November 20-22 Potentially Significant Winter Storm

Model guidance continues to increase snowfall amounts in the winter storm expected to impact Friday through the weekend.

Instant Weather Maps

The latest GFS model has shifted snowfall amounts further to the north since we last analyzed the system yesterday. We now see forecasted totals in the 3-6" range across northern Nebraska into extreme southern South Dakota. Amounts in the 6-10" range are then forecasted in most of Iowa, with lesser amounts in the southern portion of the state. Amounts exceeding 12" are projected to hit southern Wisconsin, including Madison and Milwaukee. Northern Illinois experiences an intense gradient, with the city of Chicago receiving under 3" and areas along the Illinois-Wisconsin border receiving 12".

Instant Weather Maps

The latest NAM model takes a different approach to the storm. It drops 3-10" across southern South Dakota, with the lower end of the gradient in the western portion of the state and heavier amounts in the eastern part of the state. Northeast Nebraska is in line for 6-10" of snow according to this model, with a sharp gradient to the south of that heaviest snow axis. Iowa is projected to be slammed with snow across the board, with heaviest amounts in the western and northern portions of the state. Amounts then drop off as the storm moves into the Midwest. 6-8" amounts are forecasted to hit in a thin line along the Illinois-Wisconsin border, heading right into downtown Chicago, Illinois. Lesser amounts in the 3-6" range are then found in southern and central Michigan.

To summarize:

- A potentially significant winter storm is expected to impact the Plains, Midwest and Great Lakes Friday into Sunday.
- Considerable uncertainty still exists with respect to the track of this system.
- Amounts in excess of 6" are possible, especially in Iowa, southern Wisconsin, and northern Illinois.

Andrew