168
FXUS63 KGRR 050605
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
205 AM EDT Wed Aug 5 2026
.KEY MESSAGES...
- Periods of Rain and Thunderstorms Into Next Week
&&
.DISCUSSION...
Issued at 205 AM EDT Wed Aug 5 2026
- Periods of Rain and Thunderstorms Into Next Week
The moisture and instability axis with the front currently extends
from north central IL into the eastern UP. This is where
scattered showers and a few thunderstorms have developed over the
past few hours. This axis will slowly shift east into western
Michigan this morning. MUCAPE values around 500 to 1000 J/kg will
advect into the area throughout the day as well continuing the
potential for thunder. Not expecting any severe storms with shear
around 20 to 30 knots. However precipitable water values
approaching 2 inches and the slow moving front could result in
training over the same area creating an environment where some
spots could see higher rainfall amounts in the 1-3 inch range.
Overall trends for these higher amounts have decreased slightly,
but the HREF still shows a signal.
A lull in showers and thunderstorms is possible this afternoon
before we see another surge of positive vorticity advection move
in this evening. Instability drops off around 11pm with scattered
showers likely continuing across much of the area overnight.
Showers and thunderstorms will likely be focused along and south
of a Holland to Alma line during the day Thursday. Instability on
the HREF picks up a little higher than today with values around
1000 to 1500 J/kg. Could see more of a diurnal trend with
thunderstorm activity where chances become more likely during the
afternoon and then drop off as we get closer to sunset.
After Thursday the pattern becomes more uncertain as we remain in
a broad upper level trough with the potential for multiple
shortwaves to move through the region. Each shortwave will bring
chances (20 to 40 percent) for showers and thunderstorms. Not any
one day looks to be a washout as these shortwaves will quickly
move through. Either way, keep an eye on the forecast if you have
any outdoor plans as timing will likely change as we get closer.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 205 AM EDT Wed Aug 5 2026
Ceilings will slowly lower throughout Wednesday as the surface
front and associated moisture move into the area. Isolated to
scattered showers and thunderstorms are expected along the front
with the best chances (20 to 50 percent) this morning at MKG and
GRR. A lull is then possible in the afternoon before shower and
thunderstorm chances pick back up Wednesday evening. JXN may stay
dry through 6Z Thursday.
Within the area of showers and thunderstorms ceilings will drop to
MVFR with the potential for some MVFR visibilities within areas of
heavier rain. MKG will see these lower ceilings Wednesday morning,
but elsewhere these lower ceilings will be slower to move into the
area until Wednesday night. Winds will be from the southwest at
about 5 to 15 knots.
&&
.MARINE...
Issued at 205 AM EDT Wed Aug 5 2026
Scattered showers and a few thunderstorms are expected through
tonight and may linger south of Holland into Thursday. Lower
visibilities will be possible within any shower or thunderstorm.
No severe thunderstorms are expected. Largely southwest winds
around 5 to 15 knots are expected today before becoming more
northerly Thursday. Southwest winds return Friday before becoming
westerly Saturday. Periods of showers and thunderstorms exist this
weekend into next week, although there is uncertainty with the
exact timeframes for showers or storms to occur. Overall winds and
waves are expected to remain below Small Craft Advisory and Beach
Hazard Statement levels.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...RAH
AVIATION...RAH
MARINE...RAH
NWS GRR Office Area Forecast Discussion
