SWOP Weekly Weather Discussion

HEADLINE

After another bout of wintry conditions over the next couple of days, a return to warmer weather is expected for the remainder of the month.  

DISCUSSION

A deep upper-level low currently evident on water vapor imagery over Manitoba will dig southeastward into the Great Lakes, allowing a surge of Arctic air to plunge into the Midwest.  Scattered snow-showers will develop in advance of the cold airmass on Wednesday, December 11th...with accumulations of up to a half inch on grassy surfaces.  Windy and sharply colder conditions will develop behind the front as overnight lows drop into the single digits and teens...and wind-chill values dip below zero along and north of the I-72 corridor by early Thursday morning.  In addition to the cold, several computer models are showing a weak disturbance creating a band of snow across parts of central Illinois Thursday afternoon and evening.  Given the very cold airmass and expected high snow-to-liquid ratios, a light accumulation of around 1 inch of dry, fluffy snow will be possible where the band develops.  Model solutions vary at this time, but consensus suggests locations along and north of a Macomb to Bloomington line are most favored.  As Canadian high pressure shifts east of the region and a southerly return flow develops, a light wintry mix will be possible across the Illinois River Valley during the morning of Friday, December 13th before temperatures rise and any light precipitation changes to rain by afternoon.     

Further out, both the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) are progged to become positive...strongly suggesting the return of a warmer weather pattern.  Climate models support this trend as well.  In the short-term, high temperatures will climb well into the 40s this weekend...then will push into the lower 50s by Monday, December 16th.  While there will still be some temperature ups and downs through the remainder of December, no extremes appear to be on the horizon as the overall trend favors warmer than normal conditions. 

The latest 6-10 day outlooks (Dec 16-20) from the Climate Prediction Center (CPC) suggest ABOVE normal temperatures and ABOVE normal precipitation across central Illinois.

Issued: 12/10/24