Saturday, March 3, 2007

Winter '06-'07 Review

From the NWS in Indianapolis...

Winter 2006-2007 in Review
Warmer than normal?
With March 1 comes the end of meteorological winter, a period defined as covering the months of December through February. The winter of 2006-2007 in Central Indiana was marked by two extremely different periods, one much warmer than normal and nearly snowless, and the other much colder than normal with abundant snowfall.
When it was all said and done, the winter of 2006-2007 actually ended up being warmer than normal. This fact may seem hard to believe, given the prolonged bitter chill of February, but it was not enough to balance out the extreme warmth that December and January had brought.
The following is a review of weather conditions experienced in Central Indiana during the winter season of 2006-2007.
December 2006 began on a cool note. 7 of the first 8 days of the month were at or below normal for temperatures. This was capped off by the season’s first measurable snowfall on the 7th, when 0.3 inches fell. However, this early cold was not here to stay, and by the 10th, high temperatures soared into the 50s with lows only in the 30s and 40s. The warmth continued, and not one day saw a high temperature below freezing during the final 21 days of the month. Some light snow fell again on Christmas night on the tail end of an all day rain storm. But this too did not stick around, as high temperatures nudged toward the 60 degree mark on the final three days of 2006. The month ended up being well above normal on both temperatures and precipitation, and well below normal for snowfall.
Average Temperature
Total Precipitation
Total Snowfall
Highs below freezing
December 2006
Normal December
2006 Difference from Normal
December 2006 All-Time Ranks:
Temperature: Tie- 12th warmest December
Precipitation: 11th wettest December
Snowfall: Tie – 34th least snowiest
January 2007 started up right where December had left off, extremely mild and wet. With a moderate El Nino taking place, it seemed that this winter might never come. Remarkably, the first 15 days of the month of January saw only a trace of snow. Throughout the first half of the month, highs were in the 40s and 50s on several occasions, again approaching 60 degrees on the 4th and 5th. But this was not to last. Winter seemed to finally decide to begin around the middle of the month. Temperatures finally returned to near normal in the second half of the month, and were even occasionally below normal. The first substantial snowfall of the season came on the 21st, with 3.5 inches measured in Indianapolis. The cold intensified towards month’s end, and lows in the single digits came on the 29th and 31st. However it was too little, too late, and January ended up being above normal for temperatures. Precipitation was also easy to come by, again registering well above normal. While snow finally made an appearance, the month ended up below normal in that category as well.
Average Temperature
Total Precipitation
Total Snowfall
Highs below freezing
January 2007
Normal January
2007 Difference from normal
January 2007 All-time Ranks
Temperature: 38th warmest
Precipitation: 24th wettest
Snowfall: 54th snowiest
February 2007 brought an extreme and drastic change to the weather. The month started out cold, and then became extremely cold for the better part of the month. Temperatures plunged below zero on 6 days. The last time a temperature below zero had been recorded in Indianapolis was January 18, 2005. From the 3rd through the 10th, high temperatures did not even reach 20 degrees, with lows in the single numbers or below zero. A significant snow came to Central Indiana on the 6th, with 5.2 inches recorded in Indianapolis. It was a very light and fluffy snow, with high temperatures only in the middle teens in the area. It was just a few days longer before the most significant snowfall in several years came to Central Indiana. Beginning on the night of the 12th and continuing into the early morning hours of the 14th, a powerful snowstorm blasted the region. Snow totals at Indianapolis officially measured 8.5 inches for the three day period, with 7.4 inches falling on the 13th, a record for the day. In fact this was the fourth snowiest day in February ever. Snow totals in northern portions of Central Indiana exceeded a foot in many locales, with up to 17 inches reported. Winds of 35 to 45 mph whipped the snow into drifts as high as six feet. The storm was classified as a blizzard in North Central Indiana. In the Indianapolis area, winds were not quite strong enough, and extensive mixing with freezing rain and sleet cut down on the snow. It was still one of the most substantial winter storms in several years, either slowing down or stopping nearly all activities in the metro area for days. Following the snow came more bitter cold, ensuring that a snow pack would lie on the ground for the rest of the month. An additional 3.7 inches fell on the 17th, thus bringing the total snow depth on the ground to the highest amount in 25 years. By the 20th, a moderation in temperatures was experienced. Highs went above normal for a few days, but not significantly above. On the 24th, a storm brought a quick 0.7 inches of snow to Indianapolis, in addition to strong winds and a glaze of freezing rain that created minor travel problems and power outages. By month’s end, the final tally showed a month that was well above normal for snowfall and well below normal for temperatures.
Average Temperature
Total Precipitation
Total Snowfall
Highs below freezing
February 2007
Normal February
2007 Difference from Normal
February 2007 All-Time Ranks:
Temperature: 3rd Coldest
Precipitation: 49th wettest
Snowfall: 4th Snowiest
Average Temperature
Total Precipitation
Total Snowfall
Highs below Freezing
Lows Below Zero
Winter 2006-2007
Normal Winter
Difference from Normal
Winter 2006-2007 All-Time Ranks
Temperature: 31st Warmest
Precipitation: 5th wettest
Snowfall: 16th snowiest
The Winter of 2006-2007 was one of extreme ups and downs. It seemed through the first half of the winter that cold and snow would stay locked up over northern Canada. But a large scale pattern shift and a rapid decay of the moderate El Nino conditions brought extreme cold to the area by February. It was in fact the coldest February since 1979. However, the early winter warmth was too much to be overcome by the February chill. With an overall temperature that averaged almost one degree above normal, it is important to see that even in a winter that is above normal, periods of extreme cold can and will still occur.

Data Prepared by Logan Johnson, Climate Services Focal Point
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Temperature and Precipitation Records Cover 1871-2006 in the Indianapolis Area.
Snowfall Records Cover the period 1884-2006 in the Indianapolis Area.
Normals refer to reference period 1971-2000.