(9:00PM - 1/21/20) What seems to be a never ending pattern we are stuck in recently, yet another late week/weekend winter storm will affect the state, from Wednesday through Saturday. This storm system will be of long duration, with light to moderate accumulations of wintry precipitation are likely across a large portion of the state.
A complex setup is expected to unfold across the region the middle of this week on into the weekend. Several upper air disturbances moving through the region will interact with each other during this time. The result will be the development of a storm system, which will loop through the region. During this period, an extended period of precipitation is likely across the state from Wednesday through Saturday. Wintry precipitation will be favored for much of Northern and Central Illinois for most of this period, with rain and a mix more likely across Eastern and Southern Illinois. Even with the complex nature of this period, model guidance is in decent agreement regarding this event. It should be noted that temperature profiles will be marginal most of this time during this period, and is of concern. Thus, for now we will continue hold of the side of caution, and go on the lower end of guidance regarding wintry precipitation amounts.
Snow, perhaps with some mixed precipitation, will first move into Northwest and Western Illinois by midday Wednesday. This activity will then slowly expand across the rest of the state Wednesday night and Thursday morning. Precipitation will then continue across much of the state from this point right on into Saturday, before slowly ending Saturday afternoon. Precipitation will be generally on the light side much of this period. However, more organized and moderate to heavy snow may be possible across portions of Northern and central Illinois, Friday into Saturday. Much of Northern and Central Illinois has a good shot at seeing most of the precipitation during this period fall as snow, with only small periods of mix/rain being possible. Across Eastern and Southern Illinois, much of the precipitation will fall as rain and a mix of precipitation.
Below are maps featuring estimated start times of precipitation Wednesday/Wednesday night. These visual representations will be much better than several sentences of text, which gets confusing.
Final snowfall totals are expected to be widespread in the 1-3" range across much of Northern and Central Illinois, with higher amounts in excess of 3" expected across Northwest and Western Illinois. Again, will stress for now that we are holding on the side of caution, and going on the lower end of model guidance on snowfall amounts.
Below is our TAM snowfall forecast for this event.
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