January 25-31, 2007
Midwest Weekly Highlights - January 25-31, 2007
The Arctic Opens Up
The final week of January featured temperatures generally below average for this time of year. Temperature departures this week were warmest in the northwest portions of the region, and coolest in the southeast reaches. In central and northern Wisconsin, and much of Minnesota, temperature departures ranged from 0-1 °F above normal, while in southern Kentucky and southern Missouri, departures were 5-8 °F below normal (Figure 1). Elsewhere, temperature departures were 4-6°F below normal, especially in a 900-mile wide band from Iowa eastward into Ohio.
Precipitation during the final week of January was exceptionally below normal, except in the favored areas downwind of the Great Lakes. The highest precipitation totals were found across the Upper Peninsula of Michigan and extreme northeastern Ohio were totals were 100 to 125% of normal. Meanwhile, a large portion of the Midwest saw just 0-2% of normal precipitation this week, including most of Iowa, Missouri, Illinois, Indiana, and western Kentucky (Figure 2). Drier than normal conditions were also found across most of Michigan, Ohio, and back northwestward into Wisconsin and Minnesota.
Snowfall this week was light and sparse, with the heaviest falling in favored lake-effect regions (Figure 3). The heaviest snowfall this week was found across the Upper Peninsula of Michigan, were up to 16 inches of snow was reported. Generally speaking, however, a coating of 4-10 " was found across the eastern Lakes, from western Michigan to northern Indiana and into northern Ohio. At the conclusion of the final week of January, snow depth was running greater than five inches across portions of northern Iowa, most of Michigan, and small isolated areas in Wisconsin (Figure 4). The lack of precipitation in the northern Midwest did little to aid the drought status there, and largely across the remainder of the Midwest drought conditions remained unchanged from last week.
Lake-Effect Snow
On January 26-27, another fast-moving Alberta Clipper roared through the region, producing some snow showers across the Midwest (Figure 5). More importantly, however, was that the system ushered in some very cold temperatures in the middle and lower layers of the atmosphere. These cold temperatures then spread over the Great Lakes, producing snow squalls in Michigan, Indiana, and Ohio (Figure 6). Several inches of snow was deposited in nearby locales, causing numerous accidents, spin-outs, and in general, simply dangerous travel conditions. Intense lake-effect snow was also evident in southern Lower Michigan and in northern Indiana, as strong convective snow squalls raced eastward off of Lake Michigan (Figure 7). Total snow depth across the Midwest ranged from a trace to as much as 15+ inches of snow by the 29th (Figure 8).
Cold Air Outbreak - First of Many?
A potent cold front descended on the Midwest on January 29, producing additional light snow showers (Figure 9). The air behind the cold front was of arctic origin, from the depths of Canada where snowcover is abundant and sunshine is minimal, allowing the coldest and deepest airmasses to develop under massive sprawling high pressure centers. Minimum temperatures on the 29th (Figure 10) dropped to the single-digits across a good portion of the Midwest, with several northern locations below zero. The following night was also cold, with nearly all of Iowa, Minnesota, and most of Wisconsin experiencing overnight temperatures that were -5 to -15°F (Figure 11). During the daylight hours on the 30th, temperatures struggled to rise over the snowpack, despite abundant sunshine. Maximum temperatures remained in the single digits above zero across Iowa, and generally in the 12-17°F range for most of Minnesota, Wisconsin, Iowa, parts of Missouri and Illinois (Figure 12).
Finally, as the week and month came to a close, temperatures slowly moderated ahead of the next approaching winter system, which brought some light to moderate snows across Missouri and eventually Illinois by dark (Figure 13).
The outlook for the first week of February is for colder than normal conditions. How low will temperatures go next week and will we see any daytime high temperatures failing to reach zero? Find out in next week's edition of the Midwest Climate Watch.
Kruk