Peoria, Ill. (WMBD) – The National Weather Service has issued a Winter Storm Watch for much of Central Illinois from Tuesday evening through Thursday evening. A prolonged period of accumulating snow is expected to lead to hazardous if not impossible travel by Wednesday afternoon.

Key Takeaways

  • Rain develops Tuesday afternoon, changes to snow Tuesday evening
  • Moderate to heavy snow expected Tuesday night – Wednesday morning with another round possible Wednesday night – Thursday morning
  • Lower confidence in the Wednesday night – Thursday snow forecast
  • Minor ice accumulations possible Tuesday evening along I-55
  • Strong winds Wednesday night and Thursday will lead to blowing and drifting snow
  • Hazardous if not impossible travel by Wednesday night
  • A few power outages likely

Tuesday Night through Wednesday Morning
Forecast Confidence: Mod-High

A Canadian cold front will move through Illinois on Tuesday bringing rain showers to the region Tuesday afternoon. This rain is expected to change to snow west of the Illinois River by sunset and before midnight along I-55 as temperatures drop below freezing. Roads will quickly become snow covered and slick west of the Illinois River.

A few hours of freezing rain will also be possible along I-55 Tuesday evening before the change over to snow occurs. This could leave a glaze of ice along and east of I-55, particularly in McLean County.

Snow is likely to continue at various intensities Tuesday night and Wednesday morning as the front slows or stalls across far southern Illinois. This creates an overrunning scenario where a warmer airmass is moving over a colder one at the surface resulting in snow. One uncertainty regarding the intensity of snowfall across Central Illinois is the end location of a Frontogenesis (F-Gen) snow band which may develop as a result of a tightening temperature gradient. These F-Gen snow bands are often narrow and can produce snowfall rates over an inch an hour. Unfortunately, forecasting the location of these bands is difficult outside of 12-24 hours from the event, but we suspect it will be somewhere between the Illinois River and I-57.

Snow accumulations from this first round will range from 3 inches in the west to 8 inches in the east by noon Wednesday. Locally higher amounts will be possible where any small scale snow bands develop.

Wednesday Afternoon Through Thursday
Forecast Confidence: Low – Mod

The forecast for this second round of heavier snow remains a bit more uncertain due to subtle shifts in the storm track. For now we’ll take a more conservative approach and assume the storm takes a more southern route.

While snow is likely to be continuous for many along I-55, snowfall rates are expected to decrease for a period of time Wednesday afternoon. As the next wave approaches from the southwest snow will ramp back up Wednesday evening with moderate to heavy snow likely along and east of the Illinois River through Thursday morning.

This second round of snow will be a lot drier and fluffier compared to the snow that falls Tuesday night. As wind speeds increase to 15-25 mph from the north with gusts over 30 mph, blowing and drifting snow will become an issued Wednesday night and Thursday morning region wide. The Thursday morning commute is likely to hazardous, if not impossible, along and east of the Illinois River.

Snow accumulations from this round will range from 1 inch in the northwest to 6 inches in the east. Snow ratios with this round of snow will be a lot higher compared to the first round, so even a few tenths of an inch of moisture will result in several inches of additional snow. If this wave of the storm tracks slightly further north, accumulations would be even higher.

Storm Total Snowfall Forecast

By 6 pm Thursday snow accumulations will range from 2-4 inches near Kewanee to more than a foot in Bloomington/Normal. The influx of drier air from the northwest should keep snowfall rates a bit lower along and north of a Macomb to LaSalle/Peru line. Meanwhile, relatively narrow bands of heavier snow should allow snow to pile up along and east of the Illinois River. The highest snow totals will be along I-55 where snow will be a bit more constant and are likely to see the brunt from the two waves of heavier snow.

Should the second wave moving in Wednesday night – Thursday track further north snowfall amounts would need to be increased where as a track further south would result in slightly less snow. Additional adjustments are likely over the next few days so be sure to monitor the forecast closely in the coming days.