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(12:00PM - 4/7/20) Multiple disturbances will move through the region through Wednesday, bringing a daily chance of severe t'storms to the state.
Monday morning - Monday night recap... Scattered showers and isolated t'storms occurred across portions of Northern Illinois Monday afternoon and evening, near a warm front that lifted northward into Northern Illinois through the day. As a main disturbance moved through the area, additional scattered showers and t'storms developed and spread across Northern Illinois Tuesday night...some of which were strong, producing small hail.
This afternoon - tonight...
Isolated to scattered showers and t'storms are expected to develop in the vicinity of a advancing cold front later this afternoon...across Southern/Eastern Wisconsin, Northern Illinois and Eastern Iowa. This activity will then sweep southeastward across Northern and portions of Central Illinois, from late this afternoon into early tonight. An environment featuring low to moderate instability, decent moisture, decent forcing and decent shear will be in place. This will help support a minimal to limited severe t'storm threat across Northern and portions of Central Illinois. Large hail and damaging winds will be the main threats, though an isolated tornado cannot be ruled out.It should be noted that there is a spread among model guidance regarding possible scenarios for today...Ranging from little in the way of t'storm/severe potential, with stronger capping in place, to more widespread t'storm/severe potential. However, given a good chunk of consistent guidance favoring a more active scenario and a favorable t'storm/severe environment in place, we have held steadfast through updates with a minimal to limited severe t'storm threat for aforementioned areas...But will note there is some potential for a dry frontal passage should the other solutions come to fruition. It is possible that some activity may also back-build and develop along the cold front down into Central/Southern Illinois and Missouri, which would then push across Central and Southern Illinois this evening into tonight. However, this scenario is highly in question given stronger capping in place with southward extent... Thus, will maintain general t'storm area and a conditional minimal severe t'storm risk, as the environment will be favorable for the potential for a few severe t'storms, should t'storms develop.
Wednesday morning - Wednesday night...
Areas of showers and t'storms will be ongoing across Iowa and vicinity Wednesday morning into afternoon, associated with the next disturbance moving through the region. Additional scattered showers and t'storms are expected to develop in the vicinity of a advancing cold front, from Iowa down into Missouri Wednesday afternoon. This activity will then sweep eastward across Central and Southern Illinois, from Wednesday afternoon into Wednesday night. An environment featuring low to moderate instability, mediocre moisture, good forcing and good shear will be in place. This will help support a minimal to limited severe t'storm threat across much of Central and Southern. Large hail and damaging winds will be the main threats, though an isolated tornado cannot be ruled out. Below is the severe t'storm forecasts for this afternoon - tonight and Wednesday morning - Wednesday night.
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(9:30PM - 4/6/20) Multiple disturbances will move through the region tonight through Wednesday, bringing a daily chance of severe t'storms to the state.
Tonight... Scattered showers and isolated t'storms occurred across portions of Northern Illinois this afternoon and evening, near a warm front that lifted northward into Northern Illinois through the day. Tonight there will be a better focus for elevated scattered shower and t'storm development across Northern Illinois and vicinity. This activity will then continue to be possible overnight and into very early Tuesday morning, across portions of Northern and Eastern Illinois. A marginal environment will be in place, but will be enough to support a minimal severe t'storm threat across portions of Northern Illinois. Hail will the the main severe weather threat.
Tuesday morning-Tuesday night...
A few lingering showers and t'storms may be ongoing early Tuesday morning across portions of Northeast and Eastern Illinois, which will quickly clear the area by mid morning. In the wake of this early activity, clearing and destabilization is expected to occur ahead of the next approaching disturbance. Scattered showers and t'storms are expected to develop in the vicinity of a advancing cold front, across Wisconsin, Northern Illinois and Eastern Iowa. This activity will then sweep southeastward across Northern and Central Illinois, from Tuesday afternoon into early Tuesday night. Some activity is likely to back-build down into Missouri, which would likely push into Southern Illinois Tuesday evening into Tuesday night. It should be noted that there is some disagreement on extent of development with activity for Tuesday, and it will have to be monitored for changes in later updates. An environment featuring low to moderate instability, modest moisture, modest forcing and decent shear will be in place. This will help support a minimal to limited severe t'storm threat across much of the state. Large hail and damaging winds will be the main threats, though an isolated tornado cannot be ruled out.
