Rain is going to be 'pretty persistent' into next week

A flood advisory for parts of southeast Michigan has expired but additional rainfall is expected through the weekend, adding to totals topping several inches, the National Weather Service said Friday evening.

"It's going to be pretty persistent into next week," meteorologist Trent Frey told The Detroit News.

Downpours moving east had mostly pushed out of the region by 10 p.m. but the weather service predicts more showers and thunderstorms after 3 a.m. as temperatures hover near 70.

There's an 80% chance of more precipitation on Saturday as highs reach the 80s with gusts as high as 25 mph, the weather service said. The forecast for Sunday and Monday is nearly identical.

"We’ve got a stalled frontal boundary that is draped over the central Great Lakes," Frey said. "We’ve got this humid air mass that is able to trigger all these showers and storms."

Before the flood advisory expired at 9:30 p.m. for parts of Macomb, Oakland, Wayne and Washtenaw counties, the system brought surprisingly high rainfall, amounts and flooded some roads Friday night.

Some 2.67 inches fell in four hours in Farmington Hills, leaving a total of more than 3.3 inches through 9 p.m., the NWS reported, and Shelby Township bested that with 3.87 inches.

Other totals included 4.14 inches in Pontiac, 4 inches in Armada, 2.87 inches in Troy, 2.65 inches in Bloomfield Hills, 2.7 in Westland, 2.01 in Royal Oak, 1.42 in Ypsilanti, 1.21 inches in St. Clair Shores and 1.05 in Romulus, according to the website.

More than 1.69 inches of rain had fallen in Ann Arbor by 7 p.m., with about 1.10 inches arriving in a 30-minute period and flooding was reported on some streets, according to the NWS website.

The Michigan Department of Transportation reported flooding on the Southfield Freeway and Interstate 96 in Wayne County. 

Michigan State Police reported standing water on Interstate 696 near Telegraph, the right northbound lane of I-75 at Nine Mile as well as numerous side streets.

"Remember, don’t drive through standing water or around barricades," the agency said on Twitter. "You will never know how deep it is till it’s too late."

The lingering wet weather raises the potential for flooding across the state.

"Rounds of heavy rain have begun across Lower Michigan, and will continue through early next week," the National Weather Service's Grand Rapids office said. "All rivers will see significantly rising water levels. Flooding on some of our rivers is possible as early as this weekend. The best estimates are that 2-4 inches of rain will fall across a wide area in Lower Michigan. Because these rounds of rain will include thunderstorms, local rain totals of 5 inches or more are likely by the end of the weekend."

On the state's west side, a flood watch is in effect through Sunday morning for Muskegon, Montcalm, Ottawa, Kent, Ionia, Allegan, Barry, Eaton, Van Buren,

Kalamazoo and Calhoun counties.

In southeast Michigan, "very moist conditions will hold through at least the weekend," the Detroit/Pontiac office of the National Weather Service said. "This environment combined with passing low pressure systems and upper-level disturbances will bring several rounds of on and off heavy rain showers in addition to periods of embedded thunderstorms. Shower and thunderstorms will be likely today with best chances occurring (Friday) afternoon and evening."

Early Friday afternoon, the weather service in Detroit raised the chances for severe weather in southeast Michigan to a "slight risk" up from marginal. "Main threats will be damaging wind gusts, heavy rainfall, and the potential for isolated tornadoes," it said.

Rain amounts will be dependent on storm activity, the National Weather Service says, and the system will linger into next week, perhaps as late as through Wednesday.

"Through the weekend there is a risk for some severe weather and particularly for heavy rain and flooding," the Grand Rapids office says. "The time frames of greatest concern would be today and then again later on Saturday."