SPEARFISH — The National Weather Service in Rapid City said this spring’s flood and water resource outlook through June is above average in the Rapid City Hydrologic Service Area.
That area includes northeastern Wyoming and western South Dakota, and the main river basins include the Little Missouri, eastern Powder, Belle Fourche, Grand, Moreau, Cheyenne, Bad, White, and Keyapaha river basins.
According to the weather service, there is also a high potential for ice-jam-related flooding.
While the weather service cautioned people about the potential, much will depend on the weather conditions — additional rain and snow as well as the timing of peak flows.
“With all the snow and ice in in the rivers, that combination, that is why we have it listed as above average,” said Melissa Smith, a hydrologist with the National Weather Service in Rapid City.
Smith said the amount of snow that has fallen in the Spearfish and Belle Fourche areas since Jan. 1 is about double that of normal.
“There are a lot of areas that February was among their snowiest month — in the top five,” Smith said. And the area’s snowiest months, March and April, are now upon us.
She said usually the flooding occurs in the Northern Hills along the Belle Fourche and Red Water rivers.
“We usually don’t see too much in the Spearfish area,” she said. But she noted that Spearfish Creek had frozen completely over in some areas.
“It has been since 2008 or 2009 that I’ve seen ice in Spearfish Creek,” she added.
In higher elevations of the Black Hills, flooding from winter and spring snows generally begins toward the end of April. Plains flooding from ice jams occur throughout a wider timeframe — February through May.
February was one of the coldest months on record forming ice on area rivers and streams. When warm conditions do return to the area and that ice begins to break up, large chunks the ice may jam together in areas, causing the water to overflow banks. Snow cover will add to the flooding.
With the summer of 2018 so wet, and then a warm beginning of February, moisture froze two to three feet down in many areas on the plains, and even deeper at higher elevations. That means that it will take a while for the ground to thaw and any runoff or rain that falls, will flow across that land rather than being absorbed, Smith said.
Smith said the long-range outlook indicates weak El Nino there is not a prediction for summertime weather yet.
“We’re kind of in that dividing area,” Smith said. “Warmer to the west and moist air to the south of us.”
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