679
FXUS63 KGRR 221146
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
746 AM EDT Fri Aug 22 2025

.KEY MESSAGES...

- Fog and low clouds dissipating this morning

- Showers and thunderstorms Friday night and Saturday

- Much cooler Sunday-Tuesday with lake effect rain showers possible

- Moderating temperatures after Wednesday, rain possible Thursday

&&

.DISCUSSION...
Issued at 322 AM EDT Fri Aug 22 2025

- Fog and low clouds dissipating this morning

We expect fog and clouds to dissipate relatively quickly this
morning, yielding mostly clear skies, although as noted previously
we will see an increase in high clouds later today.

- Showers and thunderstorms Friday night and Saturday

Estimated QPF for this event is expected to remain below a tenth
of an inch. Convection is expected to remain sub-severe given its
expected passage during max diurnal convective stability. The
best chances for thunder would be in the afternoon from the US-127
region eastward.

- Much cooler Sunday-Tuesday with lake effect rain showers possible

Went above guidance PoPs Sunday and Monday given a continued strong
signal for lake effect rain. Our northwest zones may stay wet the
longest given a prolonged period of favorable trajectories off
Lake Superior. As there will be several reinforcing PV maxima
rotating through the mean trough, we could be looking at multiple
episodes of mostly light rain through Tuesday.

- Moderating temperatures after Wednesday, rain possible Thursday

Short wave ridging and an associated surface high will provide
higher confidence for dry conditions on Wednesday. However, as noted
previously, another shortwave trough diving southeast will provide
another chance for rain. Lower tropospheric temperatures by this
time should be warm enough to prevent lake effect from being a
factor. Forecast PoPs are currently low, but would expect an
increase in rain chances with subsequent updates if this pattern
holds.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 746 AM EDT Fri Aug 22 2025

Fog was not quite as extensive as expected this morning. We have a
couple of terminals that should remain IFR/LIFR for a very short
while longer. Afterwards, starting around 13Z, we expect VFR
conditions that should persist through the day.

Winds will be light and potentially quite variable in direction
given that surface high pressure will be centered over the area.
The exception will be MKG which should experience a lake breeze
beginning this afternoon.


&&

.MARINE...
Issued at 322 AM EDT Fri Aug 22 2025

Wind and waves will remain below advisory levels through Friday.
However, a cold front will move through Saturday and west-northwest
winds behind it will cause winds and waves to increase; a Small
Craft Advisory (SCA) will likely be needed by Saturday afternoon and
SCA conditions are expected to persist well into Monday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

DISCUSSION...TJT
AVIATION...TJT
MARINE...TJT