Severe StormsThe Storm Prediction Center has issued a moderate risk for severe thunderstorms this afternoon, highlighting the risk of large hail (quarter to golf ball size or larger), a heightened risk of tornadoes, and a high risk of strong, damaging winds.
Supercells will form this afternoon across parts of Minnesota and will begin very quickly moving east into Wisconsin. These supercells will provide the highest chances of large hail and strong tornadoes. Later in the afternoon, these supercells will merge into a line of storms and the threat will transition to spin-up tornadoes along the edge of the line, as well as very strong straight-line winds. The moderate risk was issued not only because of the tornadoes, but because there's a good chance of one or more derechos forming this afternoon. A derecho is a long-lived, powerful line of thunderstorms that produces very strong winds that can cause lots of damage over large areas.
The following image shows the risk for severe weather today. Green is general non-severe thunderstorms. Yellow is a slight risk for severe weather. Red is a moderate risk for severe weather.
This shows the risk for tornadoes today. This depicts the risk for tornadoes within 25 miles of any point within the shaded area. For example, in eastern Minnesota, there is a 10% chance of a tornado within 25 miles of any point within the yellow shading. Given that a 2% chance usually warrants concern, 10% is relatively dangerous.
This map shows the risk for wind damage today. The same rules apply to this map as did to the tornado map, meaning that in the magenta shaded area, there's a 45% risk for wind damage within 25 miles of any point in the shading. 45% means that there's a very high risk for wind damage today.
This map shows the risk for hail today, within 25 miles of a point as with tornadoes and wind. Hail shouldn't be too big of a risk, but hail up to the size of golf balls is possible in the strongest storms.
I won't be able to keep up a liveblog today if things get really bad, so please pay attention to the Storm Prediction Center and your local National Weather Service office for updates.
Tropical Storm Beryl in our future?The National Hurricane Center gives a low pressure system off the Florida coast a 40% (medium) chance of developing into a tropical system. The NHC says that surface observations in the area show the low slowly gaining organization and already has surface wind gusts of tropical storm force in some spots.
The models are showing the system becoming Tropical Storm Beryl within the next day or two. Wind shear in the area will relax over the next day or two, which will allow deep storms to develop around the center of the low and should allow organization and strengthening of the storm. A few of the models show a ridge of high pressure forming in the Atlantic, which, if it plays out, should keep the system confined to the southeastern US. Some other models show it shooting out to sea. Given the divergence in the forecast models right now, anyone from Florida to Virginia needs to keep a close eye on this system for possible development and movement.
National Weather Service Main Page
National Weather Service -- Grand Forks ND
National Weather Service -- Sioux Falls ND
National Weather Service -- La Crosse WI
National Weather Service -- Duluth MN
National Weather Service -- Minneapolis MN
National Weather Service -- Green Bay WI
National Weather Service -- Milwaukee WI
National Weather Service -- Chicago IL
National Weather Service -- Quad Cities
National Weather Service -- Des Moines IA
Storm Prediction Center Main Page
Storm Prediction Center -- Current Severe Weather Watches
Storm Prediction Center -- Convective (Severe Weather) Outlooks
Storm Prediction Center -- Mesoscale Discussions
Storm Prediction Center -- Storm Reports
Storm Prediction Center -- Mesoscale Analysis Pages
National Hurricane Center
Wunderground's Detailed Radar (click the + nearest to you to see your local radar)
NOAA Weather Models