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(12:00PM - 5/23/20) A compact and strong disturbance will be moving through the region on today, which will bring a severe t’storm threat to a large portion of the state.
Synopsis... As a strong and compact disturbance is moving through the area, an arc of showers and t’storms has developed across portions of Eastern Iowa, Northwest Illinois and Central Illinois. Some of this activity will strengthen, along with new development being likely this afternoon. All of this activity will then spread eastward across Northern Illinois and portions of Central Illinois, during the afternoon and evening. The environment in place will feature low to moderate instability, good moisture, good shear and good forcing. This will all aide in upwards of a limited severe t’storm threat across Northern Illinois. All modes of severe weather will be possible. Things are being monitored for a potential upgrade in severe t'storm probabilities in future updates. For now we have outlined an elevated risk area in dashed lines, representing where higher severe probabilities could exist, but is conditional.
Additionally, scattered showers and t’storms have developed across portions of Central and Southern Illinois. This activity, along with additional development, will continue to move across these areas through early tonight. Less favorable conditions will exists across these areas...However, upwards of a minimal severe t'storm threat will exist for these areas. Things are being monitored for a potential upgrade in severe t'storm probabilities in future updates, should they be needed.
Below is the severe t’storm forecast for this event. 
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9:30PM - 5/23/20) A compact and strong disturbance will be moving through the region on Saturday, which will bring a severe t’storm threat to a large portion of the state.
Synopsis... While a few isolated to scattered showers and t’storms are possible across the state Saturday morning, the main focus will be Saturday afternoon into evening. As a strong and compact disturbance moves in through the area, and arc of showers and t’storm are expected to develop Saturday afternoon, across Eastern Iowa into Northwest Illinois. This activity will then spread eastward across Northern Illinois and portions of Central Illinois, during the afternoon and evening. An environment expected to be in place that will feature low to moderate instability, good moisture, good shear and good forcing. This will all aide in upwards of a limited severe t’storm threat across Northern Illinois. All modes of severe weather will be possible. Things are being monitored for a potential upgrade in severe t'storm probabilities in future updates.
Additionally, scattered showers and t’storms will be possible across portions of Central and Southern Illinois, Saturday afternoon into early Saturday night. Less favorable conditions will exists across these areas...However, upwards of a minimal severe t'storm threat will exist for these areas. Things are being monitored for a potential upgrade in severe t'storm probabilities in future updates.
Below is the severe t’storm forecast for this event. 
(11:45AM - 5/23/20) A compact and strong disturbance will be moving through the region on Saturday, which will bring a severe t’storm threat to portions of the state.
Synopsis... While a few isolated to scattered showers and t’storms are possible across the state Saturday morning, the main focus will be Saturday afternoon into evening. As a strong and compact disturbance moves in the the area, and arc of showers and t’storm are expected to develop Saturday afternoon, across Eastern Iowa into Northwest Illinois. This activity will then spread across Northern Illinois during the afternoon and evening. An environment expected to be in place will feature low to moderate instability, good moisture, good shear and good forcing. This will all aide in upwards of a limited severe t’storm threat across Northern Illinois. All modes of severe weather will be possible.
Additionally, scattered showers and t’storms will be possible across portions of Central and Southern Illinois. Less favorable conditions will exists across these areas...However, an isolated severe t’storm will be possible.
Below is the severe t’storm forecast for this event. 
(9:30AM - 5/17/20) The same storm system that will bring the chance for severe t'storms to the state on Sunday, will also bring heavy rain and flood potential to portions of the state as well, through Monday morning.
Synopsis... Areas of rain and t'storms have been moving across the state Saturday afternoon through this morning. Upwards of 0.50-3.00" of rain has already fallen across much of the state, with some locally higher amounts. Some flooding has also occurred in some areas.
