As we hurdle towards spring, officially beginning at 10:50 PM Thursday, Iowa's weather tends to get pretty volatile. Case in point: the forecast this week. Our first round of severe will be possible Thursday.
The severe weather threat will be tied to a potent warm front that will move in Thursday afternoon and could be the catalyst for severe weather into the afternoon and evening. Afternoon temperatures will surge into the 60s south and 50s north with dew points pushing into the 50s and 60s south, meaning the air will contain a sufficient amount of moisture. Wind shear, the change in speed or direction of the wind with height, looks to be enough to develop supercells, or rotating storms capable of producing severe weather. Along the warm front will exist a chance for tornadoes where the low level winds are changing directions.
The last ingredient typically needed for severe weather is instability. Some models hint at an unstable atmosphere for tomorrow afternoon, especially if the clouds can clear a little bit prior to storm development. Ongoing storms and rain in the morning may hinder severe potential in the afternoon. Even without much sunshine, there may be enough energy associated with the system to give enough fuel for storms.
The big conditional question mark will be on the rain and storms in the morning. If those linger more into the afternoon, severe potential will be squashed.
Since there may be more people at home than normal and this year's severe weather awareness week hasn't happened yet, I wanted to give you a heads up on what to look for tomorrow, how to prepare, and how to stay weather aware.
Timing: A round of showers and thunderstorms will move through in the morning to early afternoon followed by a brief break in most of the rain. These storms may hold a marginal severe hail threat with heavy rain. Scattered showers and thunderstorms will redevelop in the mid afternoon through the evening as the warm front moves through. This second round of activity will have the best chance of being severe from 3 PM to 10 PM.
In the animation below, the timing and location of the storms may vary from what is shown.
Hazards: All modes of severe weather possible including: damaging winds (58+ mph), large hail (1"+) and even a few tornadoes. Heavy rain will also be possible and may lead to a rise in river levels.
Where: Most of eastern Iowa as well as central and southern Iowa.
How to prepare: Closely monitor the forecast via KWWL through our app and on television. Changes are possible (and likely) as we make our way through the next 24 to 36 hours. The best way to stay ahead of the storm is to know the forecast and what the day might hold.
Have a way to receive watches and warnings, including a weather radio. Wireless emergency alerts may be automatically sent to your phone depending on your location and the KWWL weather app will send you alerts as well. Once a warning is issued, KWWL will break into programming to keep you aware of the situation.
Take time before the storm to note where you would take shelter if a warning is issued (imminent threat), especially if you live in a mobile home. Questions you should ask are: what would the evacuation route be, what is the communication plan for each family member, are all family members (including pets) accounted for in the plan, and do I have an emergency kit ready? A watch is issued when conditions are favorable for severe weather over the next several hours. Be on standby to take action as soon as a warning is issued.
For more, here are last year's severe weather awareness topics from KWWL:
5. Flash floods
While severe weather doesn't typically take place this early, it has happened in years prior including tornadoes.