296
FXUS63 KGRR 241905
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
Issued by National Weather Service Detroit/Pontiac MI
305 PM EDT Mon Aug 24 2026
.KEY MESSAGES...
- Areas of fog tonight and Tuesday morning
- Thunderstorms possible later Wednesday, less likely Thursday
&&
.DISCUSSION...
Issued at 305 PM EDT Mon Aug 24 2026
Upper low over western Quebec is wobbling east out of the region
and releasing it`s influence. Narrow surface ridge will wash
across the Lower Peninsula tonight and early Tuesday. As a
consequence the fresh northwest flow will quell out early this
evening. The light flow and very good radiative cooling potential
will support some fog development tonight. Fog will lift into a
cumulus field by late morning. Otherwise, a quiet late summer day
is in store Tuesday with partly cloudy skies and highs around 80F.
The next shortwave in the westerlies, currently over the southern
Canadian Prairies will carve into the Great Lakes region on
Wednesday. The wave will undergo some level of capturing by the
larger Hudson Bay closed low over the next day or so. This process
will induce height falls to the north of the wave centroid,
coaxing the best forcing north. Therefore, the main forcing
across Western Lower Michigan will be the attendant cold front -
with the primary wave ascent shunted north across the northern
Lakes region.
An uptick in south-southwest flow on Wednesday in advance of the
cold front, will squeeze in some better moisture content and
actionable instability - MLCAPE values approaching 1-kJ/kg.
Showers and scattered thunderstorms are expected to develop along
the advancing buoyancy gradient during the mid/late afternoon,
with a second impulse of development along the cold front during
the evening hours. Still plenty of timing wiggle room in the
forecast, given this system still has two more diurnal convective
cycles to augment the forcing before arrival. Severe potential
will be limited with only modest deep layer shear due to weakening
mid-level flow.
Not much a of cool down on Thursday behind the front with ample
late summer sun. A stray shower or storm is certainly possible
along and south of I-96, with some lingering modest instability
lingering.
Overall flow pattern appears poised to support greater ridging
aloft over the Great Lakes region as we progress through the
upcoming weekend and into next week. Global ensembles are starting
to gel around the notion of a period of above average temps
starting Sunday.
&&
.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1248 PM EDT Mon Aug 24 2026
Occasionally gusty northwest flow will temper through the late
afternoon. A couple pockets of small scale cumulus will linger
around AZO/BTL and LAN for the next couple of hours, as near
surface drying continues. Center of the incoming high will slide
just to the south - staging very light wind conditions tonight.
Fog formation is expected overnight - with the best potential
across the interior where soil moisture availability is higher.
Fog is expected to thin and dissipate by mid morning.
&&
.MARINE...
Issued at 305 PM EDT Mon Aug 24 2026
Northwest winds are slowly relaxing this afternoon and the wave
field continues to follow. Winds will become light tonight as
high pressure moves across the region. South-southwest winds will
emerge on Tuesday - with speeds increasing into the 10-15 kt range
north of Muskegon during the afternoon. Speeds will continue to
slowly climb through Tuesday night as the next system approaches
from the west. Waves will quickly respond early Wednesday -
likely warranting small crafts and beach hazards.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Mann
AVIATION...Mann
MARINE...Mann
NWS GRR Office Area Forecast Discussion
