713
FXUS63 KGRR 161028
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
628 AM EDT Wed Sep 16 2026

.KEY MESSAGES...

- Patchy Dense Fog Possible This Morning

- Showers and Thunderstorms Through Tonight

- Heavy Rain Possible This Weekend

&&

.DISCUSSION...
Issued at 229 AM EDT Wed Sep 16 2026

- Patchy Dense Fog Possible This Morning

Areas of fog have developed under breaks in the clouds this morning
as light winds favor enhanced radiational cooling. At times we`ve
seen some obs such as Freemont, Charlotte, and Marshall go dense fog
with sub 1/4SM visbys. This is likely to continue through shortly
after daybreak where we get pockets of clearing. The greatest fog
potential looks to be areas east of US131, especially near and
south of I96.

- Showers and Thunderstorms Through Tonight

A frontal boundary nearby will lead to periods of showers and
thunderstorms through tonight, with high PWATs favoring the
potential for heavy rain. The best chance will come tonight with a
low-level jet interacting with the frontal boundary to our south.
This will being the best shower and thunderstorm potential along and
south of I96, especially near I94. Drier conditons then take hold
for Thursday and Friday as the frontal boundary is shunted south,
though isolated showers/storms cannot be ruled out.

- Heavy Rain Possible This Weekend

Attention then turns to this weekend as a mid-level wave slowly
drives a low pressure system across the region. Rain starts Friday
night continuing into Saturday. The slow nature of this system in
addition to high (aoa 2") PWATs supports a heavy rain threat.
Probabilistic data shows a 70-80% chance of over 1" of rain across
much of the area with a 40-50% chance of exceeding 2" mainly across
the southern half. This aligns well with the Slight (2/4) Excessive
Rainfall outlook from WPC which we agree with. Marginal instability
will support some thunder risk, albeit low given the best
instability remains south.

The forecast becomes more nebulous into early next week as southwest
flow with embedded shortwaves develops across the area as larger
scale troughing arrives upstream. Dependent on placement and timing
of key features, additional showers and thunderstorms are possible.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 628 AM EDT Wed Sep 16 2026

Intermittnent fog and low clouds have developed at LAN/JXN, and
are expected to become more widespread expanding into AZO/BTL in
the coming hours. MVFR to IFR conditions are expected. AZO/BTL/JXN
then stay MVFR all day before crashing to IFR/LIFR tonight as
showers develop in an already moist environment. Further north,
lower coverage will support VFR this afternoon (borderline MVFR at
LAN) falling to MVFR tonight.

&&

.MARINE...
Issued at 229 AM EDT Wed Sep 16 2026

Winds and waves have fallen below hazardous levels, and are expected
to remain there over the next few days with a weaker gradient. The
next chance for hazardous winds and waves arrives Friday into early
next week as a strong system moves across the region increasing the
gradient. A few thunderstorms are possible through tonight south of
Holland.

&&

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

&&

$$

DISCUSSION...Thomas
AVIATION...Thomas
MARINE...Thomas