow in Nebraska as of Tuesday, but that was also true last year in early February.
"We're putting (snowfall) risk into the below-level category," Pearson said. "I got to put an asterisk by it though because we can still get more snow, and we probably will."
The NWS predicts no significant storms in eastern Nebraska over the next several days. But storms may begin tracking through the area by mid-February. The storms would likely bring snow, Pearson said, as the NWS predicts temperatures to dip below normal by mid-February and into March. Rain is also something to watch for, he said.
"If we get into a situation where it's going to be active weather … That will be something to be aware of," Pearson said.
Rain and snow could be an issue for runoff into rivers that are already running at high levels, he said, because soils around the state are already saturated due to more than normal precipitation over the last few months.
"This is not going to get better … You don't lose soil moisture in February," Pearson said.
Two factors that contributed to widespread flooding across the state in 2019, however, are currently at a below-average risk factors for flooding this year. Pearson said the depth of frozen ground this year is much lower compared to the same time last year thanks to mild winter temperatures thus far. As of Tuesday, there is also less risk of ice jams on rivers compared to 2019.
"I don't mean to say that's not an issue," Pearson said of ice jams, referencing one near Scriber on Tuesday. "We have ice on the rivers, some river sections have no ice."
He said last year there was many places along rivers with two feet of ice, while this year there is about six to eight inches. The few days left of warmer weather before the predicted cold should help with ice in rivers, Pearson added.
A few warmer days could also help with frozen ground. Pearson said the depth of frozen ground was already less this year compared to last.
"We're not anywhere near last year," he said.
Pearson added, however, there is potential for frozen ground depth to increase due to predicted cold weather later this month and into March.
"It gets pretty risky with weather that far out," Pearson said of the predicted cold. "You can't necessarily say it's going to be 10 degrees outside, but you can look at trends at least, and these trends have been looking steady the past few days."
Pearson said snow pack, rainfall, frozen ground and ice jams all contributed to flooding along rivers last year.
"Last year it was snow, right? It wasn't just snow, it was snow and rain. It wasn't just snow and rain, it was snow and rain and frozen ground. Several things altogether," he said.
Though some of those factors such as frozen ground depth and ice jams are below-normal flood risk right now, that other factors such as high river levels and soil moisture are at an above-normal risk lead to an overall above-average risk for flooding this spring.
"What we know is what we know today," Pearson said. "Where we are now and where we're going to be a month from now, we all know could change dramatically. This is just a first look at the situation."
The NWS official spring flood outlook will be released Thursday. The outlook will be updated twice through the beginning of March.
Pearson's presentation as well as audio and video from Tuesday's meeting can be found on the NWS website. Pearson also said information is put on social media and the NWS in Valley welcomes information and calls from people concerning rivers. He also said contacting county emergency managers before flooding is imminent can be prudent.
Washington County residents can sign up to receive alerts from the county emergency management office through the county website's "offices" tab and then the "emergency manager" link.