Wednesday morning-Wednesday night...
Areas of showers and t'storms will be ongoing across Iowa and vicinity Wednesday morning into afternoon, associated with the next disturbance moving through the region. Additional scattered showers and t'storms are expected to develop in the vicinity of a advancing cold front, from Iowa down into Missouri Wednesday afternoon. This activity will then sweep southeastward across Central and Southern Illinois, from Wednesday afternoon into Wednesday night. An environment featuring low to moderate instability, modest moisture, good forcing and good shear will be in place. This will help support a minimal to limited severe t'storm threat across much of Central and Southern. Large hail and damaging winds will be the main threats, though an isolated tornado cannot be ruled out. Below is the severe t'storm forecasts for tonight, Tuesday morning - Tuesday night and Wednesday morning - Wednesday night.
(12:30PM - 4/6/20) Multiple disturbances will move through the region today through Wednesday, bringing a daily chance of severe t'storms to the state.
This afternoon-Tonight... A warm front has been rapidly lifting northward across the state today. A few isolated showers and t'storms will be possible across Northern Illinois this afternoon and evening, as the warm front lifts into the area. As a disturbance moves across the area, there will be a better focus for elevated scattered shower and t'storm development across Northern Illinois and vicinity, this evening into tonight. This activity will then continue to be possible through very early Tuesday morning, across Northern and Eastern Illinois. A marginal environment will be in place, but will be enough to support a minimal severe t'storm threat across portions of Northern Illinois. Hail will the the main severe weather threat.
Tuesday morning-Tuesday night...
A few lingering showers and t'storms may be ongoing early Tuesday morning across Northeast and Eastern Illinois, which will quickly clear the area by mid morning. In the wake of this early activity, clearing and destabilization is expected to occur ahead of the next approaching disturbance. Scattered showers and t'storms are expected to develop in the vicinity of a advancing frontal boundary, across Southern Wisconsin, Northern Illinois and Eastern Iowa. This activity will then sweep southeastward across Northern and Central Illinois, from Tuesday afternoon into early Tuesday night. It should be noted that this is some disagreement on extent of development with this round of activity, and it will have to be monitored for changes in later updates. An environment featuring low to moderate instability, modest moisture, modest forcing and decent shear will be in place. This will help support a minimal to limited severe t'storm threat across Northern and Central Illinois. Large hail and damaging winds will be the main threats, though an isolated tornado cannot be ruled out.
Wednesday morning-Wednesday night...
While it is still a bit too far out to go into specifics, it is looking increasingly possible that another disturbance will move through the area on Wednesday. It appears conditions will be favorable for some severe t'storms risk across Central and Southern Illinois, Wednesday afternoon into early Wednesday night. More information regarding the severe t'storm threat on Wednesday will be provided in future updates. Below is the severe t'storm forecast for this afternoon-tonight and Tuesday morning-Tuesday night.
(9:30PM - 4/5/20) Multiple disturbances will move through the region Monday through Wednesday, bringing a daily chance of severe t'storms to the state.
Monday morning-Monday night... A warm front is expected to lift northward across the state on Monday. A few isolated showers and t'storms will be possible across Northern Illinois Monday afternoon and evening, as the warm front lifts into the area. As a disturbance moves across the area, there will be a better focus for elevated scattered shower and t'storm development across Northern Illinois and vicinity, Monday evening into Monday night. This activity will then continue to be possible through very early Tuesday morning, across Northern and Eastern Illinois. A marginal environment will be in place, but will be enough to support a minimal severe t'storm threat across portions of Northern Illinois. Hail will the the main severe weather threat.
Tuesday morning-Tuesday night...
