Spring flood outlook lower than average

The snow may be coming down more often than it has over recent years, but the National Weather Service (NWS) is not predicting it will cause flooding when the spring arrives.

According to the outlook for the Rapid City Hydrologic Service Area, the severe drought conditions that led into winter – along with lower streamflows and minimal frost – have reduced the chance for spring floods, despite the abundance of the snowpack.

At this time, there is below average potential for flooding in northeastern Wyoming.

The NWS predicts less than a 5% chance for the Belle Fourche River to flood this spring, for example.

Across the Black Hills and Bear Lodge Mountains, the snow cover is above average. Snow depths range from ten to 20 inches at lower elevations, with more snow in the higher parts of the Hills.

Snow cover is minimal across the plains, but have reached over two feet in some parts of the Black Hills and Bear Lodge Mountains, with water equivalents between three and six inches.

Soil moisture, however, is below average. The NWS reports less than a foot of frost in the ground over northeast Wyoming and says the drier-than-average soil conditions have led to porous soils that allow for water infiltration, despite the ground being frozen.

Ice thickness in this region ranges from eight to 18 inches and is expected to remain in place for the next couple of weeks. Despite milder temperatures, the NWS anticipates that night-time lows will drop below freezing and keep the ice cover in place.

As March and April can often be very snowy months, the NWS cautions that the flood potential may change if precipitation is above normal during that time.

Ice jam flooding typically occurs in late February and March, along with river ice breakup. Ice cover on streams, lakes and rivers is expected to begin the melting process over the next few weeks.

Flooding from the snowmelt, on the other hand, doesn’t usually take place until later in the year. The potential for this will depend on how much additional snow and rain the area receives and the timing of peak flows in rivers and streams.

The NWS predicts that the weather outlook for the rest of the winter will favor drier conditions thanks to a transition from La Niña to the more neutral El Niño Southern Oscillation.