Wed-Thur, Feb 16-17th Winter Storm Recap

(6:00PM Monday - 2/28/22) A brief recap regarding the Wed-Thur, Feb 16-17th winter storm that brought a swath of accumulating snow/sleet/ice, heavy rainfall with localized to scattered flooding, and an isolated severe t'storm risk across the region and state during this time.

Overview...
A storm system impacted the region Wednesday, Feb 16th through Thursday, Feb 17th, bringing a swath of accumulating snow/sleet/ice, heavy rainfall with localized to scattered flooding, and an isolated severe t'storm risk across the region and state during this time. Model guidance showed the potential for this winter storm several days out, and in the end this winter storm produced overall very close to forecast expectations. A cold front moved through the region Wednesday and Wednesday night, associated with a storm system moving through Southern Canada. This frontal boundary became nearly stationary by Thursday morning, near the Ohio Valley in the region and Southern Illinois. Furthermore, a storm system developed in the Southern Plains Wednesday night, and then tracked through the Ohio Valley on Thursday, and eventually into the Northeast on Friday. This storm system brought a renewed push of precipitation and main impacts of this period across the region and state, Thursday morning through Thursday evening.

Wintry (Snow/Sleet/Ice) Aspect Summary...
Wednesday Night - Thursday Morning, Feb 16-17th ~ Cold Front/Lead Wave Event:
A cold front moved through the region Wednesday and Wednesday night, associated with a storm system moving through Southern Canada. This frontal boundary became nearly stationary by Thursday morning, near the Ohio Valley in the region and Southern Illinois. Precipitation in the form of rain developed ahead of the cold front, across portions of Missouri, Iowa, Northern/Central Illinois and Wisconsin, Wednesday afternoon. This area of rain continued to expand as it further developed and pushed northeastward, spreading into other portions of Northern and Central Illinois, Wednesday afternoon and evening. This activity continued across Northern and Central Illinois Wednesday night, and also started to push into Southern Illinois as well early Wednesday night, with it then continuing overnight Wednesday night. Isolated to scattered t'storms occurred with this activity across much of the state through Wednesday night as well. Colder air filtered in behind the cold front across Northern and Western Illinois, Wednesday night. As this colder air filtered in, rain transitioned to a mix of rain/freezing rain/sleet/snow across portions of Northern and Western Illinois overnight Wednesday night, which then continued into early Thursday morning. Some minor snow/sleet/ice accumulation occurred across portions of affected areas of Northern and Western Illinois, Wednesday night into early Thursday morning. In addition to precipitation, windy conditions featuring wind gusts of 30-45MPH occurred across the state much of the day on Wednesday

Thursday Morning - Thursday Evening, Feb 17th ~ Main Winter Storm Event:
​As the main storm system moved through the region, an associated renewed push of precipitation moved across the state and region with the main impacts, Thursday morning through Thursday evening. This renewed push of precipitation, in the form of snow/sleet/ice, pushed into Western Illinois by mid morning Thursday. This area of precipitation continued to spread across portions of Northern and all of Central Illinois through late Thursday afternoon, before ending Thursday evening. A transition zone set up and was in place much of the day Thursday across portions of Central Illinois, generally near and between I-72 and I-70. Across this zone, precipitation types will from south to north ranged from freezing rain to sleet to snow. This transition zone eventually changed over to snow for a time, before precipitation ended Thursday evening. North of this transition zone across affected areas of Northern and Central Illinois (Near/north of I-72), most precipitation fell as snow. Periods of moderate to heavy snow occurred at times, with snowfall rates of 1-2" an hour having occurred at times. Additionally, windy conditions occurred Thursday morning through Thursday evening across a large portion of the state. During this time wind gusts upwards of 20-40MPH occurred, which caused some blowing and drifting snow for areas experiencing snow, and near blizzard conditions at times. 

​​​Below are map representations of the final forecasts and observed snowfall/sleet and ice totals across the state and adjacent areas. 

Observed Snowfall Totals

Observed Ice Totals

Final Snowfall Forecast

Final Ice Fore​cast

​Severe T'Storm Risk/Heavy Rain/Flooding Aspect Summary...
Thursday Morning - Thursday Evening, Feb 17th ~ Severe T'Storm Event:
​The main risk for an isolated severe t'storm risk existed across far Southern Illinois, Thursday morning into Thursday afternoon. Areas of rain and isolated to scattered t'storms were ongoing Thursday morning across Southern Illinois, in the vicinity of a nearly stationary frontal boundary in place. An isolated severe t'storm was possible with that activity, but none reached that level. As the main storm system moved through the region, an arc of rain and t'storms accompanied the low pressure and cold front that swept across Southern Illinois, Thursday morning into Thursday afternoon. Ahead of this activity, an environment was in place supportive of some severe t'storm risk with this activity. However, in the end the severe t'storm activity ended up occurring just to the south of the state.

Wednesday Afternoon - Thursday Evening, Feb 16-17th ~ Heavy Rain/Flooding Event:
Persistent periods of rainfall occurred across the southern half of the state Wednesday afternoon through Thursday afternoon, associated both with a frontal boundary becoming stationary across Southern Illinois and the main storm system moving through. During this period of time, periods of heavier rainfall occurred as well. Widespread rainfall totals of 1-4" occurred across the southern half of the state during this period of time, with locally higher amounts. Due to the combination of frost depth/frozen ground and the heavy rainfall that occurred, localized to scattered flooding occurred. Further north across Northern and Central Illinois, rainfall totals of 0.50-2.00" occurred Wednesday afternoon through early Thursday morning, which lead to some instances of localized flooding, due to frozen ground not being able to absorb lingering snow melt and rainfall.

​​Below is a map representation of the observed rainfall totals across the state and adjacent areas. 

Wrap Up...
-An axis of accumulating snowfall occurred across the heart of the state, with snowfall totals upwards of 4-9" in the main corridor. Snowfall amounts quickly tapered north and south of this main axis, across Northern and Central Illinois.
-An axis of freezing rain/ice accumulations of a glaze to 0.10" occurred across portions of Central and Southern Illinois, with locally higher amounts of 0.10"+.
​-An isolated severe t'storm threat was possible across Southern Illinois Thursday morning through Thursday afternoon, however this activity stayed just south of the state.
-Widespread heavy rainfall occurred across the southern half of the state, with widespread rainfall totals of 1-4". These rainfall totals will cause localized to scattered flooding for affected areas.
-Windy conditions on Wednesday of 30-45MPH and Thursday of 20-40MPH, which caused blowing and drifting snow across the heart of the state on Thursday.
-Significant and widespread travel impacts occurred across much of the state, especially across the heart of the state.​

JP