Winter 2010-2011 Climate Summary

Winter 2010-2011
in Review
With March 1 comes the end of meteorological winter, a period defined as covering the months of December through February. The winter of 2010-2011 in Central Indiana was colder and snowier than normal.  A persistent trough of low pressure over the eastern United States kept a cold Arctic airmass over central Indiana for much of the winter.
The following is a review of weather conditions experienced in Central Indiana during the winter season of 2010-2011.
Temperatures remained below normal across central Indiana for much of the month as a persistent trough of low pressure brought continuous surges of colder temperatures to much of the eastern continental United States. After the first significant snow storm of the season on the 4th, colder air filtered into central Indiana with high temperatures mainly in the high teens and lower 20s from the 6th to the 8th.  High temperatures briefly warmed up into the 40s on the 10th and 11th, before another significant winter storm impacted the Great Lakes and Ohio Valley with accumulating snowfall. Several inches of fresh snow cover for much of the region combined with a cold arctic airmass settling over central Indiana and much of the Midwest contributed to the coldest air of the month.   Beginning during the evening of the 12th, temperatures remained below freezing until the 20th, with several locations in central Indiana experiencing subzero temperatures in the early mornings of the 14th and 15th.
The airmass modified in the week before Christmas, with temperatures returning to near normal levels for late December with highs in the lower and middle 30s. After another surge of colder air in the wake of a storm system that brought snow to central Indiana on Christmas Eve and Christmas Day, the warmest temperatures in nearly five weeks arrived during the last couple days of the month with temperatures warming all the way into the lower 60s on the 31st. For Indianapolis, the 61 degrees recorded on the 31st was the warmest temperature experienced on New Years Eve since 1965. Despite the warmer temperatures to finish out the month, December 2010 ended up as the coldest December at Indianapolis since 2000.
There was only one rain event during the first four weeks of December. One quarter to three quarters inches of rainfall occurred on the 11th in central and southern Indiana.   A more significant storm system impacted the region with rain and a few thunderstorms on the 31st as milder air surged into central Indiana. Many locations had received one half to one inch as the calendar switched to 2011. 
December 2010 was one of the snowiest months ever for portions of central Indiana including the Indianapolis area. Monthly snowfall of 12 to 19 inches occurred in portions of central Indiana. Indianapolis officially received 16.6 inches at the airport, making it the third snowiest December on record, and the most snow for the month since 1973, when 27.5 inches fell at the airport. Snowfall was lighter in the remainder of central and southern Indiana. Monthly totals ranged from 3 to 9 inches in these areas. An inch of more of snow occurred 5 times during December. This happened on 4th-5th, 12th-13th, 15th-16th, 20th-21st and 24th-25th. A trace or more of snow covered the ground in central Indiana almost the entire month. The snow cover was the deepest on the 21st when 4 to 8 inches blanketed much of central Indiana.   Snowfall on Christmas Eve gave Indianapolis the classic Christmas morning scene and one of the deepest Christmas snow depths of record. The mild weather at the very end of December melted all of the snow cover.

Average Temperature
Total Precipitation
Total Snowfall
Highs below freezing
December 2010
Normal December
2010 Difference from Normal

December 2010 All-Time Ranks:
Temperature: 19th Coldest
Precipitation: 35th Driest
Snowfall: 3rd Snowiest
2011 rang in mild as temperatures were in the 50s with thunderstorms across central Indiana. The warmup was short-lived as a strong cold front moved across the state prior to daybreak on the 1st, with temperatures falling throughout New Years Day. In fact, the mid and upper 50s recorded at cities across central Indiana during the early morning of the 1st would end up being the warmest temperatures of the entire month as the persistent upper level trough across the eastern United States reestablished by the end of the first week of the month. This enabled repeated surges of very cold polar air to expand across the Great Lakes and the Ohio Valley. After the warm temperatures early on the 1st, temperatures remained below 45 degrees for the rest of the month across central Indiana. In fact at Indianapolis, the temperature only managed to break 40 degrees twice after the 1st, on the 3rd and again on 18th when temperatures warmed to 41 degrees.
Low temperatures surged into the single digits in many locations on the mornings of the 8th and the 9th, with several locations dropping to near or just below zero. The coldest air of the month arrived on the 21st in the wake of an upper level disturbance that brought another round of accumulating snow to central Indiana. Skies cleared during the evening of the 20th, allowing temperatures to plummet to below zero across much of the region. Indianapolis dropped to -3, the lowest temperature experienced in the Circle City since February 5, 2009. Shelbyville fell all the way to -12 on the morning of the 21st. The coldest daytime temperatures of the month followed, with many locations struggling to get back to 10 to 15 degrees on the afternoon of the 21st. Within a few days, temperatures returned back to near normal with highs in the lower and mid 30s common throughout the final week of the month. 
The heaviest of the rainfall throughout the month occurred during the first twelve hours of January as a strong cold front traversed central Indiana. Many locations across the eastern half of central Indiana received one half to one inch as the front tracked east. As colder air then settled into the region for much of the remainder of the month, the predominant precipitation type was snow. The only other significant system to bring precipitation other than snow came on the 31st as the initial wave of the ice storm that would impact central Indiana during the first two days of February, began during the evening. Some light snow did occur to the north of Indianapolis, with precipitation transitioning to freezing rain and sleet across much of the area. Many locations received from a quarter inch to just over one half inch on the 31st.
January 2011 continued the snowy trend from December with the second consecutive above normal month for snowfall as much of the eastern United States remained cold. Most of the snow throughout the month came as a result of the passage of upper level disturbances or Alberta Clippers, with the two largest snows falling on the 11th and on the 20th. Snow fell for much of the day on the 11th as low pressure passed through the region. Much of central Indiana received 3 to 6 inches of new snow. The heaviest snow fell just south of Interstate 70 and across the southern portions of the Indianapolis metro area. From Morgan County east through Johnson, southern Marion, and into Hancock, Shelby, Rush and Decatur Counties many locations received 4 to 6 inches. The second major snowfall of the month came as an upper level disturbance passed through central Indiana on the 20th. Light snow persisted began prior to daybreak and persisted throughout the day. The heaviest snow fell south of Interstate 70, where 3 to 5 inches of new snow were on the ground by the evening. Further to the north, most locations generally received 2 to 3 inches. Indianapolis ended up with 11.8 inches of snow for the month of January, 2.5 inches above normal for the month. 

