Summer is definitely starting a bit early this year across the state as our “summertime-type weather,” consisting of 90s for highs, dew points in the 70s, popcorn showers and thunderstorms, and mesoscale convective systems begin ramping up in frequency.

It will be another toaster across the state Tuesday with high temperatures likely ranging from the low 80s northwest to the low 90s southeast. Additionally, dew points will cause for another humid day once again – sitting in the low-to-mid 70s. This will create moderate-to-high instability across much of the state, in the likes of 2500-3500+ J/KG CAPE in the far southwest. This type of environment is easily conductive for severe thunderstorm develop to occur. Shear will also be modest enough for organized development.

One issue, as it always seems to be with severe weather events in Iowa, is convection from the previous day affecting the amount of instability available. Hence, the amount of confidence at this point is not as high as it could be. Rain-cooled air and cloud debris can and has frequently impacted forecasts for later in the day – this is something that will need to be monitored and tweaked as we look at things later tonight. If enough peak heating can occur, storms should be able to re-fire and take advantage of the ripe environment around. Beyond this, further issues such as boundaries will need to be looked at.

The primary threats with this system will revolve around large hail to 2-3″ and damaging winds to 70 MPH initially. An isolated tornado-or-two also cannot be ruled out; however, this threat will be somewhat marginal with the lack of a lot of veering with height or vertical shear. A few storms may be able to get enough rotation to form a tornado, though these will not be long-lasting or violent by any means.

During the overnight hours Tuesday, cells should cluster into a few different areas of activity, as a squall line. As this occurs, the primary threat will transition to damaging winds, potentially upwards of 80 MPH. This is very typical of the summertime systems we see here in Iowa, in regards to the upscale growth of the system into a damaging winds-producing squall line. In any case, the threat for severe weather will likely continue into the night as it moves east-to-southeast across the threat area.

The Storm Prediction Center currently has an enhanced risk of severe weather outlined for much of the state, generally south of Highway 3 and west of Interstate 380/Highway 218. The greatest threat will occur in the southwest with continued issues as you go east. I would expect that the northernmost portions of the enhanced risk may get downgraded to an elevated risk as the overall threat as aforementioned is moreso to the southwest.

It’s important to highlight that flash flooding will begin to become more of a concern in areas where rainfall has been more abundant as of late. The Weather Prediction Center has an elevated concern for flooding over nearly the entire state. Those over the northernmost sections of the state, especially in low-lying areas and places near rivers, creeks, and streams should monitor conditions carefully and be prepared to take appropriate actions if necessary.

Stay tuned to the Iowa Weather Network for the latest information!