Multiples rounds of rain and t'storms will continue to move across the state, through late tonight or early Monday morning. This activity will be widespread, with much of the state seeing multiple rounds of activity during this period. Given there will be high atmospheric moisture content for efficient rainfall, repeated rounds of activity, and training potential, a low to moderate flood potential will exist for a large portion of the state. Additionally, for areas across portions of Northeast Illinois that were recently affected by heavy rain and flooding a few days ago, high flood potential will exist across this area given saturated soils and some flooding still ongoing. Final event rainfall totals for this period will be widespread in the range from 1.00-3.00"+ range across much of Central and Southern Illinois, with isolated amounts of 2.00-5.00" being possible. Further north, rainfall totals of 2.00-5.00"+ will be more common across Northeast Illinois and vicinity, with locally higher amounts in excess of 5.00” possible. Far Western and Northwest Illinois may escape the worse, with more int he range of 0.50-1.50" rainfall totals likely, with locally higher amounts.
Below is the flood and rainfall forecast for this event. 
(9:00AM - 5/17/20) A storm system moving through the region will bring the chance for severe t'storms to portions of the state today.
Synopsis... While a main storm system will be moving through the region, several smaller disturbances will also be passing through the area, leading to a complex and messy overall setup. Clusters of early day showers and t'storms are ongoing across portions of the state this morning. Some of this activity is likely to continue into the afternoon for some areas, while other areas potentially clear out and destabilize a bit. This will set the stage for some regeneration of ongoing activity and development of new showers and t'storms for some areas, including along and ahead of a cold front that will be sweeping eastward across the state during the afternoon. Both new activity and previously ongoing activity will continue to push northeast and east across the state, through the day and into the evening, slowly ending from west to east across the state. As previously mentioned, there may be pockets of clearing and destabilization to occur. An overall environment expected to be in place will feature low instability, good moisture, good forcing and good shear. This will help support upwards minimal to limited severe t'storm threat across a good portion of the state. Damaging winds and isolated tornadoes will be the main threats. Below is the severe t'storm forecast for this event. 
Good morning everyone, a decent start to the weekend has once again turned into wet weather as we move into a new week. Two to four inches of rain fell Thursday across the region with another two to five anticipated through early Monday. For more information about that please reference this article - www.illinoisstormchasers.com/forecasts/sat-mon-may-16-18th-heavy-rain-flood-threat-update-1
Let's take a look at what's going on above us tomorrow from left to right. An upper level low across the central U.S. is slowly sending multiple disturbances out into the plains while a deepening surface low evolves over Nebraska/Iowa. Winds will respond to the deepening low and back winds across most of eastern Illinois through the afternoon and evening. Bulk shear is more than supportive for severe weather. It's not your classic severe weather set up by any means, but any amount of wind shear in May generally can cause a couple of problems across the region.
What's needed for a more substantial severe weather severe weather episode is heat and instability. We have more than enough moisture in place (above right) and if model data is correct (above left) we will sufficiently warm to create an unstable air mass (below).
High-res convective allowing models show numerous showers and thunderstorms across central through northern Illinois through the day Sunday. What intrigues me is the overall lack of convection across eastern Illinois during peak heating. While I do not think it will be completely clear, any breaks in cloud cover to allow surface heating could cause trouble. Temperatures in the mid to upper 70's progged by models lead me to believe that there is some opportunity for a break in cloud cover.
Much of the convection shown [HRRR - left; Nest - right] is within a larger shield of precipitation across the I-39 corridor. Severe weather threat here is still possible, but I suspect that would be more in the way of gusty winds versus tornadoes. What I am eyeing is the pre-frontal convection developing over eastern Illinois. This would be the "instability" based convection with the greatest potential for producing a few tornadoes.
As a result we are introducing a minimal risk for severe thunderstorms across the eastern half of the state. Trends will be monitored if an upgrade to limited will be needed.
DNEAL
(11:45PM - 5/16/20) The same storm system that will bring the chance for severe t'storms to the state on Sunday, will also bring heavy rain and flood potential to portions of the state as well, through Monday morning.
Synopsis... Areas of rain and t'storms have been moving across the Central and Southern Illinois this afternoon into tonight, and have now recently overtaken Northern Illinois as well. Upwards of 0.50-3.00" of rain has already fallen across portions of Central and Southern Illinois this afternoon into tonight.
