A long shot for a chase on Saturday, with the main event for eastern Iowa on Sunday. There are a number of questions surrounding this threat. The biggest of which is the warm front that will set up shop somewhere in Iowa on Saturday.
Of secondary concern is a cap that any storm development will have to overcome. This could not only limit the area of severe weather development but also delay it, leading to a stormier evening. Either way, we will continue to monitor the run to run trends of the models as the weekend draws closer.
Now, onto Sunday. The Storm Prediction Center has another extended forecast risk out, this time for eastern Iowa. The SPC also warns of a more widespread severe weather event as a shortwave pushes through the upper Midwest.
As of now this appears to be the primary chase day for us. Besides the shortwave, forecasters will again watch the cold front we’ll be monitoring on Saturday. There is also a cold front/dry line setup to our south that could also trigger storms. Of course not all of this is our concern, but the eventual development along any of these boundaries could greatly impact the severity of development in our area.
This setup, although similar to last week, appears a bit more promising. There are fewer doubts that the warm front will make it into Iowa. Last week the front really set up shop in Missouri, limiting our severe threat. This time it appears set to move much further north and the timing of the system looks favorable for Sunday.
Many have commented in recent days about the lack of severe weather nationwide in May. The chart to the left from Iowa Mesonet compares tornado and thunderstorms warnings from this year and last year nationwide. You can see a distinct drop in both thunderstorm and tornado warnings in June.
Unlike most “summer months,” there is still plenty of cold air to play with in the upper Midwest. With Iowa continuing a trend of below normal temperatures, our April-like conditions could lead to an increased threat of severe weather over the next few weeks.