Tue-Thur, Feb 1-3rd Major Winter Storm Update #1

​(11:45AM - 1/31/22) A major winter storm is set to significantly impact the region and state, Tuesday afternoon through Thursday evening. This winter storm is expected to produce a swath of accumulating snow/sleet/ice across the region and state during this time.

Summary...
Over the past several days model guidance has been honing in on the potential for a winter storm to affect the region and state, Tuesday through Thursday. Model guidance had been in significant disagreement regarding this storm system for the past several days. However, over the past 12-18 hours model guidance has started to come into better agreement, with an overall consensus solution beginning to form. With that said, there still does continue to be some disagreement within model guidance at this time, so some changes to the forecast can be expected until full agreement on the situation is reached. Stay tuned to updates over the next several days regarding this winter storm.

​A cold front will move through the region on Tuesday, associated with a storm system moving through Southern Canada. This frontal boundary will then become nearly stationary across the region and southern half of the state Tuesday night into Wednesday. With ample advection from the south over-topping this frontal boundary, a widespread overrunning precipitation event is expected across the region and state, Tuesday afternoon through Wednesday night. Furthermore, a storm system will develop in the Southern Plains on Wednesday, and will then track through the Tennessee Valley on Thursday, and eventually into the Mid-Atlantic region on Friday. This storm system will bring a renewed push of precipitation across the region and state, Wednesday night through Thursday evening.

​​​Forecast...
Tuesday Afternoon - Wednesday Night, Feb 1-2nd ~ Overrunning Precipitation Event:
A cold front will move through the region on Tuesday, associated with a storm system moving through Southern Canada. This frontal boundary will then become nearly stationary across the region and southern half of the state Tuesday night into Wednesday. With ample advection of mild/moist air from the south over-topping this frontal boundary, a widespread overrunning precipitation event is expected across the region and state, Tuesday afternoon through Wednesday night. Precipitation in the form of rain will develop across portions of Missouri and Central Illinois midday Tuesday. This area of rain will expand as it further develops and pushes northeast, spreading into other portions of Northern, Central and Southern Illinois Tuesday afternoon and evening. As colder air filters in on behind the slowing cold front pushing through the state, rain will transition to a mix and snow across affected areas of Northern and Central Illinois Tuesday evening into Tuesday night. Snow will then be likely in varying intensity across a large portion of Northern and all of Central Illinois, from transition time Tuesday evening/night through Wednesday night. Periods of moderate to heavy snow will be possible at times, with more lull-like periods of lighter snows likely as well. Snowfall rates upwards of 1"+ an hour will be likely at times in the heavier periods of snow, especially Tuesday night through Wednesday afternoon. Across southern portions of Central Illinois, this is where the overall transition zone will set up with mixed precipitation being likely. Across this zone, precipitation types will range from south to north will range from freezing rain to sleet to snow. This transition zone will likely slowly shift southward through the day on Wednesday.

Wednesday Night - Thursday Evening, Feb 2-3rd ~ Main Storm System:
As the overrunning precipitation continues across the state into Wednesday night, the main storm system will also move into the region. A renewed push of precipitation will move across the state and region associated with the main storm system, Wednesday night through Thursday evening. This renewed push of precipitation, in the form of snow, will move into Western Illinois later Wednesday evening. This area of snow will then spread across Central Illinois through Wednesday night and much of the day on Thursday, before ending by Thursday evening. Periods of moderate to heavy snow will be possible at times, with snowfall rates of 1"+ an hour likely at times. Additionally, a period of windy conditions is possible Wednesday night through Thursday afternoon. During this time wind gusts upwards of 25-40MPH will be possible, which will cause blowing and drifting snow. Further south across Southern Illinois, the transition zone of mixed precipitation that had been across portions of Central Illinois Tuesday night into Wednesday evening will shift southward, settling across much of Southern Illinois Wednesday evening through Thursday afternoon. Across this zone, a precipitation types will range from south to north will range from freezing rain to sleet to snow. This transition zone will eventually change over to snow as precipitation ends Thursday evening.

In additional to the synoptic aspect to this winter storm period, conditions will be favorable for lake enhanced and lake effect snow across portions of Northeast Illinois, Wednesday evening through Thursday evening. This could enhance snowfall a bit for affected areas.

Impacts...
-An axis of of significant snowfall totals across the heart of the state, with upwards of 7-15"+ in the main corridor. Snowfall amounts will quickly taper north and south of this main axis, across Northern and Southern Illinois.
-An axis of significant ice accumulations of 0.10-0.50"+ across Southern Illinois.
-Significant and widespread travel impacts likely across much of the state, Tuesday evening through Thursday evening.

​Below are the snowfall and ice forecasts for this winter storm.

JP