National Weather Service United States Department of Commerce

Forecast commentary -

Conditions across southeast Michigan will continue to be quiet through the weekend. Only minor
weather issue is the chance for showers this afternoon. A quick moving shortwave moving through the
longwave troughing is what will bring a chance for showers to the area, especially locations in
eastern portions of the Thumb. This wave will also bring in more cooler air resulting in high temps
only in the 60s to around 70 degrees today. While temps do moderate somewhat through the remainder
of the week into the weekend, they will remain a little below normal for this time of year.

High pressure coming down from Canada then builds in behind the departing trough as heights begin to
build across the region. Dry conditions will hold through the weekend before the potential for
another wave comes in early next week. Lots of uncertainty going into the extended forecast for the
beginning of next week, along with the potential tropical systems. This means the area may or may
see some tropical moisture depending on how they interact with the overall setup across the region.

. . posted at 324 AM EDT Thu Aug 24 2017

Quiet stretch of weather at least through the weekend as expansive area of high pressure tracks
across Ontario and the northern Great Lakes before stalling slightly over Quebec and the ne
Contiguous U.S. for a couple more days. Positioning of the high will send steady feed of cool and
dry air into the region. This will result in temperatures remaining a few degrees below normal for
the coming week. Normal highs are around 80 and lows are around 60.

The mid levels are a bit more exciting with a compact vort max diving through southern Michigan
Thursday. This wave is the next trough to rotate around the dominate upper level low lifting ne out
of western Quebec. This wave will increase cloud cover over se Michigan Thursday morning with a
small chance of seeing some isolated showers in the afternoon. The early morning clouds may prevent
any shallow fog from developing. Moisture depth is thin with precipitable waters only around a half
inch. Better chance of precip will occur across the eastern Thumb as northern flow behind the trough
axis excites lake effect clouds and possibly some showers as cool air advects over the warm lake.

After Thursday the high will take a firm grasp over the area with a mid level shortwave ridge
working into the Great Lakes. Upper level flow becomes very weak across much of the country as
strong westerlies emerge across Canada. This is where model solutions start to diverge. A mid level
wave will cut off over the midwest and try to drift into the state but may take a few days with no
steering flow. One thing to watch will be remnants of the developing tropical system harvey over the
western Gulf of Mexico. Airmass will be quiet dry early next week when the trough tries to drift
across lower mi, but if the system finds itself a bit further north and east after making landfall,
the trough may be able to tap into it for moisture.

. . posted at 355 PM EDT Wed Aug 23 2017