Tue-Thur, Feb 1-3rd Major Winter Storm Update #4

​​(11:45PM - 2/1/22) A major winter storm will continue to impact region and state, through Thursday night. This winter storm is expected to produce a swath of significant accumulating snow/sleet/ice across the region and state during this time.

Summary...
While model guidance continues to be in fairly good agreement regarding this period, there has still been a bit of wavering of the consensus solution, even now that the winter storm is now impacting the state. What this means is that some changes could be necessary, as we continue to monitor both model guidance and real time observations. Stay tuned to updates over the next several days regarding this winter storm.

​A cold front moved across the region on Tuesday, associated with a storm system moving through Southern Canada. This frontal boundary is becoming stationary across portions of the region and Southern Illinois 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, through Wednesday evening. 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 night.

Forecast...
Tonight - Wednesday Night, Feb 1-2nd ~ Overrunning Precipitation Event:
A cold front moved through the region on Tuesday, associated with a storm system moving through Southern Canada. This frontal boundary is now slowing and will 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, this afternoon through Wednesday evening. Precipitation, in the form of rain, developed and spread across the state Tuesday morning into Tuesday evening. As colder air filtered in on behind the slowing cold front pushing through the state, rain transitioned to a mix and snow across affected areas of Northern and Central Illinois Tuesday evening into Tuesday night. Snow will continue in varying intensity across a large portion of Northern and all of Central Illinois, from transition time this Tuesday evening/Tuesday night through Wednesday evening. 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 1-2" 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 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, eventually stalling out across Southern Illinois by Wednesday afternoon and evening.

Wednesday Night - Thursday Evening, Feb 2-3rd ~ Main Storm System:
As the overrunning precipitation continues across the state into Wednesday evening, 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 afternoon will shift southward, settling across much of Southern Illinois Wednesday afternoon/evening through midday Thursday. Across this zone in Southern Illinois, precipitation types from south to north will range from freezing rain to sleet to snow. This transition zone will eventually change over to snow Thursday morning, continuing into Thursday evening before ending.

In additional to the synoptic aspect to this winter storm period, conditions will be favorable for some 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 9-17" 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