373
FXUS63 KGRR 241944
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
344 PM EDT Wed Jun 24 2026
.KEY MESSAGES...
- Scattered Showers and Thunderstorms Through Thursday
- Hot With Thunderstorms Possible Next Week
&&
.DISCUSSION...
Issued at 202 PM EDT Wed Jun 24 2026
- Showers and Thunderstorms Through Thursday
Radar shows a batch of showers crossing the area this afternoon,
with additional development expected this evening. The advection of
slightly better mid-level lapse rates across the area this evening
will lead to an increase in MUCAPE to 500-1000 J/kg supporting
embedded thunder potential. Given a low-level jet impinging on the
southwest CWA late this evening cannot completely rule out a strong
storm, however confidence is low with limited instability as a
significant limiting factor. These storms should wind down by early
Thursday morning. There are some signals for additional showers and
storms to develop Thursday afternoon with low passage, with the best
chance across the northeastern CWA.
- Hot With Thunderstorms Possible Next Week
Late this week into this weekend will feature a transition into a
large scale ridging pattern across the Central and Eastern CONUS.
Generally fair weather is expected. 850mb temps are forecast to
climb into the 20s C by next week translating into surface temps
into the 90s. Given dewpoints in the 70s, this could translate into
heat indices into the 100s early next week. This would bring the
potential for increased heat related illness/impacts and needs to be
closely monitored over the next week. The pattern is favored to
continue into the Independence Day weekend. However any thunderstorm
activity could impact how hot things get.
The other concern is for thunderstorm potential into next week. The
hot and humid airmass will lead to significant instability across
the area with forecast GFS/ECMWF MUCAPE values north of 2000 J/kg at
times. Given our forecast position on the northern periphery of the
ridge, and the signal for embedded shortwaves within the large scale
pattern, the potential for organized convection across the Great
Lakes region exists. However, certainty in where and when any
thunderstorms would develop is low given the reliance on small-scale
waves in the large scale pattern. Refinement of the forecast is
expected as we get closer.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 115 PM EDT Wed Jun 24 2026
Batch of showers with some small scale convective elements is
slowly migrating east across the Southwest Lower Michigan
airspace. Reductions in visibilty to or below 2SM are possible
with the heavier showers - with GRR and AZO being the most
susptible with the current batch. Ceilings have been VFR with this
activity an is expected to remain the case. Additional showers
are should expand from the scattered activity over southern
Wisconsin. There may also be a few embedded thunderstorms, but
coverage is expected to limited. The primary window for convective
activity will be as early as 22z in the west and as late as 04z
in the east. Current indications are for low-clouds and fog to
emerge prior to daybreak. TAFs advertise entry level IFR
conditions for consideration.
&&
.MARINE...
Issued at 344 PM EDT Wed Jun 24 2026
Observations from the Port Sheldon buoy currently have south winds
around 17 knots gusting to 23, a significant wave height of 3.4
feet, 10th percentile wave height of 4.4 feet, and maximum wave
height of 5.4 feet. This moderate to high swim risk will continue
into this evening for Port Sheldon and Grand Haven and north
toward Ludington, with the south side of south piers having the
most dangerous currents and largest waves.
High pressure then arrives later Thursday into Friday causing
winds and waves to subside. Showers are likely with thunderstorms
possible this afternoon and evening across the waters.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 10 PM EDT this evening for MIZ037-
043-050-056.
MARINE...Small Craft Advisory until 10 PM EDT this evening for LMZ846>849.
&&
$$
DISCUSSION...Thomas
AVIATION...99
MARINE...CAS/Thomas
NWS GRR Office Area Forecast Discussion
