December 15-21, 2007
Midwest Weekly Highlights - December 15-21, 2007
Wild Start, Quiet End
A stormy weather pattern continued into the third week of December, bringing more snow and cold weather to portions of the Midwest.
The coldest weather this week was found across the central third of the region where snow and ice covered the ground. Temperatures were 1°F to 3°F below normal from eastern Michigan back through Iowa (Figure 1). Temperatures were as much as 4°F below normal in far southwestern Iowa. In contrast, temperatures in the northern half of Minnesota ran 3°F to 6°F above normal this week. It was also warmer than average across the southern half of Missouri eastward into the western half of Kentucky.
Precipitation was well above normal in a wide band extending from the Missouri boot heel northeastward into Ohio and lower Michigan (Figure 2). This band of precipitation was largely due to the winter storm that curved through the Midwest on December 15-16. Northern Iowa, much of Minnesota, and northwestern Wisconsin continued to be dry, with little if any precipitation this week. There was little change in the Drought Monitor this week (Figure 3), with small areas of moderate drought dotting parts of six states and with a small portion of southeastern Kentucky still in extreme drought.
Snowfall was much above normal across the southern half of the Midwest (Figure 4), but little if any snow fell across the northern half of the region except for downwind of the Great Lakes (Figure 5). Almost all of this snow came at the very beginning of the period.
Another Weekend, Another Storm
For the third weekend in a row a winter storm was taking aim on the Midwest, even as utility crews in Missouri were still trying to restore power to more than 50,000 customers who lost power in the ice storm the previous week. Outlooks issued by NOAA's Hydrologic Prediction Center for December 15 indicated a high probability of a significant band of 4 inches of snow (Figure 6) and a moderate probability of a band of 8 inches of snow across the central Midwest (Figure 7). On the morning of December 15 low pressure was organizing over the Texas/Louisiana border, and a large shield of precipitation extended north through Missouri and Illinois (Figure 8). Snow became heavy during the day from eastern Missouri into central Illinois. There were several reports of thunder and lightning with the snow across this area during the late afternoon and evening as the low continued to deepen and moved northeast into the Ohio Valley. As the winds increased out of the northeast and north late on December 15, lake-enhanced snow piled up along the lee shores of Lake Michigan. Snowfall from the south end of Chicago across northern Indiana and into lower Michigan reached 12 inches. By the morning of December 16 a blanket of snow covered much of the Midwest to the Ohio River (Figure 9), with 7 to 12 inches of new snow on the ground from central Illinois into northern Indiana. Strong winds caused by the intense low now over northern Ohio (Figure 10) resulted in considerable blowing and drifting of the snow and caused widespread travel problems.
High pressure drifted over the Midwest and the rest of the week was quiet. Temperatures gradually warmed the rest of the week and by December 21 the southern extent of the deeper snow had retreated to northern Missouri across central Illinois to northern Ohio (Figure 11).
Flooding Persists in Wake of Earlier Storms
The effects of heavy precipitation the first two weeks of December were being felt in eastern and southern portions of the Midwest as many rivers and streams continued to rise and approach or exceed flood stage. In Illinois and Indiana the Wabash River was in minor flood at a number of locations (Figure 12). Moderate flooding was occurring on several rivers and streams in western Kentucky (Figure 13). The Green River in western Kentucky (Butler County) was rising above flood stage and had completely submerged a dam at Rochester, KY. Emergency authorities were monitoring the dam for a possible breach. Should the dam breach, it would result in the loss of the water supply for 46,000 people in three Kentucky Counties.
SDH