Midwest Weekly Highlights - November 8-16, 2007

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Mild, Dry, and Changeable

The middle nine days of November were marked by several cold front passages that brought reinforcing shots of cold air to the eastern half of the region and limited precipitation. Despite the cold frontal passages, temperatures during the period of November 8-16 were generally above normal over the region except for the extreme southeast. Average daily temperatures ranged from 9°F above normal in northwestern Minnesota to 1°F below normal over extreme southeastern Kentucky (Figure 1).

Precipitation was largely limited to areas around the Great Lakes and the southeast half of the region (Figure 2). Rainfall across central Indiana and much of Kentucky was well above normal for the period. The rain further chipped away at the drought in Kentucky. However, this was not reflected in the November 13 U.S. Drought Monitor (Figure 3) as the rain came after the monitor was issued. Several inches of snow fell early this period from northeastern Minnesota across northern Wisconsin and into northern lower Michigan (Figure 4).

 

Cold Start, Cold End

A broad upper level trough of low pressure covered the eastern half of the U.S. as the period began (Figure 5), bringing colder weather to much of the Midwest with temperatures running 2°F to 5°F below normal. Snow fell in the lee of the Great Lakes as a surface low pressure system moved through the central Midwest. Only very light showers were scattered across the region south of the low and ahead of the attendant cold front. As the upper trough moved out over the Atlantic warmer air began to return to the central Midwest, and some showers and thunderstorms broke out ahead of an advancing cold front on November 10 in eastern Illinois and central Indiana, and in Indiana and Ohio on November 11. Showers and some thunderstorms persisted in the Ohio Valley on November 13 as the cold front slowed to a crawl and washed out as another much more potent system dropped south out of Canada into the northern Midwest. This second front surged through the Midwest on November 14 (Figure 6), and triggered showers and thunderstorms across Kentucky. Most locations in the state received at least a half inch of rain, with the central and eastern portions of the region receiving generally one to two inches of rain, with more than 2.50 inches of rain at a few locations. A few severe storms were reported as well, including one producing a tornado in Laurel County, KY which resulted in minor structural damage.

High temperatures ahead of the cold front reached into the mid 50s to upper 60s across the Midwest, but behind the front on November 15 high temperatures were only in the low 30s across northern Minnesota and the upper 40s along the Ohio River. Lows dropped into the low to mid 20s across most of the region on November 16 as the center of a ridge of high pressure settled over the Midwest.

SDH