SWOP Weekly Weather Discussion

HEADLINE

The much-anticipated late January thaw is here.

DISCUSSION

The upper air pattern during the month of January has consistently featured ridging along the west coast of North America with corresponding downstream troughing east of the Rockies. The deep-layer northwesterly flow within the trough has ensured a nearly continuous flow of Arctic air into central Illinois, resulting in much below normal temperatures. After nearly a month of dominance, the western ridge will begin to break down over the next several days...allowing a zonal west-to-east flow to develop across the Midwest. Temperatures will return to more seasonal values in the 30s this weekend, then will climb well into the 40s next week as upper heights rise. Dry weather is initially anticipated: however, medium range computer models suggest a series of systems may impact the region late next week into the following week as the flow becomes increasingly southwesterly. At this point, it appears the atmosphere will be warm enough to support mostly rain: however, we will need to monitor smaller scale thermal details as the time nears in order to make the final determination on exact precipitation types and amounts.

The Arctic Oscillation (AO) has become strongly positive and is expected to remain positive for the next week. Meanwhile the North Atlantic Oscillation (NAO) is currently neutral, but progged to become weakly positive in the next few days. This favors above normal temperatures for central Illinois for the remainder of January into early February as Arctic airmasses will tend to remain locked well to the north or drop southeastward into eastern Canada and New England rather than the Midwest.

The latest 6-10 day outlooks (Jan 30-Feb 3) from the Climate Prediction Center (CPC) suggest ABOVE normal temperatures and ABOVE normal precipitation across central Illinois.

Issued: 1/24/25