Sun-Mon, March 6-7th Snow/Severe T'Storm/Heavy Rain Event Update #1

(10:45PM - 3/5/22) A storm system is expected to impact region and state, Sunday evening through Monday afternoon. This storm system is expected to produce a swath of accumulating snow/sleet, heavy rainfall with localized to scattered flooding potential, and an isolated to sporadic (levels 1-2) severe t'storm risk across the region and state during this time.

Summary...
Model guidance continues to be in fairly good agreement regarding many aspects of this storm system, thus little to no change to the forecast was needed with this update.

​A storm system will develop across the Southern Plains during the day on Sunday, with it then tracking through the Ohio Valley Sunday night into Monday morning, and eventually into the Northeast by Monday night. This storm system is expected to produce a swath of accumulating snow/sleet, heavy rainfall with localized to scattered flooding potential, and an isolated to sporadic (levels 1-2) severe t'storm risk across the region and state during this time.

Wintry (Snow/Sleet) Aspect Forecast...
Sunday Evening - Monday Afternoon, March 6-7th ~ Snow/Sleet Event:
Precipitation in the from of a snow/sleet/rain mix will move into Northwest and Western Illinois later Sunday evening or early Sunday night. With colder air filtering in on the north side of the storm system, with precipitation will quickly turn to all snow with time across the northern half of the state. Periods of snow will then be possible from transition time, through midday Monday, before ending by early Monday afternoon. Snow will vary in intensity, but generally light to at times moderate, with snowfall rates of 0.5"+ an hour at times. A transition zone is also expected to set up, from roughly the southern Chicago metro area down into Western Illinois. In the vicinity of this transition zone, precipitation types may vary.

​Below is the  ice forecast for this event.

Severe T'Storm Risk/Heavy Rain/Flooding Aspect Forecast...
Sunday Evening - Monday Afternoon, March 6-7th ~ Severe T'Storm Event:
​The main risk for an isolated to sporadic (levels 1-2) severe t'storm risk will exist across the southern half of the state, Sunday evening through midday Monday. As a storm system develops and moves into the region, a warm front will lift northward into the southern half of the state Sunday evening through Sunday night. This frontal boundary will be a focal point of potential severe t'storm activity. Additionally, as the storm system moves through and passes the region, a cold front will the moves southward across the southern half of the state Monday morning. This frontal boundary will also be a focal point of potential severe t'storm activity. In all, periods of rain and t'storms are expected across the southern half of the state, Sunday evening through midday Monday. An environment will be in place supportive of some severe t'storm risk with this activity. This environment will feature low instability of up to 1,500J/KG, dew points in the upper 50's to low 60's, good shear, good forcing, and good lapse rates of 6.0-8.0C. This environment will be supportive of upwards of an isolated to sporadic severe t'storm risk (levels 1-2) across the southern half of the state. Damaging winds, hail and an isolated tornado will be the severe weather threats.

Sunday Evening - Monday Afternoon, March 6-7th ~ Heavy Rain/Flooding Event:
Multiple periods of rain and t'storms are expected across the southern half of the state, Sunday evening through midday Monday. Heavy rainfall will be possible at times, with widespread rainfall totals of 1-3" expected in a corridor across Southern Illinois during this period of time, with locally higher amounts possible. Due to the combination of recent heavy rainfall/flooding during mid-late February and the expected rainfall, localized to scattered flooding is expected.

Below are the severe t'storm and heavy rain/flooding forecast for this event.

​Impacts...
-Snow/sleet accumulation of 1-3" across the northern half of the state, Sunday evening through Monday afternoon.
​-An isolated to sporadic (levels 1-2) severe t'storm threat across the southern half of the state, Sunday evening through midday Monday.
-Widespread heavy rainfall across the southern half of the state, with a corridor of widespread rainfall totals of 1-3" expected. These rainfall totals could cause localized to scattered flooding potential for affected areas.
-Travel impacts likely both for the northern half of the state due to the snow/sleet and across the southern half of the state due to the heavy rain/flood potential.

JP