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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