260
FXUS63 KGRR 081055
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
655 AM EDT Wed Jul 8 2026
.KEY MESSAGES...
- Scattered Showers and Storms This Evening Through Thursday
- Mostly Dry Weekend Favored and Heating Back Up
&&
.DISCUSSION...
Issued at 327 AM EDT Wed Jul 8 2026
- Scattered Showers and Storms This Evening Through Thursday
Overall a decent signal for a few rounds of scattered
thunderstorms between late this evening and late Thursday, but
fairly unimpressive environment and dynamics that will keep
details of predictability low (when and where exactly it will
storm) low and also cap potential at just a marginal threat of
wind/hail. But the confidence is fair via the HREF for three main
windows for storms: late evening weakening storms crossing the
lake toward areas north and west of Grand Rapids, then some
elevated Thu morning thunderstorms in west-central and central
Michigan, then more surface-based storms Thu afternoon east of
US-131. Also early this afternoon, can`t rule out a weakening
thunderstorm surviving into Ludington.
Much about this setup is on the positive but weak side for
supporting storms: the sagging cold front, the upper-level jet
dynamics, the moistening low-levels and 850 mb moisture transport,
the cooling mid-upper levels that will yield about 500-1000 J/kg
of CAPE (perhaps more Thu afternoon), and about 20 knots of deep-
layer shear. Despite the midlevelds also expected to be rather
moist, the well mixed lower atmosphere both this evening and Thu
afternoon should support about 500 J/kg of DCAPE per the HRRR,
allowing for a chance for a coalesced cold pool to sweep into West
Michigan this evening with 30-40 mph gusts, then isolated near-
severe wind gusts in mid/southern Michigan Thu afternoon.
- Mostly Dry Weekend Favored and Heating Back Up
PoPs are about 10 percent through the weekend as upper level
ridging and surface high pressure is most favored over Lower
Michigan. A heat wave is expected to develop this weekend to early
next week from the Intermountain West into the Northern Plains,
with 500 mb heights potentially reaching 600 dekameters over the
Dakotas on Monday per the ECE. This plume of 21-24 C air at 850 mb
may advect into Michigan from the west-northwest, making highs in
the 90s possible Mon to Tue/Wed. The ECE and CMC are the most
aggressive with the heat, and GEFS a little less but still quite
warm. Dew points may be in the mid 60s this time, less humid than
last week`s heat wave.
&&
.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 655 AM EDT Wed Jul 8 2026
Fog has developed at Holland (BIV), and vicinity Muskegon (MKG)
and Fremont (FFX) as seen on webcams and nighttime microphysics
satellite images. Patchy shallow fog may also be present in a
number of other locations. This fog will mix away quickly with
daytime heating underway. Expecting few to scattered clouds at or
above 5,000 feet today.
Thunderstorm development in Wisconsin today will eventually move
toward MKG and GRR (and north) after 00 Z. Confidence in the
storms reaching MKG and GRR is fairly low but worth a prob30.
Those storms may bring a northwest wind shift and briefly gustier
winds. Scattered thunderstorms may continue to develop into
Thursday morning mainly north of MKG, GRR, and LAN.
&&
.MARINE...
Issued at 327 AM EDT Wed Jul 8 2026
Winds over the water will mostly be from the south-southwest 5 to
15 knots today, though weakening showers or thunderstorms
crossing the lake this afternoon and/or evening may cause shifting
winds to west/northwest and gusts 20-30 knots or perhaps
stronger.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert until midnight EDT tonight for MIZ050-056-057-
064-065-071.
MARINE...None.
&&
$$
DISCUSSION...CAS
AVIATION...CAS
MARINE...CAS
NWS GRR Office Area Forecast Discussion
