Despite how it feels outside, Spring is fast approaching and soon we'll be shifting focus to severe storms instead of snow. Our first go at it appears to be Saturday afternoon, mainly across extreme southern Illinois as a powerful Spring storm systems moves overhead. Illinois (well, a very small part of it) has been placed in its first ENHANCED risk for severe storms of 2019 by SPC.
Deep low pressure system will rapidly develop and move across the midwest as the result of a powerhouse, negatively titled trough. This system will swing through the midwest on Saturday bringing a rapid influx of warm moist air along with the potential for thunderstorms - some severe - rain, and wind.
There are still some minor discrepancies in the storm track. A more southern track could bring a potential for a brief bout of mixed winter precip and backside snow across far northern Illinois, but current indications are we will mostly be in the warm sector and see rain.
Timeline of expected hazards:
Rain and general thunderstorms should begin developing overnight Friday and Saturday morning, first across southern Illinois and then spreading north. Models indicate a fair amount of elevated instability so we do think overall chances for thunder are pretty good. Better dynamics will not be in place for severe weather, but in these types of of scenarios, some brief bouts of small (keyword SMALL) hail never surprises me.
Later in the day, better system dynamics arrive from the west as the system further strengthens. More forcing for ascent should promote another round of rain/storms across much of the state.
Across far southern Illinois, there may be better surface based instability coupled with even greater forcing along a quickly advancing front. This should lead to the development of a narrow squall line that should race across the middle and lower Mississippi valleys. Due to very strong wind shear, damaging winds may be possible with this line. Additionally, circulations within the line could promote an isolated QLCS tornado threat. Further south of the state this threat will be greater.
Central and Northern Illinois will be farther removed from better surface instability and system dynamics, therefore we are not seeing much of a severe threat with any storms in those areas at this time.
As the system moves on throughout the day Sunday it will continue to deepen (strengthen.) Attention will then turn to synoptic winds - especially across northern and eastern Illinois - Sunday morning and into the afternoon. Sustained winds of 25-30mph and gusts over 50mph will be possible. Wind headlines may be needed if that is indeed the case.
Depending on the exact track we can't rule out some back-side snowflakes either as colder air filters in behind the system. An accumulating snow event does not appear likely at this time, however.
With the exception of far southern Illinois, overall this system may not be too big a deal. Some rain, some lightning, some wind and the typical hazards they all bring. We'll be providing more detailed updates, especially regarding the severe potential across the southern end tonight and tomorrow.
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