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Frost is on the way
The F-word is back in the forecast.
After what's been one of the hottest, driest summers on record in some parts of the country, the key word in the weather this week is frost. Parts of the northern Corn Belt and Midwest could see temperatures down into the 20s this week just days after Monday's 90-degree-plus high temperatures in more central points in the nation's midsection and south, forecasters say.
The end of the growing season will definitely arrive later this week in northern and central Minnesota as well as northern Wisconsin as a cold front trails the system that has temperatures in the upper 80s and lower 90s in the Midwest Monday.
"With this cold air, some frost is expected across northern and central Minnesota and northern Wisconsin, where temperatures will drop below the freezing mark and the growing season will likely come to an end," says MDA EarthSat Weather meteorologist Kyle Tapley. "The risk is to the cold side, and the freezing line could reach as far south as far northern Iowa and the Wisconsin/Illinois border on Friday morning."
Though the sharply cooler temperatures will be widespread, that's just within frost range. The real freeze threat will be limited to a few spots, according to Monday's Ag Weather report from Commodity Weather Group (CWG).
"Cold air drops into the Midwest this week, leading to frost in North Dakota, Minnesota, Wisconsin and Michigan," according to CWG on Monday. "The coldest conditions are likely to occur on Thursday morning in Minnesota. While isolated pockets of freeze damage are possible, there is only a 25% probability of an extensive damage event in that area."
The earlier-than-normal frost comes at a bad time for Minnesota, where the crops -- especially the state's soybeans -- could get nipped. "On Thursday morning, I would look for lows of 32 degrees or lower for the far eastern Dakotas, far northern Iowa, western Wisconsin, and just about anywhere in Minnesota with some places getting to the upper 20s," says Freese-Notis Weather, Inc., meteorologist Craig Solberg. "A few scattered locations in Michigan and Wisconsin may reach 32 or a little lower on Friday morning as well. With NONE of the Minnesota soybean crop dropping leaves as of September 4 and with only four percent of the Minnesota corn crop mature at that time, it looks like that cold will cause damage (at least in quality if not quantity) to the crop in that state."
Even if the frost does damage some fields, that's not expected to be widespread. Even so, though, if you've got crops that have some developing to do before they're ready for harvest, your window could be closing, says University of Nebraska Extension state climatologist Al Dutcher.
"Because of the spring planting delays due to excessive moisture and below normal May temperatures, a considerable amount of acreage in the frost/freeze forecast area has not reached physiological maturity. Many of these areas need to see normal temperatures into early October to escape significant damage," Dutcher says. "Even if the freeze doesn’t occur, crop maturity will grind to a halt as daily highs from Sept. 14 to Sept. 22 will struggle to reach the lower 60s."
The cold snap -- which on Friday could send Minneapolis below 38 degrees, the record low for that date set in 1873 -- won't be limited to the northern climes, either. Friday will also see temperatures down to the lower 40s in teh Mississippi River valley south to around St. Louis, according to another report from MDA EarthSat.
"The unseasonable cold reaches as far south as the Mississippi Valley these days, with St. Louis falling into the 40s Friday morning as well," according to MDA. "The cold front moves into the Northeast Friday through Sunday. While not as extreme as over the Midwest, temperature anomalies will drop considerably here as well."
Adds MDA meteorologist Bob Haas: ""This cold shot will be the first sure sign that winter is not too far off, as widespread 30s appear likely in the Midwest by later this week."