672
FXUS63 KGRR 101900
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
300 PM EDT Wed Sep 10 2025

.KEY MESSAGES...

- Chance for Showers and Storms Saturday, Otherwise Dry

&&

.DISCUSSION...
Issued at 300 PM EDT Wed Sep 10 2025

- Chance for Showers and Storms Saturday, Otherwise Dry

Our weak trough moving through may bring a few sprinkles,
otherwise dry conditions continue until another trough moves
through Saturday. There is still some uncertainty with the exact
timing of the trough axis along with the strength as seen in the
cluster analysis. A couple of the clusters show a deeper trough
and stronger low level jet with the trough axis moving through
Saturday night. The other clusters are overall weaker with the jet
and trough with not much of an axis moving through. Mean MUCAPE
values in the different clusters are similar with values
increasing into the evening around 500 J/kg and 0-500mb shear
around 30 knots. Additionally in the cluster analysis
probabilities of a hundredth or more have increased though drop of
quickly above a tenth of an inch. Hence the increase in PoPs to
30 to 40 percent for Saturday.

Dry conditions move in behind the trough Sunday with upper level
ridging into next week. Temperatures over the next week will be
persistent with highs in the upper 70s to low 80s and lows in the
40s and 50s.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 135 PM EDT Wed Sep 10 2025

Aviation concerns remain NIL over Southwest Lower MI, with VFR
conditions and light winds into Thursday. Patchy upper level
cloudiness will continue this afternoon and tonight before
diminishing as weak upper trough axis weakens and eventually pushes
east of the region. A nearly non-existent surface pressure
gradient will result in light and variable winds, with perhaps a
small tendency to turn NE by Thursday - in response to high
pressure strengthening ever-so-slightly NE of the Great Lakes.

Consistent with observations the past two nights, forecast will
include patchy fog after midnight at JXN.

&&

.MARINE...
Issued at 300 PM EDT Wed Sep 10 2025

Mariners can expect *very* quiet weather over the nearshore waters
of Lake Michigan through Thursday. A weak pressure gradient will
support light winds (generally 10 kt or less)... and therefore
minimal wave action. Wind directions will largely be variable, with
an enhanced onshore lake breeze component this afternoon and again
Thursday afternoon.

&&

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

&&

$$

DISCUSSION...RAH
AVIATION...Smith
MARINE...Smith