629
FXUS63 KGRR 132322
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
722 PM EDT Tue Oct 13 2026
.KEY MESSAGES...
- Showers and isolated storms tonight
- Showers and a few storms Thursday into Friday
- Temperatures up and down through the 7 day forecast
&&
.DISCUSSION...
Issued at 257 PM EDT Tue Oct 13 2026
- Showers and isolated storms tonight
A few showers and isolated thunderstorms have developed this
evening in the far southern row of Michigan counties. This
activity looks to sweep east and south of the area late this
afternoon. The reasoning for this is the front is surging in the
same direction and winds are becoming slightly divergent off of
Lake Michigan.
We expect additional precipitation to develop tonight however as
the front drifts south into Northern Indiana. Mid level shortwaves
working eastward through the Southern Great Lakes will interact
with the nearby front and showers and a few storms will develop
after sunset. The best chances for rain will come along the I-94
corridor, but we will have chance pops all the way north into the
I-96 corridor. Rainfall will be on the light side on the order of
a tenth of an inch or less.
- Showers and a few storms Thursday into Friday
The most impactful weather of the forecast period will come
Thursday into Friday as a fall system moves through the Great
Lakes. The low will be deepening as it heads east, approaching
990mb at it moves well east of the area. Winds will increase on
the backside of the low on Friday with gusts over 40 mph certainly
possible.
The system will be deepening as shortwaves from both the northern
and southern streams phase over the Great Lakes region. The result
is the low swinging through along with deep moisture and lift.
Rainfall will not be overly heavy with 0.25 to 0.75 inch amounts
common. Some thunder is possible given the dynamic nature of the
system, especially towards I-94 given surface dew points rising
back in the lower 60s for a time.
Lake effect rain showers are expected on Friday along with the
driving northwest wind. Delta T`s will push into the upper teens
on Friday. It will be a wet day along the lakeshore for this
reason.
- Temperatures up and down through the 7 day forecast
Temperatures will be on a bit of a roller coaster with 60s to
around 70 for highs tomorrow. Highs will only reach the 50s on
Friday and Saturday given the cold air aloft. We should push back
towards 70 next Tuesday.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 718 PM EDT Tue Oct 13 2026
Skies are mostly clear across the terminals, but showers and
storms are developing in southwest Wisconsin along a frontal
boundary. This boundary will be over southern Lower overnight and
act as a focus for precipitation after 04z. Included a prob30 for
showers, but it`s possible there could be some thunder near the
I-94 terminals. precipitation will end prior to sunrise. MVFR cigs
are expected near the I-94 terminals Wednesday morning. Conditions
will improve late in the period.
&&
.MARINE...
Issued at 257 PM EDT Tue Oct 13 2026
Waves continue to subside this afternoon and the Small Craft
Advisory was allowed to expire on time at 200pm. The Whitehall
spotter buoy is reporting a 2.4 foot wave at the present time,
with South Haven at 1.6 feet. A downward trend should continue
into tonight as high pressure builds in. There will be a increase
in wave heights Wednesday into Wednesday evening as north winds
funnel down the lakeshore in advance of the high. We feel these
waves will likely stay below advisory criteria in the 2-4 foot
range.
The next time frame we are monitoring is Thursday night into
Friday behind the passage of a fall low pressure system. Northwest
wind crank up rapidly. We are likely looking at gale force winds
with this system as cold air advection will be effective at
building waves.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Duke
AVIATION...04
MARINE...Duke
NWS GRR Office Area Forecast Discussion
