Summer 2025 may well be remembered for a couple of things – warmth, and wet.
After a winter that saw St. Michael, Albertville, Hanover and Otsego fall more than 5 inches behind in terms of precipitation – relatively about 20 inches of wet snow – the NWCT area has more than made up for it with storms that have ripped through the area since early June.
Wednesday, July 23 saw Wright County get swamped with downpours in the afternoon. Sunday, July 27 brought another round of storms in the evening hours, this time with high winds, hail and, again, heavy rain in the Buffalo/Hanover area that saw an inch of rain in just minutes.
Today, Monday, July 28, seems like it will host more of the same. With temps in the 80s around noon – the heat index was well into the 100s. That’s due to air saturated with humidity, making conditions ripe for severe weather tonight.
The National Weather Service in Chanhassen and Novak Weather have both pointed to the possibility of a derecho storm – heavy winds that are tornado-like, but come in straight line winds. More than 100 mph winds could come with such a system, as well as downpours that can flood streets in mere minutes.
NWCT will rely on our Facebook feed to run any warnings by you later today.
Here’s
the statement from NWS:
There are still several scenarios on what could happen with storms later today in Minnesota and Wisconsin, and we will take a bit of a deeper dive into some of the modeling within this post. At this point, we are sure everyone has seen the model output from the HRRR yesterday from various outlets showing a potential Derecho over portions of Minnesota this afternoon and evening, including potential winds over 100mph. While this is within the realm of possibility today, it is far from the only potential outcome and taking a single model forecast as fact is a recipe to be disappointed.
The attached picture is from the 12z High-Resolution Ensemble Forecast (HREF) showing what is called Postage Stamps of all the ensemble membership Composite Reflectivity at a specific time, in this case 00z or 7pm this evening. Each box contains a separate model run for a total of 9 different forecasts from 5 different models, which includes two runs of the same models from different time steps, referred to as time-lagged members. As you can see from the forecast reflectivity, there are significant differences in not only location, but also structure and shape of storm reflectivity depending on which model you look at. Even the time lagged members, which are the same models run 12 hours apart, show some fairly significant differences. What this means is there is still low confidence in the placement and timing in regards to storms later, especially as storms currently ongoing in North Dakota will have a large role to play in what happens in Minnesota later on.
So what is actually going to happen? We have plenty of heat and humidity to give us a large amount of instability to work with, so we expect to see thunderstorms today. We also have a large degree of deep-layer atmospheric shear, which would favor a linear storm structure as storms form and move across the region. The atmosphere typically likes to track storms along a gradient of instability, and today that gradient looks to roughly follow the Minnesota River Valley from western MN to Mankato or south-central MN, which is also what the majority (but not all) of the morning guidance is showing as the most likely track to a line of storms. We have the variables in place to produce winds in excess of 80mph, however not everyone who sees storms will see the peak strength.
Thank you for reading, and please stay safe today!
