020
FXUS63 KGRR 032328
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
728 PM EDT Thu Jul 3 2025

.KEY MESSAGES...

- Scattered Showers and Storms Possible Today and Friday

- Showers and Storms Possible Saturday Night into Sunday

- Hot Weekend, Then Slightly Cooler

&&

.DISCUSSION...
Issued at 246 PM EDT Thu Jul 3 2025

- Scattered Showers and Storms Possible Today and Friday

Visible satellite imagery has showed significant cumulus development
across much of the CWA in recent hours, except for areas in the
lake shadow. A few showers and storms have already been observed
across Kent and Allegan Counties. Mesoscale forcing may result in
additional scattered showers and storms through the evening, with
increasing mid-level heights and the lack of strong convergence
tempering more widespread convection. The best chance of isolated
showers and storms is areas east of US131 and south of M20.

There are two potential sources for a few showers and storms for
Independence Day. First will be driven by weakening storms crossing
the lake from Wisconsin. If these storms can survive the crossing,
they would reach the lakeshore Friday morning, with the best signal
between Allegan and Muskegon Counties. The second is for mesoscale
convergence to develop in the afternoon supporting additional
potential for shower and storm development. Even though West
Michigan will be in the peak of low-level height rises, the ample
instability may bring precipitation to areas near and east of US131.
However for many, Independence Day will remain dry.

- Showers and Storms Possible Saturday Night into Sunday

A mid-level wave driving a cold front across West Michigan will lead
to the potential for areas of showers and storms Saturday Night into
Sunday. Mid-level winds are weak keeping shear marginal. However
with PWATs above the 90th percentile of model climatology heavy
downpours are possible and isolated storms may contain gusty winds.
However this latter possibility in particular is dependent on
frontal timing with the NAM/GFS still running ahead of the ECMWF.
The difference between models is less than yesterday but still
enough that timing and available instability are uncertain.

- Hot Weekend, Then Slightly Cooler

The building ridge and associated return flow into the weekend will
bring hot weather to the area this weekend. Temperatures in the
upper 80s to low 90s with mid 60s dewpoints will produce heat
indices in the low 90s Friday and well into the 90s for Saturday
and Sunday away from the lake. This does bring at least moderate
concern for heat stress for those vulnerable to heat, such as those
active outdoors or without air conditioning. Dewpoints fall into the
mid 50s to low 60s behind Sunday`s cold front keeping heat indices
in the 80s during this time.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 726 PM EDT Thu Jul 3 2025

Radar shows a few showers close to LAN that developed on outflow
boundaries. As the sun fades, the showers will too, leaving
generally clear skies. There may be patchy fog overnight,
especially near JXN. Otherwise skies will be mostly clear.

&&

.MARINE...
Issued at 127 PM EDT Thu Jul 3 2025

High pressure over Michigan will drift east Saturday. Southwest
flow will increase as this occurs and waves will build to 3 to 5
feet north of Holland by Saturday afternoon. Swim risk will rise
accordingly with lowest swim risk near South Haven and highest
north of Muskegon. Prior to Saturday afternoon waves will aob 2
feet.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert from midnight tonight to midnight EDT Friday
     night for MIZ050-056-057-064-071.
MARINE...None.

&&

$$

DISCUSSION...Thomas
AVIATION...04
MARINE...04