Snow has melted quickly over the last couple of days. While rivers and streams are high, no serious flooding has occurred because there wasnâ??t that much precipitation this spring and the melt has been gradual. That wasnâ??t the case 29 years ago.
Early spring 1985 was a snowy one in Upper Michigan. March was â??book endedâ?? by two major storms. The first, in the early part of the month, was a mighty cyclonic whirl that buried vast sections of the Rockies and Plains. It brought over 20 inches of snow to the NWS site in Negaunee Township. The second storm dumped just as much; it began on the last day of March and extended into April Fools Day.
Wintry weather then held on through the first week of the fourth month. Another half-foot of wet snow fell on the 6th, leaving a thick, waterlogged covering that would inevitably melt at some point over the next few weeks. The pattern began a gradual change; a deep, cold trough that dominated the early part of the month slowly lifted out and weakened, while the flow over Upper Michigan brought milder air in off the Plains (Images 1 above). More typical spring weather followed the second week, promoting some slow melting of the dense snow pack.
The natural evolution of the spring pattern brought drastic changes during the third week. A mild, moist, southwesterly flow developed, which led to thunderstorms (Image 2). Heavy rain poured into the remaining snow cover over the Upper Peninsula. Over three inches fell on April 19. The rain was immediately followed by record warmth.
Floodwaters made it in to hundreds of residences along rivers and streams in central Upper Michigan. Marquette County bore the worst of the snowmelt flood; at its peak, officials estimated as many as 500 homes were affected. This figure did not include summer camps. Numerous roads were closed by flooding and at least one bridge was washed out on a county road. In Alger County, four secondary roads were washed out.
Some officials termed the Flood of â??85 a 100 year flood: a flood of historic proportions that is likely to occur on average just once every hundred years. The elements needed for a deluge like this were all in alignment; a thick, waterlogged snow cover, followed by heavy rain, followed by record heat. Ironically, these same conditions lined up in a similar fashion over a good share of Upper Michigan just 17 years later in 2002.
Our spring melt will slow down this week as colder air takes hold on north winds starting tonight. Late this week, a storm now off the West Coast will move across the northern U.S. This system will likely bring us cold rain and even some wet snow late in the week.