You may have gotten a notification or noticed a post for a snow squall warning this afternoon. If you found yourself confused thinking to yourself "What is this, I've never seen this before?" Don't feel bad. It is a brand new warning service product the NWS will be issuing starting this year.
The official criteria for the NWS to issue a snow squall warning is as follows:
These types of warnings are intended for quick hitting snows that will cause travel issues. The amount of snow that will accumulate has little to do with the warning. In fact, many snow squalls will fail to produce more than an inch of snow due to their fast hitting nature.
Also, the strong, sometimes severe winds that can be produced with snow squalls will cause minor damage, similar to what is seen with straight line winds in thunderstorms. Additionally, snow squall warnings could be issued during a large scale event where say, a winter storm advisory is issued. It is important to note the details in each warning product that is issued to understand the hazards. An un-warned snow squall near Des Moines, IA today (Monday December 9th) caused a pile-up on I-80 with at least one Injury. The snow only accumulated to an inch or less, but the quickly changing conditions made for extremely dangerous travel. It is these types of scenarios this new product is intended to make people aware of. 
So, be on the lookout for these types of warnings this winter season! They will show up on most radar apps as well.
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(5:00PM - 11/21/19) The Alpha Monocerotid meteor shower is expected tonight, also known as the "Unicorn" meteor shower. This event has quickly gained media and public attention across the county. However, upon further review by Bill Cooke, a NASA researcher, this meteor shower will only be lower end and only partially visible for half of the US...which being much more pronounced across the Atlantic. More information from Bill Cooke can be found at the following link...
https://blogs.nasa.gov/Watch_the_Skies/2019/11/19/about-the-upcoming-maybe-alpha-monocerotid-meteor-shower-outburst/ With that said, Illinois will already be on the lower end of the spectrum for meteor shower potential. On top of that, with a series of storm systems moving through the region, cloud cover will prevent any viewing across much of the state tonight.
JP
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(1:30PM - 11/19/19) This week is winter weather preparedness week for Illinois. This might seem a bit late given much of the state has already received accumulating snow and cold temperatures the past several weeks, but now is the time to be prepared for the long haul of winter that will be soon upon us. This is a good time to review all home/vehicle/personal/pet preparedness/safety.
We have put together a page with several useful links, which can be accessed from the link below. From school closings, to preparedness/safety tips for your home and vehicle, to helpful tips for your pets...we have you covered. https://www.illinoisstormchasers.com/illinois-winter-weather-info.html
JP
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All it takes is a little snow and Illinois roads turn into an icy slip and slide. We saw this earlier today as I-74 was briefly stopped in both directions due to numerous accidents. Drone footage from Sky 3 shows just how bad the roads became during the peak snowfall. Once again it goes to show that even just an inch of snow can cause problems on the roadways. It's not only the snow though, it's also the distracted/aggressive drivers that are not paying attention to the conditions. Situations like these are why we advocate not driving in the wintry conditions. It may not be you driving poorly, but unfortunately as many have found out, you may be in the wrong place at the wrong time.
Icy conditions will continue through the next 36 to 48 hours across the state. Portions of northern Illinois may even see more snow on Wednesday which may further complicate travel. Stay tuned for further updates and please be safe out there on the roads!
(12:00PM - 11/2/19) It's that time of year again...Time to push the clocks back 1 hour at 2AM tonight. Gaining an hour of sleep tonight will be nice for some. However, having to get used to the time change can be hard for some, especially since it will be getting darker earlier in the evening. It's also another sign that the holidays and winter are around the corner! This is also a good time ti check batteries in your smoke detectors, carbon monoxide detectors and weather radios.
JP
Please consider becoming a Patreon as a way to say thanks and support us for what we do! www.patreon.com/user?u=16598980 To receive text alerts via our in-telligent groups text ISC to 833-369-3800  Radar image of Hurricane Dorain as of 10:30AM.
(11:50AM - 9/1/19) While relatively quiet weather is being seen across Illinois, most attention for the country has been focused on what is now Major Category 5 Hurricane Dorian.
Hurricane Dorian was upgraded to a category 5 hurricane earlier this morning. As of 11:50AM, Dorian currently features a minimum pressure of 911MB, sustained winds of 185MPH with gusts to 220MPH. Rapid intensification has been occurring this morning, as the eye of the hurricane approached the Bahamas. As of this post, Hurricane Dorain has made landfall at Elbow Cay, Bahamas. This makes Dorain tied for the strongest hurricane on record (wind wise) to make a landfall in the Atlantic basin, as well as the 6th strongest hurricane on record pressure wise to make a landfall. Dorain is also among the strongest hurricanes on record for the Atlantic basin overall, now tied with three other storms for having the 2nd highest winds on record...as well as being just outside of the top 10 hurricanes with the strongest minimum pressure on record. The storm will make a direct hit to Abaco Island and Grand Bahama today, bringing a combination of 185MPH winds, storm surge of 18-23', waves of 20-30' and 12-24" of rain. This will lead to destructive and catastrophic damage for these areas.  Microwave loop of Dorian from this morning.
Beyond the Bahamas, Dorian is expected to curve to the north and the northeast, as it runs along the periphery of the Florida, Georgia and South Carolina coast. Along this track, it will bring some significant impacts to the coastline including; high winds, high surge, high waves and heavy/flooding rains. Fortunately, the absence of a direct landfall across these areas will help prevent more catastrophic and destructive impacts. Towards the end of the week, it is possible Dorain could come close, if not make landfall, in South Carolina or Northern Carolina. This still far out, and changes are likely at this distance.
Below is the latest NHC forecast for Hurricane Dorain.