A few lingering showers and t'storms may be ongoing early Tuesday morning across Northeast and Eastern Illinois, which will quickly clear the area by mid morning. In the wake of this early activity, clearing and destabilization is expected to occur ahead of the next approaching disturbance. Scattered showers and t'storms are expected to develop in the vicinity of a advancing frontal boundary, across Southern Wisconsin, Northern Illinois and Eastern Iowa. This activity will then sweep southeastward across Northern and Central Illinois, from Tuesday afternoon into early Tuesday night. It should be noted that this is some disagreement on extent of development with this round of activity, and it will have to be monitored for changes in later updates. An environment featuring low to moderate instability, modest moisture, modest forcing and decent shear will be in place. This will help support a minimal to limited severe t'storm threat across Northern and Central Illinois. Large hail and damaging winds will be the main threats, though an isolated tornado cannot be ruled out.
Wednesday morning-Wednesday night...
While it is still a bit too far out to go into specifics, it is looking increasingly possible that another disturbance will move through the area on Wednesday. It appears conditions will be favorable for some severe t'storms risk across Central and Southern Illinois, Wednesday afternoon into early Wednesday night. More information regarding the severe t'storm threat on Wednesday will be provided in future updates. Below is the severe t'storm forecast for Monday morning-Monday night and Tuesday morning-Tuesday night.
(5:00PM - 3/28/20) A brief update regarding the ongoing severe weather threat across the state, into tonight...
As was mentioned in our midday update, areas of showers and t'storms from this morning were more widespread and were going to linger around much longer than previously expected prior to today. We had adjusted severe t'storm probabilities in our midday update today based on observations and guidance available. Since that earlier update, it has become even more clear that a significant cut in coverage and level of severe t'storm probabilities are needed, once again based on observations.
Early day showers, t'storms and cloud covered lingered across a good portion of the state for much of the day, which has hindered destabilization for many areas. However, there will still be the chance for some severe t'storms across portions of the state, into tonight.
Across Southern Illinois, isolated to scattered severe t'storms currently across Arkansas are expected to lift northeastward across the area this evening and early tonight. All modes of severe weather will be possible with any storm that becomes severe. Further north, there have been a few t'storms that have recently become severe across Western Illinois. Additional showers and t'storms are expected to develop across Iowa, Northeast Missouri and Western Illinois late this afternoon and into the evening...along and ahead of a front sweeping into the area. This activity will then sweep northeastward across Northern and portions of Central Illinois, into early tonight. Some t'storms will be severe, with all modes of severe weather being possible. Below is the updated severe t'storm forecast, through tonight. 
(12:15PM - 3/28/20) A storm system moving with continue to bring the threat for severe t'storms to the state, through tonight. With this update we have adjusted severe probabilities based on latest observations and guidance.
Friday morning-Friday night recap... Several areas of showers and t'storms moved across the state Friday morning through Friday night. Some of this activity was severe across Central and Southern Illinois, producing large hail. Additionally, heavy rainfall and some flooding occurred for some areas, as training of activity occurred.
Saturday morning-Saturday night...
Areas of showers and t'storms have been ongoing this morning across much of the state. Some of this activity has been severe across portions of Central Illinois, producing large hail. This activity and associated cloud cover has been more widespread than expected, and will likely linger further into the afternoon that previously expected. Activity across portions of Central and southern Illinois will continue in periods through the afternoon and evening. Some of this activity will continue to pose a severe thereat, with all modes of severe weather bring possible. Further north, activity has been ending across Northern and portions of Central Illinois. Some clearing is expected to occur, allowing for destabilization to occur, as a warm front lifts northward. Additional showers and t'storms are expected to develop across Iowa and Eastern Missouri this afternoon. This activity will quickly sweep northeast across Northern and Central Illinois later this afternoon into early tonight. Severe t'storms will be possible to likely, with all modes of severe weather being possible, including tornadoes. A favorable severe weather environment will be in place, with low to moderate instability, good moisture, great forcing and great shear expected. Upwards of an elevated to considerable severe t'storm risk exists across portions of the state. All modes of severe weather are possible, including an increased tornado risk due to the environment expected to be in place. Trends are increasing for the potential for a significant severe t'storm event across the state on Saturday. With this update we have adjusted severe t'storm probabilities based on observations and guidance. It is possible another update may be needed based on how trends progress the next few hours. This has turned into a complex scenario, given the aforementioned more widespread and lingering activity from this morning across the state...which is throwing a wrench into the forecast. Below is the severe t'storm forecast for this afternoon-tonight. 
