491
FXUS63 KGRR 250321
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
1121 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 /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1121 PM EDT Wed Jun 24 2026
Latest radar shows scattered showers and isolated thunderstorms
will continue over the next few hours. Have amended the LAN TAF
to time thunder through the airport. so far the showers along the
I 94 corridor do not have thunder. So while it is possible, will
only have PROB30 for that potential. Once these showers move
through, around 08Z, Low clouds and fog will develop with IFR
conditions favored and pockets of LIFR possible. Any low clouds
scatter out by late morning Thursday given strong June sunshine.
Shower and thunderstorm development Thursday afternoon is expected
to focus north and east of the terminals.
&&
.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...None.
MARINE...None.
&&
$$
DISCUSSION...Thomas
AVIATION...Ceru
MARINE...CAS/Thomas
NWS GRR Office Area Forecast Discussion
