Thursday, June 07, 2007

High Risk

5:08 p.m.: The severe weather threat appears to be over, and the tornado watch will likely be cancelled in the next hour or so. Severe thunderstorms moved through southeast Minnesota and western Wisconsin, resulting in some wind damage, very large hail, and possibly producing a tornado near Bangor. The storms have moved into northeastern Wisconsin, where several tornadoes have been reported. A tornado was reported just south of downtown Wisconsin Rapids, along with softball-sized hail. A tornado watch is in effect for eastern Wisconsin as well, but storms have not developed there yet. Overall the severe weather was not quite as widespread as expected over western Wisconsin, perhaps due to this morning's cloud cover. Another factor may have been the fact that the boundary that the storms formed along moved into the region a little quicker than expected. Still, this was a significant outbreak in areas mainly north of the Kickapoo Valley, but not as bad as feared.

12:40 p.m.: A Tornado Watch is in effect until 10:00 p.m. This is a PDS watch (Particularly Dangerous Situation), which means the threat for severe weather is very high. Destructive tornadoes, hail up to 2.5 inches in diameter, and wind gusts up to 80 miles per hour are possible. We remain under a high risk for severe weather, and the threat for tornadoes is slightly higher this afternoon than it was this morning. Thunderstorms are rapidly developing across northern Iowa and southern Minnesota, and several warnings have already been issued there. These storms will move north and east toward Wisconsin during the afternoon. The temperature has warmed into the lower 80s and dewpoints are well into the 60s, so the atmosphere is quite unstable. This is a very volatile situation and can change rapidly, so monitor the situation closely as the afternoon progresses and be prepared to seek shelter if these storms approach.

10:08 a.m.: Instead of eroding, the cloudcover has actually increased this morning. This could work to suppress the severe thunderstorm risk this afternoon. However, wind shear remains very high, and dewpoint temperatures have climbed into the middle 60s. Skies are also more clear across parts of Iowa and Minnesota where convective initiation is expected in the next few hours, so the threat for severe weather is still very real.

8:37 a.m.: There is a rare high risk of severe thunderstorms today across all of Wisconsin and adjacent parts of Minnesota and Iowa. All of the parameters for a significant severe weather outbreak still appear to be coming together. It is becoming increasingly warm and humid this morning, with some scattered clouds. Most of Iowa and southern Minnesota is cloud-free at this time, and this clear area is expected to move into Wisconsin as the morning progresses. This will allow the atmosphere to become more unstable. Wind shear values are already high, so thunderstorms are expected to rapidly develop by early afternoon and then move east. Tornadoes, damaging winds and hail are all possible. There is also a threat for some strong tornadoes and widespread damaging winds, with gusts up to hurricane force possible. There is still some chance that this forecast may be a bust, but it looks more and more like it will be a stormy afternoon across the area.

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