A very active weather period is ahead this week with several rounds of showers and thunderstorms in the forecast through the weekend, including severe weather chances. This will make for a very challenging forecast as a whole as minor differences in a single day’s forecast can have an impact on the rest of the week.
A look at the radar this morning shows a large mesoscale convective system (MCS) over the northern-to-central Plains pushing southeastward. The southern extent of the system is weakening fairly quickly, while the main squall around the Sioux City area remains healthy. A gradual weakening of this precipitation will be seen by mid-morning. Temperatures right now are ranging from the mid 50s in southeast Iowa to the low 60s in northwest Iowa – these will climb quickly by noon with highs sitting in the mid 70s west to the mid 80s east.
This Afternoon…
Additional thunderstorm development is expected this afternoon and evening in western Iowa. Some uncertainty exists in regards to the favorability of severe thunderstorms, due to the ongoing MCS to the northwest. Any lingering cloud cover could impact peak heating in the risk area, and therefore impact instability as well – making this risk conditional on if we can get clearing or not by early afternoon.
Nonetheless, whatever boundary that is left behind will set the stage for thunderstorm development later today. Models are pegging this to be draped from southwestern Minnesota through southeastern South Dakota to northeastern Nebraska. Storms should fire in the mid-afternoon hours and continue through the evening hours as things evolve into yet another mesoscale convective system. The overall severe parameters today are a bit on the low-side with the greater issues being seen farther south. Though, some cells may produce some marginally large hail and perhaps an damaging wind gust. The SPC has an elevated risk outlined for these areas. Flooding issues are possible in areas that have already received rain this morning.
Tuesday…
Active pattern will continue Tuesday as the bountiful amounts of moisture and instability continue. Wildcard with all of these proceeding day events is where the boundaries get laid out and how they will interact with that days forecast. A warm front will also be setup across the region, potentially hanging around southern Iowa. The placement of all of this will contribute to determining the highest risk areas Tuesday.
The MCS aforementioned from today will likely be ongoing in the early-morning hours on Tuesday. There isn’t a lot of confidence in regards to how long this system will stick around on Tuesday morning, and this will be crucial to know in regards to development Tuesday afternoon and evening. If precipitation and cloud cover remains around too long, which may be the case with moisture coming in from the southwest, the severe threat Tuesday afternoon will be greatly diminished. But if dry air can clear things out Tuesday morning, the threat will be good to go for the afternoon and evening hours.
The severe weather parameters for Tuesday look a bit better than today, if the correct variables work out. Plenty of moisture with strong shear and decent instability will be favorable for the development of supercellular thunderstorms, with associated threats of potentially very large hail and damaging winds. An elevated risk of severe weather has been posted for much of the state for this reason. Development should occur as the frontal boundary moves northward into the area in the mid-afternoon. The boundary will likely stall and storms will be ongoing through the night, though the severe threat will be over on a large-scale after sunset.
Wednesday…
As with prior days, showers and thunderstorms will more than likely be ongoing Wednesday morning across the region. With multiple systems being before Wednesday, a large amount of uncertainty exists in regards to the severe threat. Things will depend on how much the atmosphere can destabilize and be favorable for thunderstorm development. One-or-more mesoscale convective systems may occur, creating for a messy situation overall. Parameters and a strengthening low-level jet may spring up the threat for large hail and damaging wind. An isolated tornado also cannot be ruled out. Elevated risk exists essentially for areas along and south of Interstate 80 for this reason.
Thursday…
Another surface low and boundary will exist over the state Thursday, bringing the threat of scattered showers and thunderstorms into the area. Keep in mind, the exact severe weather threat area is definitely subject to change in the coming days as forecast confidence increases. The best threat on Thursday will be to the south where an enhanced risk exists, though some large hail and damaging winds will be possible to the north… depending on how things work out today and tomorrow. More details on this will be worked out as we get closer.
Friday/Weekend…
Severe weather will definitely continue into the week, though the SPC does not want to graphically denote any areas due to uncertainty. The surface low from Thursday will push east and continue severe weather issues across the region through the weekend.
Flooding is also a serious threat that will need to be monitored near the end of the week. Very heavy rain, potentially exceeding three-to-four inches, is possible this week, as shown in the featured image. Flash Flood Watches or Areal Flood Watches wouldn’t be surprising to see for the end of the week due to the continued precipitation forecasted. Those in low-lying areas or areas prone to flooding should monitor the forecast carefully over the next couple of days and be prepared to take appropriate action if necessary.
Stay tuned to the Iowa Weather Network for the latest information!