Thur-Fri, April 16-17th Snowstorm Recap

(12:00PM - 4/20/20) A late season snowstorm affected portions of the state, Thursday into Friday. This event was significant and even record breaking, for mid-April standards.

​A lead disturbance and an associated area of snow pushed across portions of Southern Iowa, Northeast Missouri and West-Central Illinois Wednesday night through Thursday morning. This snow was previously not expected to amount to much of anything...However, like usual the weather always has surprises...As a dusting to 2" of snow occurred across portions of West-Central Illinois, with even upwards of 2-6" having occurred across portions of Southern Iowa and Northeast Missouri.

As has been the case much of this winter, model guidance struggled quite a bit with this event. Heading into this event, most guidance was favoring higher snowfall totals much further south. However, we decided to base our forecast on furthest north solution, was was the "Euro" model. This idea was based on history in similar circumstances in the past. However, the axis of snowfall ended up with further north than all model guidance, including the "Euro" model our forecast...This lead to higher snowfall totals than expected across far Northern Illinois, and much lower than expected snowfall totals south of I-80. We played the right card on going north of just about all model guidance, but did not go far enough north...It would have been hard to to push fore forecast much further north though, with absolutely no model guidance support at all.

A mix of rain and snow moved into Western Illinois late afternoon early into early evening on Thursday. This activity will then steadily spread across Northern and Central Illinois Thursday evening into Thursday tonight. This activity then continued overnight and into Friday morning, before ending from west to east across the aforementioned areas by early to mid Friday morning. Precipitation fell as all snow across Northern Illinois, with the rain/snow transition zone setting up across Central Illinois. Periods of moderate to heavy snow with increased snowfall rates upwards of 1"+/hour occurred across portions of Northern and Central Illinois, early Thursday night into early Friday morning.

Final storm snowfall totals ranged from 2-5" across much of Northern and Western Illinois, with a higher corridor of 4-8" totals nosing into Western Illinois. Several snowfall records for the date of April 17th were broken for affected areas, along with this being the biggest snowstorm on record for portions of Western Illinois...for mid-April or beyond.

​Below are map representations of final snowfall totals across the state and adjacent areas. 

JP

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