Portage, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

315
FXUS63 KGRR 242325
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
725 PM EDT Tue Jun 24 2025

.KEY MESSAGES...

- Several Rounds of Showers and Storms This Week

- Hot and Humid Weather Continues

&&

.DISCUSSION...
Issued at 229 PM EDT Tue Jun 24 2025

- Several Rounds of Showers and Storms This Week

A stalled front across Southern Michigan is serving as a focus for
thunderstorm development this afternoon. MLCAPE in excess of 2000
J/kg and 20-30 knots of effective shear will support multicell
thunderstorms. The strongest storms will be capable of wet
microbursts with wind gusts of up to 60 mph. Frequent lightning
and heavy rain are possible with all thunderstorms that develop
today. The best coverage of storms looks to be near and south of
the stalled front which extends roughly from Lansing to Kalamazoo.

This pattern continues Wednesday as the front drifts south of the
state. A passing mid-level wave will lead to scattered
thunderstorms, especially in the afternoon, with the best chances
south of I96. The front then surges north again Thursday as a
warm front bringing showers and storms to much of the area. A
surface low then drives a cold front across the state Friday
bringing additional shower and thunderstorm chances. Questions
remain on specific timing and coverage of storms as that depends
on placement of forcing mechanisms and impacts of upstream storms
as they move into the region. Given the ample moisture, surface
based instability, and marginal shear, a risk for damaging winds
from wet microbursts will remain possible over the next few days
in the strongest storms. The threats for heavy rain and frequent
lightning will also continue. Rain chances then decrease for much
of the weekend before an approaching wave and surface low brings
precipitation back into the forecast.

- Hot and Humid Weather Continues

The rest of the work week will feature highs in the 70s to 80s with
dewpoints in the mid 60s to low 70s. While there will be an
improvement over the last several days, it will still be quite
muggy with heat index values topping out in the 90s Thursday and
Friday. A warmer airmass and higher dewpoints arrive again this
weekend bringing the potential for heat indices to approach or
exceed 100F.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 722 PM EDT Tue Jun 24 2025

Radar continues to show a decrease in echos as a result of
atmospheric stabilization due to waning insolation.

Visible loop shows a mid cloud deck moving in from the lake and
that should remain in place overnight. Given earlier rainfall, we
may see some fog and MVFR cigs overnight, but that will burn off
and lift by late morning/early afternoon.

&&

.MARINE...
Issued at 229 PM EDT Tue Jun 24 2025

Overall, winds and waves are forecast to remain below Small Craft
Advisory/Beach Hazards Statement criteria through at least the
weekend as gradient flow remains weak. The primary concern for
marine interests is chances of thunderstorms each day for the rest
of the work week. The best chances will be in the afternoon and
evening hours. Locally higher winds and waves are possible in any
thunderstorms that develop.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory until 8 PM EDT this evening for MIZ064>067-071>074.
MARINE...None.

&&

$$

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