National Weather Service United States Department of Commerce

Conditions as of: March 16, 2017

Next Update: End of February 2018

Area Covered

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, Bad, White and Keyapaha River Basins.

Current Flooding
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Flood Outlook Summary

At this time, the probability of spring flooding from March through June is below average. However, the flood potential is still very dependent on weather conditions this spring. The amount of additional snow and rain combined with the timing of peak flows will have a significant effect on the flooding.

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.

Precipitation

Since October 1 2016 precipitation has varied from below average across most of northeastern Wyoming and portions of far western South Dakota to above average across central South Dakota. 

Temperatures in February were above average across the entire area. Precipitation amounts were slightly below average across the northern sections and slightly above average south of a line from Wright, WY to the central Black Hills to Winner, SD. Overall, about half of the days in February some form of precipitation fell, either in the form of rain or snow. However, the precipitation amounts were mostly light. 

So far in March, temperatures have been above average and precipitation has been below average. Average high temperatures for March range from 40 degrees in northwestern South Dakota to around 50 degrees in southwestern South Dakota. Average lows are usually around 20. Precipitation typically ranges from a half inch on the plains to just over an inch in the Black Hills.

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

Central Plains

Percent of Normal Precipitation since October 1

Wyoming

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

Precipitation Maps from the High Plains Climate Center

 

Snow Cover and Liquid Water Content

Minimal snowpack remains across the plains of northeastern Wyoming and Western South Dakota with a few scattered higher drifts in the draws and creek bottoms. The majority of the snowpack is confined to the higher elevations of the Black Hills and Bear Lodge Mountains. March and April are typically the two snowiest months, when a third of the seasonal snowfall usually happens.

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 slightly below average due to the recent warm and windy conditions. Most of the frost has left the ground across the lower elevations of western South Dakota and northeastern Wyoming. 

Calculated Soil Moisture Anomaly

Modeled Snow Moisture from Climate Prediction Center

 

Lake and River Conditions

Ice has begun to diminish from most creeks, streams, and rivers. Some ice cover remains on lakes in northwestern South Dakota and in the higher elevations of the Black Hills and Bear Lodge Mountains. According to the Bureau of Reclamation, reservoir levels are slightly above average for this time of the year with the exception of Shadehill Reservoir, which is slightly below average. Most river basins in the area are reporting above normal to much above normal streamflows due to the recent snowmelt.

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, SD
Belle Fourche Reservoir, SD
Deerfield Reservoir, SD

Current Reservoir Data for Angostura Reservoir

Current Reservoir Data for Belle Fourche Reservoir

Current Reservoir Data for Deerfield Reservoir

 
Keyhole Reservoir, WY
Pactola Reservoir, SD
Shadehill Reservoir, SD

Current Reservoir Data for Keyhole Reservoir

Current Reservoir Data for Pactola Reservoir

Current Reservoir Data for Shadehill Reservoir

 

Precipitation and Temperature Outlook

Water temperatures in the tropical Pacific Ocean are around average, indicating neutral conditions. The outlook for the spring and summer is for neutral conditions to continue. Neutral conditions generally bring a warmer and wetter pattern to the southern half of the United States with a cold polar jet stream diving across Canada into the northeastern United States. The northern plains will be in the transition zone between the two air masses that would create varying conditions for the northern plains.

Climate Prediction Center Temperature and Precipitation Outlooks

8 - 14 Day Temperature Outlook
8 - 14 day Precipitation Outlook


The outlook for the rest of March indicates odds tilted toward slightly above average temperatures with odds favoring near average precipitation.

Temperature Outlook
Precipitation Outlook

Monthly Temperature Outlook

Monthly Precipitation Outlook


The three month outlook for March, April, and May calls for a somewhat increased chance for normal to slightly above normal temperatures with odds favoring 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, SD  57701
605-341-9271
melissa.smith@noaa.gov