669
FXUS63 KGRR 220742
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
342 AM EDT Wed Apr 22 2026
.KEY MESSAGES...
- Slight chance of afternoon shower or thunderstorm near I-94
- Showers and storms Friday afternoon and Friday night
- Increasing confidence for rainy and breezy weather Mon-Tue
&&
.DISCUSSION...
Issued at 342 AM EDT Wed Apr 22 2026
- Slight chance of afternoon shower or thunderstorm near I-94
Patchy fog near and south of I-96 will mix out shortly after
sunrise. Light winds are expected today, and it will be mostly
sunny and dry in Central Michigan, while partly sunny with some
daytime cumulus in Southern Michigan.
Better low-level moisture pooled up in southern Michigan,
especially near and south of Allegan-Jackson, is supporting an
afternoon buildup of 500-1000 J/kg of mixed layer CAPE in some of
the overnight CAMs. Capping may be weak and could be overcome with
weak convergence along a subtle surface trough extending through
Southwest Michigan, especially if there is a tendency for a weak
mesoscale low to form along the trough as depicted in some models.
Have introduced slight chance of thunderstorms near I-94 this
afternoon, though somewhat higher chances exist to the south in
Michiana.
If a thunderstorm cell or two were to develop, isolated hail and
gusty winds would be possible as cells propagate toward the east-
southeast with a congealing cold pool in a lightly sheared
environment.
- Showers and storms Friday afternoon and Friday night
The influence of a Northern Plains upper-level low (the left foot
of an omega block pattern) is expected to nudge into Lower
Michigan late Friday. Scattered showers and thunderstorms are
expected in the vicinity of a frontal triple point passing through
the area. CAPE and shear should be relatively modest, in the
ballpark of 500-1000 J/kg and 20 knots, so the potential for
severe storms is low. Rainfall amounts may broadly be 0.25 to 0.50
with isolated 1 inch possible.
- Increasing confidence for rainy and breezy weather Mon-Tue
A plurality of ensemble members solutions producing rain over
Lower Michigan Monday into early Tuesday is now a majority. The
southern branch of the upper level jet will strengthen over the
Southwest US to south-central Plains, with a low developing in the
exit region of this jet, making its way into the Midwest. Not
clear if the track of the low will keep Michigan on the cool side
or on the warm side, but there are plenty of members showing CAPE
and generally breezy conditions with this low. This will have to
be watched for thunderstorm potential, perhaps a nonzero threat of
severe weather also. The median rainfall totals among the
ensembles are a little higher with this system than with Friday`s,
although naturally the spread is higher with some drier and some
much wetter solutions also possible.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 239 AM EDT Wed Apr 22 2026
Patchy fog is favored through 12 Z near and south of MKG-GRR-LAN,
then VFR is likely later in the morning once the fog mixes away.
Moisture will be higher during the day in southern Michigan, so
AZO, BTL, and JXN has a chance of afternoon shower development,
perhaps isolated to scattered thunderstorm cells based on some
runs of the latest short-term models. Confidence is low as this
is a recent uptrend in probability, and still the chance of
thunderstorms is more favored to the south in Indiana and Ohio.
&&
.MARINE...
Issued at 342 AM EDT Wed Apr 22 2026
Light winds and low waves are expected today. Generally offshore
flow this morning will become more onshore during the afternoon.
Areas of fog may be present over the lake today into Thursday.
Hazardous winds and waves for small craft will likely develop
north of Grand Haven Thursday night into Friday with south winds.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...CAS
AVIATION...CAS
MARINE...CAS
NWS GRR Office Area Forecast Discussion