(11:15PM - 3/27/20) A storm system will be moving through the region over the coming days, and along with it will come a severe t'storm threat, tonight through Saturday night. With this update, we have slightly expanded severe t'storm probabilities for Saturday/Saturday night...as the potential continues to increase for a significant severe weather event across the state on Saturday.
Tonight... Areas of showers and t'storms moved across portions of Central and Southern Illinois earlier this morning. Some of this activity was severe, with large hail having occurred. Additional areas of isolated to scattered showers and t'storms then pushed across portions of the state this afternoon and evening, though no severe t'storms occurred. Additional areas of showers and t'storms will move across Northern and Central Illinois tonight, with potential for some severe t'storms. A marginal environment will be in place, but will be enough to support a minimal to limited severe t'storm threat across Northern and Central Illinois. Large hail will the main severe weather threat.
Saturday morning-Saturday night...
Areas of showers and t'storms will be ongoing across Northern and Central Illinois Saturday morning, as a warm front quickly lifts northward across the state. Some of this activity may be severe, with large hail being the main threat. This activity will quickly clear out of most of the state by late morning to early afternoon, as the aforementioned warm front lifts into Northern Illinois by early to mid afternoon. Along and south of the warm front, a favorable environment will be in place, with low to moderate instability, good moisture, great forcing and great shear expected. Scattered showers and t'storms are expected to develop along a front, which is expected to be in the vicinity of the Mississippi River by mid afternoon. This activity will quickly race northeast across the state, posing a severe weather threat, potentially significant. Upwards of an elevated to considerable severe t'storm risk exists across portions of the state. All modes of severe weather are possible, including an increased tornado risk due to the environment expected to be in place. Trends are increasing for the potential for a significant severe t'storm event across the state on Saturday. Below is the severe t'storm forecast for this afternoon-tonight and Saturday morning-Saturday night.
Significant severe weather is expected tomorrow, that is no longer news to any of us if we've been paying attention. Now lets talk about the timing. Multiple rounds of severe weather will occur, so what you should expect with them and where?
The first round will begin during the overnight and early morning hours ahead of the approaching warm front. This is a common scenario with dynamic systems such as the one we'll be dealing with. These storms are typically elevated due to the surface layer being stable with overnight cooling. Large to very large hail is the primary threat with these storms. We could even see 2" hail or larger as the atmosphere is VERY cold aloft, and the forcing is quite strong. The most favored corridor for these storms will generally be I-70 through about US-24. Perhaps reaching I-80, but right now it looks like areas further south of 80 are favored. These storms will be quite loud too! 
By mid to late morning, most of these storms should be shifting out of Illinois. The forecast starts to get a little iffy after this point, because that first round of storms will affect what happens later. Our current thinking is they will clear out of the area. This will allow the warm front to continue lifting north to I-88 and maybe even into Wisconsin.
Around this time (8am-12pm) there will be showers and thunderstorms hanging around near the front. Some of them could be severe with a hail/wind threat, but overall the ingredients won't be in place yet for the significant severe. 
Once these move through, assuming we clear out and destabilize as currently forecast, the stage will be set for the big show. The system will be fully mature, a pacific front will swing into the ripe, unstable warm sector characterized by extreme wind shear and the stage will be set for explosive supercell development.
These should first form somewhere near the MS river and QUICKLY (over 60mph) move northeast across the state. These are the storms that will be capable of producing strong, long track tornadoes in addition to damaging winds and more hail up to baseball size (or perhaps larger?) This 3rd round, while the most significant of the bunch, is also the one most prone to failing. Cloud cover may hang around too long, or the front timing could be off by an hour - but if neither of that happens - a severe weather event will unfold. These storms could get going as early as 2pm - give or take an hour - and track through the rest of the state into the evening. As they progress towards the eastern part of Illinois and the Chicago metro area, the chance for them to begin congealing into more linear complexes will begin, with a damaging wind/hail threat taking over as the dominant threats, although tornadoes will still certainly be possible. 
