281
FXUS63 KGRR 081026
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
626 AM EDT Tue Sep 8 2026
.KEY MESSAGES...
- Showers/storms tonight/Wednesday
- Low chance of showers Saturday
- Stronger system possible Monday
&&
.DISCUSSION...
Issued at 308 AM EDT Tue Sep 8 2026
- Showers/storms tonight/Wednesday
A cold front stretches from eastern North Dakota to central South
Dakota. Radar and IR imagery shows abundant convection firing
ahead of the front currently. As the front approaches Michigan
tonight, we`re likely to see showers and thunderstorms move over
the far northwest cwa late this afternoon and slowly move south
across the cwa tonight and Wednesday. All of the ECMWF ensemble
members show precipitation. Upper level flow is largely parallel
to the front so we`re not going to see the front plow through
quickly.
A nocturnal LLJ will move over the cwa tonight advecting in
moisture-rich air from the south; pwats climb to around 2 inches,
which could result in moderate to locally heavy rainfall. However,
MUCAPE is only a couple hundred j/kg. Thus thunderstorms may not
be very robust and severe storms are not anticipated. RRFS model
data has back off on thunderstorm strength during the past couple
of model runs. That said, bulk shear values are in the 30-40kt
range tonight and a bit higher Wednesday which may allow for
locally stronger cells. Total qpf expected is a quarter inch or
less south of I-96 and a quarter to two thirds north of I-96.
Precipitation will diminish Wednesday afternoon as the front moves
south and high pressure begins to move in from the northwest.
- Low chance of showers Saturday
Another front will approach Saturday, but the strongest dynamics
with the system will be north in Canada, closer to the low over
James Bay. Moisture return ahead of the front also isn`t stellar,
so we only have 15-20 PoPs in the grids for this.
- Stronger system possible Monday
A better chance of rain will arrive next Monday when another front
approaches. This time, though, there`s a much stronger shortwave
accompanying it. Models show a tighter pressure gradient which
could mean a breezy day ahead of the system. Most of the ECMWF
ensemble members show precipitation with this system, and a few
point toward heavy rain; there`s time to flesh out the details as
it is almost a week away.
&&
.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 625 AM EDT Tue Sep 8 2026
As a cold front moves closer today, we`ll see an increase in cloud
cover and a gradual lowering. However, VFR conditions are still
expected throughout the TAF period. Light rain showers will be
possible near the I-96 terminals after midnight.
&&
.MARINE...
Issued at 308 AM EDT Tue Sep 8 2026
Southwest winds will increase today ahead of the next cold front
that will move through Wednesday. Highest waves will be north of
Holland and we issued a small craft advisory and beach hazards
statement for this. Waves will increase to 3 to 6 feet and become
hazardous to small craft this afternoon before decreasing
Wednesday night.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 2 PM EDT this afternoon through
Wednesday evening for MIZ037-043-050-056.
MARINE...Small Craft Advisory from 2 PM this afternoon to 8 PM EDT
Wednesday for LMZ846>849.
&&
$$
DISCUSSION...04
AVIATION...04
MARINE...04
NWS GRR Office Area Forecast Discussion
