Severe Weather (Aug. 21)

10:15 Update: Thunderstorms moving into northeast Iowa have increasingly become severe with the potential for damaging winds. Floyd, Butler & Chickasaw counties are currently under warnings. Counties to the east of those should keep an eye/ear out to local information as the storms head their way. Another storm in Sac county has also became severe with the potential for damaging winds and large hail. Expect the next couple of hours to feature pulses of severe storms, while a majority of the storms say below severe limits. Nonetheless any storm could be capable of some small hail and wind gusts to 50 mph, dangerous cloud-to-ground lightning and torrential rains capable of causing flash flooding.

9:45 PM Update: A line of thunderstorms over Iowa continues to move to the east, mainly non-severe at the moment. It extends in from MN to Mason City to Hampton, then back to Ida Grove where the line then becomes less defined. Storms may pulse up and become severe for the next couple of hours, mainly capable of moderate sized hail and damaging winds up to 70 mph. The main concern with these storms is now the flash flooding, especially over parts of central Iowa where storms are beginning to 'train' or follow the same path. Several counties are already under Flash Flood Warnings, several more may be added as the night continue.

8:10 PM Update: Severe Thunderstorm Watch #635 has been issued for portions of northeastern Iowa. Thunderstorms will continue to develop and spread eastward into the overnight hours. Expect mainly damaging winds and large hail as the severe threats as the storms will be mainly linear or multicellular in nature.

7:50 PM Update: Warnings continue to be issued in northwest Iowa as storms eastward, now beginning to enter portions of north-central Iowa. Severe thunderstorm warnings are issued for Woodbury & Palo Alto counties; more recently a Tornado Warning has been issued for Humboldt and Pocahontas counties. The towns of Rolfe, Bradgate and Ottosen are in the path of this storm and possible tornado. Currently only radar has detected rotation, no on-site reports have been received.

7:00 PM Update: Tornado Watch #634 has been issued for much of the northwestern quarter of the state. This watch is in effect from 6:50 until 2 AM tonight, thunderstorms have already initiated ahead of storms in NE/SD over northwestern Iowa. Cherokee county is currently under a severe thunderstorm warning as a storm is capable of nickel sized hail. Expect storms to continue to strengthen over the next couple of hours as the cells move northeast. Storms should congeal into more linear segments capable of damaging winds and large hail, possible tornadic condition could still exist late tonight, but not likely.

4:45 PM Update: A Severe Thunderstorm Watch & a Tornado Watch have been issued for portions of Nebraska and South Dakota. The tornado watch is in effect until 10 PM for the counties included, hugging the northwestern Iowa county lines. Thunderstorms should develop in the watch area within the next couple of hours and move to the east/northeast into the state just after sunset. Expect that a severe or possibly a tornado watch will be issued later this evening for some portions of the state as storms begin to threaten the area. Later updates will continue to reveal any information on possible storms & severe weather.

10:15 AM Update: More severe weather is possible this evening and overnight tonight across the state. Thunderstorms expected to develop over central Nebraska once again, moving eastward into Iowa this evening. There is once again a highlighted area that may see a better chance at some of the individual cells capable of large hail and perhaps a tornado. This area stretches from about Norfolk, NE through Sioux City to around the Storm Lake, IA area; 30 miles north and south of that line. Other portions of the state may see thunderstorms as well, but there is no enhanced threats and the main concern may once again be damaging wind and some smaller sized hail. Updates on the severe weather tonight are possible once again...