2013 Annual Climatic and Hydrologic Summary for Western South Dakota and Northeastern Wyoming
 
 
Temperature and Precipitation Summary
 
Temperatures averaged 0.5 degrees below normal across the entire region for the year. A majority of months during 2013 were near average. The exceptions were April (7 degrees below average), September (5 degrees above average), October (4 degrees below average), and December (6 degrees below average). April and October temperatures were hampered by an abundance of snowfall, and December saw a couple of Arctic intrusions that spilled into the area. A fairly persistent ridge of high pressure kept temperatures above average for much of September. Temperatures cooled to near average for the final week of September.
 
Precipitation averaged 125% of normal across the entire region, with the average surplus around 5.00 inches. After a near normal January, February and March were only 50 to 60% of average. April was near average despite above average snowfall. The spring rains finally came in May, with 150% of average precipitation. Summer started off slightly below average, but August and September made up for the June and July deficits. October ended up being very wet, with the blizzard early in the month, and two other very wet storm systems moving through the area shortly after the blizzard. The area finally dried out in November, and December finished out the year slightly above average. The highest annual precipitation total was at Lead, where 49.52 inches of precipitation fell. Wright 12W was the driest location, with 13.00 inches. The wettest location by percentage was Camp Crook, receiving 190% of normal precipitation (33.97 inches). The driest location by percentage was Martin, receiving only 87 percent of their yearly average precipitation (16.97 inches).
 
Snowfall averaged 165% of normal across the entire region, with the average surplus around 20 inches. The snowiest month was April, with most locations receiving between 16 and 24 inches of snowfall. October was a close second, with many locations receiving between 10 and 20 inches of snowfall. The highest annual snowfall total was at Lead, where 237 inches fell. Camp Crook had the least amount of snow, with 46 inches for the year. The snowiest location by percentage was Interior, receiving over 300% of normal snowfall (91.4 inches). The location with the least amount of snow by percentage was Gillette, WY, receiving 102 percent of their average yearly snowfall (59.7 inches).
 
 
2013 Notable Weather Events
 
Blizzard shuts down western South Dakota – A severe blizzard hit the Black Hills region shortly after the start of autumn.  Rain soaked the region Thursday, October 3 before changing to snow over northeastern Wyoming and the Black Hills overnight, and on the plains of western South Dakota Friday, October 4. Heavy snow and strong winds continued through midday Saturday, October 5. As much as 55 inches of snow fell over the northern Black Hills.  The plains received six to 24 inches, with accumulations abruptly decreasing east of a line from McIntosh to Dupree, Midland, and Mission. Seventy mile per hour wind gusts whipped the snow into deep drifts.

Downtown Rapid City’s 19.0 inch snowfall on October 4 almost doubled the previous October daily record of 9.9 inches set October 19, 1919. The total snowfall of 23.1 inches is the second highest snowfall from one storm, exceeding 22.4 inches measured just six months earlier on April 8-10, behind 32.2 inches that fell April 12-16, 1927. Lead, where heavy fall snow is more common, received 42 inches of snow on October 4, which broke the previous October daily record of 38.9 inches recorded on October 26, 1996.
 
Travel was almost impossible for two days as most roads were closed.  The heavy, wet snow damaged trees and downed power lines, and many customers were without electricity for a week or longer. The heaviest toll was the loss of livestock. Thousands of cattle, sheep, and horses died of hypothermia after being soaked by the rain and chilled by the colder temperatures and strong winds, suffocated in deep snow drifts, or drowned.
 
Light winter snow…Snowfall during the first three months of 2013 was generally below normal. A storm on January 11th produced six to 12 inches of snow over the Black Hills and southwestern South Dakota; another on February 9-10 left three to eight inches of snow across south central South Dakota. Localized storms on March 16 and March 22 left heavy snow around Rapid City and central Black Hills, but most stations had well below normal snowfall, raising concerns about the ongoing drought and wildfire potential.
 