JP
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What seems like a never-ending loop of poor weather for Illinois recently continues to get worse. While the main headlines for the past couple weeks have been the consistent severe weather, the rain from all these storms is causing historic flooding along the Mississippi and Illinois Rivers in parts of western and southwest Illinois. Along many points along the Mississippi River, the forecast crest is expecting to be the second highest crest in recorded history with most locations coming within 4 feet of the all-time crests and some as low as an inch!
The Illinois River is also feeling the strain, specifically from Beardstown and points south. Valley City, IL is expecting to break the record crest in just a few days and locations such as Hardin and Meredosia are coming within 2' of their all-time crests.
Living in the area (Alton), I'm quite familiar with the devastation flooding can cause. In fact, today in West Alton, a levee has already breached and we still have close to 3 feet to go before the Mississippi River crests here. The impacts of these flood waters are going to be felt for months to come. Communities are scrambling to save their homes and businesses as noted by the rash of posts across social media calling for sandbaggers to do every thing they can to hold back the rising flood waters. That's not to mention the commutes these people will have just to get to work with the number of road closures occurring. If anyone in these communities needs volunteers to assist with sandbagging, please comment on this post on our Facebook so any of our followers in the area can see it and potentially come out to provide assistance.
While the emphasis right now is on protecting our communities from the rising flood waters, we must not forget about our farmers either. The exceptionally wet pattern we have been in has drastically reduced the amount of planting our they have been able to get done. As you can see in the graphics below (Midwest Ag Service), this year compared to the 5-year average shows we're still about 60% below where we should be for this week in terms of acres planted and with the recent rains, we will continue to fall behind until our fields can dry out.
What we've been facing for a couple weeks now has been been a persistent ridge of high pressure in the southeast and a trough of low pressure over the west coast. This pattern (seen in the graphic below provided by Adam) allows Gulf moisture to surge north and provides an ideal track for systems to move and sometimes stall over our area resulting in round after round of severe weather and heavy rain. Sound familiar? Fortunately, it looks as though that may be moving off and we will enter a pattern where we get ridging over the southwest and central plains that will induce northwesterly flow over Illinois. While this can still bring heavy rain and severe weather, it isn't as conducive. For our farmers and the sake of these river communities, we certainly hope this upcoming pattern provides some relief.
As always, all of us here at ISC will be monitoring these conditions as we see them develop and we'll have forecasts and live severe weather coverage as needed. If there are any questions, feel free to message us!
We appreciate your support! - Billy
This afternoon a unique visual and radar feature began migrating its way across the Chicagoland area - gravity waves.
What are gravity waves? A gravity wave is vertical wave in the atmosphere. In order for gravity waves to develop, there must be something a triggering mechanism to displace the parcel of air. A simple way to understand them is to envision a rock being tossed into a pond. In today's example, a round of showers and thundershowers moved through the area and displaced the stable parcel of air that was sitting in place over the Chicagoland area. Gravity waves require stable air to be in place before the disturbance moves through. If the air was unstable, the air would continue to rise without creating a wave(s). When the parcel of air is displaced, it initially will rise but since the parcel is stable, it will then sink in an attempt to restore equilibrium. However, the momentum the initial displacement creates will cause the air to overshoot its equilibrium level in the vertical (both above and below). This is why you see the ripples. This rising and sinking motion will continue a certain distance away from the initial displacement until the air once again stabilizes and reaches equilibrium. It's also important to note that the upward motion in a gravity wave is the most favorable region for the development of clouds. Thanks to our community of followers, several images have already been shared with us of roll-type clouds giving us a great visual cue of the gravity waves traversing the area. Conversely, the sinking region of the gravity wave is not suitable for cloud development which is why we often see rows of clouds. 
In the radar GIF above I have the typical reflectivity and velocity products displayed in order to easily see the gravity waves traversing the region. At the beginning of the loop you can see what is left of the triggering mechanism (the region of showers and thundershowers) as it moves off into Indiana.
We've seen several reports of winds gusting over 35mph with these gravity waves as well. Just another interesting weather phenomenon to add to what has been a crazy week here in Illinois. 
History may have just been made in Illinois, and not the good kind of history either. Early reports are that around 12:30 this afternoon the official observation at Rock Island Arsenal recorded a river height of 22.64 ft - eclipsing the iconic record of 22.63 ft set on July 9th, 1993.
The record rains are a combination of heavy snow melt from a snowy winter across the northern and central plains and recent heavy spring rains. It is possible the levels could inch up just a little bit more and the official forecast calls for a crest at levels above the previous record. 
The good news for residents tired of battling these floodwaters is that dry weather is expected this weekend. Unfortunately, more heavy rains look to arrive early next week as the next weather system approaches the area. The residents along the Mississippi River undoubtedly have a long road ahead of them.
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Southwest Illinois had a pretty neat little mesoscale feature pass through this morning - a wake low. Right before 3am we had a significant pressure drop of about 7mb over the course of 15 minutes with 5mb falling in 1 minute (which is highlighted in the graph below from my weather station). That was quickly followed by strong wind gusts - I peaked at 36mph here at the house but I've seen reports of 60mph just across the river in Missouri. 
So what is a wake low and what caused it to happen? A wake low is an area of lower pressure that we typically see on the backside of a squall line or in stratiform rain (much like we got this morning as you can see in the radar screenshot below). It appears as though the rain-cooled air built up a small region of higher pressure (several millibars higher than the surrounding air) as it moved through the area creating a strong pressure gradient over a short distance. Since nature is always working to be in equilibrium, that sharp of a pressure gradient is unsustainable. Eventually, this pressure bubble 'burst' in and when it did, it sent out a rush of strong winds that prompted numerous damage and high wind reports across the St. Louis metro and southwestern IL.
If you have any questions, inquiries or suggestions, feel free to shoot us a message! We'll be happy to help. - Billy
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