(9:30:11 PM) nwsbot: Local Storm Report by NWS LOT: 4 NE Poplar Grove [Boone Co, IL] trained spotter reports HAIL of golf ball size (M1.75 INCH) at 09:20 PM CDT -- thunderstorm wind damage snapped 15 inch tree. hunter road and leroy center road.
A Severe Thunderstorm Warning has been issued for Northeast Winnebago, Boone and McHenry counties until 9:30pm.
Severe Thunderstorm Warning for Rock County until 9pm this evening. This storm is located between Janesville and Beloit and moving southeast at 30 mph. Wind gusts to 60 mph are possible. Also, this storm did have a little rotation with it earlier. It wasn't strong, but worth watching. Heads up if you live in Sharon, right along the Rock/Walworth and Boone counties line.
8:05pm Update: Currently there are no warnings in place for the immediate area, but a line of stronger storms southwest of Sterling to Amboy could contain winds over 35 mph and pea to dime sized hail. Storm is moving southeast at 25 mph - very slowly.
7:50pm Update: The Tornado Watch for Jo Daviess County has been canceled. Still continues for the rest of Northern Illinois.
7:30pm Update: Storms so far have had a hard time developing locally, while to the north in Wisconsin and just to the south severe thunderstorms have rapidly developed. The storms north in Wisconsin have been forming with an area of low pressure. The storms to the south have formed along an old outflow boundary and washed out warm front. We've been stuck in the middle with no real trigger mechanism to get storms to develop. The instability is there - you can feel it outside!
The severe weather to the south won't have an impact on us. What we have to keep our eyes on is what's developing north in Wisconsin as that moves southeast. The Severe Thunderstorm Warning continues for Green County until 8pm.
Severe Thunderstorm Warning for Green County until 8pm. This storm is located near Blanchardville and moving southeast at 50 mph. This is a storm that has had history of rotation, and did have a tornado warning with it earlier. If you are in the path of the storm, seek shelter immediately. Wind gusts to 60 mph and quarter sized hail possible with this cell.
A Tornado Watch has been issued for all of Northern Illinois until 11pm. The cap on the atmosphere remains in place, however, we're beginning to see it erode away and this has helped thunderstorms develop within the next couple of hours. Thunderstorms have been developing in Wisconsin and Iowa, and are expected to increase in coverage through Northern Illinois.
A Severe Thunderstorm Watch has been issued for Green, Rock and Walworth counties until 9pm. Also, there's a 95% chance from the Storm Prediction Center that a weather watch will be issued for Northern Illinois within the next couple of hours. Damaging wind gusts are going to be the primary concerns. Secondary - hail/isolated tornadoes.
The Storm Prediction Center in Norman, Oklahoma is currently monitoring a growing area of instability in Wisconsin this afternoon. A weather watch will likely be issued later this afternoon.
1:30pm Update: Both Meteorologist Kristin Cwynar and Candice King just wrapped up a conference call with the Chicago National Weather Service regarding the potential for severe weather development later this afternoon and evening.
As you may have noticed, skies have cleared and this has allowed our atmospheric instability to greatly increase. In fact, instability parameters are nearly off the charts this afternoon. Scattered severe storms are likely later today, but where exactly those develop is what's still in question.
Every morning and every night, many National Weather Service offices conduct upper air balloon launches, giving us a snap shot of what the atmosphere is like above us. When severe weather threatens in the summer time, and winter weather threatens in the winter time, weather service offices will conduct 'special' upper air balloon launches either around Noon or 1pm. This is to not only give us an idea of what's going on during the prime heating of the day, but to also provide better data that feed into our weather computer models to help us predict damaging thunderstorms.
The Quad Cities National Weather Service launched a balloon earlier today, and one very interesting feature it shows is a pretty strong cap, or lid, on our atmosphere at the moment. This means we have a lot of warm air above and, initially, it will be hard for air at the surface to rise to develop thunderstorms. This likely means we've got a couple more 'dry' hours before we begin to see storms develop late this afternoon. The atmosphere really has to work to erode away at the cap.
When storms develop, they will likely be what we refer to as HP (High Precipitation Supercells). These supercells can produce tornadoes, but are most known for excessive damaging winds, large hail and flooding rains. However, tornadoes can't be ruled out. With this type of environment, any surface based thunderstorms will rapidly develop and turn severe. We're still looking at the time frame for storm development between 3pm and 5pm in southern Wisconsin and northern Illinois. Storm motion would drive storms to the southeast, and not very fast, as the upper level flow isn't that strong.
We will continue to monitor the weather throughout the afternoon, and provide updates as needed. Make sure you have a way of receiving watches/warnings and keep a watchful eye to the sky for building cumulus clouds later today.
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After one round of severe
storms tracked across the Stateline this morning, another round of severe weather is
possible again this afternoon and evening. The highest risk area, the moderate
risk, has mainly shifted to the south of the Stateline, but northern Illinois is still under an enhanced risk this afternoon. As of now storms look to fire up in the early afternoon, possibly in southern Wisconsin and northern Illinois where we are seeing quite a bit of clearing and more heating taking place. This should allow for the atmosphere to 'recharge' and become more unstable. There also looks to be quite a bit of instability as well as vertical wind shear (when winds change direction with height in the atmosphere) for supercells to form before coming together in another fast moving bow echo.
All severe weather hazards are possible today, including large hail, tornadoes, strong damaging winds, as well as very heavy rainfall. Make sure to have a way to receive warnings should we get them today.
All severe weather hazards are possible today, including large hail, tornadoes, strong damaging winds, as well as very heavy rainfall. Make sure to have a way to receive warnings should we get them today.
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