Residents along Wisconsin’s Lake Michigan shoreline will experience yet another rare cold weather phenomenon today.
A “pneumonia front” is passing over the western Lake Michigan shore, according to the National Weather Service Milwaukee/Sullivan office.
Bob McMahon, a senior forecaster for the NWS, said the front isn’t unusual in spring and is accelerated by chilly conditions on Lake Michigan as the water recovers from a frigid winter. The term was first coined by the Milwaukee Weather Bureau office in the 1960s and describes an extreme change in temperature that can result in flash thunderstorms or a microburst.
“The waters are only in the 40s at best and still some 30s,” McMahon said. “What we refer to as a pneumonia front is a push of cooler, dryer air that comes down the lake. It is chilled by those cool waters — a combination of the frictionless environment and smooth surface of the water.
“There are no hills to impede its path down the lake.”
That causes the front to move quickly along the lake front where temperatures can drop more than 20 degrees in a short amount of time. Inland temperatures aren’t expected to drop as dramatically.
“There is a northeast wind along the lake shore right now. We have temperatures here at the Milwaukee/Sullivan office cooled down to 66,” McMahon said. “We were in the mid-to-upper 70s. The temperatures toward the lake, Milwaukee County and into Kenosha County are in the 50s right now.
“There’s a 20-degree temperature difference from the warm side of the front and the cold side.”
Lake Michigan beach-goers decked out in shorts and t-shirts will notice the difference immediately and everyone from a corridor that extends up to Marathon County and down to the Wisconsin/Illinois border will experience a dip in temperature.
“It’ll probably be sometime tomorrow before that wave moves far enough west to allow the cold front to sag south and high pressure to fill in,” McMahon said. “It will kind of hang up in that I-94 corridor by morning.
“Everyone is going to see lower temperatures but not that dramatically cold that far inland.”
Temperatures in the Fond du Lac area are forecast to be in the mid-70s with a 10 degree change caused by the front. No severe weather is expected ahead of the front. There is potential for small hail, but none has been reported along this cold front.
“Fond du Lac, Sheboygan and Ozaukee are pretty much entrenched in the cool air already,” McMahon said. “It’s a little more stable and less susceptible to heavy thunderstorms.”
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