Stormy Pattern Developing - Excessive Heat - Then Cooler
By Justin Poublon
July 16, 2019 - 2:00 PM CST | 1,255 0
The rest of the week will feature excessive heat and storminess, ending in a cool down Sunday into next week.
It's not just the air temperature which could reach the lower 90°s (common in summer). It's the humidity, moisture, and dew points that will be noticeably thicker. Typically a dew point of 60°F or greater can be considered uncomfortable and common in mid-summer. 70°F+ is darn right oppressive no matter where you are. There has been more moisture in the region this summer due to heavy rain across the midwest/plains, late & snowy winter, and slow evolving summer AMO. Lately the remanants of tropical storm Barry dragging moisture north. This has contributed to a very slow severe weather season in Wisconsin so far but I wouldn't write the season off yet.
Strong Westerlies and Low Level Jet Intersection
In addition to the excessive heat, a reinvigorated mid-upper level jet and stronger dynamics will help to organize and drive t-storm complexes Weds PM through Saturday. Still can't be very specific/detailed but at least we can share some meteorology context behind what's happening. The low level element is important because it is loaded with moisture. As these two jets interact it will kick off thunderstorm complexes across the state. This setup is not rare for July; it's mainly the combination of westerlies and oppressive humidity that intrigues me.
The big picture suggests it will be much wetter than average over the next five days (see below)
Strong to Severe Storms Possible Weds PM to Saturday
I gave all outlooks this week a lower t-storm threat zone just to start. I will escalate as needed. Also the timing and details are always subject to change. We are going to challenge ourselves with trying to nail these things from several days out. The images will not be updated so if you are reading this later this week please check out our Member Forecast page.
We are likely to see thunderstorms Wednesday PM into Thursday AM. There are two scenario's depending on what happens with Wednesday daytime storms to the west. Last time we had more than one scenario's the end result was a blend between the two. We'll see this time. Some could be strong to severe, possibly widespread. You can read the Weds PM - Thu AM Members only discussion here.
Assuming Wednesday PM into Thursday is a widespread event, Thursday night will probably be more localized. Models keep the warm front across central WI. Isolated to scattered develop possible somewhere across Wisconsin as excessive heat/humidity pushes north during the early evening or overnight hours. Nothing could happen too due to weak forcing but models have been consistent with what I've mentioned above. You can read the Thursday Members only discussion here.
The warm front will still be in place across Wisconsin Friday with excessive heat to the south of it. Where that front is exactly cannot be known right now. It won't take much to touch off strong to severe thunderstorms. Question is where specifically? Hmm... Will keep an eye on it. This could be another widespread event. You can read the Friday Members only discussion here.
Sandwiched between the heat, humidity, and storminess of the week and approaching cooldown. It's possible by this point the warm front will have been shoved into southern WI or perhaps northern Illinois/Iowa? Plenty of uncertainty here but my guess is for continued storminess at least Saturday. Excessive heat and humidity still on the table across the south. A more organized low pressure system will take aim late this weekend or Monday
Big Cooldown To Follow
TV and mainstream news loves to pump up the heat, but a relatively bigger cooling period is ahead for next week. The upper level jet stream will bend down across the Great Lakes and Northern Plains. This might remind you of the historic cold outbreak in January or early March? Similar pattern. The difference in mid-summer is this contributes to very comfortable temperature and low humidity, borderline chilly at night!? Not as exciting/newsworthy as a heat outbreak I guess.
Thanks for reading and I will keep you updated!
Unfortunately this is the most turbulent time of my life. Anxious waiting, anticipation, uncertainty, and stress. I am not myself but it's temporary! Things will work themselves out soon. I've been called to action and ready to get my hands dirty. All I really want to do is crush this. Lets go.