562
FXUS63 KGRR 142356
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
756 PM EDT Tue Apr 14 2026
.KEY MESSAGES...
- Risk for Severe Thunderstorms and Flooding Tonight
- Continued Thunderstorms Chances Wednesday
- Active Stretch of Weather Continues into Weekend
&&
.DISCUSSION...
Issued at 250 PM EDT Tue Apr 14 2026
- Risk for Severe Thunderstorms and Flooding Tonight
Severe thunderstorms with the risk of damaging winds, large hail,
tornadoes, and heavy rain expected largely between 7PM tonight to
4AM early Wednesday.
Significant clearing has occurred across the area allowing for
instability to build this afternoon. HREF is highlighting around
2000 J/kg of surface based cape largely along and south of I-96
with similar MUCAPE values extending further north. Upper level
divergence will be in play along with low level jet convergence as
it moves in between 7PM-10PM this evening. It is in this window
we expect storms to develop. Effective shear of around 40-50 knots
will aid in storms becoming more organized with 0-1km storm
relative helicity values of 200 m2/s2 largely along and south of
I-96 and mid level lapse rates around 7-8 C/km. With this setup
all hazards are in play. The highest risk for tornadoes will be
along and south of I-96 due the greater storm relative helicity
values and surface based CAPE. Storms may begin isolated before
congealing into a line that moves southeastward through the
state. Quick spin-up tornadoes and damaging winds will be
possible with the line.
Corfidi vectors may aid in some backbuilding behind storms this
evening which would increase the flooding potential. HREF highlights
local probability matched mean amounts of 2 to 4 inches in portions
of western, central, and southern Michigan. With these signals the
flood watch has been extended to the entire area.
- Continued Thunderstorms and Flooding Chances Wednesday
Conditional risk for severe thunderstorms Wednesday late Wednesday
afternoon into Wednesday night.
The low level jet should help sustain rain and thunderstorms into
Wednesday morning, especially for areas along and south of I-94. The
threat for severe thunderstorms later Wednesday will be directly
tied to if we are able to recover from the morning convection. If we
aren`t able to recover enough, garden variety thunderstorms with
heavy rain are expected. If we are able to recover, damaging
winds and tornadoes will be possible. Mean HREF values currently
have surface based CAPE values improve to around 500 to 1000 J/kg.
Meanwhile minimum surface based CAPE values are 500 less than 500
J/kg and maximum values are 2000 J/kg or greater along and south
of I-96. This large spread points to the large uncertainty with
how tomorrow will play out.
However, with any rainfall, the flooding risk will continue due
to the already saturated conditions from the previous rounds of
rainfall. Check the HYDROLOGY section for more information.
- Active Stretch of Weather Continues into Weekend
An upper level low moves through the region Thursday, continuing
rain and thunderstorm chances into Thursday evening. Pressure
heights increase Thursday night into Friday, giving the area a
brief break in the rainfall. However, southwest flow returns
ahead of a deep trough, bringing rain and thunderstorm chances
back to the area Friday night into Saturday. There is a potential
for severe thunderstorms as well, which is outlined in the SPC day
5 outlook.
Colder air moves in behind the low Saturday with lows Saturday night
into Sunday dropping into the 30s. This could result in some snow
mixing in on the backside. Highs Sunday are only expected to be in
the 40s, and with breezy west to northwest winds, this will
probably keep wind chills in the upper 20s to 30s.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 756 PM EDT Tue Apr 14 2026
Clusters of thunderstorms are beginning to move over western Lake
Michigan at the beginning of this TAF period. Based on storm
motion, the likely time of arrival at the MKG site will be between
0130z-0200z. Thunderstorm wind gusts in excess of 40 kts are
likely with this activity, and depending on storm strength it is
possible that 50 kt gusts or greater could occur at MKG and GRR
with this intial activity. Clusters of storms will likely congeal
into a line that will likely sweep across all terminals in the
02z-06z time frame. Periodic wind shear of around 40-50 kts at
2000 ft is possible especially early in the period. A more
prolonged rain event could set up especially from AZO to BTL and
JXN after the initial line of storms moves through (post 05z-06z)
and trends will need to be monitored for potentially a few hours
of rain with embedded TSRA.
&&
.MARINE...
Issued at 250 PM EDT Tue Apr 14 2026
Wave heights will continue to fall below Small Craft Advisory
conditions this afternoon, therefore the Advisory has been
cancelled. Dense fog is slowly clearing as well. Will keep the dense
fog advisory for now, but it could be cancelled early if conditions
continue to improve.
Thunderstorms are expected tonight with the potential for damaging
winds, large hail, and tornadoes. 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.
Flood Watch through late Thursday night for MIZ056>059-064>067-
071>074.
MARINE...None.
&&
$$
DISCUSSION...RAH
AVIATION...Hoving
MARINE...RAH
HYDROLOGY...AMD
NWS GRR Office Area Forecast Discussion
