(3:00PM - 1/12/20) Two lead disturbances, and then a main storm system, moved through the region Thursday through Saturday. During this period nearly every weather hazard occurred across the state...heavy rain, flooding, severe t'storms, high winds, snow, sleet and ice. While most aspects of this period were well modeled and forecasted, the snowy aspect was not handled well at all by model guidance, thus lead to a busted snowfall forecast from us for most areas.
Let's just get right to it and start with the bad, the snowfall aspect of this period...
We failed, busted, were terrible...In whichever way you want to say it, our snowfall forecast sucked to say the least. Model guidance had an extreme difficulty in getting a handle on the strength and track of this storm system, even as the storm was ongoing. In turn, the poor handle on the storm system lead to a wide range of potential snowfall outcomes over a short period of time, not only leading up to the event, but also as the event was ongoing. As close in as 12-24 hours of the event beginning, a good deal of model guidance was showing an axis of 6-12" of snow across portions of Iowa, Illinois and Wisconsin. We had this depicted in our snowfall forecast Thursday night and Friday morning, just 12-24 hours before the main event. Most guidance then quickly backed off of these higher snowfall amounts and shifted more moderate totals to the east, as they came in with a weaker and further east track of the main storm system. By Friday night and Saturday morning, we reflected the changes in guidance and real-time observations to our forecast, then depicting an axis of 3-9" across Central Illinois up into Wisconsin. Guidance Saturday morning then backed off even further, depicting an an even weaker and further east track of the storm system, then showing only minor/low snowfall amounts everywhere. By this time we decided just to go down with the ship, and make no additional significant changes to our snowfall forecast.
In finish... This was a very difficult storm system to forecast snowfall amounts for due to the poor model guidance performance. As guidance changed and real-time observations came in, we adjusted our snowfall forecast the best we could, before just calling it all together and going down with a terrible snowfall forecast. Meteorology and weather forecasting is far from a perfect science. We rely on model guidance to create a forecasts, and when it fails, we in turn fail. This was not only an issue for us, but one that was an issue for many outlets. We strive to provide to best forecast you, and will continue to do our best to do that.
As for the heavy rain/flooding/severe t'storm/high wind/ice aspects...These aspects for this period were well modeled and well forecasted. The issues model guidance had with track and strength of the storm system were not detrimental to these aspects, as was seen with the snowfall side.
Rainfall: As expected, widespread rainfall totals across the state were 2-4", the only exception being across Northern and Western Illinois, where 1-2" was more common. An axis of 3-7" rainfall totals also occurred across portions of Central and Southern Illinois, which is where the greatest flooding occurred.
Severe T'Storms: Isolated to scattered severe t'storms occurred Friday evening through Saturday morning across Southern Illinois. Damaging winds were the most common threat, though small hail also occurred.
High Winds: A period of high winds occurred across the state Thursday morning into Thursday evening, with widespread wind gusts of 25-45mph. A second period of high winds occurred across the state Friday evening through Saturday evening, when 25-50mph wind gusts were common, with isolated higher gusts.
Ice: An axis of 0.10-0.25"+ of freezing rain/ice occurred across Northwest into far Northern Illinois Friday evening into Saturday morning. Some tree damage and power outages occurred in some areas.
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