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(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. 
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(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.
(12:30PM - 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 continues in periods across these areas into Friday afternoon. Re-newed development of showers and t'storms will occur across Oklahoma, Arkansas and Missouri Friday afternoon, with this activity then likely to push northeast into Central and Southern Illinois 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. Damaging winds and large hail will the the severe weather threats.
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 and great forcing expected. Scattered showers and t'storms are expected to develop along a dry line, which is expected to be int he vicinity of the Mississippi River by early to mid afternoon. This activity will quickly race northeast across the state, posing some severe weather threat. All modes of severe weather will be possible. While it is a bit too early to delineate specific risk levels at this time, the next update will likely feature the first outlook for Saturday. Below is the severe t'storm forecast for Friday morning-Friday night. 
(7:30PM - 3/22/20) A brief short term update regarding the ongoing snow event across portions of the state...
Snow has been spreading across Northern and Central Illinois from this morning, through this afternoon and now into this evening. Upwards of 1-3" of snow has already occurred across a good portion of Northern and Central Illinois, with a narrow axis of more 2-4" snowfall amounts having already occurred near I-80, in a Yorkville-Joliet-Kankakee corridor. Steady light to moderate snow, with periods of heavier snow, will continue across Northern and portions of Central Illinois into tonight. Activity will slowly end from west to east later tonight on into early Monday morning. Final snowfall will be widespread in the 1-3" range across Northern and Central Illinois, with 3-6" amounts being more common in the aforementioned Yorkville-Joliet-Kankakee corridor and nearby vicinity. 
(12:15PM - 3/22/20) Another sign that winter is hanging on from time to time...It continues to look like that a minor snow event will occur across Northern and Central Illinois, today into Monday...as a weak storm system moves through the region. With this update we have only had minor adjustments, based on real-time observations and guidance.
Synopsis...
A weak storm system will be moving through the region, today into Monday. Model guidance has been in agreement on this event occurring, snowfall amounts and snowfall axis location. Precipitation spread into West-Central and Southwest Illinois this morning, with a dusting to 1-3" of snow having already occurred across these areas. Precipitation will continue to spread across much of the state through the day and through tonight. Across Northern Illinois, all of this event is expected to be snow, with the transition zone of rain to snow expected to set up across Central Illinois. Precipitation will continue into very late tonight night or early Monday morning, before ending. Given the recent mild/warm temperatures and expected marginal temperatures during this event, snow will likely not efficiently accumulate. Thus, highest accumulation will be on colder surfaces (such as grass), with road accumulation far less. These temperature factors will also play a roll in final snowfall accumulation amounts as well. Final snowfall totals upwards of a dusting to 1-3" are expected across Northern and Central Illinois. 
(12:15AM - 3/22/20) Another sign that winter is hanging on from time to time...It continues to look like that a minor snow event will occur across Northern and Central Illinois, Sunday into Monday...as a weak storm system moves through the region. With this update we have adjusted the location of the snowfall axis, given latest information.
Synopsis...
A weak storm system is expected to push through the region, Sunday into Monday. Model guidance has been in agreement on this event occurring, snowfall amounts and snowfall axis location...though we have recently seen a shift southward in snowfall axis location. Precipitation is expected to spread into the western half of the state Sunday morning. Across Northern Illinois, all of this event is expected to be snow, with the transition zone of rain to snow expected to set up across Central Illinois. Precipitation will continue into very late Sunday night or early Monday morning, before ending. Given the recent mild/warm temperatures and expected marginal temperatures during this event, snow will likely not efficiently accumulate. Thus, highest accumulation will be on colder surfaces (such as grass), with road accumulation far less. These temperature factors will also play a roll in final snowfall accumulation amounts as well. Final snowfall totals upwards of a dusting to 1-3" will be possible across Northern and Central Illinois. 
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