…until April. Three snowstorms during the month produced record snowfall and precipitation with snowfall averaging 400 percent of normal across the region.  The first storm on April 8-10 set snowfall records over a large portion of the region. More snow fell on April 16-17 and April 21-22. Both the Rapid City Regional Airport and the downtown Rapid City National Weather Service office set all-time greatest monthly snowfall records with 43.4 and 39.5 inches respectively.
 
Active thunderstorm season - Thunderstorm season started later than usual in mid-May and continued through the entire month of September. The largest hail reported was  softball size (4.25” diameter) from storms in eastern Custer County on the morning of June 21; north of Johnson Siding, South Dakota on August 30; and near Rozet in eastern Campbell County, Wyoming on September 8.  The strongest measured thunderstorm wind gust was 87 mph west of Edgemont, South Dakota on July 6. Wind gusts estimated at 90 mph blew down power lines east of Pine Ridge, South Dakota on August 30.
 
Large hail pounded sections of Rapid City five times during the summer and caused millions of dollars in damage to vehicles and roofs. A thunderstorm dropped ping pong ball size hail from neighborhoods southwest of Rapid City to downtown May 18. The southern sections of town received quarter size hail June 17. Central Rapid City to Rapid Valley saw hail to the size of half dollars (1.25 inch diameter) July 19. Much of the city was bombarded by 2.5 inch diameter hail for 20 minutes July 20, which disrupted outdoor activities. Hail as large as baseballs fell for 45 minutes and heavy rain caused street flooding along many major streets August 30.  
 
In addition to widespread rain that led to flooding in May, individual thunderstorms produced localized flash flooding. Two golf courses in west Rapid City were flooded May 29; high water on Rapid Creek covered the bike path and reached structures in Rapid Valley. Heavy rain over a large portion of western Tripp County covered highways and damaged gravel roads during the night of July 14-15.  A small flash flood destroyed ranch buildings southwest of Newcastle July 28. Flooding occurred over the Rosebud Indian Reservation after heavy rain July 30. Much of Wright, Wyoming was flooded August 1.     
 
Four small tornadoes were confirmed. A tornado destroyed a house and mobile home on the south edge of Allen, South Dakota on May 28. A tornado blew down trees along the Mickelson Trail and Needles Highway south of Hill City on August 11. Two brief tornadoes were observed near Philip on July 30 and east of Hermosa on August 30, but neither caused damage.
 
 
2013 Flooding Summary
 

Drought conditions persisted across northeast Wyoming and western South Dakota during the first few months of 2013. Rivers and streams were at low flows and some creeks were dry. Temperatures during the spring were colder than average with three large snowstorms during April.

In May, significant rain fell across northeastern Wyoming and portions of western South Dakota. Several roads were inundated with water during the evening of May 18 in Ziebach and Haakon counties, when three to four inches of rain fell in less than two hours. From May 19-21, three to six inches of rain fell over the northern Black Hills, Bear Lodge Mountains, and northwestern South Dakota. Some low lying areas and low water crossings reported water over them; however, most flooding was minimal. On May 25, strong thunderstorms produced a quick inch or two of rain around Bear Butte and across northern Perkins County. Some ponding of water in low-lying areas was observed with these storms. On May 26, a strong thunderstorm northwest of Gillette produced flash flooding as it cut one foot ruts into a gravel road and left water ponding along the railroad tracks. On May 27, slow moving thunderstorms with heavy rain caused flooding in portions of northeastern Meade County. Two to three inches of rain fell in less than two hours causing small streams to overflow their banks and culverts to become overwhelmed. Pastures were flooded, fences were damaged, and water was reported over roads due to the flooding. On May 29, thunderstorms formed along the east side of the Black Hills. As the storms moved slowly northwest, they became anchored along the eastern foothills. Rainfall amounts of four to six inches were reported from Nisland to Sturgis to Rapid City within three hours. Flash flooding occurred in Rapid City with numerous streets inundated with water and Rapid Creek quickly rose which flooded areas along the greenway in town. In Rapid Valley, water surrounded a few structures along the creek. Street flooding was reported in Sturgis. Around Nisland and Vale, several private stock dams failed and small creeks and streams quickly flooded the area. As the water made its way to the Belle Fourche River, the flow went from around 300 cfs to 12,700 cfs in 18 hours. The Belle Fourche River near Sturgis along Highway 34 crested just below flood stage on May 30.
 
