Mon-Wed, Feb. 11-13th Winter Storm Update #3

(12:30PM - 2/11/19) Update on the winter storm that will affect the state today through Wednesday morning, bringing several different significant weather impacts to the state...

An area of rain that has been ongoing across Southern Illinois since yesterday is beginning to shift northward, and will push into Central Illinois with time this afternoon. With colder surface temperatures in place, some of this may fall as freezing rain for a time across portions of Central Illinois. An isolated occurrence of sleet is possible too, for areas far enough north in Central Illinois. As temps rise, this activity will turn to plain rain for all of Central Illinois by early to mid evening. Only up to a glaze of ice is expected for areas that see the brief period of freezing rain in Central Illinois. 

Across Northern Illinois... All precip types will be likely across Northern Illinois during this event, including snow, sleet, freezing rain and rain. Model guidance still is at some disagreement with how the event unfolds, even only hours away from the start of the storm. However, things have trended towards a better consensus overall. The rain/freezing rain that will be pushing across Central Illinois this afternoon, will push northward into Northern Illinois during the later afternoon and early evening. This activity will fall as all snow across Northwest Illinois, with a mix of snow/sleet/freeing rain elsewhere across Northern Illinois, with even a period of plain rain for areas south of I-80. This activity will then continue into into Tuesday morning at varying intensities, before colder air wraps in and precip changes to snow for all areas on the backside of the system, finally ending by early Wednesday morning. Snow is looking likely to even extend down into Central Illinois on the backside of the system as well now on Tuesday and Tuesday night. At this time we expected a north-south gradient of high/lower snow/sleet totals, from around 6" near the Illinois/Wisconsin border and Northwest Illinois, to less than 1" south of I-80. An axis of 0.10-0.25" (Locally higher) will run west-east across Northern Illinois as well, in the vicinity of I-80.

Across far Southern Illinois, periods of steady and moderate to heavy rain during the period will produce rainfall totals of 1-2" (Locally higher). This new rainfall, combined with recent heavy rains, will lead to widespread and significant flooding potential.

Below are our updated TAM snowfall, ice and flood forecasts for the state for this event. Further updates and information are likely regarding this storm over the next two days.

​JP

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