Spring Flood and Water Resource Outlook for Western South Dakota and Northeastern Wyoming

Updated: February 19, 2015
Next Update: March 5, 2015

Spring Flood and Water Resource Outlook

This spring flood and water resource outlook is for the Rapid City Hydrologic Service Area (HSA) which covers northeastern Wyoming and western South Dakota. The main river basins include the Little Missouri, Eastern Powder, Belle Fourche, Grand, Moreau, Cheyenne, Upper Missouri, White and Keyapaha River Basins.  

Current Flooding

To obtain the latest watches, warnings, statements, and advisories, go to: http://www.crh.noaa.gov/hazards/unr

Conditions as of March 5, 2015

Flood Outlook Summary

The overall flood potential for this spring is average to below average.

At this time, the potential for flooding due to snowmelt is low. However, there is still more than enough of the winter season left to provide significant snowpack before the onset of the spring melt. The two snowiest months in the northern plains are March and April. Typically half of the snowfall received across the area occurs after February 1.

The flood potential for ice jam related flooding is below average on rivers and streams. Most of the ice has dissipated from the lakes and streams already due to the warmer than average winter season. Only minimal amounts of ice remain on lakes, rivers, and streams.

For the Black Hills and higher elevations, flooding from snowmelt typically begins in late April and May. Flooding on the plains due to snowmelt and ice jams typically occurs between February and May.

The potential for rainfall-induced flash flooding is not quantifiable because this type of flooding is usually caused by localized thunderstorms during the spring and summer.

The flood potential is still very dependent on weather conditions from now until the spring melt. The amount of additional snow and rain, the timing and rate of the spring thaw, and the timing of peak flows will have a significant effect on the flooding.


Since October 1, 2014 precipitation has been below average. 

Click here for preliminary monthly precipitation amounts for northeastern Wyoming and western South Dakota.

Central Plains
Percent of Normal Precipitation since October 1

Departure from Normal Precipitation

South Dakota
Departure from Normal Precipitation

Image of Percent of Normal Precipitation for the Water Year

Current Climate Summary Map

Current Climate Summary Map

Monthly Percent of Normal Precipitation from the High Plains Climate Center

Snow Cover and Liquid Water Content

Current snowpack is confined to the higher elevations of the Black Hills and Bear Lodge Mountains. Snow cover at lower elevations is minimal at best.

Snow Depth

Snow Water Equivalent

Thumbnail image of Snow Depth

Thumbnail image of Snow Water Equivalent

Modeled Snow Analyses from National Operational Hydrologic Remote Sensing Center

Cole Canyon

North Rapid Creek

Blind Park

NRCS Snotel Graphic for Cole Canyon

NRCS Snotel Graphic for North Rapid Creek

NRCS Snotel Graphic for Blind Park

Black Hills and Bear Lodge Mountain Snotel Data from the Natural Resources Conservation Service

Soil Conditions and Frost Depths

Soil moisture is average to above average across most of the area according to the latest calculated values produced by the Climate Prediction Center.  Frost depth values are a foot or less.

Calculated Soil Moisture Anomaly

Modeled Snow Moisture from Climate Prediction Center

Lake and River Conditions

Most of the ice cover on the larger lakes on the plains has begun to deteriorate with some open water reported near the shores. Quite a bit of the ice on rivers and streams has come off, with only minimal amounts of ice remaining. Most lakes in the Black Hills and Bear Lodge remain ice covered with an ice thickness of 10 to 16 inches.

Reservoir levels are above average for this time of the year. This is due to the wetter than average conditions since October of 2013 and the above average inflows reported in January and so far in February. All river basins in the area are reporting normal to much above normal streamflows.

Monthly-Average Streamflow

Streamflow Mapping provided by the USGS

Current Reservoir Data from the Bureau of Reclamation

The graphs below denote reservoir storage levels. The line labeled active is the point where the reservoir is considered "full" which is when the pool elevation is at the top of the active conservation pool. Most reservoirs have additional storage above this level for surplus or to hold flood waters.

Angostura Reservoir

Belle Fourche Reservoir

Deerfield Reservoir

Current Reservoir Data for Angostura Reservoir

Current Reservoir Data for Belle Fourche Reservoir

Current Reservoir Data for Deerfield Reservoir


Keyhole Reservoir

Pactola Reservoir

Shadehill Reservoir

Current Reservoir Data for Keyhole Reservoir

Current Reservoir Data for Pactola Reservoir

Current Reservoir Data for Shadehill Reservoir

Precipitation and Temperature Outlook

Conditions through the end of February into early March will remain highly variable with large swings in temperatures from day to day. Precipitation is expected to be minimal over the northern plains. The main storm track will arc around the area extending from the Pacific Northwest through the Southern Plains into the Great Lakes Region.

Climate Prediction Center Temperature and Precipitation Outlooks

8 - 14 Day Temperature Outlook

8 - 14 Day Precipitation Outlook

According to the Climate Prediction Center, the outlook for March indicates equal chances of below average, above average, or average temperatures and precipitation. For March, the average high temperature is in the middle 40s and the average low temperature is around 20 degrees. The average precipitation is around an inch on the plains with two and a half inches for the Black Hills and Bear Lodge Mountains.

Temperature Outlook

Precipitation Outlook

Monthly Temperature Outlook

Monthly Precipitation Outlook

According to the Climate Prediction Center, the three month outlook covering March, April, and May indicates equal chances of average, below average, and above average temperatures with a slightly greater chance of above average precipitation.

Three Month Temperature Outlook

Three Month Precipitation Outlook

Three Monthly Temperature Outlook

Three Monthly Precipitation Outlook

Questions or Comments

If you have any questions or comments about this spring flood and water resource outlook please contact,

Melissa Smith
Service Hydrologist
National Weather Service
300 East Signal Drive
Rapid City South Dakota 57701
Telephone 605-341-9271

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