The rain continued on May 30 and 31 and into early June. Five to seven inches of rain fell from Newcastle to Four Corners and over six inches of rain fell north and west of Sundance in the Bear Lodge Mountains and in the northern Black Hills. Numerous county roads, Forest Service roads, and Forest Service recreational areas were flooded and sustained damage. The rain continued through the beginning of June with flooding observed on the Belle Fourche River, Redwater Creek, Redwater River, Sand Creek, Bear Creek, and Spearfish Creek. High water was also observed on the Little Missouri River.
 
On June 21 flash flooding and debris flows occurred in the Oil Creek Fire Scar in Weston County, WY when a half inch to an inch of rain fell in less than an hour. West Plum Creek, which is normally dry, suddenly was flowing eight feet deep and 30 feet wide. Plum Creek Road, Big Plum Road, and Oil Creek Road were damaged when water and debris flowed over the roads.
 
During the early morning hours of July 8, flash flooding and debris flows occurred after two to five inches of rain fell in about two hours across southern Custer County. Runoff from heavy rainfall caused flooding of Cold Brook Creek above Cold Brook Reservoir and Cottonwood Springs Creek above Cottonwood Reservoir. Debris flowing down Cold Brook Creek piled up in the channel along Argyle Road causing water to flow over Argyle Road. The debris filled five dump trucks when it was removed. Along Cottonwood Springs Creek, water created a 12-foot wide channel into Cottonwood Reservoir and washed gravel off rural roads. Other rural roads in southern Custer and northern Fall River counties were also damaged as culverts were overwhelmed from the excessive runoff.
 
On July 14-15, runoff from three to six inches of rain in a few hours caused flooding in western Tripp County. Highway 44 was flooded in six locations and numerous county roads were damaged. Cottonwood Creek, Two Nations Creek, and Little Dog Creek in northwestern Tripp County over-flowed and Sand Creek in southwestern Tripp County flooded.
 
During the evening of July 28, runoff from three to six inches of rain caused localized flash flooding in southern Weston County along Lion Creek. A flash flood washed away two pole barns and their contents, the contents of a nearby shop, and collapsed the foundation of a ranch house. Lynch Road was overtopped at Lion Creek, damaging the culvert and downstream side of the road.

On July 30, runoff from heavy rain and debris flows from the 2012 Longhorn Fire Complex caused flash flooding in north-central Todd County. Debris clogged the outlet works at Ghost Hawk Dam and Rosebud Dam causing the dams to overflow with water. Several culverts and roads were damaged by the flooding, including Ghost Hawk Road and Grass Mountain Road. The Little White River near Rosebud went from less than 100 cfs to over 1000 cfs in less than four hours, with a peak flow of 1300 cfs. The flash flooding ended during the early morning hours of July 31 and the creeks quickly receded to less than 100 cfs within 12 hours of receiving the heavy rain.

During the evening of August 1, golf ball sized hail and runoff from heavy rain caused flooding of low lying areas in and around Wright, WY. Drainage systems plugged with hail caused flooding of roadways, yards and basements. The dam on Panther Pond was overtopped; the Wright Golf Course was flooded; and some roads, including Wright Blvd and rural roads on the south side of Wright, were covered with two feet of water.

On August 3, heavy rainfall of three to five inches fell in a few hours causing minor flooding along rural roads in northern Campbell County. Hail drifts and water covered portions of Sam Adam Rd and Broyles Rd when drainage culverts were quickly overwhelmed from the excessive runoff. Nearly dry stock ponds quickly filled from the runoff as well.
 
