433
FXUS63 KGRR 151801
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
201 PM EDT Wed Apr 15 2026
.KEY MESSAGES...
- Severe storms have passed, flood risk continues
- Thunderstorm chances again this evening
- Further chances for storms late this week
&&
.DISCUSSION...
Issued at 308 AM EDT Wed Apr 15 2026
- Severe storms have passed, flood risk continues
Front has passed to the west and the south with lingering
showers and a few isolated storms along the I 94 corridor.
Most of southwest Michigan is in the downsloping drier air.
The boundary will continue to move to the south and east slowly
overnight. A few clusters of storms are expected to follow along
the stalled boundary and move along the I 94 corridor overnight
into early this morning. The atmosphere is mixed over with little
if any dynamics so further severe is not a concern. However,
potential hydro concerns remain. The heaviest rainfall occurred
north of the I 96 corridor with bullseyes of 2 to 4 inches of radar
estimated rainfall.
Latest CAMS do have a line of showers and storms through southern
Michigan, but that boundary has shifted to the south. So will
continue to watch for potential hydro threat this morning but the
heaviest rainfall should be along the southern row of counties of
Michigan .
- Thunderstorm chances again Wednesday
The thunderstorm chances will keep on coming. There is a greater
potential for weak convection this morning. Any clouds and
rainfall will inhibit any atmosphere recovery today. Temperatures
are expected to get into the mid 70s with Dewpoints into the 60s.
The mid to upper level dynamics are far weaker than the previous
two days. That said, another surface low and corresponding frontal
patter will move through the region tonight into Thursday. Mid
level moisture and weak forcing will accompany that system into
far southern Lower Michigan. The best LLJ and helicity will be in
Indiana. If that forcing shifts to the north then there could be a
better chance for severe Wednesday evening into Thursday. Due to
the above conditions SPC has far southern Lower in a slight risk.
Main threat will be wind. Given the wet pattern we have been in,
hydro will remain a concern. Latest soundings are fairly moist
with weak mid level flow, so definitely more of a rain sounding.
There is quite a few areas of stable air so access to mid level
moisture could be a concern. WPC continues to keep the region in a
slight risk for excessive rainfall.
- Further chances for storms late this week
Michigan could see a reprieve from showers and storms Thursday
into Friday. This break will probably be short lived as another
large upper level system is trending to move through the region
Saturday into Sunday. Latest mid range models are in fair
agreement ion the passage of a large upper level low Saturday.
that low should bring a system with decent QPF through Saturday.
There remains a deepening elongated mid level trough associated
with that upper level pattern. SPC does have southern Michigan
outlooked for potential severe weather through this timeframe.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 201 PM EDT Wed Apr 15 2026
Current radar loop shows an area of rain moving east-northeast
across northern Indiana and southern Lower Michigan with lightning
presently confined to south of Michigan. This activity may brush
our southeast terminals early this afternoon. Additional
thunderstorms are developing over Iowa and will affect the
terminals early tonight. Another factor is marine dense fog over
Lake Michigan, which is already producing IFR/LIFR conditions at
MKG with the onset of onshore flow. We expect a prolonged period
of MVFR/IFR restrictions well into tonight with the thunder threat
continuing towards and after 06Z. For the sake of brevity, have
not provided much detail after that, but it`s looking likely that
IFR ceiling restrictions will be common into and possibly beyond
12Z Thursday.
&&
.MARINE...
Issued at 333 AM EDT Wed Apr 15 2026
Thunderstorms are expected overnight with the potential for
damaging winds and large hail. Higher waves will also be possible
with any thunderstorm. Thunderstorms will gradually taper off in
the southern zones Wednesday morning, but there is a chance they
could linger through the day. Otherwise thunderstorm chances
return late Wednesday afternoon into Wednesday night.
&&
.HYDROLOGY...
Issued at 250 PM EDT Tue Apr 14 2026
Bottom line: The most significant flood in recent years is likely
upcoming on the Muskegon River, with several locations expected to
pass Major flood stage.
Another 1-2 inches of rain fell last night, primarily in
upper/headwaters portions of the Muskegon River Watershed. This
joins the previous 2-5 inches of rain in the area that is all
finding its way toward the river. A significant and impactful flood
on the Muskegon River will be developing over the next few days,
with a crest expected in the Friday timeframe.
Meanwhile, additional rounds of heavy rain are expected to shift
south a bit starting today, with the Grand River basin the more
likely to be impacted. With 1-2" across a large area, and locally
3"+ bullseyes expected, we are expecting some localized flooding to
develop overnight tonight, especially if the thunderstorms track
over urban areas repeatedly. This will also eventually get the Grand
River water levels increasing again over the next few days.
Currently, this looks like we`ll largely repeat the minor flooding
(on the Grand River and tributaries) that occurred in the last few
weeks. Further south, the Kalamazoo River has been a bit drier
lately, so no flooding is expected to develop there, though urban
and poor-drainage area flooding will definitely be possible over the
next day or two as the thunderstorms move through.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch through late Thursday night for MIZ037>040-043>046-
050>052-056>059-064>067-071>074.
MARINE...Dense Fog Advisory until 8 AM EDT Thursday for LMZ845>849.
&&
$$
DISCUSSION...Ceru
AVIATION...TJT
MARINE...Ceru
HYDROLOGY...AMD
NWS GRR Office Area Forecast Discussion
