April 2012 Cooler than March 2012

After record-setting warmth in March, April temperatures were near normal. We decided to take a look at how April compares with March because the average temperature for March 2012 was actually warmer than the normal average temperature for April. Officially, the average temperatures for April at both Fort Wayne and South Bend were cooler than March's final numbers. This has only happened one other year (1907) since climate records began in the late 1890s.This is exceptionally rare especially since this April averaged slighty above normal temperatures!

	1907 Average Temperatures		2012 Average Temperatures		Normal Average Temperatures
(degrees F)	March	April	March	April	March	April
Fort Wayne	44.6	41.5	52.6	51.1	38.4	50.0
South Bend	41.7	39.0	52.8	49.5	37.5	49.0

So why was March warmer than this April has been? The difference can be linked to the overall weather patterns for both months. March featured a persistent ridge of high pressure that allowed warm, moist air to flow into the Great Lakes region from the Gulf of Mexico due to southerly winds. A persistent trough of low pressure remained over the western U.S. The upper level jet stream remained well to the north and west of the region, which kept cooler air trapped in Canada. This led to record-breaking temperatures across the eastern half of the country and cooler than normal temperatures across the western states (shown in the image below).

April, on the other hand, has seen a weather pattern more typical of spring. Low pressure was located to the north of the Great Lakes while high pressure dominated over the western U.S. This caused the jet stream to shift south of the region, allowing cooler air from Canada to infiltrate the Great Lakes region.

Obergfell/NG
Updated 5/2/2012 11 am

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