Average Temperature
Total Precipitation
Total Snowfall
Highs below freezing
January 2011
Normal January
2011 Difference from normal

January 2011 All-time Ranks
Temperature: 36th Coldest
Precipitation: 64th Driest
Snowfall: 21st Snowiest
February 2011 started off cool, with the coldest air arriving by the 10th of the month. After a couple of snowfalls added to snow cover, arctic air moved into central Indiana on the 8th. By the morning of the 10th, temperatures had dipped to below zero across much of the area. Northern sections of central Indiana saw the coldest temperatures since January 2009. Readings dipped to 18 below zero at Frankfort, 13 below zero near West Lafayette, and 10 below zero near Tipton. Average daily temperatures were about 20 degrees below normal. Within a few days of the arctic freeze, temperatures warmed to above average as the flow of cold air was cut off from the area. Temperatures topped out in the 60s at many locations around the 16th of the month. On the 17th, many areas saw low temperatures in the 50s. At Indianapolis, the low temperature of 52 degrees set a record for the warmest low temperature for the date. The above average temperatures continued until a cold front brought a return to reality, with highs only in the 20s and 30s again on the 22nd. A strong storm system moved in for the end of the month, ushering in warm air again ahead of it. Highs on the 27th and 28th reached the 60s for many areas. Some areas on the 28th even saw 70 degrees, including Shelbyville. The high temperatures on the 28th actually occurred in the first few hours past midnight, with temperatures falling during the day as colder air returned. 
For the Indianapolis area, February 2011 was the only winter month to average warmer than normal.
Most of the precipitation across central Indiana fell during the second half of the month. A large winter storm brought a wintry mix of precipitation during the first couple of days of the month, with many areas seeing a round of snow on the 5th as well. A dry period followed for the next couple of weeks. A series of storms brought rain every few days for the latter part of the month, with the heaviest rain falling at the end of the month. Thunderstorms with heavy rain moved across the area on the late on the 27th and early on the 28th, with some locations seeing storm totals of over 5 inches. Extensive flooding developed as a result of these rains. At Indianapolis, record daily rainfall amounts of 1.11 and 1.17 inches were recorded on the 27th and 28th respectively. For the Indianapolis area, February 2011 was the wettest February since 1990.
The beginning of the month saw severe winter weather. A large part of the area saw significant snow, sleet and ice accumulation, which caused travel problems for a few days. The ice accumulation on trees and power lines caused power outages in several counties. Most of the snow fell across northern sections of central Indiana, with some locations seeing over 4 inches. A few days later another winter system moved through, and this storm again targeted the northern half of the area, with widespread 3 to 5 inch snowfalls. The warm spell in the middle of the month melted most of the snow, and little snow fell until the 25th, when the final significant snow fell. Once again this snow fell mainly across the northern half of the area, with widespread 2 to 5 inch amounts. This snow melted with the warmer temperatures and significant rainfall at the end of the month. The water from this melted snow added to the flooding issues at the end of the month. The snowfall total at Indianapolis was 7.5 inches, which was 1.4 inches above normal.
At the end of the month a strong storm system moved across the state, ushering in warm air and plentiful moisture. This led to the development of severe thunderstorms, which produced damaging winds, heavy rain, and a tornado across central Indiana. The tornado touched down near Ingalls in Madison County early in the morning of the 28th and was rated EF-1 with winds just over 100 mph. The storm brought widespread 2 to 4 inch rainfall with localized amounts over 5 inches. This created extensive flooding along area streams, creeks, and low lying areas. The above averagerainfall for the month also led to flooding along many area rivers by the end of February.

Average Temperature
Total Precipitation
Total Snowfall
Highs below freezing
February 2011
Normal February
2010 Difference from Normal

February 2011 All-Time Ranks:
Temperature: 45th Warmest
Precipitation: 9th Wettest
Snowfall: 32nd Snowiest

Average Temperature
Total Precipitation
Total Snowfall
Highs below Freezing
Lows Below Zero
Winter 2010-2011
Normal Winter
Difference from Normal

Winter 2010-2011 All-Time Ranks
Temperature:  32nd Coldest
Precipitation: 47th Wettest
Snowfall: 7th Snowiest

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