Area Climate Summary for 2011

Areal Climate Summary for the Year 2011

The year 2011 for this region turned out to be generally a little cooler than normal.  Rainfall was generally near to above normal, with some notable extremes.       

The year was characterized in general by a cool late winter and spring, mild and wet conditions in the late spring into early summer transitioning to very warm and dry conditions from mid-summer into fall, then closing out closer to normal.  The overall weather pattern was affected by the presence of La Nina, which was at moderate to strong strength early in the year.  It dissipated for a time by summer but reappeared at weak to moderate strength in the fall.

Temperatures:
 

Average temperatures across the region for the year turned out to be a little cooler than normal, with the central and northern Nebraska panhandle being a little warmer than normal. Much of the warmer than normal average there can be attributed to very warm temperatures in July and August.  The following table summarizes the average annual temperature, average daily high and low temperatures, and the departures from normal for select sites over the area:

City

2011 Average Temp.

Departure from normal*

2011 Average High Temp.

Departure from normal*

2011 Average Low Temp.

Departure from normal*

Cheyenne

45.8

-0.5

58.2

-0.3

33.3

-0.9

Laramie

40.2

-0.7

53.7

-0.7

26.6

-0.8

Rawlins

42.2

-0.2

55.0

-0.4

29.3

-0.1

Chadron

47.5

+0.3

62.1

-0.5

32.8

+0.8

Scottsbluff

49.2

+0.4

64.0

+0.5

34.4

+0.4

Sidney

49.6

-0.5

64.3

0.0

34.9

-1.1

* based on new normals for the period 1981-2010.

The warmest and coldest temperatures of the year and the number of days with highs 90 or higher and lows of zero or lower are depicted for select cities in the following table:

City

Highest Temperature

Date(s)

Lowest Temperature

Date

Number of days with highs 90 or above

Number of days with lows zero or below

Cheyenne

94

Jul 4, Aug 25

-24

Feb. 2

15

12

Laramie

90

August 25

-39

Feb. 2

1

34

Rawlins

93

July 25

-36

Feb. 2

12

17

Chadron

105

Jul 31, Aug 25

-28

Feb. 2

55

25

Scottsbluff

102

August 23

-20

Feb. 2

58

16

Sidney

102

Jul 31, Aug 23

-19

Feb. 2

52

14


Precipitation
:

Precipitation across the area was generally near to above normal, though a significant amount of the precipitation fell in the first half of the year, with the second half somewhat on the dry side.     There were some extremes of note.  Sidney, Nebraska recorded their wettest summer on record as an impressive 16.19 inches of rain was recorded in June through August.  Cheyenne recorded its 2nd wettest July on record with 5.63 inches of rainfall.  At the other extreme was Chadron Nebraska which had a very dry summer.  Only 2.48 inches recorded there. In addition, it was the driest August on record for Chadron as only a trace of rainfall was recorded in that month.

The following table tabulates the 2011 precipitation and snowfall amounts, departures from average and the percent of normal:

City

2011 precipitation  

Departure from normal*

2011 Snowfall

Departure from normal*

Cheyenne

19.25

+3.31 (121%)

68.7”

+8.4”

Laramie

10.42

-0.50 (95%)

----

----

Rawlins

9.77

+0.52 (106%)

----

----

Chadron

17.82

-0.23 (99%)

----

----

Scottsbluff

18.85

+3.06 (119%)

38.5”

-3.6”

Sidney

27.76

+9.22 (150%)

----

----

* based on new normals for the period 1981-2010

Other Notable Weather Events during 2011:

- Significant river flooding occurred in late spring into early summer due to snow melt from unusually high snowpack over the mountains.

- First severe thunderstorm event over the area occurred on May 9th over east central Wyoming and the northern Nebraska Panhandle.  Hail up to 2.75 inches in diameter fell south of Chadron while a brief tornado was spotted east of Harrison, Nebraska.

- Damaging hail up to 1.75 inches in diameter fell in Sidney on June 13th resulting in many broken windows.

- Severe hailstorm struck Cheyenne on July 12th resulting in widespread damage to roofs and vehicles with hail up to 2 inches in diameter.  Over 2 inches of rain fell in about ½ hour as well resulting in some flooding.

- Last severe thunderstorm event occurred on August 29th with some large hail and a brief tornado over the extreme northern Nebraska Panhandle.

- A couple of significant early season snows occurred in October.  The first occurred on October  8th at elevations generally above 6000 feet.  The snow was rather heavy and wet and caused tree limbs to snap and in some cases fall onto power lines which resulted in power outages, especially northwest of Cheyenne.  Snowfall amounts from 3 to 8 inches were common in these areas.  A second heavy snow occurred on the 25th into the 26th and produced generally 5 to 10 inches across parts of the area.

- High winds over parts of the area December 29th and 31st with gusts to 77 mph measured in Cheyenne and up to 90 mph northwest of Cheyenne.  The winds caused some damage to roofs as well as blew over several trucks on roads.  The winds gusts were ranked in the top 10 strongest on record for Cheyenne.



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