Multiples rounds of rain and t'storms will continue to move across the state, through late Sunday night or early Monday morning. This activity will be widespread, with much of the state seeing multiple rounds of activity during this period. Given there will be high atmospheric moisture content for efficient rainfall, repeated rounds of activity, and training potential, a low to moderate flood potential will exist for a large portion of the state. Additionally, for areas across portions of Northeast Illinois that were recently affected by heavy rain and flooding a few days ago, high flood potential will exist across this area given saturated soils and some flooding still ongoing. Final event rainfall totals for this period will be widespread in the range from 1.00-3.00"+ range across much of Central and Southern Illinois, with isolated amounts of 2.00-5.00" being possible. Further north, rainfall totals of 2.00-5.00"+ will be more common across Northeast Illinois and vicinity. Far Western and Northwest Illinois may escape the worse, with more int he range of 0.50-1.50" rainfall totals likely, with locally higher amounts.
Below is the flood and rainfall forecast for this event. 
(12:30PM - 5/16/20) The same storm system that will bring the chance for severe t'storms to the state on Sunday, will also bring heavy rain and flood potential to portions of the state as well from today through Monday morning.
Synopsis... Multiples rounds of rain and t'storms will move across the state, from this afternoon through Monday morning. This activity will be widespread, with much of the state seeing multiple rounds of activity during this period. Given there will be high atmospheric moisture content for efficient rainfall, repeated rounds of activity, and training potential, a low flood potential will exist for a good portion of the state. Additionally, for areas across portions of Northeast Illinois that were recently affected by heavy rain and flooding a few days ago, moderate flood potential will exist across this area given saturated soils and some flooding still ongoing. Final event rainfall totals for this period will range from 1.00-3.00" across the main corridor across the state, with localized higher amounts possible. Outside of this main corridor, rainfall amounts of 0.25-1.25" will be more common. Below is the flood forecast for this event. 
(11:30AM - 5/16/20) A storm system moving through the region will bring the chance for severe t'storms to portions of the state on Sunday.
Synopsis... While a main storm system will be moving through the region, several smaller disturbances will also be passing through the area, leading to a complex and messy overall setup. Clusters of early day showers and t'storms will be ongoing across portions of the state Sunday morning. Some of this activity is likely to continue into the afternoon for some areas, while other areas potentially clear out and destabilize a bit. This will set the stage for some regeneration of ongoing activity and development of new showers and t'storms for some areas, including along a cold front that will be sweeping eastward across Northern and Central Illinois during the afternoon. Both new activity and previously ongoing activity will continue to push northeast and east across the state, through the day and into the evening, slowly ending from west to east across the state. As previously mentioned, there may be pockets of clearing and destabilization to occur. An overall environment expected to be in place will feature low instability, good moisture, good forcing and good shear. This will help support upwards minimal severe t'storm threat across a good portion of the state. Large hail and damaging winds will be the main threats, though an isolated tornado can't be ruled out. It is possible an upgrade in severe t'storms probabilities will be needed in a later update, should an area of better focus for severe t'storms become evident. Below is the severe t'storm forecast for this event. 
(12:00AM - 5/16/20) A storm system moving through the region will bring the chance for severe t'storms to portions of the state ton Sunday.
Synopsis... While a main storm system will be moving through the region, several smaller disturbances will also be passing through the area, leading to a complex and messy overall setup. Clusters of early day showers and t'storms will be ongoing across portions of the state Sunday morning. Some of this activity is likely to continue into the afternoon for some areas, while other areas potentially clear out and destabilize a bit. This will set the stage for some regeneration of ongoing activity and development of new showers and t'storms for some areas, including along a cold front that will be sweeping eastward across Northern and Central Illinois during the afternoon. Both new activity and previously ongoing activity will continue to push northeast and east across the state, through the day and into the evening, slowly ending from west to east across the state. As previously mentioned, there may be pockets of clearing and destabilization to occur. An overall environment expected to be in place will feature low instability, good moisture, good forcing and good shear. This will help support upwards minimal severe t'storm threat across a good portion of the state. Large hail and damaging winds will be the main threats, though an isolated tornado can't be ruled out. It is possible an upgrade in severe t'storms probabilities will be needed in a later update, should an area of better focus for severe t'storms become evident. Below is the severe t'storm forecast for this event. 
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