758
FXUS63 KGRR 080727
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
327 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 /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 132 AM EDT Wed Jul 8 2026
Still just a weak signal in the models for patchy early morning
shallow fog. Any such visibility restrictions will end shortly
after sunrise. Expecting few to scattered clouds at or above 5,000
feet today. From the complex of storms currently in northwest
Wisconsin, there is a slight chance of them reaching Ludington
(LDM) as diminishing showers after 16 Z. Additional thunderstorms
developing in Wisconsin this afternoon may nose in toward MKG to
GRR after 00 Z, though this is only supported by a few models
among the HREF. Any surviving shower or thunderstorm complex would
produce some northwest shifts in wind against the prevailing
light southwest winds.
&&
.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