Just before midnight on August 5, two to three inches of rain fell in less than an hour near the Rushmore Mall in Rapid City. Runoff from the heavy rainfall caused minor flooding at Maple and Disk Drives and washed a car into a ditch. At the intersection of Crestwood and Racine, rapidly rising water flooded adjacent backyards and basements. In Rapid City near the fairgrounds, Rapid Creek was a foot from exceeding its banks. The water quickly receded, within twenty minutes at most locations.
 
On August 7, runoff from heavy rain caused flash flooding in eastern Weston County and northern Fall River County. In Fall River County, two to three inches of rain in less than an hour, caused flooding in Hot Springs, around Cold Brook Reservoir, and in the Minnekahta Valley area. Six inches of water was flowing down Highway 18 and water was over the curbs on a couple of other streets in Hot Springs. Minor flooding occurred in Hot Brook Canyon along Hot Brook Creek. Cold Brook Reservoir reached its second highest pool level at 3585.42 ft. In Weston County, runoff from heavy rain caused flooding along Skull Creek Road, Oil Creek Road, Green Mountain Road, and Purvis Road. On the north side of Highway 16 west of Newcastle, ponding water was close to overflowing the highway. North of Four Corners, 1.5 inches of rain fell in 20 minutes.
 
During the evening of August 9, runoff from heavy rainfall and hail overwhelmed culverts and caused flooding in southern Campbell County. Porcupine Creek, Spring Creek, and their tributaries flooded Highway 59 in spots for nine miles as runoff from heavy rainfall overwhelmed culverts. Highway 59 had to be closed from seven miles south of Wright to the Converse County line due to flooding.
 
A large area of heavy rainfall fell across potions of southern South Dakota on August 13. Rainfall estimates of two to three inches fell in two hours, with some locations receiving an inch in a half hour. Runoff from this rainfall caused ponding of water, minor flooding of low-lying areas, and small creeks to overflow their banks. South southeast of Kadoka, minor flooding was reported along Pass Creek. Three miles north northwest of Hot Springs, 0.93 inches of rain fell in 30 minutes, with ¾ inch in 15 minutes. Water briefly ran over the two low water crossings in Hot Springs. Cold Brook Creek backed up behind Argyle Road and also covered the Campground Road with a few inches of water at Cold Brook Reservoir.
 
During the late evening of August 27 through the morning of August 28, flash flooding and flooding occurred when three to six inches of rain fell over central Perkins and northern Ziebach Counties. Several creeks and streams including Thunder Butte Creek, Hart Creek, Twin Butte Creek, Worthless Creek, Beaver Trap Creek, and their tributaries overflowed their banks. Rural roads were flooded when culverts were quickly overwhelmed from the excessive runoff.
 
On the afternoon of August 30, large hail and runoff from slow moving thunderstorms caused street flooding in Rapid City and Rapid Creek quickly rose into the greenway through town. Over an inch of rain fell in less than an hour. Most roads from West Blvd. to Mt. View were flooded from curb to curb. Several roads and intersections were flooded as well including Soo San Drive and the intersection of West Blvd. at St. Joseph Street.
 
During the evening of September 7, slow moving thunderstorms over northwestern South Dakota produced significant rainfall amounts of two to six inches fell within a few hours. Runoff from this heavy rain caused flash flooding along the Grand River and its smaller tributaries. Most roads in northeastern Harding and northern Perkins counties were inundated when culverts were overwhelmed or damaged from the significant runoff. East of Ludlow, 3.7 inches of rain was reported. Five inches of rain was estimated northeast of Ralph. In Perkins County, localized street flooding was reported in Lemmon. Five to six inches of rain was reported west of Lodgepole and three to five inches of rain was reported around Bison and Shadehill Reservoir. Two to three inches of rain fell around Lemmon. Shadehill Reservoir rose over 2.5 feet from September 8 -14 from the excessive runoff.
 
