(12:00PM - 4/27/19) The expected historic, record breaking, late season snowstorm has started to impact Northern Illinois this morning, and will continue to into tonight...
Rain overspread much of Northern Illinois earlier this morning. This rain quickly mixed with and changed to snow for areas around and north of I-88, as dynamic and evaporative cooling occurred. Snow is expected to continue for areas north of I-88 into tonight, before ending prior to midnight. Model soundings show conditions highly favorable for banding of heavier snow, very heavy snowfall rates and thundersnow. Further south in the vicinity of I-88, the rain/snow line will likely waver around this area through the afternoon and evening, which will lead to periods of rain and snow. As the storm system track south of the area later, precipitation will change to all snow for this area...and perhaps down to near I-80 for a time before precip ends tonight.
Final snowfall accumulations will be 6-9" in an axis across portions of Northern Illinois. South of this main axis, with locally higher amounts possible. Snowfall amounts will quickly taper south of the main axis, with a very tight gradient setting up. The gradient may be as significant as seeing a difference from a dusting to 5" of snow within a few miles distance. We have tried to depict this tight gradient as best as we could in our TAM snowfall forecast map, which is below.
This will be a very heavy and wet snow, due to marginal temperatures and the time of year. Given temperatures have been overall warm and trees/bushes have leafed out, some damage is possible...in additional to power lines/poles potentially being affected. The heavy and wet nature of the snow could also lead to damage to flowers and plants that have recently grown or been planted. Caution should be taken when shoveling this type of snow as well.
Below is our update TAM snowfall forecast for this event.
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