December 8-14, 2001

Above normal temperature conditions greeted the Midwest again during the second week of December. There were some variations in the magnitude of the warmth, with the northwest and southeast portions of the Midwest having the largest anomalies (+10 to +14°F), while the zone from the southwest Missouri to Illinois was only 2-8°F above normal (Figure 9). The highly unusual stretch of above normal conditions reached 48 days in a row at La Crosse, WI, by the 14th. Des Moines, IA, NWS reported that the first two week of December were the warmest on record. Chicago - O'Hare, IL, had experienced no days through mid-December with a minimum temperature at or below 20°F. Marquette, MI, recorded its warmest maximum temperature on the 10th and tied the record on the 11th. A number of places in Wisconsin were also close to setting their all-time records for the most delayed onset of measurable snow at the end of the period, including La Crosse (latest ever), Green Bay (2nd latest), and Madison (2nd latest). Chicago almost reached its record for latest measurable snow, but 0.1 inches of sleet on the 14th ended that streak 2 days before the all-time record would have been set.

As the week began, a frontal boundary moved out of the Ohio Valley, leaving some moderate rain in Kentucky on the 8th. After a few dry days, a change in circulation pattern starting on December 11 brought widespread light rain to the southern half of the Midwest, exceeding 0.5 inches of rain in most places. More importantly, a substantial low pressure area entered the region in southwest Missouri and brought very heavy rain to western Kentucky the next day. At the end of the period, a weak low traveled across the same region, as the upper level jet stream moved systems along the same storm track. Total precipitation for the week exceeded one inch in southern Missouri and Illinois, and 2 to 4 inches in Kentucky (Figure 10). Meanwhile, the northern Midwest was quite dry, well below normal in precipitation for the time of year (Figure 11). Snowfall totals were also quite measly in the northern Midwest (Figure 12), although the official cooperative observer station at the Illinois State Water Survey (location of the MRCC) recorded 1.0 inches of snow on the 14th.