First of all, Happy Memorial Day to everybody. Today is normally a day where many of you spend a lot of time outdoors. It was a beautiful start to the holiday with comfortable temperatures and plenty of sunshine this morning. However, strong to severe storms will make for a stormy end to this Memorial Day. We currently have the first round of thunderstorms making their way through. You can expect heavy downpours and frequent lightning with this round. The second round that arrives during the mid-afternoon is what we are concerned about.
That is all because of a lifting warm front. The cold front that came through yesterday stalled out over central Illinois and then became a warm front. As we progress into the afternoon, this warm front is going to lift northward close to or over our region. Behind the warm front is the area of the low pressure system known as the “warm sector”.
This is defined as the area between the cold front and the warm front of the low. This is where the wind flow will be out of the south/southwest and where the transport of moisture from the Gulf of Mexico happens. It is in the warm sector where the storm potential is at its greatest because of how fast the atmosphere is known to recover or recharge.
At this time, the Storm Prediction Center has all of our northern Illinois counties under an Enhanced Risk (a 3 out of 5) for severe potential. This means that numerous severe thunderstorms are possible, with any one of them capable of producing all severe weather hazards For today’s set up, thunderstorms (some strong to severe) are expected to develop in eastern Iowa and northwest Illinois around 2 PM and track into an environment favorable for tornadoes, damaging winds, and large hail.
Here is the 8 AM tornado probabilities from the Storm Prediction Center. The 10% hatched tornado contour (yellow shaded area with black lines) includes a majority of our northern Illinois counties including all of Carroll, Ogle, Lee, Dekalb, and Whiteside county. If you know someone inside the black outlined area, make sure that they also have a plan ready to go and know the forecast.
While celebrating Memorial Day today, it is also important that you are weather ready. Have somewhere safe to take cover in case a tornado warning is issued. Please do not rely on outdoor tornado sirens to alert you of tornado warnings. They are only designed to be heard if you’re outdoors. It is also important to have multiple ways to receive watches and warning in case severe weather moves into your area.