Spring Flood Risk Returns
Fargo, N.D. and Moorhead, Minn.
The flooded Red River separates Moorhead, Minnesota (R) from neighboring Fargo March 22, 2010 in Fargo, North Dakota. (Photo by Scott Olson/Getty Images)
As the expansive heartland drought stretches into 2013, a critical spring awaits.
Repeated bouts of rain and/or snow are urgently needed over the next few months to replenish both surface soil and groundwater supplies before summer's stifling heat sets in.
However, there's one part of the Plains drought that may be praying for a dry spring. These folks know the drill this time of year all too well recently. Welcome to the paradox that is the Red River Valley of North Dakota and Minnesota in 2013.
In their latest spring flood outlook, the National Weather Service (NWS) in Grand Forks, N.D. said there is a "high risk (greater than 50% chance) for major flooding on the Red River at Fargo, N.D., and for moderate flooding at Grand Forks, N.D."
Virtually the entire Red River Valley is in at least moderate (or severe) drought as of early March, according to the Drought Monitor analysis from NOAA and the National Drought Mitigation Center shown above.
How is this possible?
Snow water equivalent of snowpack (inches of liquid) as of Mar. 8, 2013. Dark (bright) purple shading indicates at least 2" (3.9") of liquid in the snowpack.
First, the ground froze up for the season before a deep snowpack was in place in the Red River Valley. While not as impermeable as "concrete frost" (when the top few inches of soil is first saturated, then freezes) without snowpack, the gist here is the majority of snowmelt won't be able to percolate deep into the soil immediately, but will runoff.
Then there's the impressive snowpack. As of Friday morning, March 8, both Fargo (15") and Grand Forks (10") had at least a 10" snow depth. Since Feb. 1 (through Mar. 7), Grand Forks, N.D. picked up 20.3" of snow, in part from Winter Storm Orko and Winter Storm Saturn.
What's more important for flood forecasting is the water content of the snowpack. An analysis from NOAA's NOHRSC on Friday Mar. 8 indicated the headwaters of the Red River had from 3.9 to 5.9 inches of liquid equivalent stored in the snowpack (light purple shadings on the map above). The rest of the valley has at least 2 inches of liquid equivalent.
Of course, this snowpack has to melt. There are key uncertainties regarding the magnitude of this spring flood, however.
2-Day Rain/Snow Forecast
2-Day Rain/Snow Forecast
Forecast "Wild Cards"
Flood outlooks are notoriously difficult due to the number of "wild cards" that may factor in.
According to the NWS-Grand Forks, here are the key uncertainties:
- Magnitude of spring snowfall
- Heavy rainfall on existing snowpack and/or frozen ground
- Rate of snowmelt
- Exact timing of crests along the Red River
So, again, a dry spring is in the hopes of many in the Red River Valley in 2013.
Also, a sharp warm spell, such as what occurred in March 2012 in the Midwest, would melt the snowpack quickly, leading to rapid rises on tributaries and, eventually, the mainstem Red River. A gradual spring warm-up would be optimal.
Of course, this area is all too familiar with major floods in recent years. In Fargo, five of the seven highest crests of record on the Red River have occurred since 1997, including the Mar. 28, 2009 record crest (40.84').
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