On October 3, a low pressure system strengthened over the Rockies and moved into the area. Strong southerly flow drew large amounts of moisture northward into the northern plains creating a widespread rain event with enhanced upslope flow over the central and northern Black Hills as well as the eastern slopes. During the evening hours of October 3 and morning hours of October 4, cold air was drawn into the circulation and the precipitation turned to snow over northeastern Wyoming and western South Dakota. As the low pressure center continued to move slowly northward on Friday, the pressure gradient across western South Dakota increased dramatically producing sustained northerly winds of 35 mph and higher from mid-morning Friday through the day on Saturday October 5. Wind gusts of 65 to 70 mph were reported at several locations on the plains of northwestern South Dakota Friday afternoon and evening. By Saturday morning, the low pressure center had moved into central South Dakota and the effects of the storm began to decrease from west to east across the region. Several locations in western South Dakota exceeded their all-time snowfall records. Snowfall amounts ranged from 12 to 24 inches on the plains with amounts up to four to five feet in Black Hills.
 
From the beginning of the rainfall event on October 3 through the end of the snowfall event on October 5, liquid equivalent precipitation amounts over 4 inches were common over the northern and central Black Hills and eastern slopes. By October 6, much warmer air entered the area allowing the snowfall to rapidly melt. The initial snow melt caused streams to rise and dry creeks to begin to flow; however no flooding was reported until the next precipitation event on October 11.
 
Heavy rainfall combined with melting snow caused flash flooding in Keystone on October 11 and caused several smaller creeks and streams to approach or exceed flood stage from October 11-17. In Keystone, law enforcement reported water over the road at several locations along Winter Street and Highway 16A. Battle Creek in Keystone mainly remained within its banks; however, Grizzly Bear Creek overflowed its banks in several locations and runoff from the rainfall and melting snow caused additional flooding. Flows in Grizzly Bear Creek were estimated around 500 cfs with around 1300 cfs estimated in Battle Creek. Normal flows for Battle Creek and Grizzly Bear Creek in Keystone during October is less than 5 cfs.
 
Flooding of several rural roads and agricultural land occurred due to runoff from heavy rain combined with melting snow. (Harding, Perkins, Butte, Meade, Ziebach, Lawrence, Pennington, Haakon, Jackson, Custer, Fall River, Shannon, Bennett counties). Small streams and creeks quickly overflowed their banks. Normally dry creeks quickly inundated culverts and caused flooding. (Harding, Perkins, Butte, Meade, Ziebach, Lawrence, Pennington, Haakon, Jackson, Custer, Fall River, Shannon, Bennett counties). The flooding began on October 11 and lasted through October 17. The duration of the flooding was exasperated by an additional storm system on Sunday October 13 through Tuesday October 15 which brought an additional one to two inches of precipitation.
 
In November and December, drier conditions prevailed and colder air moved into the region. By early December arctic air entrenched the area causing most of the streams around the area to freeze for the winter.
 
 
2013 Temperature Extremes
 
Station
High
Date(s)
Low
Date
Buffalo*
103
July 11
-28
December 7
Cottonwood
105
July 12
-25
December 23
Faith*
102
July 11
-22
December 7
Gillette
99
July 11
-20
December 6
Interior
101
July 12 & 18
-19
December 11
Pine Ridge *
100
August 27
-28
December 6
Philip *
105
July 11
-28
December 23
Rapid City Airport *
101
August 27
-15
December 9 & 23
Winner
104
August 30
-16
December 8 & 9
 
2013 Precipitation Extremes
 
Station
Rainfall
Date(s)
Snowfall
Date(s)
Buffalo *
1.30
August 2
Not Available
Not Available
Cottonwood
3.03
October 5
13.0
October 5
Faith*
1.15
May 27
Not Available
Not Available
Gillette
1.93
October 4
13.1
October 4
Interior
2.23
October 5
16.0
October 5
Pine Ridge *
1.27
May 29
Not Available
Not Available
Philip *
1.54
October 14
Not Available
Not Available
Rapid City Airport
1.74
October 4
20.0
April 9
Winner
2.31
May 21
8.0
Mar 10 & Dec 4
 

* Data is from the automated weather station

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