Severe Weather: July 27

Recap: A round of storms made their way through portions of central and southern Iowa yesterday afternoon/evening. Storms developed during the early afternoon hours in response to an old MCS entering portions of northwest Iowa. As this continued, additional development occurred as this lingering MCS pushed a stationary boundary, and outflow further to the south. The intense storms began roughly around the Pocahontas to Fort Dodge areas where they continued to expand and strengthen as they headed towards the Des Moines area. As the storms entered Boone/Story counties a tornado warning was issued for the storm, as well as significant damaging winds. The storms continued to expand throughout the afternoon and evening hours as they entered southern Iowa, creating a large span of damaging winds and large hail reports over the state. Overall, a total of 5 tornado reports were received yesterday in Polk county (near Elkhart and Ankeny), Jasper county (near Valeria and Newton), and lastly in Monroe county (near Lovilia). Large hail was also a threat, the largest size in Iowa being baseballs on a few occasions, other areas with storms in northern Missouri reached up to 5 inches in diameter! Damaging straight line winds were also definitely present and the most widespread, typically 50-70 mph winds were common. However, a few measured gusts over 80 mph were also received yesterday with the storms.

A large collection of pictures, radar, etc. can be found on the Iowa Environmental Mesonet.


2:15 PM Update: The previously severe warned storm has since continued eastward and congealed into more of a linear line of storms. This line has entered, and now passed through, portion of Cerro Gordo and Franklin counties in Iowa where it became severe warned for the potential for winds greater than 60 mph. The line of storms is continuing to move east around 35 mph. Both Floyd, and northern Butler counties are now under a severe thunderstorm warning for winds greater than 60 mph and some small hail.


12:40 PM Update: The NWS has issued a statement indicating that the public reported pea sized hail with the storm as it moved through northwest Palo Alto county. This is likely going to be the largest hail size seen with this storm in its' current state, as it does appear to be weakening as it continues eastward.


12:25 PM Update: A broken line of thunderstorms moved into the state late this morning, affecting mainly extreme northwestern Iowa. This line strengthened as it entered areas that held some instability in place with broken clouds earlier in the morning. It has since passed through areas of Dickinson and Clay counties before becoming severe warned as it entered Palo Alto county. This warning continues for northern Palo Alto county until 1 PM, the storm continues to stretch from the east of Wallingford, IA south/southwestward to the west of Ruthven, IA. The main area that may be impacted by some small, and potentially severe hail, is located to the southwest of Graettinger, IA. This storm is moving to the east/southeast at approximately 35 mph and will continue to move through Palo Alto county for the next half hour.