These storms should mostly be out the state by sunset, except for maybe parts of eastern and southern Illinois, if they manage to develop that far south.
Its going to be a long day, stay vigilant stay prepared! Most of the ISC team will be out chasing, and we'll do our best to provide live updates in the field and our social media feeds! To see our latest TAM; reference this article here: https://www.illinoisstormchasers.com/forecasts/fri-sat-march-27-28th-severe-tstorm-threat-update-2?fbclid=IwAR1jiAqHFcG8mAI4NtaEf2uCK2Rj7y86yqzQ2C_RaZmxLRBWRqedTMO56dY 
(11:30AM - 3/27/20) A storm system will be moving through the region over the coming days, and along with it will come a severe t'storm threat for today into Saturday. With this update, we have increased and expanded severe t'storm probabilities for both today/tonight and Saturday/Saturday night...as potential increases for a significant severe weather event across the state on Saturday.
This afternoon-tonight... Areas of showers and t'storms moved across portions of Central and Southern Illinois earlier this morning. Some of this activity was severe, with large hail having occurred. Additional areas of isolated to scattered showers and t'storms will be possible across the state through this afternoon and evening. The main focus will be this evening into tonight...Re-newed development of areas of showers and t'storms will occur across Oklahoma, Arkansas, Missouri and Illinois this afternoon and evening, with this activity then likely to push across much of Northern and Central Illinois, this evening through tonight. A marginal environment will be in place, but will be enough to support a minimal to limited severe t'storm threat across Northern and Central Illinois. Large hail will the main severe weather threat.
Saturday morning-Saturday night...
Areas of showers and t'storms will be ongoing across Northern and Central Illinois Saturday morning, as a warm front quickly lifts northward across the state. Some of this activity may be severe, with large hail being the main threat. This activity will quickly clear out of most of the state by late morning to early afternoon, as the aforementioned warm front lifts into Northern Illinois by early to mid afternoon. Along and south of the warm front, a favorable environment will be in place, with low instability, good moisture, great forcing and great shear expected. Scattered showers and t'storms are expected to develop along a dry line, which is expected to be in the vicinity of the Mississippi River by mid afternoon. This activity will quickly race northeast across the state, posing some severe weather threat. Upwards of an elevated to considerable severe t'storm risk exists across portions of the state. All modes of severe weather are possible, including an increased tornado risk due to the environment expected to be in place. Trends are increasing for the potential for a significant severe t'storm event across the state on Saturday. Below is the severe t'storm forecast for this afternoon-tonight and Saturday morning-Saturday night.
(9:30PM - 3/26/20) A storm system is expected to move through the region over the coming days, and along with it will come a severe t'storm threat for Friday and Saturday.
Friday morning-Friday night... Areas of scattered showers and t'storms will be ongoing early Friday morning across Missouri. This activity is expected to spread eastward, into Central and Southern Illinois Friday morning. This activity will then continue in periods across these areas into Friday afternoon. Re-newed development of showers and t'storms will occur across Oklahoma, Arkansas, Missouri and Illinois Friday afternoon, with this activity then likely to push across much of the state Friday evening into night. A marginal environment will be in place, but will be enough to support a minimal to limited severe t'storm threat across Central and Southern Illinois. Large hail will the main severe weather threat.
Saturday morning-Saturday night...
Scattered areas of showers and t'storms will be ongoing across the state Saturday morning, as a warm front quickly lifts northward across the state. This activity will quickly clear out of most of the state by late morning to early afternoon, as the aforementioned warm front lifts into Northern Illinois by early to mid afternoon. Along and south of the warm front, a favorable environment will be in place, with low instability, good moisture, great forcing and great shear expected. Scattered showers and t'storms are expected to develop along a dry line, which is expected to be in the vicinity of the Mississippi River by early to mid afternoon. This activity will quickly race northeast across the state, posing some severe weather threat. Upwards of a limited to elevated severe t'storm risk exists across portions of the state, with all modes of severe weather will be possible. Below is the severe t'storm forecast for Friday morning-Friday night.
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