A life-threatening situation will continue into tonight from Upper Midwest to the Mississippi River Valley as tornadic-thunderstorms continue to organize.
Madison, Wis., and Cedar Rapids, Iowa lie in the heart of the tornado threat area that extends from central Wisconsin to central Iowa.
The potential for additional tornadoes exists into tonight as powerful winds aloft and daytime heating help fuel severe thunderstorms. Storms that produced multiple tornadoes on Saturday will re-ignite over the next few hours.
Some of the tornadoes could be very strong and remain on the ground for miles.
Dangerous Setup for Storms
AccuWeather.com Meteorologist Meghan Evans first warned of the threat for tornadoes earlier in the week, saying, "The ingredients for a tornado outbreak may come together across portions of the Plains later Saturday and Sunday"
A powerful storm that slammed into the West earlier this week is ejecting northeastward through the Plains.
The storm system, combined with a strong rush of wind aloft via the jet stream and a warm, moisture-rich air mass in place originating from the Gulf of Mexico will spark powerful thunderstorms capable of producing tornadoes into tonight.
The difference in wind direction well up in the atmosphere (from the west) and at the surface (from the south) will enhance the threat for tornadoes.
The thunderstorms that will spawn the tornadoes will also drop large, damaging hail to the size of softballs, and could produce powerful wind gusts in excess of 60 mph without the help of a funnel.
Numerous tornadoes were spawned across the Plains Saturday afternoon and overnight, but as the storm system tracks eastward, more thunderstorms capable of producing damaging tornadoes will fire late this afternoon and this evening.
The greatest risk for tornadoes will be across southern Wisconsin, eastern Iowa and western Illinois through this evening, though any location in the Upper Midwest will have the potential for tornadoes.
Portions of several major highways will be at risk, including Interstates 30, 35, 39, 40, 44, 55, 70, 72, 74, 80, 88, 94, and 380.
If you are traveling and a potential tornado is approaching, be prepared to abandon your vehicle and seek safe shelter. Better yet, stay off the roads if you hear that thunderstorms are approaching.
Because of the threat, it is imperative that you keep up to date with the weather situation over the next several days, especially into tonight. Have a plan of action before the storms develop.
Immediately head to the basement or a storm shelter if a warning is issued. Mobile homes and trailers should always be evacuated, as well.
Knowing ahead of time what to do in the event of a tornado or strong thunderstorm could save your life.
We value your tornado pics, but we value your life more. Please take shelter during dangerous situations this weekend.
Story updated by Andy Mussoline, Meteorologist
Unsettled weather for the extended Labor Day weekend will be across the Southeast, Upper Midwest, northern Rockies and the Four Corners.
Tropical Depression 14-E is several hundred miles southwest of Mexico and is expected to strengthen slowly into a tropical storm.
A stormy weather pattern will prevail through September across much of southern South America.
While lulls in tropical activity in the Atlantic will continue, a rapid end to the hurricane season in September does not always occur during an El Niño.
The combination of moisture from Erika and a non-tropical system will drench areas from Florida to the South Carolina coast through the middle of the week.
Heat will be erased by an autumnlike air mass across parts of northern Europe.
Denver, CO (1961)
Earliest snow on record; a total of 4.2 inches. A great storm raged at high elevations with 2-3 feet of snow closing roads on Labor Day weekend.
Coffeyville, KS (1970)
Hailstone 17.5/44 cm in circumference 1.671 lb/757 gm.
Long Island NY (1821)
Long Island hurricane of 1821 struck western Long Island. The storm affected a densely populated area where weather observers were common.