(8:30PM - 2/11/19) The expected winter storm has been affecting the state this afternoon and evening, and will continue to through Wednesday morning...
As mentioned in previous updates, model guidance had continued to be in disagreement on how this storm would evolve for Northern Illinois right up until the storm beginning. Watching trends and observations come in this afternoon and evening shows that warmer guidance will win out, and is the way to go. With that said...Precip this afternoon and evening had mainly been snow across the Quad Cities area, Northwest Illinois and areas of Northern Illinois near the Illinois/Wisconsin border. Further south, a mix of sleet and freezing rain had been common for all other areas of Northern and Western Illinois. However, as time has gone on this evening a wedge of "warmer" air aloft has pushed northward, which has allowed precip to turn from snow to a mix of sleet/freezing rain even further north now, and this will likely continue through the night. It looks likely that the only area that will stay all snow is far Northwest Illinois, while all other areas of Northern Illinois and Western Illinois continue to see a mix of sleet and freezing rain.
Ice accumulations of around 0.25" have already been reported northeast of Galesburg. It is looking more and more likely that an axis of significant ice accumulations of 0.25-0.75" will be likely near and north of I-80 across portions of Northern Illinois. Tree damage and power outages will be likely for some areas, which could be widespread...especially as winds increase on Tuesday. Additionally, given the warmer scenario being more likely now, snow/sleet accumulations have been cut back a bit for portions of Northern Illinois. Highest accumulations of near 3" will be near the Illinois/Wisconsin border, with in excess of 6" likely towards far Northwest Illinois.
Further south, heavy rainfall amounts is still expected to increase flood potential once again for far Southern Illinois.
Below are our updated TAM snowfall and ice forecasts for this winter storm.
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