Tue-Wed, Feb 25-26th Snowstorm Update #8

(10:30AM - 2/25/20) A snowstorm is currently starting to impact the state, and will continue to do so through Wednesday. This storm system will bring widespread accumulating snow to portions of the state during this time period. The southeast and weakening trend well noted by model guidance yesterday continues today, with heaviest snowfall amounts now shifted to the east of Illinois. Thus, we have toned down on snowfall amounts for many areas with this final main update. What was once potentially a legitimate snowstorm for the state will now be nothing more than another nuisance event on this winter.

***Synopsis and important disclaimer/information***
As has been the case much of this winter, model guidance has been downright horrible in handling this period, even in the near term. After having a consensus on Sunday among model guidance for an axis of several inches of snow across Northern Illinois, model guidance made a uniform giant jump southward on Monday. This significant change in such a short period of time and so close to the event is due in part to the several moving pieces that we discussed in previous updates. How these moving pieces interacted were going to dictate the storm track and strength...and associated location and amounts of snow. Unfortunately, model guidance clearly never had a handle on the overall situation regarding these moving pieces, as they were showing more optimal interaction, and thus a stronger/further north storm system with the axis of snow further north/higher snowfall totals. The significant changes today are fully due to the models mis-handling the interaction of the aforementioned moving pieces, now having far less interaction...leading to a weaker/further south storm system and a snow axis further south/lower snowfall totals.

​With this, we now chalk up another event this winter that model guidance heavily struggled with. Unfortunately, model guidance is one of the main factors in creating a forecast, and we have no control of their output. For those that don't know, model guidance is run by government and non-government agencies in several countries across the world. While we at ISC never try to run with exactly what model guidance shows and try to use past experience and knowledge to also aide in forecast development, when the models fail...we generally fail too. That's just how it is in the weather world.

Tuesday morning-Wednesday afternoon...
A mix of rain/snow and areas of all snow have been ongoing this morning across a good portion of Central Illinois. Upwards of a dusting to 2" of snow has already occurred for many areas. A rain/snow mix and areas of all snow will fully turn to snow during the afternoon and evening, as precipitation further develops and spreads across Central and Northeast Illinois. Precipitation will gradually change to snow across Southern Illinois tonight as well. Snow will continue across aforementioned areas into midday Wednesday, before ending. Snow will generally be light to moderate at times, with generally low snowfall rates due the the lower end intensity and marginal temperatures.

Final snowfall totals will likely range from 1-3" in the main axis across the heart of the state, with higher snowfall totals likely across Eastern Illinois.

Below is the snowfall forecast for this event.

JP

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