Otsego, Michigan Weather Forecast Discussion

675
FXUS63 KGRR 210002
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
Issued by National Weather Service Detroit/Pontiac MI
802 PM EDT Sat Sep 20 2025
.KEY MESSAGES...
- Scattered showers and Storms this evening into Sunday morning
- Showers and Storms Sunday afternoon, some could be strong to
  severe
- Continued chances for showers and storms through at least
  midweek
&&
.DISCUSSION...
Issued at 340 PM EDT Sat Sep 20 2025
- Scattered showers and Storms this evening into Sunday morning
As the saying goes, drought begets drought, until it begets
flood. While we are not expecting flooding, a period of tumultuous
weather is ahead. A positively tilted upper level ridge will be
advected to the East as a deepening trough drives through the
upper Midwest and into the Great Lakes. As that trough pushes
east, it will bring scattered showers this evening and overnight
into Sunday morning. There remains enough instability for isolated
storms this afternoon and evening, though that threat will be
mainly along the lakeshore.
Scattered showers will continue early Sunday morning. The best
areas of rainfall will be along and West of US 131 with streaks of
1 to 1.5 inches possible. East of US 131 precipitation this
evening into tomorrow becomes sparser, however a quarter of an
inch rainfall to the US 127 corridor is possible.
- Showers and Storms Sunday afternoon, some could be strong to
severe
There will be a flow shift from the current southeasterly winds
tomorrow. Winds will shift to the southwest by tomorrow afternoon.
That flow will bring in unstable air that will coincide with
halfway decent shear through the mid-levels. While the LLJ is not
overly strong, it should be strong enough to sustain storm
development.
The above features along with potentially 7 to 8 C/km Lapse Rates
and upwards of 1500 J/KG of CAPE will create an environment for
storms tomorrow afternoon. While the best shear should move fairly
quickly to the east, there is a window Sunday afternoon into
early evening for strong to possibly severe storms. Due to this
SPC has most of Lower Michigan in a marginal risk for tomorrow.
While scattered storms will be possible across southwest Michigan,
the best chance will be south of the I 96 corridor, especially
along the I 94 corridor.
- Continued chances for showers and storms through at least midweek
A positively tilted low should continue to move along the
Canadian border through the first half of the week. This will
bring a ribbon of moisture that will stretch across Michigan
bringing periods of showers, along with cooler temperatures
through midweek. Best chances for precipitation will be through
southern Lower Michigan. Models begin to diverge mid week on
passage of the low. EC keeps it to the south, with the GFS
bringing it further north. Some Ensemble runs of the EC bringing
it further north, so a chance for showers and storms will be
possible Thursday into Friday.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 754 PM EDT Sat Sep 20 2025
Scattered showers and thunderstorms spreading across terminals
early this evening may bring reductions in CIGS and VSBYs down to
MVFR and possibly IFR at times from heavy rain. Thunderstorm
activity should wane into tonight, but isolated to scattered
showers likely to linger across majority of terminals through
much of the night with the nearby warm front. Outside of shower
activity tonight, ceilings will be predominately VFR at around
5-7kft and winds out of the east to southeast to 10 knots or
less. Increasing coverage of showers and thunderstorms redevelop
after 12Z tomorrow morning.
&&
.MARINE...
Issued at 340 PM EDT Sat Sep 20 2025
Scattered thunderstorms are expected over Lake Michigan through
this evening. Some could produce small hail and wind shifts with
gusts over 30 knots. An isolated thunderstorm over the lake also
cannot be ruled out on Sunday. Waves outside of thunderstorms are
expected to be around 1 to 3 feet Sunday and Monday with generally
south/southwest winds.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Ceru
AVIATION...CAS
MARINE...CAS/Thomas

NWS GRR Office Area Forecast Discussion